Simulating the effects of induced anisotropy on liquefaction potential using a new constitutive model

2013 ◽  
Vol 38 (10) ◽  
pp. 1013-1035 ◽  
Author(s):  
H. Than Trong Tran ◽  
H. Wong ◽  
Ph. Dubujet ◽  
T. Doanh
Keyword(s):  
Constitutive Model ◽  
Induced Anisotropy ◽  
Liquefaction Potential

A Micromechanically Based Constitutive Model for the Inelastic and Swelling Behaviors in Double Network Hydrogels

2015 ◽  
Vol 83 (2) ◽  
Author(s):  
Yin Liu ◽  
Hongwu Zhang ◽  
Yonggang Zheng
Keyword(s):  
Constitutive Model ◽  
Strain Energy ◽  
Polymer Chains ◽  
Loading Path ◽  
Induced Anisotropy ◽  
Double Network ◽  
Strain Energy Density Function ◽  
Damage Process ◽  
Single Polymer Chain ◽  
Swelling Behaviors

This paper presents a micromechanically based constitutive model within the framework of the continuum mechanics to characterize the inelastic elastomeric and swelling behaviors of double network (DN) hydrogels, such as the stress-softening, necking instability, hardening, and stretch-induced anisotropy. The strain-energy density function of the material is decomposed into two independent contributions from the tight and brittle first network and the soft and loose second network, each of which is obtained by integrating the strain energy of one-dimensional (1D) polymer chains in each direction of a unit sphere. The damage process is derived from the irreversible breakages of sacrificial chains in the first network and characterized by the directional stretch-dependent evolution laws for the equivalent modulus and the locking stretch in the non-Gauss statistical model of a single polymer chain. The constitutive model with the optimized-material evolution law predicts stress–stretch curves in a good agreement with the experimental results during loading, unloading, and reloading paths for both ionic and covalent DN hydrogels. The deformation-induced anisotropy is investigated and demonstrated by the constitutive model for the free swelling of damaged specimen. The constitutive model is embedded into the finite-element (FE) procedure and proved to be efficient to model the necking and neck propagation in the plane-strain uniaxial elongation. Based on the procedure, the effects of imperfection and boundary conditions on the loading path and the material evolution during different stages of deformation are investigated.

A constitutive model for gravelly soils considering shear-induced volumetric deformation

2010 ◽  
Vol 47 (6) ◽  
pp. 662-673 ◽  
Author(s):  
Bin-Lin Chu ◽  
Yeun-Wen Jou ◽  
Meng-Chia Weng
Keyword(s):  
Hydrostatic Pressure ◽  
Constitutive Model ◽  
Triaxial Compression ◽  
Compression Tests ◽  
Induced Anisotropy ◽  
Volumetric Deformation ◽  
Proposed Model ◽  
Gravelly Soils ◽  
Deformational Behavior ◽  
Stress Induced Anisotropy

This study elucidates the deformational behavior of gravelly soils by analyzing how hydrostatic pressure and pure shearing affect deformational behavior. A series of drained, triaxial compression tests have been performed using large specimens made of gravelly soils, where the grain-size distribution curve was based on the field condition. The volumetric and shear deformations of gravelly soils have been determined by performing experiments with controlled stress paths — hydrostatic pressure was applied first followed by pure shearing. A simple and innovative constitutive model is also proposed. The proposed model is characterized by the following features of gravelly soils: (i) significant shear-induced volumetric deformation prior to failure, (ii) modulus stiffening under hydrostatic loading and degradation under shearing, and (iii) stress-induced anisotropy. In the proposed model, deformational moduli K and G vary according to the stress state. The stiffening and degradation of these moduli result in diverse deformational behavior of gravelly soils. In addition, an anisotropic factor, β, is introduced to represent stress-induced anisotropy. Moreover, the proposed model only requires eight material parameters; each of which can be obtained easily from experiments.

A New Anisotropic Damage Model for Ceramic Matrix Composites

2004 ◽  
Author(s):  
Oana Cazacu ◽  
Stefan Soare
Keyword(s):  
Constitutive Model ◽  
Damage Model ◽  
Ceramic Matrix Composites ◽  
Ceramic Matrix ◽  
Irreversible Thermodynamics ◽  
Anisotropic Damage ◽  
Strain Response ◽  
Matrix Composites ◽  
Induced Anisotropy ◽  
Brittle Matrix Composite

Within the framework of irreversible thermodynamics, a new general constitutive model for describing damage and its effect on the overall properties of anisotropic solids is proposed. The ability of the model to describe the overall stress-strain response as well as the loss of symmetry resulting from the interaction between initial and damage-induced anisotropy in a brittle matrix composite is demonstrated.

scholarly journals Analysis of Soil-Compacting Effect Caused by Shield Tunneling Using Three-Dimensional Elastoplastic Solution of Cylindrical Cavity Expansion

2018 ◽  
Vol 2018 ◽  
pp. 1-14
Author(s):  
Mengxi Zhang ◽  
Xiaoqing Zhang ◽  
Chengyu Hong ◽  
Lalit Borana ◽  
Akbar A. Javadi
Keyword(s):  
Constitutive Model ◽  
Cylindrical Cavity ◽  
Numerical Solutions ◽  
Three Dimensional ◽  
Cavity Expansion ◽  
Induced Anisotropy ◽  
Shield Tunneling ◽  
Tunnel Excavation ◽  
Cylindrical Cavity Expansion ◽  
Deformation Area

Soil squeezing effect and formation disturbance caused by tunnel excavation can be simulated by cylindrical cavity expansion due to the comparability between tunneling and cavity expansion. Although most of the existing theoretical derivation is based on simple constitutive model of soil foundation, not only the relation between principal stress components was simplified in the solution process, but also the stress history, initial stress anisotropy, and stress-induced anisotropy of structural soil were neglected. The mechanical characteristics of soil are closely related to its stress history, so there is a gap between the above research and the actual engineering conditions. A three-dimensional elastoplastic solution of cylindrical cavity expansion is obtained based on the theory of critical state soil mechanics and engineering characteristics of shield tunneling. In order to fully consider the influence of initial anisotropy and induced anisotropy on the mechanical behavior of soils, the soil elastoplastic constitutive relation of cavity expansion is described in the course of K0-based modified Cam-clay (K0-MCC) model after soil yielding. An equation with equal number of variables is obtained under the elastic-plastic boundary condition based on the Lagrange multiplier method. By solving the extreme value of the original function, the analytical solution of radial, tangential, and vertical effective stresses distribution around the circular tunnel excavation is obtained. In addition, changes of elastic deformation area and plastic deformation area for soil during the shield excavation have been analyzed. Calculation results are compared with the numerical solutions which usually consider isotropic soil behavior as the basic assumption. In this paper, a constitutive model which is more consistent with the actual mechanical behavior of the soil and the construction process of the shield tunnel is considered. Therefore, the numerical solutions are more realistic and suitable for the shield excavation analysis and can provide theoretical guidance required for design of shield tunneling.

Mechanical properties and constitutive model for artificially structured soils with an initial stress-induced anisotropy

2020 ◽  
Vol 17 (2) ◽  
pp. 46-55
Author(s):  
Chuan He ◽  
Enlong Liu ◽  
Qing Nie
Keyword(s):  
Constitutive Model ◽  
Initial Stress ◽  
Structural Parameters ◽  
Triaxial Compression ◽  
Heterogeneous Materials ◽  
Local Strain ◽  
Compression Tests ◽  
Induced Anisotropy ◽  
Structured Soils ◽  
Stress Induced Anisotropy

A series of triaxial compression tests was performed on artificially structured soil samples with an initial stress- -induced anisotropy at confining pressures of 25, 37.5, 50, 100, 200, and 400 kPa. Based on the results of these tests, a constitutive model for structured soils with initial stress-induced anisotropy was formulated. In the proposed model, the initially anisotropic structured soils are regarded as heterogeneous materials composed of bonded blocks and weaker bands. The bonded blocks (denoted as bonded elements) are described as transversely isotropic elastic– brittle materials, while the weaker bands (denoted as frictional elements) are described by the Lade–Duncan model of elastic–plastic materials. Based on the homogenization theorem for heterogeneous materials, and the introduction of structural parameters such as the breakage ratio and the local strain coefficient, the non-uniform distribution of stress and strain within a representative volume element was obtained. Finally, the parameters of the model were determined based on experimental results. The model was verified with test results, demonstrating that it can effectively capture many important features of artificially structured soils with an initial stress-induced anisotropy.

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