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DEM Studies on the Liquefaction Behavior of Particles With Different Aspect Ratios

DEM Studies on the Liquefaction Behavior of Particles With Different Aspect Ratios

Anitha Kumari S. D. (M. S. Ramaiah University of Applied Sciences, India) and Sitharam T. G. (Indian Institute of Science, India)
Copyright: © 2019 |Pages: 18
DOI: 10.4018/978-1-5225-6948-0.ch008
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Abstract

Discrete element method (DEM) provides insight into the fundamental physical principles leading to a better understanding of the complex behavior of granular materials under different loading conditions. In the reported studies adopting DEM, real particle shape is ignored, and the particles are modeled as spheres. Spherical shapes are preferred as they provide the simplest case with least computational effort in calculations and efficient algorithms. Hence, in this study, a comprehensive and comparative study on the mechanical behavior of assemblies consisting of particles with different aspect ratios is reported. The results indicate that the assemblies with lower aspect ratio lose its strength completely at less number of cycles when subjected to lower confining pressures. At higher confining stresses, the particles are not quick enough to rearrange themselves resulting in the reduction of average coordination number. This causes a drop of shear strength leading to lower resistance to liquefaction for non-spherical assemblies at high confining stresses.
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Background

The dynamic properties of the soil mass which include shear modulus and damping ratio are key parameters which control the behaviour of a soil deposit. The degradation of the strength parameters plays a very important role in the behaviour during cyclic loading. Laboratory cyclic triaxial tests and low strain tests have the limitations of providing the dynamic properties at the measured strain level. Also, in the case of laboratory tests, the difficulties associated with the preparation of samples having the same initial properties, the effect due to the rubber membrane and the non-uniform distribution of stresses and strain are very predominant. However, the numerical methods adopted for the modelling of the dynamic response of the soil subjected to earthquake loading effectively eliminates most of the problems faced by the laboratory tests. The initial arrangement of the particles in a sample or its fabric has significant effect on the liquefaction and post-liquefaction behaviour of sands. Recent studies reported by Wei & Wang (2017) indicates that an isotropic sample is having higher liquefaction resistance compared to samples with higher degrees of fabric anisotropy. The microscopic parameters obtained from the DEM studies can be related to the macroscopic behaviour. This aids in understanding the fundamental processes behind the mechanical behaviour of soils thereby helping to interpret the constitutive behaviour.

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