Experimental study on gravitational erosion process of vegetation slope under freeze–thaw

Abstract

Freeze–thaw is the major factor in gravitational erosion creep of slopes in cold regions, but gravitational erosion is influenced remarkably by vegetation cover. In order to investigate the phenomenon of the gravitational erosion process of vegetation slopes under freeze–thaw in seasonally frozen soil regions, on-site freeze–thaw tests of different vegetation slopes were conducted in the frozen soil testing ground of Kitami Institute of Technology (KIT, Hokkaido, Japan). Slope vegetation is divided into an external-soil spray seeding section and a turfed section according to its method of formation. Through field tests of four cycles, the slope temperature, frost depth, amount of frost-heave, and amount of movement were observed dynamically in real-time, initially revealing the regularity of the gravitational erosion process of the vegetation slope, which provided a scientific basis for slope stability control in cold regions. The experimental results show that the gravitational erosion of the slope is a process of irreversible gradual evolution, that the extent of erosion has a periodical fluctuation in time, that the target point of the slope surface moves in a jagged trajectory down the slope year after year, and that the maximum values of the amount of movement of the external-soil spray seeding section and the turfed section are −13.1 and –6.1 cm, respectively, after four freeze–thaw cycles. The space distribution of the slope surface has inhomogeneity. The difference in temperature and water content of each part of the slope surface is the main reason why the freezing front of the slope is not parallel to the slope surface. The amount of frost-heave of the slope toe was greater than that of the slope crest, which caused upward displacement along the slope during early freezing. The movement of the slope is closely related to the development of vegetation, and the heat insulation and reinforcement of vegetation cover effectively restrain the displacement of the slope's shallow soil. The results of this study have a certain significance in the prevention and treatment of shallow slope sliding in cold regions.