Study On The Formation Mechanism Of Xinzhuang Landslide

The 8.5 magnitude earthquake occurred in Haiyuan County in 1920.Such strong vibrations has caused a variety of tectonic deformation and large-scale geological disasters in the epicenter of the Haiyuan earthquake.This article takes the Xinzhuang landslide as the research object,the engineering geological characteristics of landslide and the mechanical properties of loess was analyzed by site survey and indoor routine test and dynamic triaxial test.Qualitative analysis and anti-liquefaction shear stress method and FLAC3 d numerical simulation and PFC2 d particle flow simulation method were used to study the liquefaction possibility and motion process of the landslide.It provides a typical example for the analysis of the formation mechanism of the low-angle loess liquefaction landslide caused by the earthquake.The following conclusions are obtained through the study.1.From the material composition and scale of the landslide,it can be seen that this landslide is a large-scale landslide.Slope body material is mainly composed of loess-like soil and silty sand and slide bed is mudstone and slide belt is located on the interface between mudstone and silty soil.Under the action of strong earthquake,the pore-water pressure increased rapidly due to the destruction of soil structure and the collapse of micropores between particles.As a result,the soil is liquefied and its strength is reduced,then the sliding body slips along the rock-soil interface and forms wavy landform on the surface of the landslide and forms crack and sink in the back edge of the landslide and forms drumlin in the front of the landslide due to push effect.2.The liquefaction possibility of the landslide can be judged from the site conditions and the physical properties of the loess and the vibration load.Anti-liquefaction shear stress analysis results show that the landslide in the earthquake intensity degree Ⅷ has the possibility of liquefaction,and the actual intensity degree of the earthquake was Ⅹ when the landslide was formed.3.The numerical simulation results show that the pore-water pressure increases sharply when the earthquake wave continues to 5s,the pore-water pressure ratio in the front and middle of the slope reaches 1.032 and 0.986.When the earthquake wave continues to 25 s,a sliding surface is formed in the slope and large-scale slippage occurred.4.Based on the numerical simulation analysis of particle flow,it is found that the liquefied loess layer slides along the sliding surface under the action of seismic forces,and expressed as acceleration-deceleration-stable motion process.The relative displacement of the front edge of the slope body is the largest and the displacement of the rear edge is small and partially sliding soils accumulate in the front valley.