Liquefaction Response Mechanism Of Terrance Underlain Sandy Silt Under Landslide Impact

The Loess Plateau in China is prone to high speed remote landslides due to the narrow gullies formed by rivers and rainfall,and the large vertical drop distance between the terraces formed by the plateau and river erosion,and the small slope.High-speed remote landslides are characterised by high speed of movement,high destructive capacity,and a wide range of damage,and are of great interest to the academic and engineering communities because of the complex mechanics they exhibit during movement.Frequent human activities(irrigation)and the special properties of loess(wetting and water sensitivity)caused the frequent occurrence of loess landslides in the South Plateau of Jingyang,and according to the survey,more than half of the loess landslides exhibit high speed and long range characteristics.Therefore,it is important to investigate and study the mechanism of high speed and long distance movement of loess landslides under the impact liquefaction of sandy silt,in order to control the risk of landslides in the South Plateau of Jingyang.In order to study the process of loess landslide movement under the impact liquefaction of sandy silt,the purpose of landslide hazard management is achieved.According to the geological phenomenon of impact liquefaction found in the field investigation,a set of impact test equipment was designed and impact liquefaction test of sandy silt was conducted,then the research results were supported by a series of means such as indoor shear strength test and moisture content test,microscopic test and numerical simulation,etc.Finally,the liquefaction mechanism of terrace-prone sandy silt under the impact action of loess landslide was demonstrated,and the following conclusions were obtained.(1)Impact loading causes the total stress and pore water pressure within the sandy silt to increase dramatically,thus causing a sudden decrease in its shear strength and contributing to the downward movement of the landslide surface and a decrease in the friction coefficient of the sliding surface.(2)The collapse of large pores in sandy silt under impact is the main reason for the high pore water pressure in sandy silt,and when the impact force is high,medium and small pores will also be compressed and blocked,and the particles and pore morphology in the soil will be redistributed and rearranged,thus triggering the impact liquefaction phenomenon.(3)Unlike the closed and undrained environment required for vibratory liquefaction,sandy silt is in a weakly drained behavioural environment when impact liquefaction occurs,and when the rate of pore pressure accumulation within sandy silt is greater than the rate of dissipation,high pore water pressure will be generated and liquefaction will occur in sandy silt.(4)The increase in pore water pressure within the sandy silt and other terrace sediments in the terrace when impact liquefaction occurs will lead to a reduction in the frictional resistance of the landslide movement path,and the higher the pore water pressure generated by the impact,the stronger the pro-slip effect.