Evaluation of Geotechnical Data15:00-15:50

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Evaluation Step

Geometric modeling

ParametersDetermination

Foundation design

Geotechnical investigation Data check

qu, E

c, Cc, py

Evaluation for Geotechnical Design

Instrumentation

Geometric modeling

geology

topographyBorehole DataBorehole locations

Material types

Depth, thickness

Nearby borehole information

Nearby construction records

Geotechnical databases

Preliminary geometric model based on existing information and reconnaissance site visits

Add new investigation results

Revised Geometric model for the site

Construction of Geometric Model

Example of Topographic Feature: Fan

Travel distanceGravel: shortSandSiltClay : long

Expected ground conditions?

Example of Topographic Feature: Delta Slope angle

Fan: large

Delta: small

Expected ground conditions?

Example of Topographic Feature: Meandering River

Slope angle

Fan: large

Delta: small

Meandering river: very small

Expected ground conditions?

Flood plane

Natural levee

Post Glacial Sea Level ChangesErosion phase to sedimentation phase

1km

Published Information

Example of Geological Map

Published Information

Example of Topographic Classification Map

Published Information

Example of Topographic Classification Map

Published Information

Example of Map showing Bottom of Holocene Deposits

Published Information

Example of Soil Cross Section

Section C-C

Data check – reliability for models and properties

During investigation at the site

Checking tools and equipment

Checking methods (application of standards)

During or after investigation at remote offices

Photographs of tools and equipment

Photographs of methods (application of standards)

After investigation at offices

Check: Variation due to different drillers

(Same soil layer – similar soil properties)

Evaluation of undisturbed soil samples

Comparison with data obtained in the past

Determination of model properties

Quantity of data

No data

A few data

Abundant data

How to determine soil parameters?

Are you comfortable with a small number of data?

• variable nature of ground

• what kind of risk ?

Variation of properties in vertical direction

in horizontal direction

Look at water contentwater content distribution Cheap tests

Tested on disturbed soil

Sensitive to change in soil types

Importance of RedundancyThere are variety of uncertainties

testing methods and procedures

sample disturbance

spatial variation of soil properties

Double check and triple check by:

using different method of investigations

increasing number of tests

numb

ers

Variable

Average

: standard deviation

Statistical considerationDesign value = average value?

Design value = average value – one standard deviation?

Design value = average value – 0.5 standard deviation?

Safety and design risk

Effects of failure

Interpretation of quality of soft cohesive soil samples