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Soil Dynamics and Geotechnical Earthquake Engineering ...
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Dynamic soil properties Soil Dynamics and Geotechnical Earthquake Engineering Joint PhD "Geo-Engineering and Water Management" Assist.Prof. STANISLAV LENART [email protected]
Transcript of Soil Dynamics and Geotechnical Earthquake Engineering ...
Dynamic soil properties
Soil Dynamics and Geotechnical Earthquake Engineering
Joint PhD "Geo-Engineering and Water
Management"
Assist.Prof. STANISLAV LENART
Content
• Introduction
• Laboratory tests on dynamic properties of soils
• Field test measurements
• Shear modulus & Damping ratio
• Stress-strain modeling
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INTRODUCTION
Soil properties needed for analysis of dynamic
loaded geotechnical structures:
- Soil density, ρ
- Poisson ratio, ν- Shear modulus, G
- Damping ratio, D
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kuucumtF ++= &&&)(
Strain dependency
LABORATORY TESTS
Low strain tests:
• Resonant column test
• Ultrasonic pulse test
• Bender element test
High strain tests:
• Cyclic simple shear test
• Cyclic torsional simple shear test
• Cyclic triaxial test
Model tests:
• Shaking table tests
• Centrifuge tests
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Hysteresis loop
Shear modulus, Damping ratio
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FIELD TEST MEASUREMENTS
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vs, vp
Soil behavior at different strain levels
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Elastic threshold
shear strain
Volumetric threshold
shear strain
(Vucetic, 1994)
Soil behavior at different strain levels
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Factors affecting deformationproperties of soil
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Strain range: γ ↑ ⇒ D ↑, G ↓
Void ratio: e ↑ ⇒ G0 ↓
Effective stress: σ ↑ ⇒ G0 ↑, G ↑, D ↓
Time after completion of primary consolidation:t ↑ ⇒ G0 ↑
Moisture content: w ⇒ G0 , D
Overconsolidation: OCR ⇒ G0 ↑
Plasticity index: Ip↑ ⇒ G ↑, D ↓
Strain rate (γ > γtv) v ↑ ⇒ G ↑
Number of load cycles (γ > γtv) :
N ↑ ⇒ G ↓
SHEAR MODULUS & DAMPING RATIO
Shear modulus reduction curve
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SHEAR MODULUS & DAMPING RATIO
Shear modulus reduction curve
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SHEAR MODULUS & DAMPING RATIO
Damping ratio variation dependence upon density
and confining stress
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SHEAR MODULUS & DAMPING RATIO
Damping ratio variation dependence upon index
plasticity
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SHEAR MODULUS & DAMPING RATIO
Initial shear modulus as function of void ratio and
effective confining stress
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Applicability of different strain range
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STRESS-STRAIN MODELING
• Equivalent linear model (e.g. SHAKE)
• Cyclic nonlinear models
– Extended Masing Models (rules for initial loading,
unloding, reloading)
– Advanced Constitutive Models (yield surface,
hardening law, flow rule), usualy requires more
parameters
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