exploring and constructing on sites underlain by colluvial ... · rockline s.i. datums.i. datum...

EE NN GG NN EEII EE RR SSGeohazards in Transportation

In the Appalachian Region Geohazards in Transportation Geohazards in Transportation

In the Appalachian Region In the Appalachian Region

Colluvial DepositsColluvial Deposits




Exploring and ConstructingExploring and Constructingon Sites Underlain by on Sites Underlain by

Colluvial Deposits Colluvial Deposits in thein the

Eastern Kentucky CoalfieldsEastern Kentucky Coalfields

Colluvial Deposits




!! Typical initial assumptions in preparing Typical initial assumptions in preparing subsurface explorations of highway cuts in subsurface explorations of highway cuts in Eastern KentuckyEastern Kentucky

!! Typical actual conditions and cut slope designTypical actual conditions and cut slope design!! Cut slope design within Cut slope design within atypicalatypical bedrock bedrock

conditions conditions !! UhUh--oh, where is bedrock?oh, where is bedrock? Welcome to Welcome to

colluvium colluvium !! Deposition of colluviumDeposition of colluvium!! Design of cut slopes in colluvial depositsDesign of cut slopes in colluvial deposits!! SummarySummary

Presentation OutlinePresentation Outline




Typical Initial Assumptions in Preparing Typical Initial Assumptions in Preparing Subsurface Explorations of Highway Subsurface Explorations of Highway

Cuts in Eastern KentuckyCuts in Eastern Kentucky

Roadway Roadway TemplateTemplate

Assumed Cut Slope Line Assumed Cut Slope Line (1.2H:1V) to Determine (1.2H:1V) to Determine Approximate Top Approximate Top Boring LocationBoring Location

Existing Existing GroundlineGroundline




Typical Design Slope ConfigurationsTypical Design Slope Configurations

Class III Nondurable Shale Class III Nondurable Shale (KY DOH Geotechnical Manual)(KY DOH Geotechnical Manual)

Class III Class III Nondurable Nondurable

ShaleShaleBase of RDZBase of RDZ

Original GroundlineOriginal Groundline

2:1 (or flatter)

2:1 (or flatter)




CoalCoal

Base of RDZBase of RDZ

Original GroundlineOriginal Groundline2:12:1

Roadside Ditch BenchRoadside Ditch Bench1/

4:1

1/4:

1

1/4:

11/

4:1

1/4:

11/

4:1

1/2:

11/

2:1

1818’’ IBIB

1818’’ IBIB

2020’’ IBIB

4040’’

3030’’

3030’’


Durable Shale Durable Shale (KY DOH Geotechnical Manual)(KY DOH Geotechnical Manual)




Base of RDZBase of RDZ 2:12:1

Roadside Ditch Roadside Ditch & Bench& Bench

1/2:

11/

2:1

1818’’ or 20or 20’’ IBIB

31.5

31.5

’’39

.539

.5’’

1/2:

11/

2:1

1515’’ OBOB

1414’’

Original GroundlineOriginal Groundline


Shaley Limestone or Sandstone Shaley Limestone or Sandstone (KY DOH Geotechnical Manual)(KY DOH Geotechnical Manual)




Base of RDZBase of RDZ

Original GroundlineOriginal Groundline2:12:1

Roadside Ditch Roadside Ditch & Bench& Bench

1:20

1:20

2020’’ IBIB 104

104 ’’

5252’’

1/2:

11/

2:1

1515’’ OBOB

1414’’

CoalCoal

ShaleShale

Intermediate Intermediate Bench on ShaleBench on Shale

2020’’ IBIB1:

201:

20

3030’’

Lift

Lift

(max

.)(m

ax.)


Massive Limestone or Sandstone Massive Limestone or Sandstone (KY DOH Geotechnical Manual)(KY DOH Geotechnical Manual)




Typical Rock Slope DesignTypical Rock Slope Design

Recommended Cut Recommended Cut Slope DesignSlope Design



Rock Disintegration Rock Disintegration Zone (RDZ)Zone (RDZ)




Typical Completed Rock CutTypical Completed Rock Cut




U.S. 119 Across Bent Mountain U.S. 119 Across Bent Mountain Pike County, KentuckyPike County, Kentucky




Atypical Bedrock ConditionsAtypical Bedrock Conditions

PhPhPcPc

PmPm

popo

crcrtmtmtt

cocoimim

Pine MountainPine Mountain

Poor

For

k Po

or F

ork

Cum

berla

nd R

iver

Cum

berla

nd R

iver

Pine

Mou

ntai

n Pi

ne M

ount

ain

Ove

rthr

ust F

ault

Ove

rthr

ust F

ault

Cow

an C

reek

Cow

an C

reek

Strip BenchStrip Bench

3200 3200 2800 2800 2400 2400 2000 2000 1600 1600 1200 1200 800 800 400400

3200 3200 2800 2800 2400 2400 2000 2000 1600 1600 1200 1200 800 800 400400

PhaPha QalQalQalQal

Geologic Cross Section of Pine MountainGeologic Cross Section of Pine Mountain




Rock Disintegration Rock Disintegration Zone (RDZ)Zone (RDZ)

Cut Slope Design Within Atypical Cut Slope Design Within Atypical Bedrock ConditionsBedrock Conditions

23 degree 23 degree DipDip


Assumed Cut Slope Line (1.2H:1V) to Determine Top Boring Location

Assumed Cut Slope Line Assumed Cut Slope Line (1.2H:1V) to Determine (1.2H:1V) to Determine Top Boring LocationTop Boring LocationRecommended Recommended

Cut Slope DesignCut Slope Design





UhUh--oh, Where is Bedrock?oh, Where is Bedrock?



Assumed Cut Slope Line (1.2H:1V) to Determine Top Boring Location

Assumed Cut Slope Line Assumed Cut Slope Line (1.2H:1V) to Determine Top (1.2H:1V) to Determine Top Boring LocationBoring Location

Recommend Cut Slope Recommend Cut Slope (Coincident with Interpolated (Coincident with Interpolated

Base of RDZ)Base of RDZ)

Colluvial DepositColluvial DepositColluvial Deposit




Deposition of ColluviumDeposition of Colluvium

Talus: coarse debris, accumulates on a slope Talus: coarse debris, accumulates on a slope at the foot of a cliff as a gravity deposit.at the foot of a cliff as a gravity deposit.

Colluvium: a mantle of loose material that Colluvium: a mantle of loose material that moves by creep down a hillside. moves by creep down a hillside.

BedrockBedrockTalusTalus

BedrockBedrockBedrockBedrock

In some places creep is indicated by the In some places creep is indicated by the bending of trees.bending of trees.

ColluviumColluvium




One EngineerOne Engineer’’s Opinion Ons Opinion On……

……How Colluvium was Deposited in How Colluvium was Deposited in the Eastern Kentucky Coalfieldsthe Eastern Kentucky Coalfields

Shale (Typ.)Shale (Typ.)

Coal (Typ.)Coal (Typ.)

Sandstone (Typ.)Sandstone (Typ.)

ColluviumColluviumTalusTalusCreepCreep

Shale (Typ.)Shale (Typ.)

Coal (Typ.)Coal (Typ.)

Sandstone (Typ.)Sandstone (Typ.)




Exploration and Design of Cut Slopes Exploration and Design of Cut Slopes in Colluviumin Colluvium

Belfry Landslide Next to U.S. 119 Belfry Landslide Next to U.S. 119 Pike County, KentuckyPike County, Kentucky




Belfry Landslide Belfry Landslide –– Available Geological Available Geological Information Information

U.S.G.S. Geological Mapping U.S.G.S. Geological Mapping (Belfry Quadrangle)(Belfry Quadrangle)

AlluviumAlluvium




US 119US 119

Slid

e Sl

ide

Mov

emen

tM

ovem

ent

950950’’(NTS)(NTS)

Approx. Limits Approx. Limits of Disturbanceof Disturbance

Top of ScarpTop of Scarp

Bulging Bulging AreaArea

Approx. Seep Approx. Seep LocationLocation

SeepSeep

Drainpipe Drainpipe (Exposed)(Exposed)

Drainpipe Drainpipe (Underground)(Underground)

Typical SectionTypical Section

BB--1 1 (MW(MW--1)1)

BB--3 3 (SI(SI--1)1)

BB--22

BB--5 5 (MW(MW--2)2)

BB--6 6 (MW(MW--3)3)

BB--4 4 (SI(SI--2)2)

BB--77

BB--99

BB--8 8 (SI(SI--3)3)

Pond Creek Pond Creek Mine Adit Mine Adit Elev. 841.0Elev. 841.0’’

Hill

cres

t D

rive

Hill

cres

t D

rive

Belfry Landslide, Pike County, KentuckyBelfry Landslide, Pike County, Kentucky

(Kentucky AML Project)(Kentucky AML Project)

Top of ScarpTop of Scarp

Scarp at RoadScarp at Road

Toe of SlideToe of Slide




Using Slope Inclinometer InformationUsing Slope Inclinometer Information……

Boring 2Boring 2 Boring 3 Boring 3 (SI(SI--1)1)

Boring 3 Boring 3 (SI(SI--1)1)

Boring 9Boring 9



Smith Smith ResidenceResidence

Scott Scott ResidenceResidence

Top of Top of ScarpScarp

Toe of Toe of DisturbanceDisturbance

Interpolated Interpolated Failure PlaneFailure Plane

Interpolated Interpolated RocklineRockline

S.I.

Dat

umS.

I. D

atum

S.I.

Dat

umS.

I. D

atum

1.01.0””

Slope Slope Inclinometer Inclinometer

ScaleScale

Slope Inclinometer Slope Inclinometer MovementMovement



1.51.5””

S.I.

Dat

umS.

I. D

atum

3.53.5””

0.40.4””

Belfry Landslide Belfry Landslide -- Typical Cross SectionTypical Cross Section

……to Determine Approximate Failure Plane Location and to Determine Approximate Failure Plane Location and Calculate Residual Shear Strength of ColluviumCalculate Residual Shear Strength of Colluvium

To U.S. 119To U.S. 119

Existing GroundlineExisting Groundline

8989’’

6161’’

8989’’2121’’




Slope Inclinometer Equipment Slope Inclinometer Equipment (Slope Inclinometer Company)(Slope Inclinometer Company)

CasingCasing CasingCasing Casing InstallationCasing Installation Probe and CableProbe and Cable

Probe Inside CasingProbe Inside Casing Readout / RecorderReadout / Recorder Inclinometer Data PlotInclinometer Data Plot




!! Undisturbed Colluvium deposits are metastable due to the nature Undisturbed Colluvium deposits are metastable due to the nature of of their depositiontheir deposition

!! Most of the deep soil deposits encountered on the hillsides of Most of the deep soil deposits encountered on the hillsides of Appalachia are probably ColluviumAppalachia are probably Colluvium

!! The composition of this Colluvium varies significantly horizontaThe composition of this Colluvium varies significantly horizontally and lly and vertically within a few feet, if not a few inches vertically within a few feet, if not a few inches

!! It is impractical to evaluate the shear strength of Colluvium usIt is impractical to evaluate the shear strength of Colluvium using ing standard testing methods standard testing methods

!! Slight changes to the geometry and/or ground water conditions ofSlight changes to the geometry and/or ground water conditions of the the slopes underlain by Colluvium can cause displacement or failureslopes underlain by Colluvium can cause displacement or failure

!! Three options to modify or stabilize Colluvium deposits on hillsThree options to modify or stabilize Colluvium deposits on hillside:ide:•• Complete removal of undisturbed or failed depositsComplete removal of undisturbed or failed deposits•• Install retaining structure socketed or anchored in bedrock to Install retaining structure socketed or anchored in bedrock to

prevent movementprevent movement•• Regrade slope based on Slope Inclinometer information when slopeRegrade slope based on Slope Inclinometer information when slope

failure has already occurredfailure has already occurred

SummarySummary

exploring and constructing on sites underlain by colluvial ... · rockline s.i. datums.i. datum...

Documents