SPATIAL-TEMPORAL DIFFERENTIATION CHARACTERISTICS AND RATE OF FREEZE-THAW EROSION OF ROCK SLOPES IN PERIGLACIAL AREA

Tianshan Mountains are a typical periglacial area with high altitude, latitude and temperature difference in China. On the basis of the air temperature data collected from meteorological stations and onsite monitoring, we establish the freeze-thaw(FT)erosion assessment model and discuss the spatial-temporal differentiation characteristics of FT erosion and its effect on erosion rate of rock mass based on field investigation by 3D laser scanning. The results show that the factors of air temperature, rock mass structure, precipitation, slope gradient, earthquake intensity and slope have a decreasing contribution value to the FT erosion in order. The lower elevation of periglacial area is about 2600 m to 2900 m above sea level in Tianshan mountainous area and the FT erosion intensity increases with the increase of altitude and latitude. The seasonal variation and the temperatures fluctuate at the 0 ℃when the freeze and thaw alternating period, thus the FT erosion is the strongest. Geomorphological evolution process can be divided into FT erosion of rock mass, rock fragment slip-slide and deposition. The FT erosion rate of granite(hard rock), sandstone(medium hard rock) and phyllite(soft rock) slope increases with the increase of FT erosion assessment index, and decreases with the increase of rock FT coefficient. The empirical relationship between FT erosion rate and FT erosion assessment index and FT coefficient is established. The results are useful to the understanding of the mechanism and process of FT erosion, for engineering construction and geohazard reduction in periglacial areas.