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MANUAL FOR

ROCKFALL INVENTORY

PREPARED BY:

THE OHIO DEPARTMENT OF TRANSPORTATION

OFFICE OF GEOTECHNICAL ENGINEERING

1980 WEST BROAD STREET

COLUMBUS, OHIO 43223 DECEMBER 2016

Manual for Rockfall Inventory – Revised 12/2016 i

TABLE OF CONTENTS

SECTION 100 INTRODUCTION .................................................................................................................. 1

SECTION 200 ROCK SLOPE INVENTORY AND DATA COLLECTION ................................................ 2

201 PURPOSE AND GENERAL PROCESS ....................................................................................................... 2 202 SITE INVENTORY AND PRELIMINARY RATING ...................................................................................... 6

202.1 General ....................................................................................................................................... 6 202.2 Office Procedures ....................................................................................................................... 6

202.2.1 ODOT Interview(s) .............................................................................................................................. 6 202.2.2 Digital Photolog ................................................................................................................................... 7 202.2.3 Other Photographic Alternatives .......................................................................................................... 8 202.2.4 Geological Reference ........................................................................................................................... 8

202.3 Field Procedures ......................................................................................................................... 9 202.3.1 Inventory Site Determination ............................................................................................................... 9

202.3.1 a) Site Determination for Ramps ................................................................................................ 11 202.3.2 Preliminary Rating of Inventory Site.................................................................................................. 14

202.3.2 a) Inventory Site Location .......................................................................................................... 14 202.3.2 aa) Beginning Mile Point (BMP) ........................................................................................... 16 202.3.2 bb) Inventory Site Length ....................................................................................................... 17 202.3.2 cc) Ending Mile Point (EMP) ................................................................................................. 17 202.3.2 dd) BMP Position ................................................................................................................... 18

203.2.2 Preliminary Rating Scoring ................................................................................................................ 19 203 TIER 1 DATA COLLECTION ..................................................................................................................25

203.1 Field Procedures ........................................................................................................................25 203.1.1 Slope Configuration ........................................................................................................................... 25

Figure 200-10. EXAMPLES OF CUT SLOPES ...........................................................................................26 203.1.2 Slope Condition .................................................................................................................................. 27 203.1.3 Photographic Documentation of Inventory Site ................................................................................. 27

204 DETAILED RATING OF INVENTORY SITES - GENERAL .........................................................................28 205 TIER 2 SITE DATA COLLECTION ..........................................................................................................29

205.1 Tier 2 Data Procedures ..............................................................................................................29 205.1.1 Geometrics and Traffic ....................................................................................................................... 30

205.1.1 a) Traffic Survey Reports ........................................................................................................... 30 205.1.1 b) Actual Site Distance (ASD) ................................................................................................... 30 205.1.1 c) Decision Site Distance (DSD) ................................................................................................ 31 205.1.1 d) Percent Decision Site Distance (PDSD) ................................................................................. 31

205.1.2 Slope Information ............................................................................................................................... 32 205.1.2 a) Slope Height ................................................................................................................................... 32 205.1.2 b) Slope Elevations............................................................................................................................. 34 205.1.2 c) Slope Undercutting/Raveling ......................................................................................................... 34 205.1.2 d) Slope Jointing ................................................................................................................................ 34 205.1.2 e) Rockfall Source Information .......................................................................................................... 35

205.1.2 f) Hydrologic Conditions ............................................................................................................ 38 205.1.2 g) Corrective Actions ................................................................................................................. 39 205.1.2 h) Catchment .............................................................................................................................. 42

205.1.2 aa) Catchment Area Shape ..................................................................................................... 42 205.1.2 bb) Catchment Area Depth ..................................................................................................... 44 205.1.2 cc) Catchment Area Width ..................................................................................................... 45 205.1.2 dd) Foreslope Angle ............................................................................................................... 45 205.1.2 ee) Slope Face Angle .............................................................................................................. 46 205.1.2 ff) Remedial Effectiveness ..................................................................................................... 48

205.1.2 i) Additional Information ........................................................................................................... 48 206 TIER 3 & TIER 4 SITE DATA COLLECTION ...........................................................................................49

206.1 Slope Geological Conditions......................................................................................................49 206.1.1 Number of Cut Slope Benches ................................................................................................... 50 206.1.2 Number of Cut Slope Angles ..................................................................................................... 50 206.1.3 Cut Slope Angles ....................................................................................................................... 50 206.1.4 Average Cut Slope Angle........................................................................................................... 52 206.1.5 Cut Slope Angles Elevations ...................................................................................................... 53 206.1.6 Bench Elevations ....................................................................................................................... 53

Manual for Rockfall Inventory – Revised 12/2016 ii

206.1.7 Bench Width .............................................................................................................................. 54 206.1.8 Competent Bedding.................................................................................................................... 54 206.1.9 Incompetent Bedding ................................................................................................................. 54 206.1.10 Undercutting Information........................................................................................................... 54 206.1.11 Joint Information ........................................................................................................................ 56 206.1.12 Potential Rockfall Estimation..................................................................................................... 58 206.1.13 Talus Accumulation ................................................................................................................... 59 206.1.14 Vegetation .................................................................................................................................. 60 206.1.15 Additional Information .............................................................................................................. 60

206.2 Slope Hydrological Conditions ..................................................................................................61 206.3 Tier 3 & Tier 4 Testing Data .....................................................................................................65 206.4 Tier 3 & Tier 4 Office Data........................................................................................................67

207 DATA COLLECTION ACKNOWLEDGEMENT ..........................................................................................67

300 RISK SCORING FOR INVENTORY SITES ........................................................................................ 68

301 ROCKFALL INVENTORY SITE RISK SCORING .......................................................................................68 302 DIFFERENTIAL WEATHERING ..............................................................................................................68 303 DISCONTINUITY ROLE ........................................................................................................................69 304 BLOCK SIZE/VOLUME OF ROCKFALL PER EVENT ...............................................................................69 305 HYDROLOGIC CONDITIONS (SEEPS AND SPRINGS) ...............................................................................70 306 ROCK SLOPE HEIGHT ..........................................................................................................................70 307 CATCHMENT/CONTAINMENT ..............................................................................................................70 308 EXPOSURE RISK ..................................................................................................................................71 309 PERCENT DECISION SIGHT DISTANCE (PDSD) ...................................................................................71 311 ACCIDENT HISTORY ............................................................................................................................72

400 INSPECTION FREQUENCY ................................................................................................................ 74

LIST OF APPENDIXES

APPENDIX A:

GLOSSARY OF TERMS

APPENDIX B:

CRITERIA FOR EVALUATION OF CATCHMENT

APPENDIX C:

FIELD GEOLOGIC PARAMETERS

APPENDIX D:

PHOTO EXAMPLES OF TIERED SITES

PHOTO EXAMPLES OF ROCKFALL RETENTION DEVICES

APPENDIX E:

GPS OUTLINE

Manual for Rockfall Inventory – Revised 12/2016 iii

LIST OF FIGURES

FIGURE NUMBER TITLE OR DESCRIPTION PAGE NUMBER

200-01 Rockfall Slope Inventory Rating Data Collection Process 4

200-02 Rockfall Slope Inventory Process…………..…………. 5

200-03 Screen Capture from ODOT Digital Photolog………… 8

200-04 Rock Slope Evaluation Based on Road Type…………. 10

200-05 Example of Rock Slope vs. Inventory Site……………. 12

200-06 Example of Curved Rock Slope vs. Inventory Site…… 13

200-07 Determined of Ramp BMP’s …………………………. 13

200-08 Positions of an Inventory Site……….……………….... 19

200-09 Potential of Rockfall to Impact Roadway

– Below the Roadway……….……………….... 23

200-10 Examples of Cut Slopes……………………………….. 26

200-11 Examples of Preliminary Rating (Tier 1) Photographs.. 28

200-11 Relationship between slope height and geometric

parameters……………………………………………... 33

200-13 Block Size Determinations……………………………… 37

200-13a Block Size Before Falling……………………………… 37

200-13b Block Size After Falling…………….…………….....… 37

200-14 Rockfall Volume Determination………………………. 38

200-15 Hydrologic Conditions………..………………………. 39

200-16 Typical Types of Corrective Actions………………….. 40-41

200-17 Catchment Area Shapes……………...………………... 43

200-18a Catchment Area……………………………………….. 44

200-18b Hydraulic Control Ditch NOT as Catchment…………. 45

200-18c Hydraulic Control Ditch as Catchment ……………….. 45

200-19 Catchment Area Configuration………………………... 47

200-20 Example of Mine Openings…………………………… 49

200-21 Slope Angle Determination…….……………………… 51

200-22 Recording Slope Angle along a Blast Hole Using a

Pocket Transit…………………………………………. 51

200-23 Recording Slope Angle using a Pocket Transit and

Non-ferric Clipboard………………………….. 52

200-24 Average Slope Calculation……………………………. 53

200-25 Example of Cut Slope Description……………………. 55

200-26 Orthogonal Joint Set/Spacing…………………………. 57

200-27 Joint Infilling…………….…………………………….. 57

200-28 Example Rockfall Shapes.…………………………….. 58

200-29 Estimating Talus Accumulation ……………………… 60

200-30 Hydrologic Conditions Winter Conditions…………… 63

200-31 Hydrologic Conditions Spring Conditions……………. 64

Manual for Rockfall Inventory – Revised 12/2016 iv

LIST OF TABLES

TITLE NUMBER TITLE OR DESCRIPTION PAGE NUMBER

200-01 Tier Type Based on Preliminary Rating Score .….…….... 20

200-02A Preliminary Rating Criteria

(Slopes Above Roadway) …………..………. 21

200-02B Preliminary Rating Criteria

(Slopes Below Roadway) …………..………. 22

200-03 Decision Sight Distance ...……………………….…………. 31

200-04 Typical Slope Values for Rock Cut Sections ..………… 52

200-05 Rockfall Parameters ..……………………………............... 58

200-06 Hydrological Prefixes ……………………………..………... 62

300-01 Hydrological Conditions (Seeps and Springs) …………. 70

300-02 Rockfall History Risk Score ...…………………………..... 73

300-03 Accident History Risk Score ...……………………………. 73

400-01 Re-Inspection Frequency ...……………………………. 74

LIST OF EXAMPLES

EXAMPLE NUMBER TITLE OR DESCRIPTION PAGE NUMBER

200-01 NFLID Coding Standard………………………………….. 15

200-02 Sites with DMI Readings starting at SLM 0.00…………... 17

200-03 Sites with DMI Readings not starting at SLM 0.00…......... 17

200-04 BMP Position Data………………………………………... 18

200-05 Preliminary Rating Score of an Inventory Site…………… 24

200-06 Determination of the Slope Configuration of the

Inventory Site…………………………………….. 25

200-07 Percent Decision Sight Distance…………………….......... 32

200-08 Calculating the Slope Height……………………………… 34

200-09 Weighted Average Calculation for Multi-Angled

Cut Slopes…………………………………........... 53

200-10 Calculation of Bench Width and Elevation………………. 54

200-11 Slope Geological and Natural Conditions………………… 55

200-12 Collection of Joint Information…………………………… 56

200-13 Hydrological Conditions of Cut Slope and Natural

Backslope………………………………………… 63

200-14 Hydrological Conditions of Cut Slope and Natural

Backslope………………………………………… 64

200-15 Slake Durability Index Test Sample Collection…………... 66

Manual for Rockfall Inventory – Revised 12/2016 v

LIST OF EQUATIONS

EQUATION NUMBER TITLE OR DESCRIPTION PAGE NUMBER

1 Percent Decision Sight Distance …………………………. 31

2 Vertical Height Calculation ………………………………. 33

3 Foreslope Angle Calculation …………..…………………. 46

4 Slope Face Angle Calculation ……………………………. 47

5 Average Slope Angle Calculation ………………………... 53 6 Exposure Risk…………………… ………………………... 71

Manual for Rockfall Inventory – Revised 12/2016 1

Section 100 Introduction

Rockfalls can constitute a major hazard along Ohio roadways, posing a risk to life, property,

and traffic safety. As a result of rockfalls, maintenance problems are constantly occurring,

resulting in a strain on the Ohio Department of Transportation (ODOT) funds and manpower.

The following terms have been defined for use in this Manual:

Rockfall: The down-slope gravitational movement of material that is comprised of at

least 51 percent rock. Where, rock is defined as: Any material found along a slope that

when freshly exposed has the characteristics of in-place bedrock. Bedrock includes, but

not limited to, sandstone, siltstone, shale, limestone, dolomite, coal, claystone, and

conglomerate.

Rock Slope: Any slope, either natural or man-made, that has in-place bedrock exposed at

the surface.

Rockfall Event: A distinct period of time during which a single or multiple rock(s) and

associated debris dislodges from a rock slope.

This Manual was developed by ODOT, Office of Geotechnical Engineering (OGE) to

inventory rock slopes, to identify potential hazardous rock slopes, to assess relative risk for

those slopes, to determine degree of monitoring required, and to allow for actions to be taken

to reduce, minimize, or eliminate the risk to the public’s safety and to protect the highway

system.

This document is not a design manual. The intent of this Manual is to facilitate the

creation of a statewide rockfall inventory process through the development of a statewide

inventory procedure and the establishment of office and field methods. These methods

should be used during the initial population of the inventory, inventory of new sites

following the initial population, and for maintenance and monitoring of the sites.

The data collection procedures are grouped into four (4) primary sections with subsections:

Site Inventory and Preliminary Rating

Tier 1 Site Rating

Tier 2 Site Rating

Tier 3 and Tier 4 Site Rating

A rockfall inventory will be performed for the state highway system as noted in ODOT’s

policy on geohazards. This inventory will include all natural and man-made slopes with

exposed bedrock. The field portion of the inventory shall be completed by a Field Team(s).

For safety concerns, a Field Team should consist of a minimum of two members. For a

multi-discipline approach, the Field Team shall consist of a geologist and either an

engineering geologist or geotechnical engineer. The optimum time for the performance of


the field work along slopes that have high relief and/or are highly vegetated is October

through April. However, it should be noted that snow may also limit field activities in

December through February. Field activities may be suspended during periods of inclement

weather as directed by ODOT. Slopes that have low relief and/or low to moderate vegetation

may be evaluated year round.

Within this Manual, slopes which are being inventoried will generally be referred to as a

“rock slope”. All rock slopes shall receive a Preliminary Rating based on basic site

characteristics. The Preliminary Rating will also segregate the lower priority sites from the

groups that will receive detailed data collection efforts. This Manual will outline a tiered

data collection methodology which will allow rock slopes within Ohio to be rated for relative

rockfall risk to the public and Ohio’s highway system. The data collected from each site will

be incorporated into an Enterprise Database and integrated into a GIS system. All

information collected by personnel in the field or office should be presented in standard

database format, Excel spreadsheets, and GIS ArcView file(s) utilizing ODOT’s standardized

file naming conventions.

The data collected from the inventory process will be stored within the Geologic Hazard

Management System (GHMS) and other related components of the ODOT GeoMS.

Appendix A presents a Glossary of Terms that should be used in association with this

Manual.

Section 200 Rock Slope Inventory and Data Collection

201 Purpose and General Process

The inventory will consist of identifying and locating Inventory Sites within the rock

slopes situated along Ohio’s highway system. Generally, this inventory will be

concerned with rock slopes located above the roadway, unless a rockfall event below the

road could result in adverse impacts to the highway system. As part of the rock slope

inventory, a Preliminary Rating of each Inventory Site will be performed on each site.

The Preliminary Rating will provide guidance as to what level of data collection

(Detailed Rating) is required.

The Preliminary Rating will be completed by the Field Team(s) by visually evaluating

two criteria for each Inventory Site. These criteria are: 1) the potential of a rockfall

occurrence from the slope and 2) if a rockfall was to occur, the potential of the rock to

reach the traffic lane. This evaluation will be based upon best professional judgment and

past experience of the Field Team(s). A rating of Low, Moderate, High, or Very High

will be used for each criteria with an associated numerical value assigned. Section

202.3.1 Inventory Site Determination discusses in detail how to select an Inventory Site

and perform the Preliminary Rating.

For those sites where a Detailed Rating is not required, the slope will be listed as a Tier 1

site, or non-rated within the GHMS, with assigned data parameters required during the


field data collection. The following Tiers are considered as Rated Sites within the

GHMS. A detailed explanation of the procedures will be presented in the subsequent

sections with a brief description of each Tiered Rating as follows:

A Tier 1, or non-rated, site will consist of rock slopes that have a low or moderate

potential of rockfall occurring from the slope, and a low or moderate potential of any

rockfall reaching the travel lane of the roadway. It should be noted that if both potentials

are moderate to very high then the site is not a Tier 1 site, but a rated site and will require

Detailed Rating data collection.

Tier 2 sites will consist of sites where the potential of a rockfall occurrence is moderate to

high, and the potential of the rockfall reaching the traffic lane is moderate.

Tier 3 and Tier 4 sites are sites that the potential of a rockfall occurrence is high to very

high and the potential of the rockfall reaching the traffic lane is high to very high. The

difference between a Tier 3 and Tier 4 site is that a Tier 4 site poses an immediate threat

to the safety of the public and/or the roadway.

The methodology for data collection is outlined in the following sections:

Section 202 Site Inventory and Preliminary Rating

Section 203 Tier 1 Data Collection

Section 205 Tier 2 Data Collection

Section 206 Tier 3 and Tier 4 Data Collection

Each section will outline the office and field procedures to collect all the required data for

the site.

All sites will require the Tier 1 data collection, which is the minimum required data

inputs, for the Rockfall Slope Inventory. Sites that are categorized as a Tier 2 site from

the Preliminary Rating will require Tier 1 augmented with Tier 2 data collection. For

sites that are categorized as either Tier 3 or Tier 4 sites from the Preliminary Rating will

require all levels (Tier 1, 2, 3 & Tier 4) of data collection. The Tiered sites are also

referenced as Non-Rated for Tier 1 locations or Rated if they are a Tier 2, 3, or 4

location.

If a debris fragment greater than 6 inches in any dimension, or debris greater than one

cubic foot in total volume, occupies the shoulder, travel lane(s) or median, the District

Geotechnical Engineer (DGE) and the Office of Geotechnical Engineering (OGE) shall

be notified within one week and the site shall be re-evaluated within one month of the


event. If an Inventory Site is determined to be a Tier 4 designation, the DGE and OGE

shall be notified within 24 hours from completion of the evaluation.

Figure 200-01 is a generalized flow chart outlining the data collection process for the

Rockfall Inventory.

Figure 200-02 is a generalized Organization Chart for the initial population of the

Rockfall Inventory and Slope Rating System.

Figure 200-01. ROCKFALL SLOPE INVENTORY RATING DATA COLLECTION PROCESS

Tier 1 Site: Data Collection Completed

Tier 2 Data Collection

(Refer to Section 205 Tier 2 Site Data

Collection)


Tier 3 & Tier 4 Data Collection (Refer to Section 206 Tier3 & 4 Data

Collection)



Rock Slope Identification and

Inventory Site Identification

Preliminary Rating Completed (Refer to Section 202 Site Inventory and

Preliminary Rating)

Tier 1 Data Collection

(Refer to Section 203 Tier 1 Site Data

Collection)

Notify DGE & OGE Immediately if

Tier 4 Site Identified

Populate

Database with

Inventory Site

Inventory Site

Routine

Monitoring


Figure 200-02. ROCKFALL SLOPE INVENTORY PROCESS

Field Team(s)

Preliminary Office

Data Collection

Site Inventory &

Preliminary Rating Tier 1

Detailed Field

Rating

Detailed Office

Data Collection

Database Input

ODOT Testing

Training QA/QC Progress

Reports Scheduling

ODOT

Project Manager

Tier 2, 3, or 4

Consultant

Testing

Tier 3 & 4

Sampling


202 SITE INVENTORY AND PRELIMINARY RATING

202.1 General

The Project Manager and Field Team(s) will begin their work based upon the

selection of the counties and routes as designated by OGE and District personnel.

Study routes will encompass Interstate Routes, US Routes, and State Routes

throughout the state including routes within municipalities. The Project Manager and

Field Team(s) will evaluate and select the most efficient travel pattern or routes for

completion of the fieldwork prior to starting the field data collection.

Priority selection of counties will be based on National Highway System (NHS)

Routes (Interstate Routes, US Routes, and designated State Routes), then the

remaining State Routes (non-arterial) within those counties. Routes that have had

historical rockfall events should be completed before routes that do not have a

historical record of rockfall.

202.2 Office Procedures

Prior to commencement of the field work, the Project Manager and Field Team(s)

should have an idea as to the location of rock slopes that have a rockfall potential in

relation to Ohio’s highways. The following sections outline the general office

procedures for the development of a work plan for site investigations.

202.2.1 ODOT Interview(s)

Prior to commencing the fieldwork, the Field Team(s) shall contact and schedule

interviews with the ODOT DGE/Geologist for each respective District, the ODOT

County/Transportation Manager(s) for each respective county, and any other

applicable ODOT personnel (e.g. highway workers) who are familiar with the

rockfall maintenance for the selected area. In addition, interviews may be

conducted with county and/or city engineers or maintenance crews for locations

where personnel outside of ODOT perform the roadway maintenance or have

additional knowledge of the roadway.

The Field Team(s) will interview all applicable ODOT personnel as to locations

of rock slopes within their county and/or District. Additionally, the interviews

should reveal where rockfall is actively occurring or has been a historical

problem. Information from these interviews should include, but is not limited to:


Straight Line Mile (SLM) location(s) of natural or cut slope(s) with exposed

bedrock

SLM locations of rockfall and frequency

Date and amount (size and volume) of rockfall

Length and width, referenced to the roadway, where rockfall debris has

accumulated

Accidents resulting from rockfall including date, damage to State or private

property, injuries, and/or fatalities

Scheduled maintenance of rock slope(s) and associated ditch line, including

but not limited to, ditch cleaning of rockfall debris, bench cleaning along cut

slopes, rock removal from shoulder or roadway, etc.

Any rockfall remediation work performed in the past

A Personnel Interview Data Form, included in Appendix G – Field Forms, should

be completed for each person or group interviewed recording the information

collected. The Interviewee data will be stored in the GHMS within Part A:

Interview Info. If paper forms are being utilized then the interviewee data will be

recorded on the Rockfall Site Inventory Site Field Form (Rockfall Form) in

Section B: ODOT INTERVIEWS. Additionally, this information will be necessary to

complete Section I: REMEDIAL WORK OBSERVATIONS to identify if, when, and/or

where corrective actions have been completed.

202.2.2 Digital Photolog

The Project Manager and/or Field Team(s) may review available Digital

Photolog(s) via the ODOT Pathweb System for each selected site or route. The

Digital Photolog System (Pathweb) was updated in 2011 to allow the user to view

the roadway, including a limited view of the side of the roadway, prior to

commencing their fieldwork. Digital Photolog(s) are available from ODOT

Office of Technical Services (OTS) and is not available through the internet.

The digital photolog is a digital recording created by driving a route with a digital

video recording device mounted on the front, back and sides of the vehicle. A

digital image of the roadway and shoulder is collected at an interval of every

0.005 mile (200 shots per mile). As part of the photolog a Log-Mileage, based on

a digital measurement instrument (DMI), and a GPS recording of latitude and

longitude are presented. The GPS readings are drift corrected geospatial data.

From the Log Mileage information, the Field Team(s) can determine the

approximate mile marker where the anticipated rock slope(s) is located.

Additionally, a GPS map will show spatially the approximate location of the

screen shots. Figure 200-03 shows a screen capture from the photolog

application.


Figure 200-03. SCREEN CAPTURE FROM ODOT PATHWEB

202.2.3 Other Photographic Alternatives

Additionally, the Field Team(s) can review available aerial stereopairs, high

resolution digital aerial photos, and orthophoto quadrangle sheets or Google Earth

Street View in an attempt to refine the rock slope locations that may be a source

of rockfall. Aerial images, including stereopairs and obliques, orthophoto

quadrangle sheets (DOQ), USGS 7.5 minute topographic quadrangle sheet (topo),

and photogrammetric maps are available from ODOT Office of Cadd and

Mapping Services. Additionally, the DOQ’s and topos can be obtained from the

United States Geological Survey.

202.2.4 Geological Reference

General geological data shall be collected for each county prior to commencement

of the fieldwork. This data can be collected from the Geologic Map of Ohio

Camera Views

County

Route

Section Coordinates


and/or the County Quadrangle Bedrock Geology Map for the respective USGS

Quadrangle. A rock description for each Geologic Map Unit associated with the

County Quadrangle Bedrock Geology Map is produced by the Ohio Department

of Natural Resources (ODNR) Geological Survey. The Geologic System/Period,

Group(s)/Formation(s), and primary rock types should be identified. Many of

these maps and others (e.g. bedrock geology, bedrock structure, bedrock

topography) are available as electronic files for GIS applications.

Additionally, the study area(s) should be evaluated for the potential presence of

known surface and underground mining, either abandoned or active. Mining

activities, both current and past, can be obtained from ODNR or ODOT as GIS

layers.

This data will be recorded in the GHMS in Part C: Geological, additional

information tab and on the Rockfall Form in Section I: GENERAL GEOLOGIC

DESCRIPTION.

202.3 Field Procedures

202.3.1 Inventory Site Determination

For each route, it is preferred that the Field Team begin at County Log Mile

(CLM) 0.00, which will have a corresponding Straight Line Mile (SLM) 0.00.

However, any known SLM referenced point can be utilized as a beginning point.

To begin, the DMI should be adjusted to zero at the county line or beginning of

the route. If starting at a known referenced point (e.g. structure or interchange)

adjust the DMI reading to the corresponding SLM. If the Field Team has to stop

for the day, or the need to re-zero the DMI is required, each structure has a SLM

recorded at its right side of the rear abutment in the cardinal direction, and a SLM

is available for each center point of roadway intersections. All mile marker

records for the rockfall inventory should be referenced to SLMs. The DMI

records will be in a True Log Mile format and will need to be adjusted to the

corresponding SLM. Straight Line diagrams referencing the SLM can be

obtained from OTS.

Using a zeroed DMI reading (from a reference point), proceed in the cardinal or

non-cardinal direction, until a rock slope is encountered.

The Field Team should evaluate each rock slope encountered. For bifurcated

highways with rock slopes encountered on both sides of the travel lane, the rock

slopes for both sides of the travel direction should be evaluated at the same time.

For divided highway, all rock slopes along the right side of the roadway should be

evaluated. Then, all the rock slopes on the opposite side of the roadway should be

evaluated while driving in the opposite direction. For non-divided highways rock

slopes can be evaluated on both sides of the roadway at the same time. Care must

be taken in correcting for the Beginning Mile Point (BMP) along the opposite

rock face. Figure 200-04 provides examples of how the rock slope shall be

evaluated based upon roadway type.


Cardinal

Direction

Non-Cardinal

Direction

Evaluate

Both

Cardinal

Direction

Non-Cardinal

Direction

Evaluate

Both

Bifurcated Roadway

Divided Highway

Non-divided Highway

Figure 200-04. ROCK SLOPE EVALUATION BASED ON ROAD TYPE

Each rock slope location can be evaluated as a single or multiple Inventory

Site(s). An Inventory Site is defined as: any continuous roadway section where a

rock slope has the same characteristics. A minimum slope height of 10-feet is

required to be an Inventory Site, unless the Field Team determines that a slope

with a height less than 10 feet poses a danger to safety of the traveling public.

These characteristics shall be based upon:

Cardinal

Direction

Non-Cardinal

Direction

Evaluate

Only

Evaluate

Only

Cardinal

Direction

Non-Cardinal

Direction

Evaluate

Only

Evaluate

Only

Cardinal

Direction

Non-Cardinal

Direction

Evaluate

Only Evaluate

Both

Cardinal

Direction

Non-Cardinal

Direction

Evaluate

Only Evaluate

Both


limits of the exposed rock face

natural breaks in the cut face or natural backslope (e.g. natural drainage

features, but not man-made drainage features)

changes in slope orientation relative to the roadway (e.g. roadway curves

around the nose of a hillside that contains a continuous cut section)

changes in the slope orientation relative to the regional joint patterns

changes in the cut face angle(s)

changes in the quality of the bedrock mass

Additionally, the following guidelines should be followed in establishing

Inventory Sites:

1. For cut slopes that contain intermittent rock exposures through

vegetation, but was obviously constructed as a single continuous cut, the

site should be inventoried as a single Inventory Site.

2. A series of small cuts should not be combined into a single Inventory

Site; because, if a problem arises from just one of the cuts, corrective

actions will only apply to the single cut in question, not all of the cuts.

3. The ends of the cuts should not be split out into short sites based only on

the change in height of the cut slope. If work is to be performed on a

large site typically the ends will be included within the project.

4. When a cut height is disrupted due to the presence of a structure abutment

with similar characteristics on either side of the abutment, the slope

should not be broken into two sites, unless the slope characteristics

change.

5. Prior to extending an Inventory Site to a distance of more than one-

half mile (+/-), contact the District Geotechnical Engineer (DGE) or

the Office of Geotechnical Engineering (OGE). In no case should an

Inventory Site extend more than one mile (+/-) or cross county lines.

A new Inventory Site should be created at a county border.

Figures 200-05 and 200-06 show examples of Inventory Sites relative to a

rock slope and Figure 200-07 shows an example for Ramp BMP’s.

202.3.1 a) Site Determination for Ramps

Sites located on ramps will be referenced to the SLM of the mainline. The

selected mainline for the SLM referencing will use the following conventions:

Interstates over US Routes and State Routes

US Routes over State Routes

If there are two Interstates, US Routes or State Routes, the lower

numbered route will be the referenced route


Figure 200-05. EXAMPLE OF ROCK SLOPE VS. INVENTORY SITE

Comments: The total extent of the rock slope is approximately 1.9 miles, or 10,032 feet. The

10,032 feet of rock slope can be divided into 4 basic segments based on topography and major

local drainage indicated in the circles. From these basic segments a total of 8 Inventory Sites

should be evaluated based upon minor drainage features, change of slope face orientation

relative to the roadway, change in slope face orientation relative to the regional joint patterns,

and change in cut slope angle(s).

N

2

EXTENT OF ROCK SLOPE

10,032 ft (1.9 miles)

Natural Drainage –

No Rock Slope

Inventory Site #5

Inventory Site #3

Inventory Site #6

Inventory Site #7

Inventory Site #8


No Rock Slope

1

3

4

Inventory Site #2

Inventory Site #1

Inventory Site #4


with Rock Slope

Rock Slope


Figure 200-06. EXAMPLE OF CURVED ROCK SLOPE VS. INVENTORY SITE

Approximate Ramp BMP Location Traffic Flow of Ramp

Figure 200-07. DETERMINATION OF RAMP BMP’s

1

4

3

3

2

Top of

Cut

Approximate

Roadway

Centerline N

Inventory Site

N


202.3.2 Preliminary Rating of Inventory Site

The Preliminary Rating of a site should be completed for all Inventory Sites as the

first step to populate the rockfall inventory. The Preliminary Rating is basically a

two part process:

1) Inventory Site Location

2) Preliminary Rating Score

202.3.2 a) Inventory Site Location

For each rockfall Inventory Site, location data will need to be recorded to

identifying the site’s specific location. The following data is required to

identify the Inventory Site Location. This data is recorded in Part A: Site

Location of the GHMS or within Section A: PROJECT LOCATION AND

INFORMATION of the Rockfall Form.

The following data is included under the Basic Information tab within the

GHMS Section Site Location.

District

County

Route System

Route Number (5-digit ODOT designated route number)

Jurisdiction Code

(C-County, H-Turnpike Commission, M-Municipal, S-State, T-Township)

Slope orientation (in degrees from north (azimuth coordinate), relative to

the BMP, running parallel to the direction of traffic flow)

Measured length of the Inventory Sites (in feet) along roadway

Beginning Mileage Point (BMP) (as the SLM value determined from the

DMI reading [Note that the BMP is the lowest SLM value for the site])

Ending Mileage Point (EMP) (as a SLM value determined based upon the

Inventory Site length and BMP)

Record if the site is located along the roadway in the cardinal direction

(Yes = northbound or eastbound, No = southbound or westbound)

Horizontal Position of the Rock Slope

(Right or Left relative to cardinal mainline direction or to driving direction

for ramps)

Driving direction: (North, South, East, West)

Vertical Position (Above, Below or Both)

USGS Quadrangle Name


The Network Linear Feature Identification Code (NLFID Code) will be auto

generated for the location (update button). The NFLID designation is a

tracking code consisting of:

Jurisdiction Code

County

Classification Code

Route Number

Default code to complete the NLFID Code (**C)

Example 200-01 presents the format for the NFLID Code

Optional Information concerning the site consists of:

Classification of roadway

Hazard width perpendicular to the road (from toe of cut)

Distance from Toe of cut to shoulder

EXAMPLE 200-01: NLFID Coding Standard

NLFID CODE - STUSUS00250**C

S TUS US 00250 **C

A B C D E

Where:

A is the Jurisdiction Code

B is the County Code

C is the Classification Code

D is the Route Number

E is the default code

The following data is included under the Roadway Information tab within the

GHMS Section Site Location:

Position Relative to the Roadway

(Mainline, On-ramp, Off-ramp)

Pavement Type

Median


Optional Information concerning the site consists of:

Classification of roadway

Hazard width perpendicular to the road (from toe of cut)

Distance from Toe of cut to shoulder

The following data is included under the GPS Information tab within the

GHMS:

Beginning Latitude

Beginning Longitude

Beginning Elevation

Offset Distance, in feet, and Bearing, in degrees from north (azimuth

coordinate), if the positional data is not able to be collected at the exact

position of the BMP location

For Rockfall Inventory Sites, only the BMP coordinates will required.

However, if field personnel have a strong GPS signal, additional points can be

collected and coordinates recorded for the Centroid and EMP locations.

The beginning and end of the Inventory Site should be indicated in the field

by placing a minimum 18-inch long white line perpendicular to the roadway

made with surveyor’s paint at either end of the site along the edge of the

pavement. The BMP should be indicated with a “B”, and the EMP should be

indicated with an “E”.

Note: it can be helpful for large sites, if while measuring the Inventory Site

length, place tick marks along the roadway shoulder at regular intervals (say

100 or 200 feet) to use in locating features.

202.3.2 aa) Beginning Mile Point (BMP)

The BMP shall be determined based upon the DMI reading recorded at the

beginning point of the Inventory Site. The BMP shall always be the lowest

SLM point of the Inventory Site. If the DMI reading at the BMP was started

at SLM 0.00 then the BMP is the adjusted DMI reading. However, if the

DMI reading recorded at the BMP was started at a location other than SLM

0.00, the BMP needs to be calculated by adding the starting point SLM and

the adjusted DMI reading. The adjusted DMI reading is the true log mile

reading adjusted for the station equations to calculate the SLM.

Record the BMP value to the nearest 0.01 miles.

Place a PK nail into the paved shoulder or the roadway to indicate the BMP.

If no paved shoulder is present, place the PK nail into the white edge line.

The PK nail should be driven either flush with, or below, the top of

pavement.

BMP of Inventory Site


202.3.2 bb) Inventory Site Length

The length of the Inventory Site is a direct measurement between the BMP

and the EMP. Generally, this measurement is made with either a measuring

tape, measuring wheel, or a laser range finder.

Record the Inventory Site Length to the nearest foot.

202.3.2 cc) Ending Mile Point (EMP)

For mainline sections, the EMP can be calculated based upon the length of

the Inventory Site divided by 5280 ft/mile then added to the BMP, and/or

recorded utilizing the adjusted DMI reading as outlined in Section 202.3.2

aa) Beginning Mile Point (BMP).

The EMP should be determined by establishing the offset location to its

referenced mainline then calculating this offset point utilizing either the

DMI or other measuring device.

Record the EMP value to the nearest 0.01 miles.

EXAMPLE 200-02: Sites with DMI Readings starting at SLM 0.00:

Inventory Site Attribute SLM

DMI Reading from SLM 0.00 = 2.91

Beginning SLM (BMP) = 2.91

Length of Site = 1850 ft

1850ft ÷ 5280ft/mile = 0.35 mile

Ending SLM (EMP) = 3.26

BMP 2.91 + 0.35 mile


EXAMPLE 200-03: Sites with DMI Readings not starting at SLM 0.00:

Inventory Site Attribute SLM

SLM at Starting Intersection = 12.58

DMI Reading from Intersection = 2.91

Beginning SLM (BMP) = 15.49

Length of Site = 1850 ft

1850ft ÷ 5280ft/mile = 0.35 mile

Ending SLM (EMP)

BMP 15.49 + 0.35 mile = 15.84

For ramps where the BMP and/or the EMP is not visible from the mainline

then that value does not need to be recorded.

202.3.2 dd) BMP Position

Record the BMP position as a GPS point at the right shoulder of the BMP.

The BMP position shall include the latitude, longitude, and elevation and be

determined using a Trimble GPS unit, or equivalent or better, as a point in

decimal degrees to six (6) digits to the right of the decimal. GPS guidelines

for data collection are presented in Appendix E.

If a GPS reading cannot be taken along the shoulder of the roadway at the

BMP of the Inventory Site due to poor signal, or physical obstruction, use an

offset reference point which has good access and an adequate GPS signal.

After recording the GPS coordinates at the offset location, collect and record

a bearing, the offset distance from the reference point to the BMP, and

change in ground surface elevation to the shoulder location at the Inventory

Site BMP position. The bearing value should be obtained in degrees from

north (azimuth coordinate), and the offset distance and change in ground

height need to be recorded as a physical measurement to the nearest foot.

The raw data collected at the site will be recorded as an .ssf file. A separate

.cor file should be created for each Inventory Site upon completion of the

post processing of the raw data. Both the .ssf and .cor files should be saved.

EXAMPLE 200-04: BMP Position Data:

BMP Latitude = 40.125524958

BMP Longitude = -81.789859546

BMP Elevation = 765 ft

Offset Bearing = 127º

Offset Distance = 185 ft

Change in Elevation = 7 ft


Figure 200-08 is a generalized diagram indicating how to determine the

positions of the rockfall Inventory Site.

203.2.2 Preliminary Rating Scoring

There are two components of the preliminary rating. The first part is the

determination of the probability of a rockfall event using best professional

judgment. Rockfall debris can be generated from either the cut slope or from the

natural backslope. Second, evaluate the potential of a rock or debris impacting

the roadway. Typically the impact to the roadway is a result of rockfall debris

reaching the traffic lane. Traffic Lane is defined for use in this Manual as: The

inside edge of the right vehicular lane in a given travel direction or the white

edge line. Potentials of Very High, High, Moderate, or Low are used, with

numerical values (10, 8, 4, 1, respectively) assigned for each potential. The

numerical value for the potential of rockfall occurrence is added to the numerical

value for the potential of the rockfall to impact the travel lane to determine the

Top of Natural Backslope

Rockfall Zone

DRAINAGE

FEATURE

DRAINAGE

FEATURE

Beginning of Inventory Site BMP @ MP 2.91

BMP Position

Latitude: 40.125524958

Longitude: -81.789859546

Elev.: 765 ft

1851 Ft.

Top of Rock Cut

Rock outcropping in

Natural Backslope

Ending of

Inventory Site EMP @ MP 3.26

“BMP” “EMP”

Inventory

Site

Length

Figure 200-08. POSITIONS OF AN INVENTORY SITE


Preliminary Rating Score. Preliminary Rating Score values may range between 2

and 20 points which is then used to determine the level of data collection, or Tier,

required for the Inventory Site.

For locations where the Preliminary Rating Scores fall between 2 and 5 points, the

Inventory Site is considered a Tier 1 site. No Detailed Rating data collection is

required for Tier 1 sites.

For Preliminary Rating Scores over 5 points, the Inventory Site is either a Tier 2,

Tier 3, or Tier 4 site requiring a Detailed Rating which will result in additional

data collection.

Table 200-01 outlines the Preliminary Rating Score breakdown for each Tier.

TABLE 200-01

Tier Type Based on Preliminary Rating Score

Preliminary Rating

Score

Tier Type

Action

2 to 5 TIER 1 SITE

No Detailed Rating Needed

8 to 11 TIER 2 SITE

Detailed Rating Needed

12 to 16 TIER 3 SITE




For rockfall sources located at such a distance that any rockfall debris will not

reach the travel lane, these areas do not need to be inventoried. Additionally, if

the slope contains an area where the catchment (ditch or barrier) does not contain

sufficient storage between either the back of the barrier or the white edge line to

contain the anticipated volume of rock and debris that could be dislodged in an

event, the Potential of Rockfall Reaching the Roadway needs to be shifted to Very

High. The Catchment Storage is defined as: the calculated volume based on the

width by depth of the catchment area based on the length of the catchment

relative to the area where rockfall could occur. The calculated volume should

take in account any barrier height along the edge of the catchment.

Table 200-02 outlines general criteria for each of the category utilized in the

Preliminary Rating.


TABLE 200-02A - PRELIMINARY RATING CRITERIA (Slopes Above Roadway)

Category LOW

(1 POINT)

MODERATE

(4 POINTS)

HIGH

(8 POINTS)

VERY HIGH

(10 POINTS) P

ote

nti

al

of

Rock

fall

Occ

urr

ence

No fresh exposures

No adverse joint

patterns

No undercutting

evident

Few to some fresh

exposures

Moderate weathering

of rock strata within a

cut section

Some jointing present

Minor undercutting

is present

Occasional cleaning

required of catchment

area

Some to many fresh

exposures

Observed minor stability

issues within slope face

Weathered rock strata

within a cut section

Significant jointing, or

adverse jointing present

Significant undercutting

present

Annual cleaning required

of catchment area

Minor amounts of rockfall

debris evident within

catchment area or

evidence of recent

cleaning of the catchment

area

Many fresh exposures

Stability issues within

slope face

Highly weathered to

decomposed rock strata


Major adverse joint, or

intersecting jointing

present

Severe undercutting

present

Significant amounts of

debris is evident within

the catchment area,

especially along the

shoulder

Frequent cleaning


area

Pote

nti

al

of

Rock

fall

to I

mpact

Roadw

ay

The distance from the

slope face to the travel

lane is greater than the

anticipated roll out

distance **


slope face to the

travel lane is greater

than the impact zone,

but less than the

rollout zone **


slope face to the travel

lane is within the impact

zone **

Slope is within three feet

of roadway

OR

Rockfall or evidence of

rockfall within the travel

lane, median, or opposite

shoulder is present

OR OR

OR

OR

An appropriately sized

barrier exists between

the slope face and the

roadway

Rockfall or evidence

of rockfall is present

along the edge of the

shoulder

Rockfall or evidence of

rockfall within the

shoulder is present

Documentation of

rockfall debris reaching

the roadway including

accidents or injury

** Impact zone and rollout width based upon the Appendix B guidelines. These guidelines provide distances based upon the cut slope angle and

height within a rock cut section. Generalized tables of distances are provided in Appendix B.


Table 200-02B - PRELIMINARY RATING CRITERIA (Slopes Below Roadway)

Category LOW

(1 POINT)

MODERATE

(4 POINTS)

HIGH

(8 POINTS)

VERY HIGH

(10 POINTS) P

ote

nti

al

of

Rock

fall

Occ

urr

ence

No fresh exposures

No adverse joint

patterns

No undercutting

evident

Few to some fresh

exposures

Moderate weathering

of rock strata within a

cut section.

Some jointing present

Minor undercutting

is present

Occasional cleaning


area

Some to many fresh

exposures

Observed minor stability

issues within slope face

Weathered rock strata


Significant jointing, or

adverse jointing present

Significant undercutting

present

Annual cleaning required

of catchment area

Minor amounts of rockfall

debris evident within

catchment area or

evidence of recent

cleaning of the catchment

area

Many fresh exposures

Stability issues within

slope face

Highly weathered to

decomposed rock strata


Major adverse joint, or

intersecting jointing

present

Severe undercutting

present

Significant amounts of

debris is evident within

the catchment area,

especially along the

shoulder

Frequent cleaning


area

Pote

nti

al

of

Rock

fall

to I

mpact

Ro

adw

ay

***

Failure within slope

will not affect

roadway

Failure within slope

will affect Right of

Way, but not

shoulder or roadway

Failure within slope will

affect shoulder, but not

roadway

Failure within slope will

affect roadway

*** Refer to Figure 200-09. POTENTIAL OF ROCKFALL TO IMPACT ROADWAY - BELOW THE ROADWAY for clarification.

Further discussions within this Manual will be limited to rockfall impacting the

roadway from sources above the roadway.

The Preliminary Rating Data is reported within the GHMS in Part A: Preliminary

Rating tab.


Figure 200-09. POTENITAL OF ROCKFALL TO IMPACT ROADWAY – BELOW THE ROADWAY

Low Risk of Rockfall to Impact the Roadway Moderate Risk of Rockfall to Impact the Roadway

High Risk of Rockfall to Impact the Roadway Very High Risk of Rockfall to Impact the Roadway

Edge of Road

Edge of

Shoulder

Right-of-Way

Edge of Road

Edge of

Shoulder

Right-of-Way

Edge of

Road

Edge of

Shoulder

Right-of-Way

Edge of

Shoulder

Right-of-Way

Edge of

Road


EXAMPLE 200-05: Preliminary Rating Score of an Inventory Site:

A site has a high potential of rockfall occurrence due to the presence of debris

within the ditch along the road shoulder “and” a moderate potential of rockfall

reaching the travel lane due to the distance from the rock face to the shoulder is

slightly less than the rollout zone for the slope height.

PRELIMINARY RATING

Potential of a

Rockfall

Occurrence

Potential of Rockfall Impacting the Traffic Lane

Very High

(10)

High

(8)

Moderate

(4)

Low

(1)

Very High

(10)

High

(8)

Moderate

(4)

Low

(1)

High Potential of Rockfall Occurrence = 8 points

Moderate Potential of Rockfall Reaching the Traffic Lane = 4 points

Total Preliminary Rating Score for Inventory Site = (8 + 4) = 12 points

Therefore:

Preliminary Rating – Tiered Scoring

Preliminary Rating

Scale

TIER Type

Action

2 to 5 TIER 1 SITE

No Detailed Rating Needed

8 to 11 TIER 2 SITE






Comments: Based on the Preliminary Rating Score of

12, this site is considered a Tier 3 Site requiring a

detailed site rating including the collection of all Tier 1

and Tier 2 data.


203 TIER 1 DATA COLLECTION

Typically, the field data collection process will be completed within ODOT right-of-way.

However, occasionally, the slope will extend onto private property, especially for natural

backslopes above the cut slope. When this occurs the Field Team should make all

possible attempts to contact the property owner to obtain permission prior to entry onto

the property.

203.1 Field Procedures

For all Inventory Sites, rated and non-rated, the Tier 1 Field Data must be completed.

This data will be recorded within Part A of the GHMS or recorded on the Rockfall

Form in Section C: TIER 1 FIELD DATA.

203.1.1 Slope Configuration

Determine the slope configuration of the cut slope. Within the GHMS this data is

reported in Part A: General Information, Basic Slope Information tab. Figure

200-10 shows examples of different slope configurations, and the following are

descriptions of each criteria:

Single-angle Slope (SA): Slope that contains the same general slope

geometry from the road to the crest of the slope

Multi-angle Slope (MA): Slope that contains at least two slope angles

from the road to the crest of the slope

Single-angle Benched Slope (SB): Slope that contains the same general

slope angles and a relatively flat bench or break between the angles from

the road to the crest of the slope

Multi-angle Benched Slope (MB): Slope that contains at least 2 slope

angles and a relatively flat bench or break between any of the slope angles

from the road to the crest of the slope

EXAMPLE 200-06: Determination of the Slope Configuration of the Inventory Site

Slope Configuration: SA MA SB MB

Where: SA is for Single-angle Slopes

MA is for Multi-angle Slopes

SB is for Benched Slope Single-angled

MB is for Benched Slope Multi-angled


Single-angle Slope (SA)

Single-angle Benched Slope (SB)

Multi-angle Slope (MA)

Multi-angle Benched Slope (MB)

Figure 200-10. EXAMPLES OF CUT SLOPES


203.1.2 Slope Condition

Record general comments about the rock slope within the Inventory Site.

Comments that can be recorded can be the amount of vegetation along the slope,

talus buildup, if any, weathering of the exposed rock strata, general performance

of the slope, etc. It should be noted that if the site will have a detailed rating

performed, these comments can be very brief, since the slope will be discussed in

detail during the Detailed Data Collection.

Within the GHMS in Part A: General Information, Slope Condition several field

are available for the general description of the slope.

Vegetation coverage: with percentage of slope coverage by shrub, trees,

grass, and other (if other is used then a text description is required).

Weathering condition: None, Slight, Moderate, Complete

Talus buildup: Yes, No

General slope performance: stable, potentially instable, unstable

Exposed rock: click all that apply

203.1.3 Photographic Documentation of Inventory Site

Upon completion of the Tier 1 Field Data measurements, take representative

pictures of the Inventory Site. For Tier 1 sites three pictures should be taken.

One picture should be taken at an acute angle from each end (BMP and EMP) of

the site, and one picture should be taken perpendicular to the maximum slope

height (MHT) of the Inventory Site. Within the GHMS, these pictures should be

uploaded in Part A: General Information, Pic/Doc Information tab. At the tab

heading a count of the number of items located in the directory are present.

It should be noted that additional pictures may be required for Rated Sites (Tier 2,

Tier 3, or Tier 4) data collection. The requirements of these pictures are presented

within each of these respective sections.

The proper naming convention for the labeling of the pictures is presented within

Appendix D. Appendix D presents examples, including photographs and

discussions, of Tier 1, Tier 2, Tier 3, and Tier 4 sites.


End Pictures of Rockfall Inventory Site

(SCI-335-2.05 looking east and west, respectively)

Picture of the Maximum Height of the Rock Slope

Figure 200-11. EXAMPLES OF PRELIMINARY RATING (TIER 1) PHOTOGRAPHS

204 Detailed Rating of Inventory Sites - General

For sites where rockfall poses a potential risk to traffic (Preliminary Rating Score >5), the

site is considered a Rated Site and a detailed site rating needs to be performed. The

amount of information required for the Detailed Data Collection is based upon the

Preliminary Rating Score completed in Section 202 - Site Inventory and Preliminary

Rating. For sites that score as Tier 2 sites, collect the information required in Section 205

– Tier 2 Site Data Collection. For sites that score as either a Tier 3 or Tier 4 site,

complete the Tier 2 data collection in addition to Section 206 - Tier 3 and Tier 4 Data

Collection.

Prior to commencement of the Detailed Data Collection, the Field Team should observe

the cut slope and natural back slope and evaluate the following:

“BMP” “EMP”

“MHT”


Limits of the Inventory Site (BMP, EMP)

Location of all potential sources of rockfall

Number of slope angles

Number of benches that comprise the rockfall section

Location of any joint/fracture set(s) (orthogonal or stress relief)

Groundwater

Surface water flow or evidence of surface water flow

General condition of the cut slope

(e.g. where undercutting may be occurring, talus buildup)

Any mine opening (sealed or non-sealed), coal seams, clay seam, or mineable

mineral seam visually present

Evidence of possible slope instability within the soil mass above the rock cut

The Field Team should then determine the most efficient and safe way to collect the field

data from the rock slope. All slope angles and benches should be numbered sequentially

from the bottom of the rock slope (ditch line) to the top of the rock slope independent of

how the data was collected.

If the Field Team feels that no safe way of collecting the field data is evident within

an Inventory Site contact OGE.

If the Field Team feels that the slope possess an immediate threat to the welfare of

the traffic on the roadway, contact the respective ODOT County/Transportation

Manager, the DGE, and OGE within 24-hours to inform them of the situation to

provide appropriate traffic control measures.

If necessary, ODOT will arrange for traffic control measures such as lane closures or

temporary barriers.

205 TIER 2 SITE DATA COLLECTION

205.1 Tier 2 Data Procedures

Upon completion of the Preliminary Rating, sites which are Rated (Tier 2, Tier 3, or

Tier 4) need to have additional information collected. The following sections outline

the detailed breakdown on the methodology for the field and office data collection.

For low height rock slopes, where both the cut slope and the natural backslope are

observable and all features are visible from the roadway, the data may be collected

from the roadway. Slope angles can be collected from the roadway with a clinometer

or profiler; otherwise, the angles should be collected as a direct measurement from

the slope. If the entire slope is not observable from the road surface, the slope face

shall be inspected and evaluated by either climbing the face or repelling from the top.

The preferred method of data collection is by direct measurements taken from the

slope face or the use of a profiler. Generally, the best way to complete direct

measurements from the slope face is by performing horizontal and vertical line

survey(s).


205.1.1 Geometrics and Traffic

The following are the office and field procedures for completion of TIER 2 -

GEOMETRICS AND TRAFFIC DATA. For the respective data locations within the

GHMS, refer to the individual item. The majority of the geometric and traffic

data within this section can be obtained through the ODOT Transportation

Information Management System (TIMS) or other resources of the Office of

Technical Services. However, it should be noted that these data fields can be

collected through physical observation or measurements.

205.1.1 a) Traffic Survey Reports

Record the Average Daily Traffic (ADT), Average Vehicular Traffic,

including Type A commercial vehicles, (AVT), and Average Truck Traffic

(ATT) values, for the section of roadway which contains the Inventory Site.

These values can be obtained from the Traffic Survey Reports which can be

accessed from the web. The traffic reports allow the user to select a report

based upon county and year that the survey was completed. A complete

report for each selected county is then provided that includes all state

highways. Each Route is subdivided based on straight line miles within a

“Traffic Section”, which gives a general description of where the data was

recorded, section length in miles, and columns for passenger & type A

commercial vehicles, type B & C commercial vehicles, and total vehicular

traffic. The passenger & A commercial vehicle column refers to the AVT

value, B & C commercial traffic column refers to the ATT value, and the total

vehicular traffic column refers to the ADT. The most recent survey should be

utilized to determine the individual counts. This data will be recorded within

the GHMS in Part B: Traffic Information.

205.1.1 b) Actual Site Distance (ASD)

The Actual Site Distance (ASD) is the shortest distance along a roadway over

which a six inch object is continuously visible to a driver, and is a physical

measurement based on the following method:

Place a 6-inch high traffic cone or hard hat near the edge of the roadway

within the rockfall section. From that point move away from the object until

it is no longer visible from a height of 3.5 feet above the road surface

(estimated height for a driver’s field of vision). From this point measure the

distance to the object. All observations should be made in the direction of the

traffic flow.

For Inventory Sites having relatively long lengths, curves, and/or varying road

slopes, collect a series of ASD beginning at the BMP and proceeding toward

the EMP. Compare the ASD values collected and utilize the smallest

recorded value as the ASD for the Inventory Site. This data will be recorded

within the GHMS in Part B: Traffic Information.


205.1.1 c) Decision Site Distance (DSD)

The Decision Site Distance (DSD) shall be determined by the latest version of

the “Geometric Design of Highways and Streets”. The following table

outlines the general DSD values for highways.

TABLE 200-03

Decision Sight Distance

Design Speed

(MPH)

DSD (ft)*

25 > 375

30 450

35 525

40 600

45 675

50 750

55 865

60 990

65 1050

70 1105

75 1180

* Based upon the 2005 edition, Exhibit 3-3, Avoidance Maneuver C.

Note: For Design Speeds less than 25 MPH use a DSD of 375 feet.

205.1.1 d) Percent Decision Site Distance (PDSD)

After the DSD has been determined for the Inventory Site, calculate the

percent decision site distance (PDSD). The following equation shall be

utilized to calculate the PDSD:

Eq. #1: PDSD = ASD / DSD * 100

If the calculated value is greater than 100 percent it is assumed that a driver

will have sufficient time to stop prior to striking a rock within the roadway.

The PDSD is an auto-calculated field within the GHMS in Part B: Traffic

Information. Example 200-07 presents the calculation of the PDSD.


Example 200-07: Percent Decision Site Distance

Inventory Site with the following field data:

BMP @ MP 2.91

EMP @ MP 3.26

Inventory Site Length = 1851 ft.

Speed Limit = 55 mph

DSD = 865 ft.

ASD Readings = 850 ft., 865 ft., 799 ft., 860 ft., 579 ft.

Site ASD = 579 ft.

PDSD = ASD / DSD * 100

PDSD = (579 / 865) * 100

PDSD = 67%

205.1.2 Slope Information

The following are the field procedures for completion on the Rockfall Form in

Section E: TIER 2 - SLOPE INFORMATION. For the respective locations within the

GHMS, refer to the individual item. It should be noted that these data fields can

be collected through either physical measurements utilizing a measuring wheel or

tape, or through calculated methods. The following sections outline in detail

procedures for the collection of the required data.

205.1.2 a) Slope Height

All slope height measurements made for the Inventory Site shall be recorded

as a vertical height recorded to the nearest foot. This data will be recorded

within the GHMS in Part C: Slope Information, Geometric Information tab.

Separate height measurements need to be recorded for the rock cut, any soil

cut, and any backslope. Additionally, in extreme cases where large ranges of

slope heights are present, especially along the Ohio River, the minimum and

maximum ranges of the slope heights should be recorded within comments

fields. Three methods of measurement can be performed to determine the

slope height.

The preferred method to determine the slope height is through the use of a

rangefinder. Using the rangefinder, the total height can be calculated through

trigonometric calculation based on the angle and distance from a fixed

reference point. Automated profilers, such as laser face profilers, will

internally calculate the distances and heights for the users. If heavy

vegetation is present across the slope obscuring the slope geometry then

this method may not be applicable.


An alternative to the profiler method is to calculate the slope height involving

trigonometric calculations using field measurements collected with a pocket

transit compass, clinometer, or transit, from the shoulder, median or roadway

surface and measured distances. This method requires the collection of

angles and and distances needed for the calculations outlined in Figure

200-12. A minimum of three measurements should be collected of each angle

and the average angle recorded to the nearest whole degree. If heavy

vegetation is present across the slope obscuring the slope geometry, then

this method should not be utilized.

Another method is to perform physical measurement of the slope. For

relatively short slope heights, a survey rod or measuring tape can be used for

the height measurement. Generally, a survey rod can be used for a slope

height less than 25 feet in height. If a measuring tape is utilized make sure

that the tape is taunt and vertical, possibly utilizing a face-pole. Additionally,

the slope height can be measured utilizing a hand or abney level and shooting

spot heights up the slope. This method may be the most applicable for

slopes that are heavily vegetated.

Pavement fromHeight HIsin

sinsinxHeight Vertical

Comments: HI =height of instrument (ft)

x = distance between the two points used for measurement of angles (ft)

and = angles measured from horizontal (degrees)

EP = edge of pavement

x

HI

Tot

al s

lope

hei

ght

EP EP

Total slope height= (x) sin * sin + HI

sin (-)

Figure 200-12. RELATIONSHIP BETWEEN SLOPE

HEIGHT AND GEOMETRICAL PARAMETERS

(adapted from Pierson et al., 1991)

Eq. #2


EXAMPLE 200-08: Calculating the Slope Height

Recorded Angle = 42º, 43.5º, 43.1º

Avg. Angle = 42.9º

Recorded Angle = 24.5º, 25º, 24.8º

Avg. Angle = 24.8º

X = 24 ft. HI = 5.3 ft

3.58.249.42sin

8.24sin9.42sin)24(Height Slope

+ 0.0

205.1.2 b) Slope Elevations

All slope height measurements collected in Section 205.1.2.a should be

converted to slope elevations based upon a Section Base Elevation. This data

will be recorded within the GHMS in Part C: Slope Information, Geometric

Information tab. The Section Base Elevation is the approximated ground

surface elevation at the edge of pavement where the height measurements

were collected. The Section Base Elevation is estimated based on the change

in ground surface height relative to the Inventory Site BMP Elevation

collected as part of the BMP position. All elevations should be recorded to

the nearest foot.

205.1.2 c) Slope Undercutting/Raveling

For each Inventory Site, estimate the percentage of the slope experiencing

undercutting and raveling. This data will be recorded within the GHMS in

Part C: Slope Information, Slope Information tab. For sites where

undercutting is occurring, any portion of the slope above the lowest location

of undercutting should be considered as experiencing undercutting.

Additionally, record the number of locations where undercutting is occurring

for both the cut slope and natural backslope. Record the maximum, and

average depth of undercutting being experienced in both the cut slope and the

backslope.

Raveling occurs when bedrock comprising the slope is completely broken

either by natural jointing and weathering or due to blast damage generated

during construction.

205.1.2 d) Slope Jointing

Record the joint pattern(s) expressed within the Inventory Site relative to the

orientation of the roadway. It is anticipated that generally this will only be

accomplished for cut slopes. Natural slopes usually will not present sufficient

Slope Height = 27 feet


bedrock exposures, except where massive competent beds are present, to

establish joint information. For sites where multiple joint patterns are

expressed, record up to 3 principal or secondary joint sets.

This data will be recorded within the GHMS in Part C: Geological

Information, Joint Information tab.

205.1.2 e) Rockfall Source Information

Determine source zone(s), or potential source zone(s), of rockfall debris along

the rock slope. Typical source zones include, but not limited to:

1. more durable rock strata underlain by a less durable rock strata

2. intersection joint sets that are susceptible to freeze-thaw and ice

wedging

3. weathered zones that are highly fractured

4. cut slope faces that have extensive blast damage from construction

5. any combinations of source zones 1 through 4

It should be noted that rockfall source zones can and are located in both

the cut slope and or natural backslope of a slope. In some areas, the

natural backslope will be a greater source of rockfall debris than the cut slope.

Estimate the percentage of the slope that contains a rockfall source zone. The

percentage of the slope is calculated by summing all the potential rockfall

source zone heights located in the cut slope and the natural backslope and

dividing by the total slope height (cut slope height added to the natural

backslope height).

Record the estimated potential rockfall that may occur from either the cut

slope or the natural backslope. Estimate the maximum and average block size

that may be produced as well as the anticipated volume which may be

produced during a single rockfall event to a tenth cubic foot (0.1 ft3).

The block size can be determined by evaluating the discontinuities (joints,

bedding, etc.) within the slope. Three components to the block size which

need to be evaluated, with measurements recorded to the nearest tenth of a

foot (0.1 ft), are; height (x), width (y), and thickness (z):

Height (x): generally the distance from top of the rock strata to the

bottom of the rock strata; or the persistence of the joint (total length

that a joint is present within intact bedrock possibly crossing bedding

surfaces) with the slope face

Width (y): distance from one joint to another joint along the face

Thickness (z): depth at which either the joints intersect or the

thickness of the undercut or the distance to a joint set depth which

runs parallel to the slope face


Figure 200-13 demonstrates the dimensions of a block before and after falling.

Estimate the anticipated total volume of debris that could be produced during

a single rockfall event. At sites where thick competent beds are broken by

regular repeating joint sets, as exhibited in the previous figure, the volume

will be equal close to the maximum block size. However, in thin to thick

bedded competent rock which is exhibiting raveling, the volume generated

during a single event may be much greater than the maximum block size.

When this is the case, debris volume can be estimated by evaluating the

discontinuities (joints, bedding, etc.) within the slope and comparing them to

how they are interlocked. Three components of the volume which need to be

evaluated, with measurements recorded to the nearest tenth of a foot (0.1 ft),

are; height (x), width (y), and thickness (z):

Height (x): generally the distance along a persistent joint within the

slope face which broken rock is located along which could dislodge

during a rockfall event

Width (y): lateral distance along the slope face along which uniformly

broken rock is located

Thickness (z): depth into the slope to which the persistent joint set

which the height is being measured along

Figure 200-14 demonstrates the dimensions of a block with the potential of

falling.


Note: The block height is dictated by both the strata thickness

and joint persistence which are the same dimensions.

Figure 200-13. BLOCK SIZE DETERMINATION

X = 7.2 ft

Y = 14.6 ft

Z = 4.9 ft Size: 7.2*4.9*14.6 = 515.1 ft3

Figure 200-13b. Block Size After Falling

Figure 200-13a. Block Size Before Falling

X = 7.2 ft

Y = 14.6 ft

Z = 4.9 ft Size: 7.2*4.9*14.6 = 515.1 ft3


Figure 200-14. ROCKFALL VOLUME DETERMINATION

Comment: Green Outline

represents the area of

potential rockfall debris

which could be generated

during an event based on

open jointing and

raveling. The arrows

indicate the dimensions.

X = 15.3 ft

Y = 13.5 ft

Z = 3.8 ft

Volume: 15.3*3.8*13.5

= 29.1 yd3

205.1.2 f) Hydrologic Conditions

Evaluate the cut slope and the natural backslope for the presence of

hydrologic conditions, both groundwater and surface water. The estimate of

the hydrologic conditions should be based on the entire surface area of either

the cut slope or the natural backslope. This data will be recorded within the

GHMS in Part C: Hydrogeologic Information, Cut Slope Information, Natural

Backslope Information, and Precipitation tabs.

Groundwater can be either flowing (spring) or non-flow (seepage) that is

discharging from the bedrock at the slope face, either the cut slope or natural

backslope. Indicate if groundwater is present in the cut slope and/or the

natural backslope. Record the percentage of the slope, cut slope and

backslope respectively, to the nearest whole percentage. If the site inventory

is conducted during winter months, the presence of groundwater may be

masked due to ice buildup on the slope face from an isolated area of

groundwater further up the slope. In this case, if the source of groundwater

cannot be isolated, then the ‘yes’ for groundwater needs to be recorded, but

the slope will need to be re-evaluated after the ice has melted and the natural

conditions can be sufficiently evaluated.


Additionally, record if surface water is present in the cut slope and/or the

natural backslope. If erosion channels are present during dry seasons record

‘yes’ for surface water. Record the percentage, to the nearest whole percent,

of the cut slope and/or the natural backslope.

Comment:

Note that heavy

seepage appears to

be originating at

the cut slope/

natural backslope

interface which is

then creating an

ice cover over the

slope masking

potential areas of

additional seepage.

Figure 200-15. HYDROLOGIC CONDITIONS

205.1.2 g) Corrective Actions

Typical types of corrective actions for rock slopes include installation of

concrete D-50 barrier, barrier fencing, construction of protective berm,

construction of catchment area, scaling the slope, and re-grading the slope.

The presence of guardrail along the road is not considered a type of corrective

actions or method of catchment.

Indicate if corrective actions were performed in the past. Define the type and

location of the corrective actions. If known, record the date of the corrective

actions, or ‘NK’ if not known. If the slope was modified, record the

percentage of the slope re-graded. If the catchment was modified, record the

retention type, if applicable. This data will be recorded within the GHMS in

Part C: Slope Information, Corrective Actions tab. The data is presented on

the Rockfall Form in Section E: TIER 2 – SLOPE INFORMATION.

Figure 200-16 presents typical types of catchment corrective actions found

along Ohio roadways.


Figure 200-16. TYPICAL TYPES OF CATCHMENT CORRECTIVE ACTIONS

Type of

Corrective

Action

Barrier Example Example Photograph

Catchment

Area:

Sufficient

area for

adequate

rockfall

debris

containment

None

PCB:

(Portable

Concrete

Barrier)

Catchment Area

Rockfall Debris

Limited Catchment Area

D50

D32


Figure 200-16. TYPICAL TYPES OF CATCHMENT CORRECTIVE ACTIONS (cont.)

CIP:

(Cast in

Place

Concrete

Barrier)

ODOT

Rockfall

Fence:

Earthen

Berm.

Limited Catchment

Area

Limited Catchment

Area


205.1.2 h) Catchment

Catchment Area is defined for use in this Manual as: The area between the

face of the rock slope and the edge of the travel lane capable of reducing the

velocity of a rock particle traveling in a downslope trajectory from a source

location along the rock slope. This definition differs from the design

catchment area as a distinction is made between design and actual rockfall

conditions.

It should be noted that the area between the rock slope face and the roadway,

which has a positive slope toward the roadway and/or is higher than the

roadway, should not be considered catchment areas. If a stream is located

between the slope and roadway, it can be counted as part of the catchment

area.

The catchment area shall be evaluated at its critical section. The critical

section is the smallest ratio based upon the width of the catchment area versus

the rock slope height, or largest volume that could be produced along the

length of the Inventory Site.

This data will be recorded within the GHMS in Part C: Slope Information,

Catchment Area tab. The data is presented on the Rockfall Form in Section E:

TIER 2 – SLOPE INFORMATION.

205.1.2 aa) Catchment Area Shape

The catchment area shape is based upon the simplified geometry of the

catchment area. The catchment area shape should not be influenced based

solely on the hydraulic control ditch, unless this ditch has sufficient size or

geometry to act as a catchment area for rockfall debris.

Basic catchment area shapes are flat, elliptical, circular, trapezoidal, or

triangular. The standard “Ritchie Ditch” utilizes a trapezoidal catchment

shape. The current FHWA/Oregon “Catchment Ditch” should be

considered a triangular catchment area shape. When the majority of the

catchment area is flatter than 8H:1V (7º from horizontal), the catchment area

should be considered flat.

Figure 200-17 presents simplified schematics of catchment area shapes and

example photos.


General Schematic Shape/ Abbrev.

Picture Example

Flat

F

Triangle

V

Trapezoidal

T

Elliptical

E

Circular

C

Figure 200-17. Catchment Area Shapes


205.1.2 bb) Catchment Area Depth

The catchment area depth is a physical measurement from the deepest point

of the catchment area referenced to the road elevation. The ditch depth of

the hydraulic control ditch (control of water runoff only) is not considered

part of the catchment system unless the ditch is wide enough to act in the

capacity of rockfall control.

To collect the depth measurement, extend a plane from the road surface,

such as a measuring tape or steel tape measure pulled taut, and determine

the distance from the base of the catchment area to the extended plane using

a folding scale or another tape measure. The depth should be an average of

five recorded depths along the length of the ditch, unless the critical section

is shallower than the remaining catchment area. The measurements shall be

recorded to the nearest 0.1-foot. For catchment areas where a barrier wall or

fence is located along the roadway shoulder, extend the plane from the top

of the footing as the reference plane and add the height of the barrier to the

depth.

Figure 200-18 shows a series of examples of the catchment area depth.

Catchment Ditch Depth

Hydraulic Ditch Depth

(NOT COUNTED since insufficient

to retain rockfall debris)

Road Elevation

Figure 200-18a. CATCHMENT AREA

Catchment Width


Figure 200-18b.

Hydraulic Control Ditch NOT as Catchment

Note: The flow line of the hydraulic control ditch

should not be measured as catchment depth due to

insufficient width for rockfall catchment.

Figure 200-18c. Hydraulic Control Ditch as Catchment

Note: This hydraulic control ditch can be

measured as catchment depth due to sufficient

width which will result in rockfall catchment.

205.1.2 cc) Catchment Area Width

The catchment area width is a physical measurement from the edge of the

travel lane to the face of the rock slope. The distance should be measured to

the rock slope face, and not the outer edge of any talus buildup, since talus

buildup can be removed as part of the ditch maintenance.

To collect the width measurement, extend a plane from the road surface to

the rock slope face, as outline in Section 205.1.2.bb Catchment Area Depth.

The measurement shall be recorded to the nearest 1-foot. For a catchment

area with a uniform width across the slope, take an average of five

measurements. If the catchment area has an area which is wider than the

remaining catchment area, such as for a drainage basin, this area should be

excluded from the measurements. However, if a section of the catchment

area is narrower than the remaining catchment area this should be

considered a critical section and the catchment width should be based on the

average width of this section.

Figure 200-18 shows an example of the catchment area width.

205.1.2 dd) Foreslope Angle

The foreslope angle is the angle measurement of the slope between the

shoulder or edge of the travel lane and the bottom of the catchment area.

This measurement shall be made from a horizontal plane extended from the

road elevation and recorded to the nearest whole degree. If multiple angles

are present within the foreslope then an average angle of the foreslope needs

Catchment Depth

Hydraulic Control Ditch

(Not Counted)

Catchment Depth

Catchment Width

Catchment Width


to be recorded. A minimum of five measurements should be recorded

across the length of the Inventory Site and averaged, excluding areas which

have been drastically modified and are not representative of the catchment

area.

To collect the foreslope angle two options are available. The preferred

method is by physical measurement by placing a two (2) or four (4) foot

level along the foreslope and then record the angle measurement utilizing a

clinometer. This method is not feasible at foreslopes where multiple angles

are present. However, the angle can be estimated utilizing a pocket transit

and visually estimating the average angle.

An alternative method is by determining the angle trigonometrically by

extending a plane from the road surface to the point of the catchment area

depth (l) measurement and record the value to the nearest foot, and the

catchment area depth (D) to the nearest foot. Use the following equation

(equation #3) to determine the foreslope angle:

Eq. #3: tan A = D / l

205.1.2 ee) Slope Face Angle

The slope face angle is the angle of the rock slope face where the slope

intersects the catchment area. This angle may not be the angle of the base of

the ditch due to modification through past maintenance activities and should

be reflective of the cut slope angle.

The foreslope angle is the angle measurement of the slope between the

shoulder or edge of the travel lane and the bottom of the catchment area.

This measurement shall be made from a horizontal plane extended from the

road elevation and recorded to the nearest whole degree. If multiple angles

are present within the foreslope, an average angle of the foreslope needs to

be recorded.

To collect the angle measurement, two options are available. The preferred

method is a physical measurement by placing a two (2) or four (4) foot level

along the rock slope face and recording the angle utilizing a clinometer.

This method is not feasible at foreslopes where large amount of talus

D

l

A


buildup is present. However, the angle can be estimated utilizing a pocket

transit and visually estimating the average angle.

An alternative method is by determining the angle trigonometrically by

extending a plane along the same elevation as the road surface and measure

the distance from the point of the catchment area depth to the rock slope

face (f), record to the nearest foot, and utilize the catchment area depth (D),

as determined in Section 205.1.2.bb Catchment Area Depth, to the nearest

foot. Use the following equation to determine the slope face angle:

Eq. #4: tan = D / f

This angle shall be recorded to the nearest whole degree less than 90º.

Figure 200-19. Catchment Area Configuration

D

f

D

f

A

l

D

l f

A


205.1.2 ff) Remedial Effectiveness

For areas were catchment areas are present or where past corrective

measures have been implemented, estimate the effectiveness of the work

expressed to the nearest 10 percent.

The work effectiveness should be based on existing catchment geometry

compared to the current guidelines outlined in Appendix B in addition to

past history or evidence of rockfall debris relative to the slope and roadway.

Inventory Sites where barrier corrective actions have been constructed does

not mean that the effectiveness is 100 percent. Barrier effectiveness should

be based on the barrier type relative to the debris type, size, volume, and

ditch geometry between the barrier and the cut slope. For example a very

large block size (>5 ft in diameter) will not be retained by a D36 or D50 cast

in place wall if the catchment width is very narrow; or if the block is

stopped by the wall the amount of debris as a result of the damage to the

wall may pose a risk to the travelling public.

Also, for Inventory Sites which may produce a large volume of debris with a

narrow catchment area and a barrier along the shoulder, check the catchment

capacity versus the potential rockfall volume. The catchment capacity is the

calculated volume based on the barrier height and catchment width relative

to the volume at the location where the high potential from which rockfall

debris could be generated. If the debris volume calculation is greater than

the catchment capacity, the remedial effectiveness should be less than 100

percent relative to the volume over the capacity.

205.1.2 i) Additional Information

Record if mine openings are evident within the cut slope or the natural

backslope as either yes or no. If yes, record within the comments section the

number of openings, including condition of the opening(s) (sealed, open,

collapsed, discharging drainage) and approximate location relative to the

BMP. Also, note if acid mine drainage is present within the ditchline. Figure

200-20 shows examples of mine openings within slopes.

Record if any evidence of slope instability is noted in either the soil cut

section or backslope as a yes or no under slope instability. If yes note the

observations within the comments field and approximate location relative to

the BMP. This data will be recorded within the GHMS in Part C: Slope

Information, Corrective Actions tab. The data is presented on the Rockfall

Form in Section E: TIER 2 – SLOPE INFORMATION.


Abandoned mine opening

not sealed but collapsed

Abandoned mine opening

Entrance sealed with bricks

Mine subsidence within a cut slope Acid mine drainage within ditch

Figure 200-20. EXAMPLE OF MINE OPENINGS

206 TIER 3 & TIER 4 SITE DATA COLLECTION

Upon completion of the Tier 2 Data Collection any site which scored as a Tier 3 or Tier 4

site should have the final data sets completed. There is no difference in data collection

between a Tier 3 and Tier 4 site. However, if a Tier 4 site is identified, OGE and the

respective DGE or designated District Rockfall Inventory Coordinator needs to be

notified within 24 hours so that appropriate actions can be taken.

Generally, the best way to complete the data collection is through direct measurements

from the slope face by performing horizontal and vertical line survey(s). If the entire

slope is not obtainable from the road surface, the slope face shall be inspected, evaluated

and sampled by either climbing the face or repelling from the top.

206.1 Slope Geological Conditions

The following information needs to be complied in Section F: Tier 3 & Tier 4 - Slope

Geological Conditions. As previously noted, the slope information should be

recorded relative from the ditch to the crest of the cut.


206.1.1 Number of Cut Slope Benches

Record the number of benches located on the cut slope by physically counting the

number of benches from the base of the slope to the top of the slope. This data

will be recorded within the GHMS in Part C: Slope Information, Slope

Information tab.

206.1.2 Number of Cut Slope Angles

Record the number of slope angles located on the cut slope by physically counting

the number of significantly different slope angles from the base of the slope to the

top of the slope. The differentiation of slope angles should be relative to gross

changes in the slope angles since cut slope angles can have variations across the

length of a cut due to construction techniques, minor physical property changes

within a rock strata, and differences on weathering over time. Typically, during a

cut slope design and construction, “slope angles” will change dramatically (i.e.

0.25:1 increment or greater). Minor incremental changes in the slope angles are

typically not discernable by the naked eye and should be considered one slope

angle. This data will be recorded within the GHMS in Part C: Slope Information,

Slope Information tab.

206.1.3 Cut Slope Angles

Collect the cut slope angle(s) along the cut slope face by recording the slope angle

from a horizontal plane using either a pocket transit, structural compass, or

clinometer. To record the slope angle use a non-ferric (aluminum or plastic)

clipboard or a 2- to 4-foot level placed against the cut slope face to estimate the

slope angle. If blast holes (half casts) are still evident within the cut slope face

record the slope angle along the central axis of the blast hole. An alternative

method is to visually line up the slope angle with the edge of a pocket transit,

structural compass, or clinometer and then determine the angle using the

clinometers needle. Figure 200-21 presents diagrams on how to determine these

angles. Collect a minimum of three readings per slope angle and use the average

value rounded to a whole degree. This data will be recorded within the GHMS in

Part C: Geological Information, Slope Information tab.


Use of a pocket transit or

structural compass for direct

measurement for the slope

surface.

(From Brunton GeoTransit

Operators Manual, 2001)

Use of a pocket transit or

structural compass for a visual

measurement of the slope angle.

(From Brunton GeoTransit

Operators Manual, 2001)

Figure 200-21. SLOPE ANGLE DETERMINATION

For slopes were talus buildup is present at the base of the slope angle, take either

direct measurement from the slope above the talus, or estimate through sighting

assuming the talus material is not present.

Figures 200-22 and 200-23 show the collection of a slope angle utilizing a pocket

transit for both a slope face and along a blast hole, respectively.

Figure 200-22. Recording slope

angle along a blast

hole using a pocket

transit


Figure 200-23. Recording slope angle

using a pocket transit

and non-ferric

clipboard

206.1.4 Average Cut Slope Angle

After all the slope angles have been recorded, the average slope angle shall be

calculated for the cut slope. The average slope angle shall be a weighted average

of all the cut slope angles recorded to the nearest whole degree. Table 200-04

provides typical design cut slope angles. Figure 200-24 and associated example

outlines the calculation of the weighted average of the slope angle.

TABLE 200-04

TYPICAL SLOPE ANGLES FOR ROCK CUTS

Slope Angle Cut Slope Ratio

76º 0.25H:1.0V

63º 0.50H:1.0V

53º 0.75H:1.0V

45º 1.0H:1.0V

34º 1.5H:1.0V

26º 2.0H:1.0V

22º 2.5H:1.0V

18º 3.0H:1.0V


206.1.5 Cut Slope Angles Elevations

Record the elevation(s) at which the cut slope angle changes using a measuring

tape, survey rod, hand level, abney level, or methods outlined in Section 205.1.2.a

Slope Height. Record the elevation to the nearest foot. This data will be recorded

within the GHMS in Part C: Geological, Single-angle tab.

206.1.6 Bench Elevations

Record the height (elevation) at which the benches are located along the cut slope

using a measuring tape, survey rod, hand level, abney level, or methods outlined

in Section 205.1.2.a Slope Height. Record the elevation to the nearest foot.

If the bench is not a true horizontal bench, but a sloping bench (such as a

stratigraphic bench), record the percent (%) slope for the bench.

This data will be recorded within the GHMS in Part C: Geological tab.

63º

Catchment Area

Figure 200-24. AVERAGE SLOPE CALCULATION

20 ft

15 ft

10 ft

30 ft

45º

26º

76º

Avg. Slope Angle = {(0.27*45º) + (0.20*63º) + (0.13*26º) + (0.40*76º)}

= 58.5º or 59º

75 ft

Roadway

Weighted Heights

A1 Height =

20’/75’ = 0.27

A2 Height =

15’/75’ = 0.20

A3 Height =

10’/75’ = 0.13

A4 Height =

30’/75’ = 0.40

Slope Angles

Angle A1 = 45º

Angle A2 = 63º

Angle A3 = 26º

Angle A4 = 76º

Bench Width

B1 = 10 ft.

A1

A2

A3

A4

B1

Eq. 5 Avg. Slope Angle = (An* Hn)

EXAMPLE 200-09: Weighted average calculation for multi-angled cut slopes.


206.1.7 Bench Width

The bench width measurement is a physical measurement made with either a

measuring tape or distance wheel. If talus material covers part, or all, of the

bench, use an estimated width for the original bench width. Record this width to

the nearest foot.

This data will be recorded within the GHMS in Part C: Geological, Bedding

information tab.

EXAMPLE 200-10: Calculation of Bench width and Elevation (From Figure 200-24)

Road Elevation (Section Base Elev.) = 879 Ft

Bench B1 Height (Elevation) = 35 Ft (914 Ft)

Bench B1 Width (Ft) = 10 Ft

206.1.8 Competent Bedding

Record the number of competent beds present within the cut slope including the

bed lithology, bedding, bedding JRC (see Appendix F for listing), and aggregate

thickness of all competent beds. Record this measurement to the nearest foot.

This data will be recorded within the GHMS in Part C: Geological Information,

Bedding Information tab.

206.1.9 Incompetent Bedding

Record the number of incompetent beds present within the cut slope including the

bed lithology, bedding, bedding JRC (see Appendix F for listing), and aggregate

thickness of all incompetent beds. Record this measurement to the nearest foot.



206.1.10 Undercutting Information

Record the number of competent beds that have undercutting within the cut slope

including the maximum and average depth of undercutting and average thickness

of undercutting. Additionally, note any undercutting that may be occurring within

the natural backslope including maximum and average depth of undercutting and

thickness of undercutting. Record the measurements to the nearest tenth foot over

an average of five measurements. This data will be recorded within the GHMS in

Part C: Geological Information, Bedding Information tab.


Figure 200-25. EXAMPLE OF CUT SLOPE DESCRIPTION

EXAMPLE 200-11: Slope Geological and Natural Conditions (from Figure 200-25)

Comments: In this example the coal/carbonaceous shale layer (4) and the

claystone layer (2) would be considered incompetent beds due to the overlying

more durable siltstone layers (3 & 5). The shale (6) located above the siltstone

(5), toward the top of the cut slope, would be considered a durable layer since

the overlying clayey shale (7) is not a more resistant layer.

Basal Talus Accumulation: 15 ft

Number of Competent Bed(s): 4

Aggregate Thickness of Competent Bed(s): 51 ft

Competent Bedding: thin to thick

Number of Incompetent Bed(s): 2

Aggregate Thickness of Incompetent Bed(s): 14 ft

Incompetent Bedding: thin to thick

Number of Competent Bed(s) with Undercutting: 2

Maximum Undercut Thickness: 3.5 ft

Average Undercut: 2.0 ft

Average Depth of Undercut: 4.0 ft

Ratio: Number of Competent to Incompetent Beds: 2.0

Ratio: Aggregate Thickness of Competent to Incompetent Beds: 3.6

(Note that the Ratios will be an auto-calculated field within the database)

Undercutting of incompetent bed beneath competent siltstone bed

6: Shale, thin bedded

7: Clayey shale, thin bedded

with partial vegetation

5: Siltstone, thick bedded

4: Coal/Carbonaceous Shale

2: Claystone, thick

bedded

3: Siltstone, thick bedded

1: Talus

80 f

t.

4ft

3ft

15ft

31ft

15ft

2ft

Block from Face

10ft


206.1.11 Joint Information

Record the information concerning the jointing of the cut slope face. Natural

backslopes may present adequate bedrock exposures within massive, competent

bedrock types in which joint information may be determined.

Indicate the type of joint(s) present within the slopes as either Orthogonal Joints

(ORTH) or Valley Stress Relief Joints (VSRJ) and the number of joint sets.

Appendix F outlines the general difference between these two types of joints.

Record the orientation of the joint set(s) utilizing a Brunton or lensatic compass,

recorded to a whole degree. Measure and record the average width of each joint

and the spacing between the joints within a joint set(s) for each of the competent

and incompetent beds using either a tape measure, folding scale, or a distance

wheel. These measurements should be recorded to the nearest tenth foot.

Visually estimate the average percentage of the joints within each joint set(s) that

contains infilling for each of the competent and incompetent beds. Record the

estimate as a whole percent. Additionally, note the type of infilling present within

the joint set (examples clay, iron precipitation, mineralization, etc.).


Joint Information tab.

Figures 200-26 and 200-27 present examples of joints and joint infilling for strata

within a cut slope.

EXAMPLE 200-12: Collection of Joint Information

Joint Orientation: ORTH / VSRJ

Orientation of Joint Set(s) = 182º; 175º

Avg Spacing of Joint (competent) = 15 ft.

Joint Width (competent) = 0.7 ft.

% of infilling of Joint = 55 %

Type of Infilling = Clay

Avg Spacing of Joint (incompetent) = 15 ft.

Joint Width (incompetent) = 0.5 ft.

% of infilling of Joint = 100 %

Type of Infilling = Clay


Figure 200-27. JOINT INFILLING

Joint Spacing

Figure 200-26. ORTHOGONAL JOINT SET/SPACING

Joint Width

100% Clay

Infilling

Joint Width

50% Clay

Infilling

No Clay

Infilling


206.1.12 Potential Rockfall Estimation

Estimate the anticipated shape of the blocks that may occur during a rockfall

event relative to the shapes modeled with the Colorado Rockfall Simulation

Program (CRSP). Three basic shapes utilized by CRSP are:

Spherical: a rock with uniform size and shape in all dimensions

Cylindrical: a rock that has one axis longer (length) than the other two

axes which are roughly equal in size

Discoidal: a rock that has a uniform diameter and length, but the thickness

is significantly less than the length or diameter (slab or flagstone)

A slab type rock typically seen within the interbedded strata typically found

within Ohio would fall into the discoidal category. All the parameters should be

recorded to the nearest 0.5-foot. Table 200-05 outlines each of the parameters

required for each particle shape. Figure 200-28 shows examples of each:

TABLE 200-05: ROCKFALL PARAMETERS

Shape Diameter Length Thickness

Spherical

Cylindrical

Discoidal

: Indicates the parameter measurement required for rock shape.

Figure 200-28. EXAMPLE ROCKFALL SHAPES

Spherical

Cylindrical

Discoidal


Estimate the maximum extent that a single rockfall event will impact the

roadway. Record the estimated limits of impact as a linear distance relative to the

roadway, both parallel and perpendicular to the slope. The impact length should

be measured as a lateral distance parallel to the slope from which debris may be

produced. The length may be greater than the estimated width (y) estimated for

Section 205.1.2 e) Rockfall Source Information. The impact width should be

estimated as the lateral distance parallel from the base of the cut slope face to

which the rockfall debris will extend. These estimates should be recorded to the

nearest foot.


Additional Information tab.

206.1.13 Talus Accumulation

For estimation of the talus accumulation, both basal and along benches, look at

the location where the maximum accumulation is present and evaluate this

location as a ‘worst case’ situation. Evaluate the ‘worst case’ location as a section

to determine the percentage of talus build up relative to the catchment or bench

width. Record this value to the nearest whole percentage. Figure 200-29

illustrates the calculation of the talus buildup along a bench.

Each bench should be calculated separately with a percentage value recorded for

each bench location.




206.1.14 Vegetation

Estimate the percentage of both the cut slope and natural backslope that contains

vegetation based on aerial extent of the slope. Record the estimate to a whole

percent. Additionally, within the comments section, record the type and size of

the vegetation. Typical category types () and sizes () are:

Grasses

Shrubs/scrub

Trees

0” - 6”

6” - 12”

> 12”

This data will be recorded within the GHMS in Part A: General Information.

206.1.15 Additional Information

Upon completion of the Tier 3 and Tier 4 Slope Geological Conditions, record

within the comments section if any anomalies are noted within the slopes (e.g.

faults, coal riders, etc.). This data will be recorded within the GHMS in Part C:

Geological Information, Additional Information tab.

Figure 200-29. ESTIMATING TALUS ACCUMULATION ON A BENCH

0 2.5ft 5.0ft 7.5ft 10.0ft

Bench Width = 10 ft.

Talus Accumulation

Along Bench Width

25%

50%

75%

100%


206.2 Slope Hydrological Conditions

The following are the procedures for completion of the GHMS Part C:

Hydrogeological Information which is also found in the Rockfall Form in Section G:

TIER 3 & TIER 4 FIELD –SLOPE HYDROLOGICAL CONDITIONS. This basic information

pertains to the groundwater and surface water conditions of the cut slope and/or

natural backslope within an Inventory Site. This data is collected through visual

evaluation and by performing physical measurements of the slope.

Evaluate the cut slope and the natural backslope for the presence of groundwater.

Groundwater can be noted as either flowing (spring) or non-flowing (seepage) that is

discharging from the bedrock or soil cover along the slope face. Record if

groundwater is present in the cut slope and/or the natural backslope. Hydrological

conditions should be noted on the site plan and details, including the location based

on the discharge point(s). All measurements should be noted from the BMP location.

Distances should be determined based along the edge of pavement until perpendicular

to the referenced location. Elevations should be determined as outlined in Section

205.1.2.a Slope Height and Section 205.1.2.b Slope Elevation. The following types

of hydrological conditions should be noted:

Spring: An isolated point within the slope where groundwater is discharging

Spring Line: A series of springs which are located along the same elevation

Seep: An isolated point of moisture within the slope which is not comprised

of flowing groundwater

Seep Line: A series of seeps which are located along the same elevation

Seep Zone: An area within the slope where seepage is noted from multiple

sources in close proximity to each other at varying elevations

Surface Flow: An erosional channel developed form the channelization of

surface water runoff

Additional measurements are required for spring and seep lines and seep zones. For

spring or seep lines, the length that the line extends along the slope face needs to be

recorded. For seep zones, the distance from the BMP should be referenced to the first

noted edge of the zone with the length being referenced to the furthest edge of the

zone. The elevation of a seep zone will be referenced to the base of the seep zone.

The hydrologic conditions for the Inventory Site should be recorded across the

Inventory Site beginning at the BMP at the base of the slope proceeding upslope then

across the site to the EMP. All springs and seepage should be assigned a site specific

ID referencing and numerically numbered in the order that they are encountered with

a prefix designation outlined in Table 200-6.


TABLE 200-6:

HYDROLOGICAL PREFIXES

Hydrogeological

Condition Abbreviation

Spring(s) SP

Spring Lines(s) SL

Seep(s) SE

Seep Line(s) SH

Seep Zones(s) SZ

Surface Flow SF

The following examples demonstrate the general outline of how to reference the site

hydrological conditions.


Figure 200-30. HYDROLOGIC CONDITIONS WINTER CONDITIONS

Example 200-13: Hydrologic Conditions of Cut Slope and Natural Backslope

Comments: Note that water is present at overburden and rock interface. However, due to the cold

conditions at the time of the site inventory the groundwater has resulted in ice formation along the

entire slope face. Thus reducing the potential for observations and identification of possible additional

hydrologic conditions within the lower slope. Surface flows are evident within the picture where the

ice buildup along the face is greatly reduced or voided, and deep erosional rills are present in the soils

natural backslope. These locations should be noted as Surface Flows within the natural backslope

since this is where they originate as evidence of the rills.

Cut Slope Info:

Site ID# Dist. From BMP (ft) Length (ft) Elevation (ft) Flow Rate (gpm)

SL1 10 520 1002 <1.0 gpm

Pictures taken at all locations: Y / N

Backslope Info:


SF1 350 NA 1085 NA

SF2 380 NA 1085 NA

SF3 460 NA 1085 NA


Spring Line

Surface Flow

BMP

GPS Obtained

Elev. 960

960

1002

1085

Elev. Ft.


Figure 200-31. HYDROLOGIC CONDITIONS SPRING CONDITIONS

25 60 115 123 148

Example 200-14: Hydrologic Conditions of Cut Slope and Natural Backslope

Comments: Note that seepage is prevalent throughout the slope. Dashed red line indicates the cut

slope/backslope interface. Areas of seepage have saturated the slope, but are not part of the seep itself.

Cut Slope Info:


SZ1 25 50 765 < 1.0

SH1 60 55 760 < 1.0

SE1 115 NA 786 < 1.0

SE3 148 NA 765 < 1.0

Comments: SZ1 is located just below natural backslope interface;

SH1 is located along a bedding plane.


Backslope Info:


SE2 123 NA 771 < 1.0

Comments: SE2 is located just above the cut slope/backslope interface.


Seepage Zone

Seepage Line

Seeps

Saturated Surface

from Seepage

Saturated Surface

from Seepage

786

771

765

760

746 (BMP Elev.) Left Side of

Picture


206.3 Tier 3 & Tier 4 Testing Data

The following are the procedures for completion of the GHMS Part C: Rock

Sampling Information which is also found in the Rockfall Form in Section H: TIER 3

& TIER 4 TESTING DATA.

Section H records the information concerning sample collection for Tier 3 and Tier 4

site. Slake Durability Index testing (SDI) will be performed on selected

representative samples collected from the slope of the rockfall sites rated as either

Tier 3 or Tier 4 from the Preliminary Slope Rating. For large sites that have many

different rock strata, collect a maximum of six samples for SDI testing. If more than

six incompetent beds are present within an Inventory Site, collect samples from the

six deepest, or worst, locations across the site.

Collect bag samples of fresh rock material from each incompetent bed located within

the slope. Coal, limestone and moderately hard sandstone strata should not be

sampled for testing. The weathered rock surface should be removed from the slope

face using a shovel, geologic hammer, mattock, and/or chisel until fresh competent

bedrock has been exposed. Once the fresh rock face has been exposed, collect a

sample of the fresh rock material and place it into a collection bag(s) or container for

preservation. The material should be collected in such a manner and placed in a

container that moisture loss and breakage of the sample will be minimal during

transport and storage prior to testing. During transport and storage the sample should

not be allowed to freeze. Refer to ASTM D 4644 for the type and amount of sample

specimen required to perform the test. On the plan view, record the approximate

locations where the samples were collected. Record the sample location by

referencing the location as a distance from the BMP to the nearest foot and elevation

relative to the BMP to the nearest foot.

Record the sample data on the sample container, or on a sample tag affixed to the

container, and on a completed chain of custody form, include the following

information:

Site Location as County-Route-Section

ODOT District

Travel Direction (Cardinal or Non-Cardinal)

Distance from BMP

Right or Left Offset

Sample ID#

Height relative to BMP

Number of containers collected per sample

Date sample collected

Person collecting the sample

The bag samples should be delivered to the respective testing laboratory within a

week of the sample collection.


Upon completion of the testing data, record the sample test results in Section H: TIER

3 & TIER 4 TESTING DATA. For sites where multiple samples have been collected,

record the number of SDI tests performed with the high and low test results with an

average test results.

Example 200-15: Slake Durability Index Test Sample Collection

Removal of weathered

bedrock for SDI sample

collection

SDI Sample collected

(including field

identification)

SDI Sample

(prior to testing)

SDI Sample

(post testing)


206.4 Tier 3 & Tier 4 Office Data

Tier 3 and Tier 4 sites, as determined from the Preliminary Rating, will require

additional traffic information not outlined in Section 205.1.1 Geometrics and Traffic.

This data includes:

Average Road Slope

Detour Distance

Detour Time – Auto

Detour Time - Truck

The detour information will not have been obtained during the interviewing process

outline in Section 202.2.1 ODOT Interview(s). The District Transportation Manager

will need to be contacted to obtain this information. ODOT has set guidelines for

how a roadway will be detoured based upon the road type and location. The District

Transportation Manager will have to determine this information for each Tier 3 and

Tier 4 site. This data will be presented in GHMS Part B: Traffic Information and in

the Rockfall Form in Section I: TIER 3 & TIER 4 OFFICE DATA.

Also, the precipitation history should be recorded for the site. The 1-day, 3-day, and

15-day precipitation history from the date of field data collection should be reviewed

and recorded. If more than one day was spent working on the field data collection for

the Inventory Site, the precipitation history should be referenced to the actual day that

site hydrogeology data was recorded. This information can be obtained commercially

from NOAA, or a request can be made to the Ohio Department of Natural Resources,

Division of Water. Web links for sites to obtain the precipitation histories are

available in Appendix B.

This data will be presented in GHMS Part C: Hydrogeological Information,

Precipitation tab and in the Rockfall Form in Section I: TIER 3 & TIER 4 OFFICE

DATA.

207 DATA COLLECTION ACKNOWLEDGEMENT

Upon completion of the field data collection, the Field Team should sign and date the

form to acknowledge that the all the information collected and presented is accurate to

the best of their knowledge. This signature can be either hand written or an electronic

stamp and is located in Section K: DATA COLLECTION ACKNOWLEDGMENT.


300 Risk Scoring for Inventory Sites

301 Rockfall Inventory Site Risk Scoring

After completion of the field data collection, Inventory Sites which are Tier 2, Tier 3, or

Tier 4 risk sites will need an associated Inventory Site Risk Score (Risk Score)

developed. The Risk Score is calculated based on ten (10) factors which are:

1. Differential Weathering

2. Discontinuity Role

3. Block Size/Volume of Rockfall per Event

4. Hydrologic Conditions (seeps and springs)

5. Rock Slope Height

6. Catchment/Containment

7. Exposure Risk

8. PDSD

9. Rockfall History

10. Accident History

Each factor will develop a raw value score based on the recorded field data. Each

evaluation parameter has a specific equation in which the site specific raw value (RV) is

a field input. A weighting factor is applied to each evaluation parameter to provide an

evaluation parameter score. The evaluation parameters values are summed to calculate

the Inventory Site Risk Score

The following sections outline the scoring for each factor.

302 Differential Weathering

The differential weathering factor is a multi-variable factor based upon the Tier scoring.

For Tier 2 sites the score will be based upon the recorded maximum visible undercut

recorded within the cut section. This information is recorded in the Geological Hazard

Management System (GHMS), Part C Geology: Additional Information Tab. The

following scoring matrix should be utilized based on the depth of the undercut (RV):

5.6*(RV³) - 30.8*(RV²) + 62.4*RV - 34.2

For Tier 3 and Tier 4 sites, where slake durability (SDI) samples were collected and

tested, the score will be based on the highest value between the SDI and undercut scores.

The testing information is recorded in the GHMS, Part C Geology: Additional

Information Tab. The following scoring matrix should be utilized based on the test

results of the second cycle slake durability index (RV):

-0.0019*(RV³) + 0.4736*(RV²) - 39.268*RV + 1099.5

A minimum of 0 points and a maximum of 81 points need to be assigned for this section.


303 Discontinuity Role

The Discontinuity Role factor is a multi-variable factor based upon the major type of

discontinuity producing the rockfall debris. Typically, one of two types of discontinuity

will be predominately controlling factor in production of rockfall debris. These are

jointing or raveling. Cut slopes can exhibit either one or both of these properties. The

slope should be evaluated for both types of discontinuities and scores based on the worst

case of the two. The following is a brief discussion of how to score each type.

Intersecting joint sets can produce blocks that can dislodge resulting in a potential hazard

to the roadway. However, if the joint sets do not intersect, then the resulting

discontinuity may not result in potential hazard to the traveling public. The scoring is

based upon how continuous the joint set(s) are and the orientation of the joint set(s)

relative to the roadway. This information is found in the GHMS in Part C: Geological

Information, Joint Information tab. The following scores are assigned based on how

continuous and the orientation of the joint(s):

Discontinuous joints with favorable orientation = 3 points

Discontinuous joints with random orientation = 9 points

Discontinuous joints with adverse orientation = 27 points

Continuous joints with adverse orientation = 81 points

For slopes where the raveling is the predominate feature producing the rockfall debris,

the score will be based on the percentage of the slope which is exhibiting the raveling

(RV). The following scoring matrix should be utilized based on the depth of the

undercut:

0.028*(RV³) - 1.36*(RV²) + 21.9*RV - 108

A minimum of 3 points and a maximum of 81 point need to be assigned for this section.

304 Block Size/Volume of Rockfall Per Event

This factor is based on the size and amount of debris which could be a potential hazard to

the traveling public. These variables are typically directly proportional to the type of

joint sets and raveling that the slope is experiencing. Typically, either large blocks

produced by the joint sets or small blocks produced by raveling is the predominate

mechanism of debris generation. Both should be evaluated and scores based on the worst

case of the two. The following is a brief discussion of how to score each type.

The first variable to look at is the maximum dimension of the anticipated or recorded

block size that could be produced for the slope. This information is recorded in the

GHMS, Part C Geology: Additional Information tab. The following scoring matrix

should be utilized based on the block size:

28*(RV³) - 136*(RV²) + 219*RV - 108


The second variable to look at is the total volume of debris that could be produced for the

slope during a rockfall event. This information is recorded in the GHMS, Part C

Geology: Additional Information Tab. The following scoring matrix should be utilized

based on the block size:

1.037*(RV³) - 15.111*(RV²) + 73*RV - 108


305 Hydrologic Conditions (seeps and springs)

The Hydrologic Condition factor is based on the percentage of the slope which has

hydrologic conditions within the slope. This information can be found within the GHMS

in Part C: Hydrogeologic Information, Cut Slope Information, Natural Backslope

Information, and Precipitation tabs. The following scoring matrix should be utilized

based on the percentage of the slope with hydrological conditions:

0.0122*(RV³) - 0.4552*(RV²) + 5.8845*RV - 16.574


306 Rock Slope Height

The fifth factor to consider in the Risk Scoring is the rock slope height from which

potential rockfall debris could be generated. For Inventory Sites where the source zone is

solely within the cut slope, the Rock Slope Height will be the Rock Cut Height. If the

Inventory Site has a source zone located within the natural backslope, then the Rock

Slope Height will be recorded as the Backslope Height. This information can be found

within the GHMS in Part C: Slope Information, Geometric Information tab. The

following scoring matrix should be utilized based on the rock slope height:

0.0035*(RV³) - 0.55*(RV²) + 28.75*RV - 491


307 Catchment/Containment

The Catchment/Containment factor is a multi-variable factor based upon existing

catchment area and any past remedial activities. For sites where a retention

(containment) system is in place (e.g. D50 wall, rock fence), the system is evaluated on

whether the system is functional or not. For sites which do not have a containment

system the site is evaluated based on the catchment area effectiveness.

A reminder, just because a wall is in place does not necessarily mean that the wall will be

effective for either very large block sizes or large debris volumes with small catchment

storage capacity. This should be reflected in the estimated remedial work effectiveness.

This data will be recorded within the GHMS in Part C: Slope Information, Corrective

Actions tab. The following scores are assigned based whether there is a functional

retention (containment) system in place:


Yes = 9 points

No = 81 points

Even though there is a functional barrier the site scores 9 points because there has been a

problem in the past which has warranted the installation of the barrier. Additionally, if

the barrier is subjected to repeated impacts the barrier may eventually fail, which is why a

score of 3 is not assigned for functional barriers.

For Inventory Sites which do not have a means of containment, all the debris control is

handled based on catchment width and geometry. The effectiveness of the catchment

area should be evaluated based on Appendix B. This data will be recorded within the

GHMS in Part C: Slope Information, Catchment Area tab. The following scoring

matrix should be utilized based on the catchment area effectiveness:

-0.0201*(RV³) + 5.2114*(RV²) - 449.15*RV + 12885


308 Exposure Risk

This factor is based on the exposure risk that the Inventory Site as expressed to the

travelling public. Exposure Risk can be calculated as following:

Eq. #6:

100*24/)*(

Risk Exposure

SpeedLimit

SiteLengthADT

Note: The site length should be reported in miles

ADT and speed limit values can be obtained from the GHMS in Part B: Traffic

Information. The site length is recorded in Part A: Site Location of the GHMS. The

following scoring matrix should be utilized to calculate the risk score for the exposure

risk of the inventory site:

0.0019*(RV³) - 0.2335*(RV²) + 9.4146*RV - 116.22


309 Percent Decision Sight Distance (PDSD)

This Risk Scoring factor is based on the percentage decision sight distance. This is

relative to the ability of a driver to react to an obstacle, such as rockfall debris, within the

roadway. Percent Decision Sight Distance can be calculated as following:

Eq. #1: PDSD = ASD / DSD


This data will be recorded within the GHMS in Part B: Traffic Information. The

following scoring matrix should be utilized based on the Percent Decision Sight Distance:

-0.0018*(RV³) + 0.4544*(RV²) - 38.36*RV + 1087


310 Rockfall History

The Rockfall History factor is based on the Inventory Site’s rockfall maintenance

records. These records are obtained from the applicable County Garage, County or

Transportation Manager, or District Geotechnical Engineer. Rating scores are assigned

as follows:

Less than Annual Maintenance = 3 points

Annual Maintenance = 9 points

Semi Annual Maintenance = 27 points

Constant Maintenance = 81 points

Table 300-01 presents the Rockfall History section of the worksheet.

Table 300-01. Rockfall History

Evaluation Parameter Rating Scores for each Evaluation Parameter

3 9 27 81

Rockfall History < Annual

Maintenance

Annual

Maintenance

Semi

Annual

Maintenance

Constant

Score

311 Accident History

The final factor is the Accident History of the Inventory Site relative to past rockfall

events. Accidents which did not involve debris generated from a rockfall event should

not be considered. This factor is based on the County maintenance records and

Department of Public Safety records with scores assigned based as follows:

No Accidents = 3 points

Minor Property Damage = 9 points

Major Property Damage = 27 points

Death = 81 points


Table 300-02 presents the Accident History section of the worksheet.

Table 300-02. Accident History

Evaluation Parameter Rating Scores for each Evaluation Parameter

3 9 27 81

Rockfall History

No Accident

Minor

Property

Damage

Major

Property

Damage

Death

Score


400 Inspection Frequency

Each Inventory Site will require periodic re-inspection to determine if the site’s risk is

remaining relatively stable, or progressing as an increased risk relative to the public safety.

The frequency of re-inspection will be based on the Preliminary Rating of the previous

inspection as presented in Table 400-01.

Table 400-01. Re-Inspection Frequency

Rating Frequency

Non-rated

(Tier 1) 10 Years

Moderate Risk

(Tier 2) 5 Years

High Risk

(Tier 3) 3 Years

Very High Risk

(Tier 4) Annually

Re-inspection will be required outside of the prescribed inspection table if one of the

following events occur:

1. If rockfall debris fragment(s) greater than 6 inches in any dimension occupies the

shoulder, travel lane(s) or median: The District Geotechnical Engineer (DGE) and

the Office of Geotechnical Engineering (OGE) shall be notified within one week and

the site shall be re-evaluated within one month of the event.

2. If rockfall debris greater than one cubic foot in total volume, occupies the shoulder,

travel lane(s) or median: The District Geotechnical Engineer (DGE) and the Office

of Geotechnical Engineering (OGE) shall be notified within one week and the site

shall be re-evaluated within one month of the event.

3. A single rockfall event which produces debris volumes which occupies more than 70

percent of the estimated storage capacity over a length of 20 feet for the catchment

area: The site should be re-inspected within three months of the event.

4. Remedial activities to the slope, partial or full, are performed on a site to reduce the

overall relative risk: The site should be re-inspected within one year upon completion

of construction activities.

APPENDIX A

Glossary of Terms

APPENDIX A – GLOSSARY OF TERMS Rock Type Terms: The following are descriptions of the basic rock types found within Ohio rock slopes. This listing is not intended to be an all inclusive exhausting listing. The following listing is presented in alphabetical order. Breccia: A coarse-grained sedimentary rock comprised of >25% subangular to angular coarse-grained sand, gravel and/or cobbles. These grains are supported by a matrix of finer sands, silt and/or clay and cemented by calcite, hematite, silica or hardened clay. Color depends on the matrix and cementing agent with typical colors of white, gray, yellow, orange, brown, and red common. CHERT: A hard dense microcrystalline or crptocrystalline sedimentary rock consisting of quartz crystals and may contain amorphous silica. Chert may be a variety of colors, but commonly range from brown to black. When broken it produces conchoidal fractures. These fractures are smooth with sharp edges. Chert forms as nodular or concretionary segregations or nodules or as layered deposits in limestone and dolomite. CLAYSTONE: A fine-grained detrital rock formed from particles finer than silt. Claystone is comprised of indurated clay having the texture and composition of shale, but lacking the laminations and fissility of a shale. Claystone may range in color from red, gray, olive, or brown, and slickensides are common. COAL: A combustible rock containing >50%, by weight, and >70%, by volume, of carbonaceous material; formed from the compaction and induration of plant remains. Colors of coals range from brown to black. Generally light weight with a shiny appearance on fresh surfaces. CONGLOMERATE: A coarse-grained sedimentary rock comprised of >25% rounded to subrounded coarse-grained sand, gravel, cobbles, and/or boulders. These grains are supported by a matrix of finer sands, silt and/or clay and cemented by calcite, hematite, silica or hardened clay. Color depends on the matrix and cementing agent with typical colors of white, gray, yellow, orange, brown, and red common. DOLOMITE: A sedimentary rock of which >50% consists of the mineral dolomite (calcium magnesium carbonate – CaMg(CO3)2) and less than 10% is comprised of the mineral calcite. Commonly interbedded with limestone, and the magnesium can be replaced with ferrous iron. Dolomite is typically white to light colored and will be slow to react with cold dilute hydrochloric acid (HCl). Generally, for dolomite to react with HCl either a fresh or powdered surface is required. FIRECLAY: See Underclay for description. LIMESTONE: A sedimentary rock consisting of the mineral calcite (calcium carbonate – CaCO3). Very fine grains may not be visible to the naked eye. Impurities may included chert, clay and minor mineral crystals. May be crystalline (hard, pure, medium to coarse texture) and/or fossiliferous (remains of organisms). Limestone is typically white to dark gray in color and reacts vigorously with dilute HCl. SANDSTONE: Clastic sedimentary rock comprised of grains of angular or rounded sand in a matrix of silt and/or clay cemented together by silica, iron oxides, or calcium carbonate. Color depends on the cementing agent with white, gray, yellow, orange, brown, and red colors common. SHALE: Fine-grained detrital sedimentary rock formed be the compaction of clay, silt or mud. Shale is well indurated and has a laminated structure, which gives it fissility along which the rock splits readily. The predominate particle size is <0.002 mm (colloidal) and commonly interbedded with sandstone. Shale can be calcareous (contains calcite), carbonaceous (contains organic materials), and/or fossiliferous (contains remains of organisms). Carbonaceous shale often grades into coal. Typical colors may be red, brown, black, green or gray.

SILTSTONE: Fine-grained detrital sedimentary rock formed from particles finer than sand, but coarser than clay. Siltstone is comprised of indurated silt and have the texture and composition of shale, but lacking the lamination or fissility. Gray, olive, or brown are typical colors of siltstone. UNDERCLAY: A layer of clay lying immediately beneath a coal bed or carbonaceous shale. This layer may be bioturbated and indurated. Chiefly comprised of siliceous or aluminous clay capable of withstanding high temperatures without deformation, and may have a high shrink/swell potential. Technical Terms: The following are descriptions of basic terms utilized within the Rockfall Manual. The following listing is presented in alphabetical order. 1-Day Precipitation History: The recorded amount of precipitation, including but not limited

to, rainfall, ice, or snow, during the previous 24 hour period (1 day) prior to the field work.

3-Day Precipitation History: The recorded amount of precipitation, including but not limited to, rainfall, ice, or snow, during the previous 36 hour period (3 day) prior to the field work.

15-Day Precipitation History: The recorded amount of precipitation, including but not limited to, rainfall, ice, or snow, during the previous 360 hour period (15 day) prior to the field work.

AADT: (Adjusted Annual Daily Traffic)

Scaled adjustment of the annual daily traffic counts preformed within the field to account for increased traffic volume over time.

Accident: An incident that resulted in an injury of loss of private property due to a rockfall event.

ADT: (Average Daily Traffic)

The total amount of traffic, both truck and vehicle, for the given section of roadway over a 24-hour period.

Aggregate Thickness: The summed total of the thicknesses of a specified rock type for the total height of the cut slope and/or natural slope.

ASD: (Actual Sight Distance)

The shortest distance along a roadway over which a 6-inch object is continuously visible to a driver (assuming a height of 3.5 feet)

ATT: (Average Truck Traffic)

The total amount of truck traffic for the given section of roadway over a 24-hour period.

AVR: (Average Vehicle Risk)

A scaled factor for the risk to a vehicle associated with potential rock fall calculated as: ADT * Slope Length (miles) / 24 Posted Speed Limit

AVT: (Average Vehicle Traffic)

The total amount of vehicle traffic for the given section of roadway over a 24-hour period.

Bedding Plane: Break between the layering of sheet-like units, called laminations, beds or strata, indicating the change in lithology and/or physical characteristics.

* 100%

Bench: A low angle, or flat, step excavated into the cut slope with higher angle slopes above or below.

Block Size: The rock size that dislodged from the cut slope to become a rockfall. Estimated or measured in cubic feet.

Cardinal Direction: The cardinal direction of travel is based on the roadway description (i.e., I-70, West/East or I-71, South/North) and not a site specific compass direction or bearing. By convention, roadways are considered to be oriented in a south to north or west to east direction.

Cleanout: The removal of accumulated materials from ditches and benches including sediments and loose materials transported down slope from the cut slope face or natural slope.

Competent Bed: Rock strata composed of materials that are resistant to weathering processes relative to the underlying or overlying strata.

County Code The county that the site is located within using the ODOT three letter county designation. The county code consists of the first three letters of the county name with the exceptions of: County Code Ashland ASD Ashtabula ATB Champaign CHP Harrison HAS Meigs MEG Monroe MOE Montgomery MOT Morgan MRG Morrow MRW A full listing of the County Codes are included in Appendix X.

Crop Line: The general term “cropline”, if not further defined, refers to the line along the ground surface where the mined mineral seam is exposed in the existing grade. The term “cropline”, with further definition, can also be utilized to define the structural contour of the top of the mined mineral seam which is covered by a uniform depth of overburden. Example: On some ODNR abandoned underground mine maps, the notation on a map line may read “30 foot cropline”. This indicates the line on top on the mined mineral seam which was covered by 30 feet of natural overburden.

Cut Slope: The constructed slope along the roadway created by removal of overburden and/or bedrock from the ground surface to the road grade.

Cut Slope Angle: The angle from a horizontal datum/plane along the face of the constructed surface called the cut slope. (See Figure 1)

Cut Slope Height: The vertical distance measured from the top of the cut slope to

the base of the cut slope. (See Figure 1)

Cut Slope Length: The distance measured parallel along the road from which the material has been removed.

Ditch Depth: The vertical distance from the bottom of the ditch to the top of the ditch at the roadway shoulder. (See Figure 1)

Ditch Width: The horizontal distance of the ditch from the top of the ditch at the roadway shoulder to ground surface projected as a horizontal plane..

Drift Entry: A horizontal mine entry into the natural outcrop of the mined mineral seam.

DSD: (Decision Site Distance)

The required spacing along a roadway from which a driver has time to avoid an obstacle within the roadway. The value can be obtained from a design chart that considers speed limit, use of roadway, and possibly curvature and grade of the roadway. (Refer to Table 5 within the Manual Text)

%DSD: (Percentage Decision Site Distance)

Ratio between the DSD and the ASD, calculated as %DSD = (ASD/DSD) * 100

Durable Rock: Rock composed of materials that are resistant to weathering processes.

Field Team Field personnel consisting of a geologist and an engineering geologist or a geotechnical engineer, who will complete the required field data collection for the rockfall inventory.

Flow Rate: Rate at which water is discharging from the ground surface in gallons per minute (gpm).

Foreslope: The slope between the roadway shoulder and the bottom of the ditch. (See Figure 1)

Foreslope Angle: The angle of the slope between the roadway shoulder and the bottom of the ditch. (See Figure 1)

Gob: Coal refuse commonly abandoned on the surface in piles at or near the mining operation.

Ground Water: Flowing or non-flowing water discharging from the bedrock at the slope surface.

Haulage Shaft A mine shaft utilized for the transportation of mined mineral to the ground surface.

Joint: A discrete break or fracture within bedrock along which there has been little or no vertical displacement.

Joint Opening: The open distance between the joint faces measured in inches.

Joint Spacing: Distance between the centers of two joints (generally measured from center of joint opening to center of joint opening).

JRC: Joint Roughness Coefficient; Method used to describe the roughness of the joint surface by using a comparison on the discontinuity surface profile with reference profile.

Incompetent Bed: Rock strata composed of materials that are not resistant to weathering processes.

Infilling: Deposition (clay, silt, sand, minerals, etc.) within the joint opening.

Median: Area located between lanes of opposite directions of traffic. The median can consist as a divided, concrete barrier or fence, or undivided, open grass.

Mine Opening: A mine entry extending either vertically (shaft entry), horizontally (drift entry), or at an inclined angle (slope entry) to an underground mine.

Mine Subsidence: Sinking, settling or subsidence of the ground surface caused by the failed and collapse of the mine’s roof support.

Mineralization: The deposition of mineral deposits on a joint surface.

Natural Backslope: The original ground surface located above the top of the excavated surface of the cut slope. (See Figure 1)

Natural Backslope Height: The vertical distance from the top of the cut slope to the top of the natural ground surface, or to the upper limit of the source area for rockfall to occur within the Natural Backslope. (See Figure 1)

Orthogonal Joint Set: Series of deep-seated regional joints created by tectonic stress, which have a general regional trend.

Potential Rockfall Size: The estimated dimensions of a potential rock size that may dislodge from the cut slope or natural backslope to become a rockfall based upon bedding, the spacing and orientation of joints, and undercutting within the cut slope.

Potential Rockfall Volume: The estimated volume of material from a potential rockfall event that may dislodge from the cut slope or natural backslope to become a rockfall based upon the bedding, spacing and orientation of joints, and undercutting within the cut slope.

Ritchie Criteria: Catchment design criteria based upon the slope height and slope angle geometry.

Ritchie Score: A mathematical comparison of the Ritchie values compared to the actual ditch measurement. Ritchie Depth + Ritchie Width Actual Depth + Actual Width

Ritchie Score =

Rock Quality Designation: (RQD)

The RQD value is the percentage of the length of a rock core run which is made up of continuous pieces of core sample, that are four (4) inches in length or greater.

Rockfall: The detachment of rock mass(es) of variable size from along a cut slope or natural backslope with movement down slope toward the base of the slope.

Rockfall Chute: The clearing zone that results from the rockfall activities.

Rockfall Debris: The accumulation of material as a result of rockfall from the slope.

Rockfall Retention Device: Devices installed on the cut slope, natural backslope, or near the slope base, that inhibits the further movement, reduces the energy of, or collects the debris from, the down slope movement or tries to controls the rockfall from entering onto the roadway.

Rockfall Volume: The amount of accumulation of the rockfall from the slope measure in cubic yards.

Route Classification: State Route, US Route, or Interstate Route along which the field team will travel and complete the required inventory.

SDI: (Slake Durability Index)

Test for rock to determine its durability. Testing to be completed in accordance with ASTM D 4644: Standard Test Method for slake durability of shale and similar weak rocks.

Seepage: Non-flowing groundwater noted discharging from the slope surface measured in gallons per minute (gpm).

Shaft: A mine entry extending vertically from the ground surface down to the elevation of the mined interval.

Shoulder: The graveled or paved area between the outside travel lane and the ditch.

Site Number: Designation number for each specific inventory site assigned by ODOT.

SLM: (State Line Mile)

Numerical designation of any point along an ODOT maintained roadway, based on the actual centerline mileage as measured from the western or southern county line or other true beginning.

Spring: Flowing groundwater noted discharging from the slope surface measured in gallons per minute (gpm).

Surface Deformation: Area(s) of surface settlement or subsidence. Deformation may be indicated by the presence of irregular drainage conditions.

Surface Water Flow: Area of flowing water along either the face of the cut slope or along the natural backslope. Generally, surface water flow will be in a down slope direction and accumulates within the ditch at the base of the slope.

Talus: The accumulated of weathered rock particles and soil along the

cut slope, on benches, or at the foot of a slope.

Travel Lane or Lane: Paved section of roadway in which vehicular traffic moves.

Troughing: Linear surface deformation extending for some distance and having a gentle curvilinear profile when viewed in section.

Undercutting: The natural removal of materials as a result of weathering out of an incompetent bed overlain by a competent bed resulting in an overhang.

Underground Mine: An underground excavation from which mineral resources were extracted.

Valley Stress Relief Joint: Steeply dipping to vertical fractures that are a result of stress relief accompanying valley formation. Typically, these joint sets are oriented parallel to or sub-parallel to the valley walls. Stress relief joints tend to attenuate with distance away from the valley walls.

Cut Slope Height

D

Ditch Depth

Foreslope/ Foreslope Angle

Cut Slope Angle

Bench

Overburden Bench Natural Backslope

Natural Backslope

APPENDIX FIGURE #1

Not To Scale

Soil/Rock Interface

Catchment Area

APPENDIX B

Criteria for Evaluation of Catchment

Appendix B – Criteria for Evaluating Catchment Ditch Widths for Various Slope Angles

Cut Slope Height, H (ft) 0-40 50 60 70 80 >90*** Cut Slope Angle Catchment Ditch Width, W (ft)

2H:1V and 3H:1V Catchment Foreslope Angle* 0.25:1 10 15 15 15 20 25 min. 0.5:1 10 15 20 20 20 25 min. 1.0:1 15 20 20 20/25** 25 30 min. 1.5:1 15 20 20 20/25** 25 30 max.

4H:1V Catchment Foreslope Angle*

0.25:1 10/15** 15 20 20 25 30 min. 0.5:1 15 15 20 20 25 30 min. 1.0:1 15/20** 20 20/25** 25/30** 30 35 min. 1.5:1 15/20** 20 20/25** 25/30** 30 35 max.

6H:1V Catchment Foreslope Angle*

0.25:1 15 20 25 30 35 40 min. 0.5:1 20 20 25 30 35 40 min. 1.0:1 25/30** 25/30** 30 35 40 40 min. 1.5:1 25/30** 25/30** 30 35 40 40 max.

*If Slope under evaluation has a different foreslope angle than options listed above, round to nearest slope angle. **Single Angle Foreslope Catchment Ditch Width / Multi-Angle Foreslope (portion flat) Catchment Ditch Width *** Slopes with a height (H) greater than 90 feet should be evaulated with Appendix B width as minimum and adjusted according to specific site conditions For situations where the portion of the rock cut slope (backslope) intersecting the ditch is flatter than 1.5H:1V, use industry practices to evaluate width criteria.

APPENDIX C

Field Parameters

APPENDIX C – FIELD PARAMETERS

BEDROCK HARDNESS CRITERIA

Hardness Abbreviation Criteria - Field Criteria – Testing

(Schmidt Hammer)Very Soft VS Can be carved with a knife and excavated easily

with a point of a pick. Can be readily scratched by fingernail and pieces 1-inch of more in thickness can be broken by finger pressure.

Soft ST Can be grooved or gouged readily by a knife or pick. Can be excavated in small fragments by moderate blows of a pick point. Small, thin pieces can be broken by finger pressure.

Medium Hard MH Can be grooved or gouged 0.05-inch deep by hand pressure of a geologist’s pick. Hand specimens can be detached by moderate blows.

Hard HD Can be scratched with a knife or pick Very Hard VH Cannot be scratched by a knife or sharp pick.

Breaking of hand specimens require several hard blows of the geologist pick.

BEDROCK BEDDING CRITERIA

Bedding Type AbbreviationCriteria

English Metric Thinly Laminated TL <0.125-in <3 mm

Laminated LA 0.215-in to 0.400-in 3- to 10 mm Very Thinly Bedded VT 0.400- to 1.000-in 1.0- to 3.0 cm

Thin Bedded TH 1.000- to 4.000-in 3.0- to 10.0 cm Medium Bedded MB 4.000- to 12.00-in 10.0- to 30.0 cm

Thick Bedded TK 1- to 3.3-ft 30.0- to 100.0 cm Massive Bedded MS >3.3-ft >1.0 m

WEATHERING CHARACTERISTICS

Weathering Abbreviation Criteria Unweathered UW No evidence of any chemical or physical alteration of the rock

mass. Slightly Weathered SW Slight discoloration on rock mass surface, slight alteration along

discontinuities, less than 10% of the rock volume altered by either chemical or physical means.

Moderately Weathered MW Discoloration evident across the majority of the rock mass, surface pitting and alteration penetrating well below the rock mass surface, weathering “halos” evident, 10-25% of the rock volume has been altered.

Highly Weathered HW Entire rock mass discolored, alteration pervading nearly all of the rock mass surface with some pockets of slightly to moderately weathered rock noticeable, some materials may be leached away.

Decomposed DE Rock reduced to a soil like state with relict tock texture evident, generally molded and crumbled by hand pressure.

TEXTURE CHARACTERISTICS

Primary Component

Secondary Description

Grain Diameter (metric – mm)

Grain Diameter (english - inch)

Boulder Large >1025 >40.5

Medium 1025 – 500 40.5 - 20 Small 500 – 300 20 - 12

Cobble Large 300 – 125 12 - 5 Small 125 - 75 5 - 3

Gravel Coarse 75 – 19 3.0 - 0.75

Medium 19 – 8 0.75 - 0.31 Fine 8 – 2 0.31 - 0.08

Sand

Coarse 2.0 – 0.5 0.08 - 0.02 Medium 0.5 – 0.25 0.02 - 0.01

Fine 0.25 – 0.125 0.01 - 0.005 Very Fine 0.125 – 0.074 0.005 - 0.003

Silt --- 0.074 – 0.005 0.003 - 0.0002 Clay --- <0.005 <0.0002

BEDROCK MODIFIERS*

Modifier Definition Arenaceous Contains a sandy, or sandy-like appearance or texture. Arillaceous Contains silt and clay-sized particles. Calcareous Contains carbonate material as either a matrix or grains. Carbonaceous Contains an abundant amount of carbon material. Crystalline Contains crystalline grains or cementation composed of crystalline cement. Ferriferous Contains an abundance of iron rich minerals or grains. Fissile The rock mass has the ability to split along preferential planes. Friable The rock mass is easily crumbled, pulverized, or reduced. Micaceous Contains an abundance of mica grains within the rock mass. Pyritic Contains an abundance of pyrite nodules or crystals. Siliceous Contains an abundance of silica rich materials as either matrix or grains. Slickensided Contains polished striations indicating a plane along which differential movement

has occurred. Stylolitic Contains irregular, suture-like contacts called stylolotes. Variegated The rock mass has a variety of colors, usually intermixed or streaked. Vuggy Contains cavities within the rock mass. * This listing is only of common modifiers and is not intended to be all inclusive.

DISCONTINUITIES CHARACTERISTICS AND DESCRIPTION

VARIABLE TABLE NUMBER Discontinuity Dip Angle NA

Discontinuity Type C-1 Aperture C-2

Infilling Type C-3 Infilling Amount C-4 Infilling Profile C-5

Surface Roughness C-6 Spacing C-7

TABLE C-1

Type of Discontinuities

Abbreviation Characteristics

Bedding Plane BP

A well defined planar surface that indicates a marked break in the deposition within sedimentary rocks. With in Ohio this is the major discontinuity type, which generally dip to the southeast at angles ranging from horizontal to 10º. Isolated areas can have dip angle nearing 30º in areas of stratigraphic pinchouts have been recorded.

Valley Stress Relief Joint

VSRJ

Steeply dipping to vertical fractures that are present near the valley walls that are a result of the stress relief associated with the valley formation. This type of joint attenuates across beds of differing strength and becomes less frequent with depth below the valley floor and distance away from the valley walls and are generally parallel to sub-parallel to the valley walls.

Orthogonal Joint

ORTH Deep-seated regional joints created by tectonic stress that are more pervasive that the valley stress relief joints.

Shear SH

A discontinuity along which differential movement has taken place parallel to the discontinuity surface, sufficient to produce slickensides. May be accompanied by a zone of fractured rock up to a few inches wide.

Fault FT Major discontinuity along which there has been an appreciable displacement and accompanied by gouge and/or a severe fractured zone within the rock mass.

TABLE C-2

Type of Aperture Abbreviation Characteristics

English (inches) Metric (mm) Wide WD 0.5 – 2.0 13.0 – 50.0

Moderately Wide MW 0.1 – 0.5 2.5 – 13.0 Narrow NW 0.05 – 0.1 1.0 – 2.5

Very Narrow VN <0.005 <1 Tight TI 0.00 0.00

TABLE C-3

Type of Infilling Abbreviation Barite Ba Clay Cl

Calcite Ca Chlorite Ch

Iron Oxide Fe Gypsum/Talc Gy

Healed Hd Manganese Mn

None No Pyrite Py Quartz Qz Sand Sd Silica Si

Unknown Uk

TABLE C-4 Amount of Infilling Abbreviation Percentage of Infilling

None No 0% Surface Stain Su 0-2%

Spotty Sp 2-5% Partially Filled Pa 5-60%

Filled Fi >60%

TABLE C-5Infilling Profile Abbreviation

Planarity F Wavy Wa Planar Pl

Stepped St Irregular Ir

TABLE C-6

Surface Roughness Abbreviation Criteria

Slickensided SLK Surface has a smooth, glassy finish with visual evidence of striations.

Smooth SM Surface has a smooth appearance and feel.

Slightly Rough SR Asperities on the discontinuity surface are distinguishable and can be felt.

Rough RO Some ridges and side-angle steeps are evident; asperities are clearly visible, and discontinuity surface feels very abrasive.

Very Rough VR Near-vertical steps and ridges occur on the discontinuity surface.

TABLE C-7

Type of Aperture Abbreviation Characteristics

English (feet) Metric (m) Very Wide VW >10.0 >3

Wide W 3.0 – 10.0 1.0 – 3.0 Moderately Wide MW 1.0 – 3.0 0.3 – 1.0

Close C 0.2 – 1.0 0.06 – 0.3 Very Close VC >0.2 <0.06

FIELD PARAMETERS FOR DETERMINING JRC

From Hoek, et al., 1995

EXAMPLES OF DISCONTINUITIES TYPES

Bedding Plane

Orthogonal Joint


EXAMPLES OF CATCHMENT TYPES

Grueberg Fence with D-36 Barrier in front of Fence

Grueberg Fence after rock catchment

ODOT Mesh Fence

Soil Berm

Open Catchment Area with Aggregate for Energy Dissipation

Open Catchment Area

Open Catchment Area with Grouted Rip Rap

D50 Concrete Wall with rock catchment

D50 Wall with Flat Catchment Area

APPENDIX D

Examples of Rockfall Tier Locations

TIER 1 EXAMPLES

BRO-62-9.6 +/-

COMMENTS: Notice that the cut section has a relatively short back slope height and has weathered with minor overhangs that would result in small amounts of rockfall due to the slope angle. Additionally, the ditch has adequate width and geometry to catch any rockfall that may occur. It should be noted that the on the other side of the road is not a Tier 1 site, but a Tier 3 site.

BRO-68-14.9 +/-

COMMENTS: Notice that the cut section has a relatively short back slope height and has weathered with minor overhangs that would result in small amounts of rockfall due to the slope angle. Additionally, the ditch has adequate width and geometry to catch any rockfall that may occur.

Slope Height = 15 ft

Minor overhangs of bedrock

HAM-52-35.2 +/-

COMMENTS: Notice that the cut section has weathered with minor overhangs that would result in small amounts of rockfall due to the slope angle.

HAM-52-35.2 +/- (Drainage Outfall)

COMMENTS: Notice that durable layers of limestone are present within the slope. However, with the talus accumulation over the durable layer they no longer become an issue along the rock slope. Additionally, the ditch has adequate width and geometry to catch any rockfall that may occur.

HAM-74-13.2

COMMENTS: Notice that the slope has weathered uniformly with no overhangs that would result in rockfall. Additionally, the ditch has adequate width and geometry to catch any rockfall that may occur.

LIC-70-26.5 +/-

COMMENTS: Notice that the slope has weathered uniformly with minimal overhangs that would result in rockfall. Additionally, the ditch has adequate width and geometry to catch any rockfall that may occur.

Minor overhangs of bedrock

MUS-70-8.1 +/-


SCI-23-15.5


TIER 2 EXAMPLES

BRO-62-6.5 +/-

COMMENTS: Notice that the slope has weathered relatively uniformly. However, overhangs that will result in rockfall are present throughout the slope including the along the slope crest. Additionally, the ditch width and geometry may be adequate to retain the rockfall from entering onto the roadway. It should be noted that the vegetation on the slope face will help reduce the rockfall energy resulting in less rocks reaching the roadway.

GUE-77-19.5 +/-

COMMENTS: Notice that the slope has not weathered uniformly. Differential weathering between the coal layer and the overlying sandstone layer has resulted in overhang rockfall. The ditch does not appear adequate to retain all rockfall from the roadway. A major portion of the sandstone blocks are not reaching the roadway, but are being retained on the highly weathered shale and coal layers within the lower portion of the slope.

Differential Weathering

with overhang

Rockfall block retained on

slope

LIC-70-19.8 +/-

COMMENTS: Notice that the lower slope has weathered relatively uniformly with little to no areas of overhang. However, within the upper vegetated slope a relatively thick to massive resistant sandstone layer has created an overhang that will result in rockfall.

LIC-70-21.2 +/-

COMMENTS: Notice that the slope has poorly weathered probably as a result of poor construction blasting that will result in rockfall. However, the ditch width appears to be adequate to retain any rockfall.

Sandstone overhang within highly vegetated slope

HAM-74-9.4

COMMENTS: Notice that the slope has weathered relatively uniformly with overhangs that will result in rockfall. It should be noted that the shale bedrock has apparently weathered to residual soil that is failing resulting in minor slope instability.

HAM-74-9.4 (D-50 Wall)

COMMENTS: The catchment area and D50 concrete wall appears to be retaining the rockfall from entering onto the roadway.

Rockfall being

retained within the catchment

area or by the D50 wall.

TUS-77-3.0 +/-

COMMENTS: Notice that the slope has weathered relatively poorly with several sources of rockfall present. However, the 42 ft width of the catchment area appears to be adequate to retain any rockfall that may be produced prior to encroachment of the roadway.

LIC-16-29.0 +/-

COMMENTS: Notice that the majority of the slope has weathered relatively well. However, the upper and outer portions of the slope are highly weathered with several sources of rockfall present. However, the width of the ditch appears to be adequate to retain any rockfall that may be produced prior to encroachment of the roadway.

52 ft

10 ft

Highly weathered, poorly performing section(s) of slope

Highly weathered,

poorly performing section(s) of

slope

Well performing section of

slope

TIER 3 EXAMPLES

ADA-52

COMMENTS: Notice that the slope has not weathered uniformly with overhangs present that will result in rockfall. It should be noted that a regional joint set is noticeable along which large blocks or volume of rockfall will occur in the future.

` ADA-52 (Ditch line)

COMMENTS: The catmint area appears to be only a hydraulic ditch, and does not appear to be adequate to retain a large rockfall that may occur from entering onto the roadway. It should be noted that the ditch line had been recently regarded and cleaned prior to photo.

Recent rockfall

ADA-52-24.1 +/- (looking East)

ADA-52-24.1 +/- (looking West)

COMMENTS: Notice that the slope has differential weathering resulting in an overhang of the massive sandstone that will result in rockfall. Additional, the ditch does not appear to be adequate to retain the large block size that will occur during the rockfall from entering onto the roadway. It should be noted that a regional joint set is noticeable along which large blocks of rockfall will occur in the future.


Edge of Pavement

BEL-149-12.4 +/-

BEL-149-12.4 Top of slope BEL-149-12.4 Ditch COMMENTS: Notice that the slope has weathered poorly resulting in several sources that will result in rockfall. This includes the upper portion of the slope that is the natural backslope which is vegetated. Additional, the ditch dose not appears to be adequate to retain rockfall that will occur from entering onto the roadway.

Top of Cut Slope

BEL-147-33.2 +/- (Looking East)

COMMENTS: Notice that the slope has not weathered uniformly with overhangs throughout the cut slope that will result in rockfall.

BEL-147-33.2 +/- (Looking West)

COMMENTS: Notice that the hydraulic ditch has been grouted rip rap to prevent erosion during high flow events. This reduces the effectiveness of the catchment area since the grout will allow for a better “bounce” of a block instead of diminishing the rockfall.

GUE-70-4.9 +/-

GUE-70-4.9 +/-

COMMENTS: Notice that the slope has not weathered uniformly with overhangs at the top that will result in rockfall. Additional, it dose not appears that the ditch will be sufficient to retain the large blocks from the rockfall from entering onto the roadway. It should be noted that the where the highly weathered shale is present that a decrease in the rockfall reaching the ditch may occur.

Differential weathering within the rock slope

Anticipated block size during a rockfall

HAM-275-47.5 +/-

HAM-275-47.5 +/-

COMMENTS: Notice that the slope has not weathered uniformly with overhangs at the top of the cut backslope that will result in rockfall. Additional, it dose not appears that there is any ditch to retain rockfall from entering onto the roadway. It should be noted that the retaining wall is only 3 to 4 inches higher than the toe of the slope and does not appear to be affective as a rockfall catchment structure.

Rockfall from the cut back

TUS-77-5.1 (Ramp C to SR 36)

COMMENTS: Notice that the slope has not weathered uniformly with overhangs within the cut slope that will result in rockfall.

TUS-77-5.1 (Ramp C to SR 36)

COMMENTS: The catchment area does not appear adequate to retain all rockfall from the roadway. Note that several sizes of rock debris is evident within the catchment area.

Area(s) of rock overhang(s)

Typical Block Size during Rockfall

APPENDIX E

GPS Guidelines

APPENDIX E - GPS GUIDELINES

GGEENNEERRAALL The majority of the field data collected during the field evaluation of the Inventory Sites will be either collected utilizing a hand held gps unit, or referenced to coordinates collected with the hand held gps unit. Three basic types of gps data can and will be collected during the field evaluation of the Inventory Site. These data types are points, lines, and areas. The following sections outline the basic parameters and guidelines established for the field work associated with the Rockfall Inventory. GGPPSS GGEENNEERRAALL PPAARRAAMMEETTEERRSS Prior to collection of any gps data, make sure the Trimble GeoExplorer (or similar unit) is utilizing its WASS correction. A minimum of four satellites with a minimum elevation mask of 15º is required for an adequate signal. A PDOP (Position Dilution Of Precision) of less than six and a SNR (Signal to Noise Ratio) of greater than 39 is required. The antenna should always be held parallel to the ground at a constant height, approximately chest level. GGPPSS PPOOIINNTTSS A single referenced item, such as a seep, centroid location, etc, will be collected as a gps point. A gps point should be collected utilizing the hand held Trimble unit set to a one second log interval. This means that a data reading is collected every second. A minimum of twenty readings should be collected to establish the point. Start collecting the data readings and hold the gps unit as steady as possible until the required number of readings have been collected then stop of the readings. The recorded gps point will consist of the averaged value of the data readings collected. GGPPSS PPOOIINNTTSS OOFFFFSSEETTSS If an insufficient signal is present to collect the gps point (refereed to as the reference gps point) the point can be offset. To offset the gps point, find a location which is relatively close where the gps signal is adequate. At this area, collect a gps point as just outlined. Then with a compass obtain a bearing from where the gps point was collected to where the reference gps point should have been collected. The bearing is a whole degree azmuth reading from north. Then measure the distance from the area that the gps point was collected to the reference gps point. From the collected gps point, the bearing and offset distance can be used to calculate the reference gps point.

GGPPSS LLIINNEESS A horizontal feature, such as a spring line or seep line, will be collected as a gps line. A gps point should be collected utilizing the hand held Trimble unit set to a five second log interval. This means that a data reading is collected every five seconds. Start collecting data readings at one end of the horizontal feature and walk at a steady pace parallel to the feature to the opposite end where the data readings should be stopped. The gps line will consist of a “normalized line” of the readings collected. If the Field Team is unable to collect the readings on top of the horizontal features, the offset function should be utilized. GGPPSS AARREEAASS An area feature, such as a seep zone, will be collected as a gps area. A gps area should be collected utilizing the hand held Trimble unit set to a five second log interval. This means that a data reading is collected every five seconds. Start collecting data readings at one point of the area feature and walk at a steady pace along the perimeter of the area until the area has been outlined where the data readings should be stopped. The gps area will consist of a polygon based upon the readings collected. If the Field Team is unable to collect the readings at the area features, the offset function should be utilized.

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