Subsurface Investigation and Geotechnical Evaluation
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Transcript of Subsurface Investigation and Geotechnical Evaluation
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NYSCHSA
January 22, 2013
Subsurface Investigation
and
Geotechnical Evaluation
Atlantic Testing Laboratories
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Designing a Subsurface Investigation Program
Subsurface Investigation Methodologies
Subsurface Investigation Log Review
CPT Log Review
Soil Classifications
Engineering Properties of Soil
Geotechnical Evaluation
Topics
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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
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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
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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)
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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)
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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
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Subsurface Investigation Methodologies
Conventional Soil Borings
Cone Penetration
Testing (CPT)
Geoprobe
Test Pits
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Conventional Drilling
Hollow Stem Augers
Flush Joint Casing
Split Spoon Sampling
Undisturbed Samples
Bedrock Coring
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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
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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
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Split Spoon Sampling
In accordance with ASTM D 1586
Sample for soil classification and future
laboratory testing
Retained in sealed glass jars
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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
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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
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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
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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
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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
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Typical CPT Log
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Cone Penetration Testing
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Data: Environmental
Sampling, Soil
Classification, Bedrock
Profile, and Groundwater
Elevation
Geoprobe
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Geoprobe
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Test Pits
Advantages
Good for fill sites
Groundwater
information
Collect bulk samples
Disadvantages
Limited depth
Cannot determine
Seismic Site
Classification
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Subsurface Investigation Log Review
Contain a wealth of information
Soil types
Soil consistency
Groundwater information
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Soil Classification
Several Systems Used
Burmister
Unified Soil Classification System
NYSDOT
USDA
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Burmister Soil Classification
Visual-manual procedure
Performed by the drillers in the field
Soil classification verified in the laboratory
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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
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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
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Unified Soil Classification
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Engineering Properties of Soil
Natural Moisture Content
Atterberg Limits Liquid Limit
Plastic Limit
Plasticity Index
Shear Strength
Internal Friction Angle
Consolidation Potential
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Soil Property Uses
Bearing Capacity
Lateral Earth Pressures
Slope Stability
Frost Heave Potential
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Geotechnical Evaluation
Geotechnical Report Contents
Optional Services
Site Visit
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Thank You
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Question & Answer
How deep can you
drill with hollow stem
augers?
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Question & Answer
In what type of soil
conditions is a
Shelby Tube most
conducive?
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Question & Answer
Does a 100 foot
boring need to be
drilled to determine
the seismic site
classification?
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Question & Answer
True or False:
Determining the
groundwater
table is extremely
important.
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Question & Answer
What type of soil parameter
does Cone Penetration
Testing (CPT) determine that
conventional soil borings can
not?
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Thank You