Study On Properties Of Landslide Soil And Formation Mechanism Of Loess-bedrock

Yan’an, located in loess plateau area, influenced by the geological conditions, the contact relationship between the loess and rock below, natural condition and engineering activities, is one of the cities that suffered landslides frequently. In this situation, people’s lives and economy are threatened. Loess-bedrock landslide as one significant part of the landslides happened there, is of highly research value.This paper takes Erzhuangke landslide in Yan’an as an example, through field investigation, resources collection, experiments and numerical simulation, researches the basic characteristics, formation condition, physical and engineering properties of in-situ soil,and the process mechanisms. The major results of this paper are:(1) The author collects the resources of that site, and investigates the geological conditions, gets the basic properties of the landslide site, and then analyzes the formation condition of the landslide.(2) The author compares the test data of soil samples taken from the site; analyzes the properties of soils in different positions; through direct shear test and regression analysis, The author gets the strength parameters(c 、 φ) in different water content and dry density of remolded soil.(3) This paper analyzes the stability of landslides by transmitting coefficient method.Combined the quantitively analysis, this landslide is for whole stable at present, although partially unstable. However, if suffered continuous rainfall, it is highly possible to be remobilized and slip again, so it is necessary to take measures to keep this landslide stable.(4) The author creates model by ANSYS, implements FLAC3 D numerical analysis to research the process mechanisms of landslide. The results are: before the slide, there are some tension cracks in the original slope, but the cracks continue to stretch and extend in the effects of destroying toe, which creates the flow path for rainfall. In this situation, when suffered heavy rainfall, it would produces weak area in the slope and at interface of loess and bed-rock,and the shear strength would continuously decrease with the continuous rain to resulting in finally inducing the driving force bigger than the resistance, which produces landslide.