Effects of Water Content and Shearing Rate on Residual Shear Stress

Abstract

Quantifying the residual stress on slip soil through ring shear tests is crucial to understanding the stability of landslides. In general, before a ring shear test, the soil samples must be saturated, although the slip soil was potentially unsaturated during the sliding process of the landslide. This discrepancy could provide inaccurate results from the ring shear test. To determine this discrepancy, 25 ring shear tests were performed on unsaturated remolded slip soils from the Zhangjiawu landslide along the bank of the reservoir of the Three Gorges Project, China. Different water contents (6, 9 and 12%), shearing rates (0.5, 5.0 and 50 mm/min) and normal stress levels (25, 50, 100, 200, 300 and 400 kPa) were considered. The results indicate that (a) at the same shearing rate and normal stress, soils with a higher water content tended to have lower residual stresses; the negative effect of water content on the residual shear stress weakened at a lower shearing rate; (b) without healing time, an increase in the shearing rate had a positive effect on the residual stress, and the influence of the shearing rate on the residual stress increased as the normal stress increased; the positive rate effect was not caused by the production of an extra clay fraction but is potentially explained by non-Newtonian fluid theory; and (c) the results of the sensitivity analysis and the relationship of the ring shear test parameters using ANN show that the water content had a slightly more significant influence on the residual stress than the shearing rate.