Critical state strength parameters of saturated clays from the modified Cam clay model

Chang, Ming-Fang; Teh, C. I.; Cao, Laifa

doi:10.1139/cgj-36-5-876

Cited by 5 publications

(5 citation statements)

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“…Traditional constitutive models for clays, such as two versions of the Cam‐clay models that were developed based on critical state theory, assume that the yield surfaces are symmetrical with respect to hydrostatic axis p in the p ‐ q plane. These traditional models or their variants can simulate the correct trends for isotropically consolidated clays and have achieved wide success in the last several decades . However, these isotropic models have been less successful in simulating the behaviors of soils subjected to either the k 0 condition or anisotropic consolidation history because the initial yield surfaces are aligned along the p axis and only isotropic hardening is considered during shearing.…”

Section: Introductionmentioning

confidence: 99%

A bounding surface model for anisotropically overconsolidated clay incorporating thermodynamics admissible rotational hardening rule

Chen

Yang

2019

Num Anal Meth Geomechanics

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Summary A bounding surface model is formulated to simulate the behavior of clays that are subject to an anisotropic consolidation stress history. Conventional rotational hardening is revisited from the perspective of thermodynamics. As the free energy cannot be accumulated infinitely upon critical state failure, the deviatoric back stress must vanish. This requires the rotated yield surface to be turned back to eventually align on the hydrostatic axis in the stress plane. Noting that most of the previous propositions violate this restriction, an innovative rotational hardening rule is formulated that is thermodynamically admissible. The bounding surface framework that employs the modified yield surface is applied to simulate elastoplastic deformations for overconsolidated clays, with which the overprediction of strength on the “dry” side can be greatly improved with reasonable results. Other important features, including contractive or dilative response and hardening or softening behavior, can also be well‐captured. It has been shown that the model can simulate three types of reconstituted clays that are sheared with initial conditions over a wide range of anisotropic consolidation stress ratios and overconsolidation ratios under both triaxial undrained and drained conditions. Limitations and potential improvement of the model regarding the fabric anisotropy at critical state have been discussed.

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Section: Introductionmentioning

confidence: 99%

A bounding surface model for anisotropically overconsolidated clay incorporating thermodynamics admissible rotational hardening rule

Chen

Yang

2019

Num Anal Meth Geomechanics

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“…Because values determined from triaxial tests and thus strictly not applicable to a plane strain problem, a sensitivity run was conducted with lower M values. These reduced M values (0.77 for the SB clay and prism and 1.03 for the trench and LSB turbidites) consider that plane strain ϕ ′ values are approximately 8% greater than those from triaxial tests and that M = √3 sin ϕ ′ for plane strain tests [ Chang et al , 1999].…”

Section: Description Of Modelmentioning

confidence: 99%

Coupled fluid flow and deformation modeling of the frontal thrust region of the Kumano Basin transect, Japan: Implications for fluid pressures and decollement downstepping

Rowe¹,

Screaton²,

Ge³

2012

Geochem Geophys Geosyst

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[1] Results of coupled fluid flow and deformation modeling illustrate the influence of frontal thrust slip on excess pore pressures and decollement downstepping in the Kumano Basin transect, offshore Japan. Although permeable trench sediments and a buried sandstone layer provide potential fluid escape pathways, the numerical modeling suggests that excess pore pressure could build beneath the frontal thrust within hemipelagic clay of the Shikoku Basin facies. Simulated excess pore pressures range between 45% and 77% of the overburden weight 3 km landward of the deformation front, and are very sensitive to the permeability of the Shikoku Basin clay and the coefficient of friction of the fault zone. Excess pore pressures increase as the fault coefficient of friction is increased, suggesting that volume change due to shear within the footwall sediments is an important contributor to excess pore pressures. Raising the coefficient of friction also increases shear within the sediments beneath the fault zone, suggesting downward migration of the decollement zone. This shearing focuses in the weaker Shikoku Basin clays rather than an underlying turbidite unit, suggesting that lithologic differences play an important role in controlling deformation location.

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“…The distribution of shear strain around the cavity of radius a can be obtained by combining Equations (18) and (23), which gives rise to…”

Section: Plastic Responsementioning

confidence: 99%

“…Generally, the value of is larger than that of . Detailed discussions on this subject have been reported by Wroth [22], Wood [17] and Chang et al [23]. The friction angle is assumed as 303 in the subsequent analysis.…”

Section: Numerical Solutionmentioning

confidence: 99%

“…where R is the isotropic overconsolidation ratio, de"ned as the ratio of the maximum mean preconsolidation stress p to p [22], as distinct from the conventional overconsolidation ratio OCR that is de"ned in terms of the e!ective vertical stress. The relationship between R and OCR has been discussed by Wood [17], Cao [11] and Chang et al [23].…”

Section: Plastic Responsementioning

confidence: 99%

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Analysis of undrained cavity expansion in elasto‐plastic soils with non‐linear elasticity

Cao

Teh

Chang

2001

Num Anal Meth Geomechanics

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SUMMARYA large strain analysis of undrained expansion of a spherical/cylindrical cavity in a soil modelled as non-linear elastic modi"ed Cam clay material is presented. The stress}strain response of the soil is assumed to obey non-linear elasticity until yielding. A power-law characteristic or a hyperbolic stress}strain curve is used to describe the gradual reduction of soil sti!ness with shear strain. It is assumed that, after yielding, the elasto-plastic behaviour of the soil can be described by the modi"ed Cam clay model. Based on a closedform stress}strain response in undrained condition, a numerical solution is obtained with the aid of simple numerical integration technique. The results show that the stresses and the pore pressure in the soil around an expanded cavity are signi"cantly a!ected by the non-linear elasticity, especially if the soil is overconsolidated. The di!erence between large strain and small strain solutions in the elastic zone is not signi"cant. The stresses and the pore pressure at the cavity wall can be expressed as an approximate closed-form solution.

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Critical state strength parameters of saturated clays from the modified Cam clay model

Cited by 5 publications

References 0 publications

A bounding surface model for anisotropically overconsolidated clay incorporating thermodynamics admissible rotational hardening rule

A bounding surface model for anisotropically overconsolidated clay incorporating thermodynamics admissible rotational hardening rule

Coupled fluid flow and deformation modeling of the frontal thrust region of the Kumano Basin transect, Japan: Implications for fluid pressures and decollement downstepping

Analysis of undrained cavity expansion in elasto‐plastic soils with non‐linear elasticity

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