A Micromechanical Study on the Effect of Initial Static Shear Stress on Cyclic Shearing Response

The cyclic shearing response of granular materials is highly influenced by various parameters such as void ratio (e), confining stress (p′), initial static shear stress (q_s), cyclic deviatoric stress (q_cyc), stress reversal and non-stress reversal conditions. Traditionally, most liquefaction studies evaluated the influence of e, p′, q_cyc and reversals on isotropically consolidated specimens where q_s is zero. However, a soil element in a level ground is normally or K₀ consolidated and hence subjected to a q_s. Extensive studies have suggested that q_s may dramatically alter the pore water pressure generation (Δu), deviatoric strain (ε_d) and soil fabric for same e, p′ and q_cyc. In order to evaluate the effect of q_s alone, it is required to produce replicated specimens through different consolidation paths to achieve different q_s. Since, it is hard to replicate specimens and assess soil fabric in laboratory, this study used an alternative approach, discrete element method (DEM), which has reproducibility and trace micromechanical parameters such as coordination number, CN and fabric. It is found that Δu, CN and fabric were significantly affected by consolidation path and corresponding q_s conditions. This study provides a good understanding on the effect of q_s on cyclic response of soils.