Abstract

The lithology of the inlet side slope of the diversion tunnel on the right bank of Wudongde Hydropower Station is dominated by thin marbled dolomite. During construction, numerous cracks form along the elevation direction, and large monitoring deformation values appear in the consequent slope section. In this study, engineering geological analysis, deformation monitoring data analysis, and three-dimensional numerical simulation are combined to investigate the formation mechanism of cracks, the range of local deformed bodies, and the deformation and failure mechanism of deformed bodies. The stability of the slope is rechecked via the rigid-body limit equilibrium method based on the above analysis. Results show that the local convex terrain in the consequent slope section is cut through unfavorable structural surfaces and form a deformable body. Under the influence of unfavorable factors, such as the bedding cut foot caused by the lower excavation unloading and rainfall, the deformation of the shallow slope surface continuously increases; as a result, the shotcrete layer cracks. The deformation force comes from the middle and rear parts of the slope, and the instability mode slides along the bottom boundary level. After prestressed cables are added, the safety factor of the deformed part can satisfy the code requirements, and the existence of the deformed part does not affect the overall slope stability. Therefore, this study can provide technical support for engineering construction and a reference for similar slope engineering research.

1. Introduction

Rock masses with natural layered structures account for about 77% of the land area in China. A layered rock mass is usually distributed with a set of dominant structural planes. The shear strength along the structural plane is much smaller than that in the vertical direction and has obvious anisotropy. Layered rock slopes are the most common and widely distributed slopes. However, layered rock masses have stability problems in human engineering activities (CHEN Zhijian, 2001, HUANG Runqiu, 2007).

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