Failure mechanism of a snowmelt-related loess landslide group in Ten-zan, China

In recent years landslides are occurring more frequently in seasonally frozen ground regions. Compared to non-seasonally frozen ground regions, whether the physical processes of snowmelt and soil freeze-thaw affect landslides requires further investigation. A giant loess landslide group occurred on May 9, 2002 in the Zeketai River in Ili region is selected as an ideal case study. The Galamput loess landslide group is evidently triggered by extreme precipitation event, but the impact of snowmelt process prior to landslide occurrence is worth further explored. The main purposes of this study are (1) to clarify the geomorphological and geological characteristics of the Galamput landslide group, (2) to reveal the formation process and failure mode, (3) to explore the deformation and failure mechanism. Based on field investigations, remote sensing interpretation, landslide surveys, meteorological data analysis, and laboratory experiments, this study investigates and analyzes the basic characteristics, formation process and failure mode of landslide group, and further reveals the triggering mechanisms. The landslide group is composed of three landslides with a total volume of approximately 17.36×106 m3, and the formation and development are a multi-stage and multiple progressive failure process lasting intermittently for 2 days. A deformation and failure model of loess slope considering meteorological hydraulic dynamic change process is proposed. The melting of accumulated snow driven by high temperatures affects the slope deformation, and extreme rainfall acts as a triggering factor for the landslide group. The special slope structure and stratigraphic combination also provide a material structural basis for the occurrence of loess landslide group. The occurrence of the landslide group is the coupling result of early snowmelt and later heavy rainfall, and the combined effect of static liquefaction of the sliding surface and sliding liquefaction at the slope toe is an important triggering mechanism. This study can provide a new perspective on the failure mechanism of loess landslides in seasonal frozen zone.