Instability in granular materials - a micromechanical investigation
JCL Perez and CY Kwok and C O'Sullivan and KH Hanley and X Huang, Geomechanics from Micro to Macro, Vols I and II, 135-139 (2015).
Static liquefaction and general instability of granular media are the cause of a number of geotechnical engineering failures involving dam tailings, hydraulically placed fills and slopes. In order to understand the failure mechanisms that induce static liquefaction, the Discrete Element Method (DEM) was used to study the behavior of a representative model of a granular sample at the micro level. Samples under different initial confining pressures and void ratios were sheared under constant- volume conditions and the changes in the macro-and micro-mechanical responses of the granular media were quantified. Characteristic states such as the instability state, quasi-steady state, phase transformation and critical state were identified in the simulations. The transitions between different characteristic states were related to micro-mechanical characteristics such as coordination number and deviatoric fabric. The instability line was found not to be unique. Furthermore, the stress ratio at the instability state was found to increase exponentially with the coordination number and the deviatoric fabric.
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