An anisotropic elastoplastic model for soft clays

2003 ◽  
Vol 40 (2) ◽  
pp. 403-418 ◽  
Author(s):  
Simon J Wheeler ◽  
Anu Näätänen ◽  
Minna Karstunen ◽  
Matti Lojander
Keyword(s):  
Experimental Data ◽  
Yield Curve ◽  
Constitutive Relations ◽  
Stress Path ◽  
Elastoplastic Model ◽  
Soft Clays ◽  
Rotational Hardening ◽  
Modified Cam Clay ◽  
Cam Clay

An anisotropic elastoplastic model for soft clays is presented. Experimental data from multistage drained triaxial stress path tests on Otaniemi clay from Finland provide support for the proposed shape of the yield curve and for the proposed relationship describing the change of yield curve inclination with plastic straining. Procedures are proposed for determining the initial inclination of the yield curve and the values of the two additional soil constants within the model. Comparisons of model simulations with experimental data demonstrate significant improvements in the performance of the new model over the Modified Cam Clay model. The remaining discrepancies are mainly attributable to the important role of destructuration in the sensitive Otaniemi clay.Key words: anisotropy, constitutive relations, elastoplasticity, laboratory tests, rotational hardening, soft clays.

scholarly journals Experimental Study of Silty Clay Plane Strain Tri-axial Test under RTC Path and Modified Cam-clay Model

2018 ◽  
Vol 4 (3) ◽  
pp. 518
Author(s):  
Tao Cheng ◽  
Yi Zhang ◽  
Keqin Yan
Keyword(s):  
Plane Strain ◽  
Stress Path ◽  
Physical Parameters ◽  
Silty Clay ◽  
Model Framework ◽  
Loading Test ◽  
Clay Model ◽  
Modified Cam Clay ◽  
Institute Of Technology ◽  
Cam Clay

The character of geomaterials is affected by stress path remarkably. Under different stress paths, the stress-strain characteristics of geomaterials are difference. For the unloading path in existing engineering situation, the physical parameters and constitutive model is usually determined by loading test. The path to uninstall the actual project conditions which may be a larger error. Therefore, this work proceeding from the actual project, deep excavation of the lateral unloading condition is analysed. The tests of CTC path and RTC path on silty clay in Huangshi city of china by multi-path tri-axial plane strain are carried on in the geotechnical Engineering Laboratory of Huangshi Institute of Technology. Then, the phenomenon under the two stress paths are compared with each other and describing the differences between them. The mechanical properties in the RTC stress path is analyzed mainly. Based on the Cam-Clay model framework, then derived this material yield equation based on Cam-clay model, Laiding the foundation for the numerical analysis.

scholarly journals Plastic anisotropy of soft reconstituted clays

2008 ◽  
Vol 45 (3) ◽  
pp. 314-328 ◽  
Author(s):  
Minna Karstunen ◽  
Mirva Koskinen
Keyword(s):  
Stress Ratio ◽  
Plastic Anisotropy ◽  
Stress Path ◽  
Test Results ◽  
Fabric Anisotropy ◽  
Induced Anisotropy ◽  
Modified Cam Clay ◽  
Model Predictions ◽  
Elastoplastic Constitutive Model ◽  
Cam Clay

The aim of the paper is to extend the experimental validation of the S-CLAY1 model, which is a recently proposed elastoplastic constitutive model that accounts for initial and plastic strain-induced anisotropy. Drained stress path controlled tests were performed on reconstituted samples of four Finnish clays to study the effects of anisotropy in the absence of the complexities of structure present in natural undisturbed clays. Each test involved several loading, unloading, and reloading stages with different values of stress ratio and, hence, induced noticeable changes in the fabric anisotropy. Comparisons between test results and model predictions with the S-CLAY1 model and the modified Cam clay model demonstrate that despite its simplicity, the S-CLAY1 model can provide excellent predictions of the behaviour of unstructured soil.

A Graphical Analysis-based Method for Undrained Cylindrical Cavity Expansion in Modified Cam Clay Soil

Géotechnique ◽  
2022 ◽  
pp. 1-35
Author(s):  
S. L. Chen ◽  
Y. N. Abousleiman
Keyword(s):  
Pore Pressure ◽  
Effective Stress ◽  
Cylindrical Cavity ◽  
Clay Soil ◽  
Stress Path ◽  
Graphical Analysis ◽  
Material Point ◽  
Modified Cam Clay ◽  
Deviatoric Plane ◽  
Cam Clay

A novel graphical analysis-based method is proposed for analysing the responses of a cylindrical cavity expanding under undrained conditions in modified Cam Clay soil. The essence of developing such an approach is to decompose and represent the strain increment/rate of a material point graphically into the elastic and plastic components in the deviatoric strain plane. It allows the effective stress path in the deviatoric plane to be readily determined by solving a first-order differential equation with the Lode angle being the single variable. The desired limiting cavity pressure and pore pressure can be equally conveniently evaluated, through basic numerical integrations with respect to the mean effective stress. Some ambiguity is clarified between the generalized (work conjugacy-based) shear strain increments and the corresponding deviatoric invariants of incremental strains. The present graph-based approach is also applicable for the determination of the stress and pore pressure distributions around the cavity. When used for predicting the ultimate cavity/pore pressures, it is computationally advantageous over the existing semi-analytical solutions that involve solving a system of coupled governing differential equations for the effective stress components. It thus may serve potentially as a useful and accurate interpretation of the results of in-situ pressuremeter tests on clay soils.

A structured Cam Clay model

2002 ◽  
Vol 39 (6) ◽  
pp. 1313-1332 ◽  
Author(s):  
M D Liu ◽  
J P Carter
Keyword(s):  
Parametric Study ◽  
Soil Structure ◽  
Constitutive Relations ◽  
Calcareous Soils ◽  
New Model ◽  
Clay Model ◽  
Proposed Model ◽  
Modified Cam Clay ◽  
Structured Soils ◽  
Cam Clay

A theoretical study of the behaviour of structured soil is presented. A new model, referred to as the Structured Cam Clay model, is formulated by introducing the influence of soil structure into the Modified Cam Clay model. The proposed model is hierarchical, i.e., it is identical to the Modified Cam Clay soil model if a soil has no structure or if its structure is removed by loading. Three new parameters describing the effects of soil structure are introduced, and the results of a parametric study are also presented. The proposed model has been used to predict the behaviour of structured soils in both compression and shearing tests. By making comparisons of predictions with experimental data and by conducting the parametric study it is demonstrated that the new model provides satisfactory qualitative and quantitative modelling of many important features of the behaviour of structured soils.Key words: calcareous soils, clays, fabric, structure, constitutive relations, plasticity.

Sensitivity Analysis of Parameters in SYS Cam-Clay Model

2014 ◽  
Vol 1030-1032 ◽  
pp. 864-870
Author(s):  
Bin Bin Xu ◽  
Toshihiro Noda ◽  
Kentaro Nakai
Keyword(s):  
Sensitivity Analysis ◽  
Coupling Effect ◽  
Stress Path ◽  
State Theory ◽  
Degradation Index ◽  
Overconsolidation Ratio ◽  
Clay Model ◽  
Structure Degradation ◽  
Rotational Hardening ◽  
Cam Clay

The SYS Cam-clay model, which is extended based on the Cam-clay model and the critical state theory, is able to describe the heavily overconsolidated and structure soils. However compared with Cam-clay model with five elasto-plastic parameters there are six additional evolutional parameters in SYS Cam-clay model and the sensitivity analysis of the new added parameters should be carried out. Through the calculation of constitutive response assuming the uniform deformation field, the sensitivities of degradation index of structure, degradation index of overconsolidation ratio and rotational hardening index are investigated respectively. It can be seen that the peak strength and the “rewinding behavior” in the effective stress path are influenced greatly while there is no coupling effect of these parameters mutually. The initial overconsolidation ratio and degree of structure also have an effect on the mechanical behavior and the initial specific volume.

Elastoplastic numerical approach for predicting the electro-osmotic consolidation behaviour of soft clays

2013 ◽  
Vol 50 (12) ◽  
pp. 1219-1235 ◽  
Author(s):  
V. Jeyakanthan ◽  
C.T. Gnanendran
Keyword(s):  
Numerical Approach ◽  
Coupled Analysis ◽  
Soft Clays ◽  
Strain Behaviour ◽  
Nonlinear Stress ◽  
Modified Cam Clay ◽  
Close Form ◽  
Fully Coupled ◽  
Fully Coupled Analysis ◽  
Cam Clay

A finite element (FE) formulation for electro-osmotic consolidation (EOC) analysis is developed in this paper which was implemented in a FE analysis (FEA) program. This formulation is integrated with the elastoplastic Modified Cam Clay (MCC) model to capture the nonlinear stress–strain behaviour of the soil during EOC using the fully coupled analysis approach. The numerical model is verified against triaxial EOC test data and close form solutions of typical one-dimensional EOC problems. Details of the formulation and the results of the validation analyses are reported in this paper.

scholarly journals A computational study on the uncertainty quantification of failure of clays with a modified Cam-Clay yield criterion

2021 ◽  
Vol 3 (6) ◽  
Author(s):  
Ambrosios A. Savvides ◽  
Manolis Papadrakakis
Keyword(s):  
Random Distribution ◽  
Failure Load ◽  
Computational Study ◽  
Soil Depth ◽  
Yield Criterion ◽  
Constitutive Relations ◽  
Compressibility Factor ◽  
Latin Hypercube Sampling ◽  
Modified Cam Clay ◽  
Cam Clay

AbstractIn this study, the quantitative effect of the random distribution of the soil material properties to the probability density functions of the failure load and displacements is presented. A modified Cam-Clay failure criterion is embedded into a stochastic finite element numerical tool for this purpose. Various assumptions for the random distribution of the compressibility factor $$\kappa$$ κ , of the constitutive relation, the critical state line inclination c of the soil, and the permeability k have been tested and assessed with Latin hypercube sampling followed by Monte Carlo simulation. It is confirmed that both failure load and displacements follow Gaussian normal distribution despite the nonlinearity of the problem. Moreover, as the soil depth increases the mean value of failure load decreases and the failure displacement increases. Consequently, failure mechanism of clays can be determined in this work within an acceptable variability, taking into account the soil depth and nonlinear constitutive relations which in the analytical solutions is not feasible as it is assumed the Meyerhoff theory which considers the elastic halfspace.

scholarly journals Probabilistic Failure Estimation of an Oblique Loaded Footing Settlement on Cohesive Geomaterials with a Modified Cam Clay Material Yield Function

Geotechnics ◽  
2021 ◽  
Vol 1 (2) ◽  
pp. 347-384
Author(s):  
Ambrosios-Antonios Savvides ◽  
Manolis Papadrakakis
Keyword(s):  
Random Distribution ◽  
Failure Load ◽  
Constitutive Relations ◽  
Latin Hypercube Sampling ◽  
Element Model ◽  
Shallow Foundation ◽  
Clay Material ◽  
Modified Cam Clay ◽  
Non Linear ◽  
Cam Clay

In this work, a quantitative uncertainty estimation of the random distribution of the soil material properties to the probability density functions of the failure load and failure displacements of a shallow foundation loaded with an oblique load is portrayed. A modified Cam Clay yield constitutive model is adopted with a stochastic finite element model. The random distribution of the reload path inclination κ, the critical state line inclination c of the soil and the permeability k of the Darcian water flow relation, has been assessed with Monte Carlo simulations accelerated by using Latin hypercube sampling. It is proven that both failure load and failure displacements follow Gaussian normal distribution despite the excessive non-linear behaviour of the soil. In addition, as the obliquity increases the mean value of failure load and the failure displacement always increases. The uncertainty of the output failure stress with the increase of the obliquity of the load remains the same. The failure spline of clays can be calculated within an acceptable accuracy with the proposed numerical scheme in every possible geometry and load conditions, considering the obliquity of the load in conjunction with non-linear constitutive relations.

scholarly journals COMPARISON AND APPLICATION OF DIFFERENT ELASTO-PLASTIC CONSTITUTIVE MODELS IN FEM ANALYSIS OF AN EXCAVATED SOIL SLOPE

2012 ◽  
Vol 18 (6) ◽  
pp. 802-810 ◽  
Author(s):  
Kunyong Zhang ◽  
Yingbo Ai
Keyword(s):  
Constitutive Models ◽  
Fem Analysis ◽  
Stress Path ◽  
Soil Slope ◽  
Modified Model ◽  
Stress Ratio Parameter ◽  
Modified Cam Clay ◽  
Frame Work ◽  
Reasonable Description ◽  
Cam Clay

A modified anisotropic elasto-plastic model is presented in this paper based on the frame work of Modified Cam-clay model and Original Sekiguchi-Ohta model by applying a new stress ratio parameter, through which the yield locus and hardening axis in the p-q plane were adjusted to give a more reasonable description of the practical excavation stress path from initial K0 state. Typical excavated soil slope was selected as the illustration example to carry out the finite element numerical analysis by applying four constitutive models (Original Cam-Clay, Modified Cam-Clay, Original Sekiguchi-Ohta and Modified Sekiguchi-Ohta). The calculated displacements of the slope with above different constitutive models were then compared with the measured infield data. It was found the field measured data agree better with the results calculated from modified model, which indicates that the modified anisotropic model is more suitable in the description of the stress path of excavated soils slope after K0 consolidation.

Numerical Simulation of Triaxial Test in Clayey Soil Using Different Constitutive Relations

2011 ◽  
Vol 243-249 ◽  
pp. 2973-2977 ◽  
Author(s):  
Mohammed Y. Fattah ◽  
Firas A. Salman ◽  
Bestun J. Nareeman
Keyword(s):  
Clayey Soil ◽  
Triaxial Compression ◽  
Constitutive Relations ◽  
Triaxial Tests ◽  
Elastic Model ◽  
Residual Soils ◽  
Stress Strain ◽  
Linear Elastic ◽  
Modified Cam Clay ◽  
Cam Clay

The stress paths to which specimens are subjected in triaxial tests together with the yield surfaces, which may be exercised in different models of such a test are simulated. A laboratory testing on undisturbed clay soil samples was performed in order to characterize the stress-strain behaviour of the residual soils in Sao Paulo sedimentary deposit. The sample is tested under isotropically consolidated drained triaxial compression. Strain controlled procedure was used to simulate stress-strain relationships of the soil. Seven models are used; namely: linear elastic, Duncan-Chang hyperbolic, Mohr-Coulomb, Cam clay, modified Cam clay, new Mohr-Coulomb and Cap model. It was concluded that the results of Cam clay and Duncan Chang models are the closest to the experimental data under low confining pressures; 49 and 98 kPa. Both models exhibit parabolic stress-strain relationships while the linear elastic model results are far away from experimental ones especially at large stress levels. At high confining pressure; 196 kPa, the modified Cam clay best correlates the stress and strain.

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