Effect of initial static shear stress and cyclic loading direction on liquefaction characteristics of saturated dense sand

Soil elements of slope are subjected to both initial shear stress and cyclic stress during seismic loading, and the directions of initial shear stress and cyclic stress are often different. In order to investigate the effects of initial shear stress and cyclic stress direction on the liquefaction characteristics of saturated dense sand, a series of consolidated undrained multi-directional cyclic simple shear tests are carried out on saturated dense sand. The test results show that the failure modes of saturated dense sand mainly include cyclic activity and cumulative plastic strain, and the failure modes are affected by the initial shear stress. The existence of initial shear stress will reduce the liquefaction resistance of saturated dense sand, but the liquefaction resistance of saturated dense sand under vertical loading mode is about 5% ~7% higher than that under parallel loading mode。It is found that the cumulative rate of energy loss increases with the increase of initial shear stress, which is the internal reason for the decrease of liquefaction resistance of saturated dense sand. The normalized curves of residual pore pressure and energy loss of saturated dense sand show a linear relationship in the logarithmic coordinate.