Numerical Modeling of the Constitutive Relationship of a Soft Rock Using a 3-D Elastic Visco-Plastic Model

2004 ◽  
Vol 261-263 ◽  
pp. 723-728
Author(s):  
Li Jun Su ◽  
Hong Jian Liao ◽  
Jian Hua Yin
Keyword(s):  
Constitutive Model ◽  
Strain Softening ◽  
Soft Rock ◽  
Time Dependent ◽  
Triaxial Tests ◽  
Flow Rule ◽  
Test Results ◽  
Stress Strain ◽  
Strain Behavior ◽  
Constitutive Formulation

In this paper, a diatomaceous soft rock is studied. Triaxial tests had been conducted on this soft rock. From the test results, it is found that the stress-strain curve of this soft rock has a notable strain-softening tendency. In order to study its time-dependent stress-strain behavior, a constitutive model that can describe not only the strain-hardening behavior, but also the strain-softening behavior must be constructed. Based on Perzyna’s fundamental assumptions of the elastic visco-palstic theory, a visco-plastic flow rule, and Yin and Graham’s 3-D elastic visco-palstic constitutive model (3-D EVP model), the constitutive formulation under a triaxial stress state is obtained in this paper. The derived formulation can be used to simulate the time-dependent stress-strain behavior of both consolidated undrained and consolidated drained triaxial tests of soils and rocks. In this paper, the constitutive formulation is used to simulate the time-dependent stress-strain behavior of consolidated undrained triaxial tests of the soft rock studied in this paper. The simulated results are compared with the triaxial test results. The comparison of the results shows that model predictions agree well with measured results. This demonstrates that the EVP model can be used to describe the time-dependent stress-strain behavior of the soft rock studied in this paper.

The Strength and Stress-Strain Behavior of the Cemented Rockfill

2012 ◽  
Vol 598 ◽  
pp. 565-568 ◽  
Author(s):  
Qi Wen Zheng ◽  
Chen Wang ◽  
Jian Wei Zhang
Keyword(s):  
Friction Angle ◽  
The Other ◽  
Triaxial Tests ◽  
Elastoplastic Material ◽  
Test Results ◽  
Maximum Volume ◽  
Volume Strain ◽  
Stress Strain ◽  
Strain Behavior ◽  
Mixing Proportion

The cemented rockfill is mixed with cement, water and the siltstone rockfill with a certain mixing proportion. To study the strength and stress-strain behavior of the cemented rockfill, two groups of triaxial tests are carried out under the saturated and consolidated-drained conditions. One group specimens don’t include cement while the other group specimens include. The test results show that the cemented rockfill is a kind of elastoplastic material and the structure of the cemented rockfill is forced due to the effect of cementation. Compared with rockfill, the initial tangent elastic modulus, strength and cohesion of the cemented rockfill increase apparently, the residual strength and internal friction angle of the cemented rockfill increase a little, the maximum volume strain of the cemented rockfill decreases apparently.

A new elastic viscoplastic model for time-dependent behaviour of normally and overconsolidated clays: theory and verification

2002 ◽  
Vol 39 (1) ◽  
pp. 157-173 ◽  
Author(s):  
Jian-Hua Yin ◽  
Jun-Gao Zhu ◽  
James Graham
Keyword(s):  
Constitutive Model ◽  
Model Verification ◽  
Time Dependent ◽  
Triaxial Tests ◽  
Creep Function ◽  
Nonlinear Creep ◽  
Stress Strain ◽  
Loading Surface ◽  
Equivalent Time ◽  
Overconsolidated Clays

This paper presents a new three-dimensional elastic viscoplastic (3D EVP) constitutive model for the time-dependent stress–strain behaviour of both normally consolidated and overconsolidated clays. There are two major new developments in the 3D EVP model: (i) incorporation of a nonlinear creep function with a limit for the creep volume strain under isotropic stressing conditions; (ii) adoption of a new loading surface function with a smooth shape on the π plane. Based on the "equivalent time" concept of Yin and Graham, the formulation of the new 3D EVP model is derived using the new nonlinear creep function and loading surface function. A new approach to determining all model parameters is presented. The 3D EVP model is calibrated using data from one conventional isotropic stress creep test and consolidated-undrained triaxial tests on soft Hong Kong marine deposits (HKMD). The model is verified by comparing model results with those from both normally and overconsolidated triaxial tests on HKMD and a mixture of kaolin and bentonite.Key words: creep, time-dependent, viscoplastic, equivalent time, stress–strain, constitutive model, verification, clay.

scholarly journals Application of a Stress-Fractional Model for Capturing the Stress-Strain Behavior of Granular Soils

2021 ◽  
Vol 2021 ◽  
pp. 1-6
Author(s):  
Wei Lu ◽  
Jiangong Yang ◽  
Jinan Wang
Keyword(s):  
Geotechnical Engineering ◽  
Stress Gradient ◽  
Filler Material ◽  
Triaxial Tests ◽  
Granular Soils ◽  
Initial Material ◽  
Test Results ◽  
Stress Strain ◽  
Fractional Model ◽  
Strain Behavior

Granular soils usually serve as the filler material in geotechnical engineering. This study presents the development and application of a stress-fractional model for granular soils with different initial material states. To capture the plastic loading and flow behaviors, a subloading surface with the fractional stress gradient is used. The developed model contains twelve parameters which can be determined through triaxial tests. To validate the developed model, the well-documented test results of Firoozkuh No. 161 sand and crushed basalt are simulated and discussed. It is found that the stress-fractional model can reasonably simulate the undrained and drained behaviors of granular soils consolidated with different densities and mean effective pressures.

Uniaxial Mechanical Properties of Sandstone under Cyclic of Drying and Wetting

2011 ◽  
Vol 243-249 ◽  
pp. 2310-2313 ◽  
Author(s):  
Hua Yan Yao ◽  
Zhen Hua Zhang ◽  
Zhao Hui Zhu
Keyword(s):  
Mechanical Properties ◽  
Constitutive Model ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Test Results ◽  
Stress Strain ◽  
Deformation And Failure ◽  
Deformation Behaviors ◽  
Uniaxial Strength

Water is an important factor that influences the mechanical properties of rock. Uniaxial compressive experiments have been carried out on sandstone under different cyclic times of drying and wetting. The corresponding complete stress-strain curves are obtained, and characteristics of deformation and failure are analyzed. Test results show that when sandstone samples are submitted to cyclic of drying and wetting, the uniaxial strength and Young's modulus of sandstone obviously decrease. Then, the improved Duncan constitutive model is developed, which can do better in describing sample’s deformation behaviors subject to different cyclic times of drying and wetting. Introduction

A new elastoplastic constitutive model for coarse granular aggregates incorporating particle breakage

2004 ◽  
Vol 41 (4) ◽  
pp. 657-671 ◽  
Author(s):  
Wadud Salim ◽  
Buddhima Indraratna
Keyword(s):  
Constitutive Model ◽  
Plastic Flow ◽  
Current Model ◽  
Particle Breakage ◽  
Flow Rule ◽  
Peak Strain ◽  
Stress Strain ◽  
Coarse Aggregates ◽  
Stress Changes ◽  
Plastic Flow Rule

A new elastoplastic stress–strain constitutive model is developed for granular coarse aggregates incorporating the degradation of particles during triaxial shearing. Coarse granular aggregates are subjected to breakage during excessive stress changes. Most of the available constitutive models do not consider the degradation of particles during shearing. In the current model, a plastic flow rule has been developed incorporating the energy consumption due to particle breakage during shear deformation. A non-associated flow and a kinematic type yield locus have been adopted in the model. A general formulation for the rate of particle breakage during shearing has been developed and incorporated in the plastic flow rule. The effects of particle breakage on the plastic distortional and volumetric deformations are incorporated in the current model. The stress–strain formulations are developed within the general critical state framework. The model can accurately predict the stress–strain and volume change behaviour of coarse granular aggregates. The plastic dilation and contraction features of coarse aggregates at various confining pressures are well captured, and the strain-hardening and post-peak strain-softening behaviour of coarse granular media is adequately represented. A particular feature of the model is its capability to predict the degree of particle breakage at any stage of shear deformation.Key words: constitutive modelling, coarse granular aggregates, particle breakage, dilatancy, non-associated flow, plasticity.

scholarly journals Uniform Nonlinear Constitutive Model and Parameters for Clay in Different Consolidation Conditions Based on Regression Method

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Tao Cheng ◽  
Keqin Yan ◽  
Huazhi Zhang ◽  
Xianfeng Luo ◽  
Shengfang Li
Keyword(s):  
Constitutive Model ◽  
Initial Conditions ◽  
Constitutive Relations ◽  
Test Sample ◽  
Maximum Relative Error ◽  
Compression Tests ◽  
Stress Strain ◽  
Strain Behavior ◽  
Nonlinear Constitutive Model ◽  
Isotropic Consolidation

The nonlinear constitutive relations of clay are investigated considering different initial conditions. Highly compressible clay is selected as the test sample. Two groups of tri-axial compression tests are performed, respectively, afterK0consolidation and isotropic consolidation. On the basis of the framework ofE~vmodel, a uniform nonlinear constitutive model is proposed by fitting the test data. With the average slope of the unloading-reloading curve selected as the unloading modulus, the unloading function is constructed as the loading-unloading criterion. Moreover, a comparison between the experimental stress-strain curves and the results predicted by the constitutive model is made. It is shown that the prediction is reasonable, which can reflect the stress-strain behavior of the soil under theK0consolidation and isotropic consolidation conditions. The maximum relative error of the two series of curves is not remarkable, less than 6%.

Effect of OCR on sampling disturbance of cohesive soils and evaluation of laboratory reconsolidation procedures

2005 ◽  
Vol 42 (2) ◽  
pp. 459-474 ◽  
Author(s):  
Marika Santagata ◽  
John T Germaine
Keyword(s):  
Effective Means ◽  
Triaxial Tests ◽  
Single Element ◽  
Cohesive Soils ◽  
Stress Strain ◽  
Overconsolidation Ratio ◽  
Strain Behavior ◽  
Preconsolidation Pressure ◽  
Strength Behavior ◽  
Undrained Strength

The paper presents the results of an experimental investigation of sampling disturbance in cohesive soils through single-element triaxial tests on resedimented Boston blue clay (RBBC). The first part of the paper discusses the effect of the overconsolidation ratio (OCR) (1–8) of the soil on postdisturbance compression and undrained shear behavior. The results demonstrate that sensitivity to disturbance decreases markedly with OCR. It is also found that for the medium-sensitivity soil tested, the estimate of the preconsolidation pressure is not significantly affected by OCR. The second part of the paper discusses laboratory reconsolidation procedures. For OCR1 RBBC, the recompression method is not effective in recovering the stress–strain behavior of the soil and, for greater disturbance, provides an increasingly unsafe estimate of the strength. For OCR4, provided the reconsolidation path reproduces the path that occurred in the field, this procedure succeeds in recovering the intact stress–strain–strength behavior of the soil. SHANSEP reconsolidation was investigated for normally consolidated RBBC only. For modest levels of disturbance, this is an effective means of evaluating both the stress–strain and the strength behavior of the soil. For greater levels of disturbance, the stress–strain behavior is not fully recovered, but the method continues to provide conservative estimates of the undrained strength.Key words: sampling disturbance, clays, overconsolidation ratio, undrained strength, recompression, SHANSEP.

Protein Forced Unfolding and Its Effects on the Finite Deformation Stress-Strain Behavior of Biomacromolecular Solids

2005 ◽  
Vol 874 ◽  
Author(s):  
H. Jerry Qi ◽  
Christine Ortiz ◽  
Mary C. Boyce
Keyword(s):  
Constitutive Model ◽  
Single Molecule ◽  
Biological Networks ◽  
Finite Deformation ◽  
State Theory ◽  
Force Extension ◽  
Stress Strain ◽  
Strain Behavior ◽  
Mechanics Model ◽  
Deformation Stress

AbstractMany proteins have been experimentally observed to exhibit a force-extension behavior with a characteristic repeating pattern of a nonlinear rise in force with imposed displacement to a peak, followed by a significant force drop upon reaching the peak (a “saw-tooth” profile) due to successive unfolding of modules during extension. This behavior is speculated to play a governing role in biological and mechanical functions of natural materials and biological networks composed of assemblies of such protein molecules. In this paper, a constitutive model for the finite deformation stress-strain behavior of crosslinked networks of modular macromolecules is developed. The force-extension behavior of the individual modular macromolecule is represented using the Freely Jointed Chain (FJC) statistical mechanics model together with a two-state theory to capture unfolding. The single molecule behavior is then incorporated into a formal continuum mechanics framework to construct a constitutive model. Simulations illustrate a relatively smooth “yield”-like stress-strain behavior of these materials due to activate unfolding in these microstructures.

Experimental and Numerical Characterization of the Stress-Strain Behavior of Weak Sandstone Formations for Sanding Assessment

2018 ◽  
Author(s):  
Nubia Aurora González Molano ◽  
Jacobo Canal Vila ◽  
Héctor González Pérez ◽  
José Alvarellos Iglesias ◽  
M. R. Lakshmikantha
Keyword(s):  
Constitutive Model ◽  
Equivalent Plastic Strain ◽  
Experimental Tests ◽  
Thick Wall ◽  
Triaxial Tests ◽  
Experimental Program ◽  
Model Parameters ◽  
Sand Production ◽  
Strain Behavior ◽  
Weak Sandstone

In this study an extensive experimental program has been carried out in order to characterize the mechanical behavior of two weak sandstone formations of an offshore field for application to sand production modeling. The experimental tests included Scratch tests, Triaxial tests and Advanced thick wall cylinder tests (ATWC) where the sand production initiation and the cumulative sand produced were registered. Numerical simulations of experimental tests were then performed using an advanced elasto-plastic constitutive model. Triaxial tests simulations allowed calibrating the constitutive model parameters. These parameters were employed for the numerical simulation of the ATWC in order to determine the equivalent plastic strain threshold required to the onset of sand production observed in laboratory for sanding assessment. Results obtained highlight the importance to use a realistic representation of the rock behavior focusing on post-yield behavior in order to build confidence in model predictions.

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