EXPERIMENTAL STUDY ON NATURAL EVOLUTION CHARACTERISTICS OF COARSE-GRAINED SOIL SLOPE IN SEASONAL FROZEN SOIL REGION

Seasonal coarse-grained frozen soil is widely distributed along the Sichuan-Tibet railway, and the stability of this type of soil slope is prominent. It is necessary to discuss the natural evolution characteristics and laws of this type of slope. This paper carries out the experimental study under the conditions of single factor and multi-factor combination and examines the variation law of coarse-grained soil slope under the conditions of rainfall, sunlight, freeze-thaw cycles. The results show that for a specific coarse-grained soil slope with steep initial slope angle, under the action of natural rainfall and sunlight, the slope can develop to a natural stable slope. Under repeated freeze-thaw action, the freezing and thawing of slope soil can lead to residual deformation. The frost deformation is about 0.09~0.1 times of the freezing depth, the residual deformation is about 0.052~0.062 times of the freezing depth, and the soil moisture of the slope surface increases by 2% ~3%. After repeated freezing and thawing, the soil structure becomes loose, the voids increase, and the density decreases. The loose soil is easy to erosion under the rainfall condition, and the slope degenerates backward. The natural evolution characteristics of coarse-grained soil slope in seasonal frozen soil area follow the following process: influence of rainfall and sunlight→slope tends to be stable→freeze-thaw action→soil of slope surface becomes loose→rainfall scouring→ slope degenerates backward→freezing and thawing of deeper soil. This process is repeated with seasonal changes, and the slope degenerates year by year.