Effect of Excess Pore Pressure on Earthquake‐Induced Displacement of Partially Saturated Sandy Soil Slopes: Flexible Sliding Block Analysis

The permanent displacement of earth slopes during earthquake shaking is a key indicator for landslide hazard assessment. Previous studies mostly attempt to evaluate the earthquake-induced displacement of dry or saturated soil slopes, while it is less common to deal with partially saturated soils. In the present study, a simplified procedure is proposed to account for the seismic-induced excess pore pressure in slopes with partially saturated sandy soils. The effect of matric suction, suction stress, and excess pore pressure on the yield acceleration of partially saturated sandy slopes is investigated, and the coupled Newmark sliding block method, known as the flexible soil columns with dynamic shear modulus and damping ratio, is modified to estimate the seismic slope displacement. Detailed discussions are made about the effect of different degrees of saturation on the excess pore pressure ratio, yield acceleration, and slope displacement. The numerical results show that the excess pore pressure ratio tends to exponentially increase with saturation, and the change of yield acceleration and displacement with saturation can be divided into suction stress dominant and excess pore water pressure dominant stages.