Influence of shearing rate on the residual strength characteristic of three landslides soils in loess area

In order to investigate the effect of the shearing rate on the residual shear strength of slip zone soils, a series ring shear tests were carried out on slip zone soils from three landslides in loess area at the two shearing rates (0.1 mm/min and 1 mm/min). The slip zone soil specimens used in present study were from the northwest of China. Results indicated that the shear displacement to achieve the residual stage for specimens with higher shearing rate is greater than that of the lower rate. Relationship between the residual friction coefficients and normal stress shows that the residual friction coefficients for all specimens under the lower normal stress were greater than that under the higher normal stress at two shearing rate. Furthermore, the difference in the residual friction angle фr at the two shearing rates, фr (1) − фr (0.1), under each normal stress level were either positive or negative values, with the maximum absolute value of фr (1) − фr (0.1) reach up to 2.218°. However, the difference фr (1) − фr (0.1) under all normal stresses was negative, which indicates that the residual shear parameters reduced with the increasing of the shearing rate in loess area.

Material Weakening of Slip Zone Soils Induced by Water Level Fluctuation in the Ancient Landslides of Three Gorges Reservoir

This experimental study investigated the effect of repeated wetting and drying on the reduction of slip zone soils taken from the Huangtupo landslide in the Three Gorges Reservoir, China. The variation process of the physical property and substance composition of the slip zone soils under the wetting-drying cycles was studied through liquid and plastic limit test and X-ray diffraction test. The results indicate that (1) the shearing strength of the slip zone soil dramatically decreased after one wetting-drying cycle and then gradually decreased until reaching a relatively stable state at the fourth cycle; (2) the plasticity index of the slip zone soil varied with increasing number of cycles and a variation process opposite to that of the strength value was observed; and (3) the clay mineral content in the slip zone soil increased and the calcite and quartz contents relatively decreased with increasing number of cycles. The variations in the plasticity index of the slip zone soil, as well as the increase in its clay mineral content, play important roles in the strength reduction. The results of this study provide a foundation for revealing the deformation and damage mechanism of landslides in reservoir banks.