Analysis Of Geological Features, Cause And Stability Of The Loess Landslide In Ili

Ili Kazak Autonomous Prefecture is located in the west of the Xinjiang Uygur Autonomous Region,and the loess landslides are widely distributed in this area. For a long time, the loess landslides have brought great loss to the economic development and people’s lives and property of this area, such as buried villages, interrupted traffic and caused casualties. Therefore, to study the characteristics, cause and stability of the loess landslides is of great importance to the prevention and treatment of the loess landslides in this area.This paper takes the Ili as the research area. First of all, the geological environmental background, the loess distribution, the loess zoning, the loess strata and the basic properties of the loess are analyzed, based on the field geological investigation, data compilation, spot and laboratory test. Secondly, the distribution,types and morphological characteristics of the loess landslides in this area are studied, and the forming reason of the loess landslides are researched in many respects. Finally, take the Jialangpute landslide as a typical example, and the stability of this loess landslide is analyzed by using limit equilibrium method and strength reduction finite element method, then, some treatment measures are put forward. The main research conclusions are as follows:(1)The soil samples which are collected at Jialangpute, Zeketai and Kuoledeneng are tested by soil mechanics experimental. Then, the basic properties include material composition, physical properties,water physical properties and mechanical properties are analyzed. The results show that the loess in Ili is mainly composed of silt particle, the mineral components of loess in this region are dominated by quartz,feldspar and carbonate minerals, and is alkaline. The natural water content and natural weight are large, and void ratio is 0.686 ~ 0.957, going with considerable collapsible. The permeability coefficient is 10-4 ~10-6cm/s, and the loess presents weak permeability.The cohesion is 7.2~26.2k Pa, and the angle of internal friction is 15.5~32.0°, and they reduced with the increase of the water content.(2)The distribution and form of the loess landslides in Ili are analyzed by field investigation.The loess landslides in Ili are mainly distributed in the lower and middle mountain area, the low hill area, and the loess slope along the river bank, by the influence of engineering geological condition and the loess distribution. The mid-eastern Ili is the area where the landslides develop most seriously. The landslides mainly occurred in April, May and June in time domain. The loess landslides and loess-bedrock interface landslides are main types of landslides in Ili, and they are mainly small scale and shallow,certainly, there are still some large-scale landslides. Four kinds of cross-sectional shape types are main plane shape of the landslides, include dust pan shape, bench shape, complex shape and fan shape, while the circular slip surface is the main longitudinal shape type.(3)The cause of the loess landslides in Ili is studied based on the field investigation. Analysis suggests that, the loess which is widely distributed in Ili provides material base for the loess landslides. The topography and geomorphology, and the stratum structure which is unconformable contact between loess stratum and bedrock provide boundary conditions, and the rainstorm is the immediate cause. On this basiss,the mechanism of the loess landslide which is induced by rainfall is analyzed.(4)Take the Jialangpute landslide which occurred in Ili as a typical example, the characteristics and genetic mechanism of this landslide are analyzed by using 2D limit equilibrium method, and the stability of the dammed lake is analyzed from three aspects which include seepage stability, anti-erosion stability and anti-slide stability. Then, Based on the two-dimensional analysis, 3D visualization and numerical model of one typical landslide are built by using three kinds of software which include GOCAD, CATIA and Hypermesh, and the further study on the stability of this typical landslide is made by 3D strength reduction finite element method. At last, some treatment measures are put forward, according to the calculation results. This may provide reference for the stability analysis of other loess landslides in Ili.