Liquefaction and Dynamic Properties of Assemblies with Particles of Spherical and Ellipsoidal Shapes: A Discrete Element Approach

Liquefaction and Dynamic Properties of Assemblies with Particles of Spherical and Ellipsoidal Shapes: A Discrete Element Approach

S. D Anitha Kumari (Indian Institute of Science, India) and T. G. Sitharam (Indian Institute of Science, India)
Copyright: © 2012 |Pages: 16
DOI: 10.4018/jgee.2012010102
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Abstract

Understanding liquefaction and dynamic response of granular soils from a grain scale level has obtained significant attention during the recent times. Discrete Element method has been adopted to understand the particulate nature, but most of the studies have focused on modeling assemblies with spherical particles. But recent researches have indicated that particle shape is significant in estimating the proper strength and dynamic properties of a soil mass. Hence in this study, a series of cyclic undrained tests are performed on three different assemblies consisting of particles with different aspect ratios. The influence of shape on the cyclic strength, dynamic properties like shear modulus, and damping ratio are investigated and presented. The results show that as the particle shape changes from spheres to ellipsoids, there is considerable change in the strength and the dynamic properties.
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Methodology Used For The Study

Soils are discontinuous in nature and hence it is appropriate to model the assembly of grains considering their discrete behaviour. The state of knowledge related to liquefaction and its associated phenomena has been studied in detail during the last few decades by analytical and laboratory experiments (Seed & Lee, 1966; Ishihara, Tatsuoka, & Yasuda, 1975, 1975; Vaid & Thomas, 1995). Generally the cyclic behaviour obtained from analytical methods is based on continuum approach. Since the continuum approach does not take into account the particulate nature of the soil mass, the deformation and failure modes may be affected. Hence it is important to consider the particulate nature of the soil assembly considered and hence discrete element method (DEM) is adopted in this study. DEM pioneered by Cundall (1971) was developed to study the rock slope which was later extended to the study of application in granular media. DEM is based on the principle that each particle is modeled as an element obeying Newton’s second law of motion. The movement of each particle is monitored by solving the equations of motion. The relative displacement at the contacts gives rise to a contact force which is evaluated by force-displacement law. DEM has been successfully used by several researchers (Ng & Dobry, 1994; Sitharam, 2003; Dinesh, Sitharam, & Vinod, 2004) to understand liquefaction.

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