Effect of principal stress rotation on liquefaction resistance of anisotropic granular materials with different densities and Vs-based characterization framework

General geotechnical loading involves coupled cyclic shear and normal stresses on soil elements, producing principal stress rotation that differs from the far-field simple shear stress path commonly assumed in liquefaction assessment. A DEM study aimed at providing insights into the effects of principal stress rotation on the characterization for liquefaction resistance is presented. Three series of HCA simulations were conducted on granular assemblies with different fabric anisotropy and void ratios. Small-strain drained shear tests were first performed to determine G max and V s , followed by undrained cyclic loading tests involving 90° jump rotation of the principal stress direction with different initial principal stress orientations. The CRR is lowest when the major principal stress is inclined at approximately 45° to the deposition direction and increases with further rotation. The influence of principal stress orientation becomes less pronounced as the density increases and fabric anisotropy decreases, and the evolution of CRR around 45° is not strictly symmetric. Quantitative micromechanical analyses indicate that the CRR variation is associated with the effective contact contribution along the loading direction, whereas the observed asymmetry is related to the dilatancy induced by the loading direction relative to the deposition fabric. A state-dependent correction function is proposed to quantify the influence of near-field principal stress rotation on CRR . By combining this function with a benchmark CRR - V s1 curve, an improved V s -based framework is developed for evaluating liquefaction resistance considering principal stress rotation effect. Application of the proposed framework to real geotechnical soils requires laboratory tests to calibrate both the correction function and the benchmark CRR - V s1 curve.