During the construction process of the left bank tail water outlet slope of Wudongde Hydropower Station, deformation phenomena such as slip and collapse along shallow surface of the plane and subvertical cracks along the elevation direction appear. In this study, combined with the engineering geological analysis, the deformation monitoring data analysis and the numerical simulation technology, qualitative analysis and quantitative evaluation of the crack generation mechanism and excavation stability of the slope are carried out. The results show that the slope is a steeply inclined consequent slope, and the slope ratio of the upper slope is nearly the same with that of the rock dip angel. The problem of cutting of the rock slope toe of the consequent slope is not exist. In addition, the unexcavated rock masses on both sides of the lower vertical slope can provide certain deformation constraint to the slope. The cracks appear during the construction process are mainly affected by the local unfavorable geological defects. The deformation of the superficial layer rock mass during the excavation unloading process causes crack in the concrete spray layer . The small faults exposed on the slope surface have great influence on the deformation of the slope, the stress of the supporting system and also the local stability. There is no overall stability problem in the slope. The research results can provide reference for the similarity of slope engineering research.

1. Introduction

The sedimentary rocks with layered structure in nature account for two-thirds of the land area (China accounts for 77.3%), and many metamorphic rocks also have layered structural features (Chen Zhijian,2001). Human engineering activities, especially in hydropower projects and traffic engineering, encounter a large number of layered rock mass stability problems. In layered rock mass engineering, the consequent rock slopes is often encountered in railways, highways, open pit mining and water conservancy construction.

In recent years, many scholars in China have carried out a lot of research works on the deformation and failure mechanism of the consequent rock slope. Sun Shuwei et al., 2008 used physical model test methods to study the deformation and failure mechanism of the consequent rock slope. By analyzing the buckling deformation factors of the rock mass in the consequent slope, Li Yunpeng et al., 2000 proposed the upper limit of the collapse behavior of layered slopes in the form of displacement. Zhang Huimei et al., 2004 summarized the common failure modes of the consequent rock slope in nature. Based on the geological background and mechanical mechanism, the simplified analysis model of the rock beam structure was abstracted by Zhang. Based on engineering geological conditions analysis, , the deformation and failure mechanism of the consequent slope is discussed in depth and the slope stability analysis is carried out by Huang Runqiu et al., 2007.

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