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Determination of Soil Stiffness Parameters Short Course on Computational Geotechnics + Dynamics Boulder, Colorado January 5-8, 2004 Stein Sture Professor of Civil Engineering University of Colorado at Boulder

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Page 1: Determination of Soil Stiffness Parametersceae.colorado.edu/~sture/plaxis/slides/Soi… · PPT file · Web view · 2004-01-05Determination of Soil Stiffness Parameters ... Average

Determination of Soil Stiffness Parameters

Short Course on Computational Geotechnics + DynamicsBoulder, ColoradoJanuary 5-8, 2004

Stein StureProfessor of Civil EngineeringUniversity of Colorado at Boulder

Page 2: Determination of Soil Stiffness Parametersceae.colorado.edu/~sture/plaxis/slides/Soi… · PPT file · Web view · 2004-01-05Determination of Soil Stiffness Parameters ... Average

Contents

General concepts and stiffness of sandHooke’s lawE-moduli from triaxial testingE-moduli from oedometer testingExamples on the estimation of E

Stiffness of claysUndrained clay behaviorDrained clay behaviorExamples on the estimation of E

Computational Geotechnics Determination of Soil Stiffness Parameters

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Idealized and real stress-strain behavior of soils

Idealized types of stress-strain behaviors: (a) nonlinear elasticModel, (b) linear elastic model, and (c) elastoplastic model

Computational Geotechnics Determination of Soil Stiffness Parameters

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Idealized and real stress-strain behavior of soils

Various types of elastoplastic behaviors: (a) strain hardening, (b) perfectly plastic, (c) strain softening, and (d) combination of a to c.

Computational Geotechnics Determination of Soil Stiffness Parameters

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Hooke’s Law of Isotropic Elasticity

Computational Geotechnics Determination of Soil Stiffness Parameters

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Hooke’s Law of Isotropic Elasticity

Computational Geotechnics Determination of Soil Stiffness Parameters

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Standard Drained Triaxial Test on Sand

Computational Geotechnics Determination of Soil Stiffness Parameters

Page 8: Determination of Soil Stiffness Parametersceae.colorado.edu/~sture/plaxis/slides/Soi… · PPT file · Web view · 2004-01-05Determination of Soil Stiffness Parameters ... Average

Standard Drained Triaxial Test on Sand

Computational Geotechnics Determination of Soil Stiffness Parameters

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Oedometer Test on Sand

Computational Geotechnics Determination of Soil Stiffness Parameters

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Oedometer Test on Sand

Computational Geotechnics Determination of Soil Stiffness Parameters

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Oedometer Test on Sand

Hooke:

Loose:

Dense:

oedoed EEE32)21(

11

( 13)

refy

ref ppE

32150

refy

ref ppE

32500

Computational Geotechnics Determination of Soil Stiffness Parameters

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Oedometer Test on Sand

y'

x'

K0

2 x'

refx

refx

ref pppE

150232150

refx

refx

ref pppE

500232500

E E50

Loose:

Dense:

This implies:

Computational Geotechnics Determination of Soil Stiffness Parameters

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Summary on Stiffness Parameters: Sand

(Laboratory based experience)

E E50 23Eoed

13

Epref

150 x'

pref

Epref

500 x'

pref

E E ref x'

pref

E 15MPa x'

pref

E 50MPa x'

pref

pref 100kPa

Loose:

Dense:

Loose:

Dense:

Unloading: About 4 times stiffer. smallComputational Geotechnics Determination of Soil Stiffness Parameters

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Selection of Moduli for FEM-Computation

E50ref 15MPa

y0

/ 70kPa

y' 50kPa

y' 95kPa

x' 50kPa

E50 15000 0.5 10000kPa

Layer 1 (extremely loose sand

Layer 1:

Average

Mohr-Coulomb model:

Example 1 (loading):

Computational Geotechnics Determination of Soil Stiffness Parameters

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Selection of Moduli for FEM-ComputationExample 2 (unloading):

E50ref 45MPa

E50ref 30MPa

15.0,4 50 refrefur EE

y' 21.5' 55kPa

x' 27.5kPa

E 4 45000 27.5100 95000kPa

x' 10kPa kPaE 3800010.0300004

Layer 1 (dense): Layer 3 (medium):

Unloading: for both layers

Mohr-Coulomb model:

Layer 1:

Layer 3:

Computational Geotechnics Determination of Soil Stiffness Parameters

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Eoed from Cone Penetration Test in Sands

qc

Eoed qc

= 1 to 3

= 3

refcoed pqE )1030(

Cone Resistance:

Correlation:

Literature NC-Sand:

Vermeer’s Experience:

Alternatively:

Computational Geotechnics Determination of Soil Stiffness Parameters

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Undrained Triaxial Test on Clay

Eu50

15000CuIp%

Eu50 3G50

Normally consolidated clay:

Cu = undrained shear strength (or Su)

Computational Geotechnics Determination of Soil Stiffness Parameters

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Idealized and real stress-strain behavior of soils

Computational Geotechnics Determination of Soil Stiffness Parameters

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Idealized and real stress-strain behavior of soils

Computational Geotechnics Determination of Soil Stiffness Parameters

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Plate Loading Tests

Duncan & Buchignani (1976)Computational Geotechnics Determination of Soil Stiffness Parameters

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Plate Loading Tests

Computational Geotechnics Determination of Soil Stiffness Parameters

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Summary on Stiffness Parameters: ClayUndrained Conditions

Do not use empirical relationships only. Get good quality experimental data from lab tests, cone penetration tests and vane tests

Computational Geotechnics Determination of Soil Stiffness Parameters

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Drained Behavior for Clays

Computational Geotechnics Determination of Soil Stiffness Parameters

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Drained Behavior for Clays

Computational Geotechnics Determination of Soil Stiffness Parameters