Abstract

More and more large-scale underground power houses are under complex geological environment of great buried depth and high in-situ stress. Meanwhile, it is complicated to analyze the long-term stability of underground caverns owing to the existence of joints in the surrounding rock mass. The joints make the degradation effect of the surrounding rock mass. According to these features, a new visco-elasto-plastic constitutive model is proposed. The model has a comprehensive consideration of geometric damage of the fractured rock mass. Besides, regarding VC++ as a terrace, we use the secondary development function of FLAC3D to make a program of this constitutive model. It is a Dynamic Link Library (DLL) and it can be used by the main program of FLAC3D. The new damage creep model of fractured rock mass is developed. In the project of Jinping I underground power houses in Sichuan, China, we use this program to analyze the long-term stability of underground caverns and guide the design of engineering. The results show that: it is quite strong feasible to use this new damage creep model to simulate the excavation of large underground caverns and analyze the long-term stability, and the analysis results can be used to guide the construction of engineering.

1. INTRODUCTION

Complex, jointed rock masses are commonly encountered in both underground excavation and slope stability engineering. The strength, deformation and time-dependent characteristics of rock masses directly affect the stability measures and reinforcement requirements for engineering design, construction, and maintenance of these rock structures. Thus it is essential, that the effect of joints be considered in the estimation of the rheological properties of the rock mass. As most of the related large-scale hydropower projects are located in the deep, narrow valleys of south west China, their underground caverns are usually subjected to very high in-situ stresses strongly influenced by the topography. Under these circumstances, brittle rock failure and associated time effects often occur during cavern excavation and construction. Concomitantly, splitting failure which adversely affects stability has been experienced in side walls and other parts of these underground hydropower station caverns.

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