Evaluation of liquefaction resistance for gravelly sands using gravel content-corrected shear-wave velocity

The current practice of evaluating the liquefaction resistance of gravelly soils with shear-wave velocity relies on the assumption that liquefiable gravelly soils behave as sandy ones. Recent laboratory tests on gap-graded gravelly sands show that the cyclic resistance is dominated by the packing conditions of the sand matrix, while the shear-wave velocity is affected by the gravel content. Taking these findings into account, the gravel content-corrected shear-wave velocity is derived based on the time-average equation of lumped gravel particles and the sand matrix. Based on analyses of case histories, a three-step procedure, which includes screening of gravelly sands, computation of stress-normalized, gravel content-corrected shear-wave velocity, and cyclic resistance evaluation using the modified correlation between the corrected shear wave velocity and the cyclic resistance, is proposed for evaluating the cyclic resistance ratio of gravelly sands. Comparisons with case histories show that the proposed procedure can significantly improve the estimation of cyclic resistance.