Study On The Motion Mechanism Of Repeatedly Failure Loess Landslides At South Jingyang Plateau

Repeatedly failure loess landslide is a special type of loess landslides,showing for the same tableland ramp with repeatedly failure characteristics.Landslides reflect in some kind of recidivity,embodying the characteristics of repeated failure in time and space.Repeatedly failure loess landslides makes the tableland edge shrinking,which threatened the production and living of residents on the tableland,and also caused destruction of land resources as well as damage to infrastructure.In this paper,taking the repeatedly failure loess landslide as the research object,on the basis of the research status and achievements of repeatedly failure loess landslides,I systematically analysis geology environment background,motion characteristics and characteristic parameters of repeatedly failure loess landslides in South Jingyang Plateau.Using Particle Flow Code simulate the sliding process in three orders of repeatedly failure loess landslides in South Jingyang Plateau,and discusses motion mechanism of repeatedly failure loess landslide.The research results have important significance for the mechanism analysis and countermeasures of repeatedly failure loess landslides.The main research contents and conclusions are as follows:(1)Combined with on-site investigation and remote-sensing interpretation:14 slopes have occurred repeatedly failure and formed more than 38 sliding,among them there are 14 slopes happened more than 2 sliding,6 places more than 3 sliding,2 more than 4 sliding.According to the mechanics mechanism of landslide at south Jingyang plateau,landslides can be classified into two categories:flow-slip and sliding.According to the order of landslide development,these repeatedly failure loess landslides can be classified into three categories:flow-slip—sliding—sliding,flow-slip—flow-slip—sliding and sliding—flow-slip.(2)Statistically analyze the characteristic parameters of repeatedly failure loess(3)andslides in South Jingyang Plateau,the results show that with increasing sliding orders,sliding volume decreased gradually,shear crack position also gradually rise,sliding distance markedly shortened,the later sliding damage position tend to occur in the first phase of the trailing edge of central location and slope position on either side of the trailing edge.(4)The results of two-dimensional Particle Flow Code simulating the sliding process of repeatedly failure loess landslides in South Jingyang Plateau:in the process of landslides first sliding,they often have high-speed and long run-out characteristics.In the front of the high-speed sliding body,strong impact effect exists,substance in leading end colliding with terrace will provoke a surge of dust,which caused by ploughing effect.Substance in leading end of landslides with high speed will push the terrace formation,scrape the corrosion terrace material and mingle them moving forward together.Loess landslides in research area exist some kind of liquefaction effect in the process of sliding.When it comes to the first failure and the sliding volume is larger,the soil nearby sliding surface is often of high water content,this part of soil under the action of extrusion and friction will produce large excess pore water pressure.When the sliding body with high velocity move on first terrace of middle and lower reaches of Jing River,accumulative formation on the surface of bench is thin,loose and waterlogged,the sliding body has enough kinetic energy breakdown the surface of terrace to contact with loose and saturated silty soil.Soil near the sliding surface will generate great pore water pressure,and is hard to scatter and disappear,which make the soil nearby sliding surface liquefy fully,lower friction coefficient,and resistance decreases or all lost.Ploughing and erosion effect will enlarge the run-out ability of sliding mass.(1)The motion mechanism of repeatedly failure loss landslides:ploughing and erosion causing landslides and sliding bed liquefaction causing landslides.When landslides came to slide,most of gravitational potential energy is converted into kinetic energy,which made the sliding body impact the terrace with high speed.During the sliding,because of ploughing and erosion effect and liquefaction effect,slip mass will develop a long distance.