Quantitative evaluation of landslide hazard under the coupling of water and earthquake: a case of co seismic landslides induced by the 2013 M_w6.6 Minxian-zhangxian earthquake

The instability evolution of loess slopes under the coupling of water and earthquake is very complex. Quantitative assessment of seismic landslide hazard has become a common challenge for engineering geologists and seismic geologists. This article takes the Yongguangcun (YGC) landslide induced by the 2013 M_w6.6 Minxian-Zhangxian earthquake to systematically study the hazard of loess slopes under the coupling effect of water and earthquake, namely their runout problem. The seismic accelerations in three directions recorded by MXT were decomposed along the sliding direction and the inclination of the slope to obtain the seismic load along the tangential direction of the sliding surface. Then, a combination of a finite element method and the Newmark method is used to study the co-seismic sliding of the YGC landslides during the earthquake, fully considering the effects of various factors such as pore water pressure, groundwater, and matric suction during rainfall on the permanent displacement of the slope. The present study yields the following research findings: 1) The pre-earthquake safety factor of the Y_W# landslide, which has a sliding surface in close proximity to the groundwater level, is reduced to 1.247 under the combined influence of rainfall and groundwater. Additionally, the critical earthquake acceleration is determined to be 0.0763 g. 2) It is observed that when the peak acceleration along the tangential direction of the sliding surface near the groundwater surface reaches or surpasses 0.175 g, the cumulative displacement of the Y_W# landslide may exceed the critical failure value of 5–10 cm. It provides a reference for the quantitative assessment of regional seismic landslide hazard, which has important theoretical and practical value.