Role of ground motion characteristics in liquefaction triggering and lateral displacements of sloping grounds

Abstract

This paper investigates the impact of ground motion characteristics on liquefaction triggering and liquefaction-induced response of sloping grounds, identifying the significance of each in predicting the system response. A three-stage harmonic waveform with varying peak ground acceleration (PGA), number of cycles at PGA ($N_{\text{hold}}$), and motion frequency ($f$) is applied at the base of mildly sloping soil columns, representing infinite sloping grounds. The soil columns are considered with different heights and slopes, each with different depth, thickness, and density of an embedded liquefiable layer. Fully coupled nonlinear dynamic analyses are conducted in OpenSees using the SANISAND-MSf v2 soil constitutive model, assessing the peak depth-averaged excess pore water pressure ratio in the liquefiable layer and the end-of-motion surface lateral displacement as engineering demand parameters (EDPs). Results show that increasing PGA enhances both EDPs, while distinct response patterns are observed at various motion frequencies, influenced by the natural frequency of the liquefied soil column. Higher $N_{\text{hold}}$ increases excess pore water pressure generation and surface lateral displacements, as the soil remains in the post-liquefaction stage for a longer duration. An exploration of the relative significance of these characteristics on system responses reveals that PGA has a significantly greater contribution to the liquefaction triggering EDP compared to $f$ and $N_{\text{hold}}$. For liquefaction-induced EDP, $f$ is the most influential factor, followed by PGA and $N_{\text{hold}}$, which contribute similarly. These insights guide the selection of efficient intensity measures for predicting liquefaction triggering and liquefaction-induced response of sloping grounds.