mannu soil irumbu thanmai stiffness
DESCRIPTION
MAANNIN IRRRUMBU THANMAITRANSCRIPT
Determination of Soil Stiffness Parameters
Short Course on Computational Geotechnics + DynamicsBoulder, ColoradoJanuary 5-8, 2004
Stein StureProfessor of Civil EngineeringUniversity of Colorado at Boulder
Contents
General concepts and stiffness of sandHooke’s law
E-moduli from triaxial testing
E-moduli from oedometer testing
Examples on the estimation of E
Stiffness of claysUndrained clay behavior
Drained clay behavior
Examples on the estimation of E
Computational Geotechnics Determination of Soil Stiffness Parameters
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
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
Hooke’s Law of Isotropic Elasticity
Computational Geotechnics Determination of Soil Stiffness Parameters
Hooke’s Law of Isotropic Elasticity
Computational Geotechnics Determination of Soil Stiffness Parameters
Standard Drained Triaxial Test on Sand
Computational Geotechnics Determination of Soil Stiffness Parameters
Standard Drained Triaxial Test on Sand
Computational Geotechnics Determination of Soil Stiffness Parameters
Oedometer Test on Sand
Computational Geotechnics Determination of Soil Stiffness Parameters
Oedometer Test on Sand
Computational Geotechnics Determination of Soil Stiffness Parameters
Oedometer Test on Sand
Hooke:
Loose:
Dense:
oedoed EEE3
2)21(
1
1
( 13)
ref
y
ref pp
E
3
2150
ref
y
ref pp
E
3
2500
Computational Geotechnics Determination of Soil Stiffness Parameters
Oedometer Test on Sand
y'
x'
K0
2 x'
refx
refx
ref ppp
E
15023
2150
refx
refx
ref ppp
E
50023
2500
E E50
Loose:
Dense:
This implies:
Computational Geotechnics Determination of Soil Stiffness Parameters
Summary on Stiffness Parameters: Sand
(Laboratory based experience)
E E50 2
3Eoed
13
E
pref150
x'
pref
E
pref500
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
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
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
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
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
Idealized and real stress-strain behavior of soils
Computational Geotechnics Determination of Soil Stiffness Parameters
Idealized and real stress-strain behavior of soils
Computational Geotechnics Determination of Soil Stiffness Parameters
Plate Loading Tests
Duncan & Buchignani (1976)
Computational Geotechnics Determination of Soil Stiffness Parameters
Plate Loading Tests
Computational Geotechnics Determination of Soil Stiffness Parameters
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
Drained Behavior for Clays
Computational Geotechnics Determination of Soil Stiffness Parameters
Drained Behavior for Clays
Computational Geotechnics Determination of Soil Stiffness Parameters