Study On Frost Heaving Characterteristics Of Frozen Slope Of Coarse-grained Soil In Sichuan-tibet Line

The proposed Sichuan-Tibet Railway will pass through a large number of seasonal coarse-grained permafrost areas in the high-cold area represented by Xinduqiao.After repeated freezing and thawing of frozen slopes of coarse-grained frozen soils,there will be a slow sliding phenomenon,and most of them are dominated by shallow surface soils.The field investigation found that the type of slope damage was mainly surface slip,slump,erosion,and hot melt slump.In this paper,the stability factors of the slope are studied by the method of indoor model test and numerical calculation model.In the indoor model test,under the same soil parameters,the frost heaving amount changes under different working conditions were measured to study the variation of frost heave.Firstly,the frost heaving characteristics of the slope under the two conditions of snow accumulation and no snow cover were studied.The indirect measurement method was used to observe the frost heave of the slope,and it was found that there was a group of snow-covered heave expansion ratios.The amount of snow frost heave must be large;Then the frost heaving amount of the slope at different slope angles was observed,and it was found that the frost heave of the slope increased with the increase of the slope angle;This experiment carried out six cycles of freeze-thaw cycles for each group of slopes,and found that the amount of frost heave expansion gradually increased with the increase in the number of freeze-thaw cycles.When the number of freeze-thaw cycles exceeded four times,the amount of frost heave would gradually increase.In stability,and in the slope surface from the top of the slope to the foot of the slope,the amount of frost heave will gradually decrease,the displacement of the top of the slope will be larger,and local damage will occur.In the numerical simulation calculations,the deformation of the slope after multiple freeze-thaw cycles was analyzed,and the variations of the deformation under different slopes,different slope heights,different surface freeze-thaw cycle thicknesses and non-bongling cycles were discussed.According to the law,with the gradual increase of the slope angle,the slope deformation gradually increases,and the maximum displacement area gradually shifts from the top of the slope to the slope foot.In addition,under the same conditions,the maximum displacement area of the slope is mainly distributed near the foot of the slope,and increases with the height of the slope,the thickness of the freeze-thaw cycle,and the number of freeze-thaw cycles.In the calculation,it was found that the slope basically moved along the freeze-thaw cycle and gradually peeled off from the foot of the slope,causing the upper soil to lose its support and thus causing damage.Combined with the measured results of deformation of the frozen soil slope in Xinduqiao area,the slope failure mode of the coarse-grained frozen soil slope is analyzed.The test results and numerical calculation results are similar to the field survey results.The research results can be seasonal for the Sichuan-Tibet Railway.The reference is provided for the engineering treatment of coarse-grained frozen soil slopes.