Study of the in situ stress field in a deep valley and its influence on rock slope stability in Southwest China

摘要

The in situ stress field in valley areas is an important factor to consider in the construction of hydropower projects in southwest China. Due to intense tectonic movement, the action of gravity, and rapid river erosion, the resulting stress has a complex distribution and a large magnitude. The availability of stress measurements is insufficient to provide adequate understanding of the regional stress state. In this research, inversion analysis for the in situ stress field of a valley in the upper reaches of the Lancang River is carried out by using stepwise regression analysis and the FLAC3D numerical simulation, and the temporal and spatial distribution characteristics of the in situ stress are obtained. Based on those results, the influence of stress unloading effects on slope stability is discussed. The results show that the formation of the modern in situ stress field is the comprehensive result of interactions among gravity, tectonic movement, and river erosion. The reliability of the inverse result can be increased by improving the mesh density of the calculated model and considering multistep river erosion. Under the influence of the unloading effects, tensile fractures were formed and the rock mass loosened near the slope surface. With the presence of bedding dipping into the slope, toppling failure was triggered by the unloading rebound that mainly occurred in the stress relaxation zone.