Analysis of characteristics and failure mechanism of Paodili seismic landslide in Qingchuan County

The problem of slope stability in high-intensity mountainous area is prominent. It is of great significance to study the relationship between geological structure and strata structure and the triggering mechanism of landslide under earthquake action. In this paper, the geological characteristics of the landslide in Qingchuan County are investigated, and the dynamic response and deformation and failure process of the 1st landslide are analyzed based on discrete element software （UDEC）. The field investigation shows that the slope of Paodili 1st landslide has a near-horizontal “upper-hard, lower-soft” stratigraphic texture, in which faults pass through the back edge of the slope. The lithologic zonation of landslide deposits shows that the lower phyllite of Paodili 1st landslide was destroyed earlier than the upper siliceous rock, and the broken time was earlier than the 2nd and 3rd landslides. The numerical simulation research reveals that the peak acceleration amplification effect is strongest in phyllite near the fault zone, with an amplification factor of 6.79. This leads to the lower phyllite first experienced tensile failure along the steep dip surface, then the upper siliceous rock mass produced tension failure. The results are in good agreement with the characteristics of the deposits in the field investigation. The dynamic response, deformation, and failure of the landslide are controlled by the fault and the upper-hard, lower soft stratigraphic texture. This study can provide a reference for seismic landslides evaluation in regions characterized by faulting and “upper-hard, lower-soft” strata.