Abstract
The paper presents 3D DEM simulation results of undrained tests for loose assemblies with varied porosities under both triaxial compression and plane strain conditions, using a periodic cell. The undrained tests were modelled by deforming the samples under constant volume conditions, which corresponds to saturated soil samples. The undrained stress paths are shown to be qualitatively similar to physical experimental results. The triggering of liquefaction and temporary liquefaction is identified by a microscopic parameter with redundancy factor (RF) equal to unity, which defines the transition from “solid-like” to “liquid-like” behaviour. The undrained behaviour of granular soils is found to be mainly governed by the evolution of redundancy factor, and a reversal of deviatoric stress in stress path (temporary liquefaction) is found to be due to temporary loss of contacts forming a structural mechanism in the system where RF is smaller than unity during the evolution.
Highlights
Interest in undrained behaviour especially for loose sand has received much attention since the pioneering experimental work [1] [2], but the undrained behavior of loose sand has not been well explained
This indicates that the undrained behaviour is much related to strain conditions
It can be concluded that the undrained behaviour is dependent on porosity and strain conditions (UPS is more resistant to liquefaction/temporary liquefaction)
Summary
Interest in undrained behaviour especially for loose sand has received much attention since the pioneering experimental work [1] [2], but the undrained behavior of loose sand (especially liquefaction) has not been well explained. The undrained behaviour was modeled using 2D DEM by [4]-[7] among others Most of these researchers use 2D constant volume simulations for mimicking undrained saturated soil tests, except that both constant volume and coupled. (2015) DEM Simulations of Granular Soils under Undrained Triaxial Compression and Plane Strain. The comparison of undrained behaviour using constant volume and fluid-particle interaction methods showed no difference essentially as indicated [6] [7]. It should be noted that the undrained condition modeled by constant volume method is only suitable for saturated soil samples, not for unsaturated samples. The paper presents results of 3D DEM simulations under both undrained (constant volume) triaxial compression (UTC) and undrained plane strain (UPS) conditions and a comparision is made. A micromechanical description of liquefaction and the related phenomena are focused
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