| Glacial till,as a special type of soil in the alpine mountain area,is affected by the special climate of the alpine mountain area,and a typical freeze-thaw "fragmentation"phenomenon occurs,which in turn causes geological disasters such as collapse,landslides and debris flow.Based on this,the glacial till in the Moxi River Basin is taken as the research object.On the basis of in-depth analysis of the domestic and foreign research results on glacial till and the basic geography,geological environment conditions,distribution characteristics and disaster characteristics of the glacial till,the particle sieve is adopted.The sub-test,CT scanning test,scanning electron microscope test and slope cyclic freeze-thaw simulation test analyze the macro,meso,micro-structural characteristics of the glacial till in the Moxi River Basin and the deformation and failure response of the cyclic freeze-thaw slope.The glacial till's fragmentation mechanism and disaster-causing effect under cyclic freezing and thawing are studied in detail,and its research results can provide a more scientific science for the safe operation of roads,railways,hydropower stations and other projects in the high-cold mountain areas and the disaster prevention and mitigation of local governments.The specific research results are as follows:(1)The glacial till in the Moxi River Basin has a wide particle size distribution and exhibits a double-peaked characteristic.It is mainly dominated by giant particles,such as boulders and boulders,and more fine particles(clay).The glacial till has a non-uniformity coefficient greater than 5 and a curvature coefficient greater than 3.In brief,the glacial till can be defined as poorly graded soil.(2)Based on the microstructure analysis of glacial till samples by CT scanning technique,it can be found that the porosity of the samples was 24.09%,and the body porosity and surface porosity are basically the same.Moreover,the pore probability density with diameter of more than 2mm is the largest.In the direction of the longitudinal section,the particle shape is close to a circle and the particle orientation is more obvious in the direction of cross section.(3)The SEM measurement is used to investigate the microstructure of the glacial till.The SEM images shows that the basic skeleton of glacial till consists of lamellae and laminates.In addition,its structural units are complex and exhibit an adhesive structure.(4)The simulation test of the cycle freezing-thawing of the slope find that the deformation of the slope during the cycle freezing-thawing process is mainly manifested as thawing and freezing effect,sliding along the slope,surface crack and front slide.More importantly,water content is the dominant factor causing these deformations.(5)The fragmentation mechanism of glacial till under cyclic freezing-thawing can be summarized as follows:cyclic freezing-thawing changes the pore structure,particle size and cementation between grains of glacial till in the microscopic aspect.The cyclic freezing-thawing effect,crack and displacement of glacial till are caused by the freezing-thawing and subsidence effect at the macro level.(6)The disaster-causing effect of glacial till can be summarized as follows:the cyclic freeze-thaw effect changes the mesoscopic and macroscopic structure of glacial till,resulting in the fragmentation of glacial till and the decreased slope stability and thus inducing geological disasters. |
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