subsurface investigation and geotechnical evaluation

NYSCHSA

January 22, 2013

Subsurface Investigation

and

Geotechnical Evaluation

Atlantic Testing Laboratories

Designing a Subsurface Investigation Program

Subsurface Investigation Methodologies

Subsurface Investigation Log Review

CPT Log Review

Soil Classifications

Engineering Properties of Soil

Geotechnical Evaluation

Topics

Designing a Subsurface Investigation

Determining the Number of Soil Borings

Former NYS Building Code

The Building Code of NYS 2002 (based on IBC 2000)

As a Rule of Thumb – 1 Boring for every 2,500 to 5,000 s.f.

of building footprint

Seismic Site Classification Determination

Code does not require a 100 foot boring

Calculate the average soil properties in the

top 100 feet. (either soil shear wave velocity,

Standard Penetration resistance, of soil

undrained shear strength)

Section 1615.1.1 allows the register design

professional to assume based on knowledge

of local geology

Seismic Site Classification Determination

Use table 1615.1.1 to determine Seismic Site

Classification (class A, B, C, D, E, or F)

Obtain the maximum considered earthquake ground

motion of 0.2 sec spectral response (Ss)

Obtain the maximum considered earthquake ground

motion of 1 sec spectral response (S1)

Seismic Site Classification Determination

Can be obtained from the maps in the code, the CD prepared by ICC, or USGS web page

Adjust Ss and S1 based on coefficients presented in Tables 1615.1.2(1) and 1615.1.2(2)

Seismic Site Classification Determination

Central New York sites typically fall into site class B, C, or D

Glacial till and/or bedrock is often found at shallow depths.

Exception is Onondaga Lake area, bedrock and/or glacial till in excess of 300 feet

Subsurface Investigation Methodologies

Conventional Soil Borings

Cone Penetration

Testing (CPT)

Geoprobe

Test Pits

Conventional Drilling

Hollow Stem Augers

Flush Joint Casing

Split Spoon Sampling

Undisturbed Samples

Bedrock Coring

Hollow Stem Augers

Auger Flights around a center sampling tube

Size refers to diameter of

sampling tube

Advantages

Quick

More Economical

Water not necessary

Ability to collect bulk samples

Flush Joint Casing

Can be Driven or Spun-in the ground

Advantages

Can be advanced through

cobbles and boulder

Can be advanced to depths

of around 300 feet

Provides a stable hole for

special testing such as

permeability testing

Split Spoon Sampling

In accordance with ASTM D 1586

Sample for soil classification and future

laboratory testing

Retained in sealed glass jars

Undisturbed Samples

In accordance with ASTM D 1587

Obtained from cohesive soils

Returned to the laboratory for multiple analyses

Provides accurate representation of in-situ conditions

Bedrock Coring

In accordance with ASTM D 2113

Double tubed core barrel with a diamond

cutting shoe

Samples are returned for classification, RQD

determination, and laboratory analysis

Cone Penetration Testing

Pushes a “cone” with electronic sensors

In accordance with ASTM D 3441

Determines:

Tip resistance

Side friction

Pore water pressure

Seismic shear wave velocity

Cone Penetration Testing

Advantages

Rapid: Can advance 200 to 400 feet per day

Accurately determines to Seismic Site Classification

Replicates pile driving

Useful in cohesive and sand soils

Cone Penetration Testing

Disadvantages

Not able to be pushed in dense soils or bedrock

No sample recovered, soil classifications relies on soil properties

Requires a large drill rig for reaction weight

Typical CPT Log

Cone Penetration Testing

Data: Environmental

Sampling, Soil

Classification, Bedrock

Profile, and Groundwater

Elevation

Geoprobe

Geoprobe

Test Pits

Advantages

Good for fill sites

Groundwater

information

Collect bulk samples

Disadvantages

Limited depth

Cannot determine

Seismic Site

Classification

Subsurface Investigation Log Review

Contain a wealth of information

Soil types

Soil consistency

Groundwater information

Soil Classification

Several Systems Used

Burmister

Unified Soil Classification System

NYSDOT

USDA

Burmister Soil Classification

Visual-manual procedure

Performed by the drillers in the field

Soil classification verified in the laboratory

Burmister Soil Classification

BOULDERS: > 12” Particle Size

COBBLES: 3” – 12” Particle Size

GRAVEL: Course: 3” - 1” Sieve Size

Medium: 1” – ½” Sieve Size

Fine: ½” - #4 Sieve Size

SAND: Course: #4 - #10 Sieve Size

Medium: #10 - #40 Sieve Size

Fine: #40 - #200 Sieve Size

SILT: #200 Sieve (0.074 mm) to 0.005 mm

CLAY: <0.005 mm Particle Size

Unified Soil Classification System

In accordance with ASTM D 2487 and ASTM

D 2488

ASTM D 2487 - laboratory analysis

ASTM D 2488 - visual manual procedure

performed in laboratory

Unified Soil Classification

Engineering Properties of Soil

Natural Moisture Content

Atterberg Limits Liquid Limit

Plastic Limit

Plasticity Index

Shear Strength

Internal Friction Angle

Consolidation Potential

Soil Property Uses

Bearing Capacity

Lateral Earth Pressures

Slope Stability

Frost Heave Potential

Geotechnical Evaluation

Geotechnical Report Contents

Optional Services

Site Visit

Thank You

Question & Answer

How deep can you

drill with hollow stem

augers?

Question & Answer

In what type of soil

conditions is a

Shelby Tube most

conducive?

Question & Answer

Does a 100 foot

boring need to be

drilled to determine

the seismic site

classification?

Question & Answer

True or False:

Determining the

groundwater

table is extremely

important.

Question & Answer

What type of soil parameter

does Cone Penetration

Testing (CPT) determine that

conventional soil borings can

not?

Thank You