Journal ArticleDOI
Anisotropy of elasticity and fabric of granular soils
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TLDR
In this article, numerical experiments using discrete element method were performed to emulate drained triaxial tests and simple shear tests at different stress levels, and the results showed that at isotropic stress states the stiffness of the numerical specimen increases, while the Poisson's ratio decreases with increasing confining pressure.Abstract:
Anisotropy of elasticity is a very important feature of granular soils. In this paper, numerical experiments using discrete element method were performed to emulate drained triaxial tests and simple shear tests at different stress levels. From these numerical experiments the macroscopic elasticity parameters were determined. The results show that at isotropic stress states the stiffness of the numerical specimen increases, while the Poisson’s ratio decreases with increasing confining pressure. The small strain shear modulus of the numerical specimen agrees well with the laboratory experimental results on a specimen with similar conditions. At anisotropic stress states, there is a threshold stress ratio (
$${ SR}_{\mathrm{th}}$$
), which characterizes the degrees of stiffness change and fabric change during the shearing. When the stress ratio (SR) is less than $${ SR}_{\mathrm{th}}$$
, the microscopic contact number does not change and its distribution remains nearly isotropic, while the distribution of contact forces change and become anisotropic to resist the applied anisotropic stress. Therefore the stiffness anisotropy of the specimen mainly results from the anisotropy of contact forces. When SR is larger than $${ SR}_{\mathrm{th}}$$
, however, the contact number decreases significantly in the minor principal stress direction resulting in the fabric anisotropy, along with the adjustments of contact forces. The stiffness anisotropy of the specimen results from both the fabric anisotropy and the contact force anisotropy. It also indicates that the stress normalized stiffness may be used as an index of the degree of fabric anisotropy. Moreover, the Poisson’s ratio of the specimen increases continuously with increasing stress ratio and its anisotropy can be approximately related to the stiffness anisotropy.read more
Citations
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Journal ArticleDOI
Dynamic properties of calcareous and siliceous sands under isotropic and anisotropic stress conditions
TL;DR: In this article, an experimental study on the shear modulus and damping ratio of calcareous and siliceous sands of different origins and their identical grain size distribution and stress-density states was conducted on reconstituted samples of two sands obtained from coastal areas.
Journal ArticleDOI
Fabric evolution and dilatancy within anisotropic critical state theory guided and validated by DEM
Rui Wang,Yannis F. Dafalias,Yannis F. Dafalias,Yannis F. Dafalias,Pengcheng Fu,Jian-Min Zhang +5 more
TL;DR: In this article, 3D DEM is used to guide the specific grain-level definition of F, the formulation of its continuum evolution equation and its effect on anisotropic dilatancy within ACST.
Journal ArticleDOI
DEM analysis of monotonic and cyclic behaviors of sand based on critical state soil mechanics framework
TL;DR: In this paper, a series of monotonic and cyclic triaxial shearing tests on Toyoura sand are simulated by discrete element method (DEM) incorporating rolling resistance.
Journal ArticleDOI
Measuring the evolution of contact fabric in shear bands with X-ray tomography
TL;DR: In this article, two different observation windows in the specimen were chosen for the contact fabric analysis: one inside and another one outside a shear band, and individual contact orientations were measured using advanced image analysis approaches within these windows.
Journal ArticleDOI
Effects of principal stress rotation on stress–strain behaviors of saturated clay under traffic–load–induced stress path
TL;DR: A series of cyclic torsional shear tests using hollow cylinder apparatus (HCA) were performed to investigate the effect of principal stress rotation (PSR) on the stress-strain behaviors of saturated soft clay as discussed by the authors.
References
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Peter Cundall,Otto D. L. Strack +1 more
TL;DR: The distinct element method as mentioned in this paper is a numerical model capable of describing the mechanical behavior of assemblies of discs and spheres and is based on the use of an explicit numerical scheme in which the interaction of the particles is monitored contact by contact and the motion of the objects modelled particle by particle.
Journal ArticleDOI
A discrete numerical model for granular assemblies
Peter Cundall,Otto D. L. Strack +1 more
TL;DR: The distinct element method as mentioned in this paper is a numerical model capable of describing the mechanical behavior of assemblies of discs and spheres and is based on the use of an explicit numerical scheme in which the interaction of the particles is monitored contact by contact and the motion of the objects modelled particle by particle.
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Journal ArticleDOI
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TL;DR: Measurements of the normal and tangential grain-scale forces inside a two-dimensional system of photoelastic disks that are subject to pure shear and isotropic compression show the underlying differences between these two stress states.