Study On The Mechanism Of Formation Of Freeze-Thaw Loess Landslides In Yili Region

The Yili region is located in the western part of the Tianshan Mountains in China and is a typical seasonal frozen soil area,the frequent occurrence of freeze-thaw loess landslides poses a serious threat to the safety of local engineering construction and human settlements,and therefore there is an urgent need to conduct research on the formation mechanism of freezethaw loess landslides.Based on the project "Comprehensive Geological Survey of Resources and Environment in the Planning and Construction Area of South Xinjiang Corps",this paper takes the typical freeze-thaw loess landslides in Kalayakaqi Township of Yining County as the research object and conducts detailed on-site surveys,on-site ground temperature measurements,in-house tests and numerical simulation analysis.Based on the field survey results and indoor data analysis,the damage process of freeze-thaw loess landslides was systematically summarized and the formation mechanism of freeze-thaw loess landslides was explored.The key research findings and outcomes are as follows:1.Through data collection,field investigation and ground temperature monitoring,we further analyze the effect of freezing and thawing,and summaries the main characteristics of the development of freezing and thawing loess landslides in the study area,and analyze the ground temperature change pattern of loess landslides during the freezing and thawing process,which offers a conceptual basis and provides data backup for the ensuing study.2.The outcome shows that as the cyclic rate of freeze-thaw loess increases,the limit breaking stress of the loess decreases on a linear basis,the cohesion of the shear resistance decreases slightly and finally becomes level,and the inner rubbing angle shows a slow upward trend with little change;after several freeze-thaw cycles,the permeability coefficient of the soil shows a development trend of first increasing and then stabilizing.3.The Sigma/w and Seep/w blocks of Geo Studio software were employed to analyze the percolation force field and tension fields of the loess landslide in the study area under the effect of freezing and thawing.The stress field simulation determines the displacement of the slope at different time stages during the freeze-thaw process.Combining the temperature,seepage and stress fields,the stability of the loess slope at different stages of the freeze-thaw process is analysed by the finite unit stress method to realize the coupling of the three fields to analyze the stability of the slope.The simulation results show that the stability of the slope increases during the freezing period,the stability of the slope increases during the thawing period and then increases,but still decreases compared with the initial slope stability.4.Describe the formation process of freeze-thaw loess landslides and summaries the two ways in which freeze-thaw induces loess landslides: the frozen layer of the slope body is affected by the freeze-thaw cycle and the frozen stagnant water effect inside the slope body.During the freezing process,the permeability coefficient of the frozen layer on the slope surface drops sharply,leading to a rise in the groundwater table and an increase in the softening range of the soil,but due to the greater strength of the frozen layer,the stability of the slope increases instead of decreasing.