ABSTRACT
Kaiser et al. (1996) summarized the failure mechanism of rockbursts into three types based on the energy analysis. (i) the failure mechanism of rockmass volume expansion induced by rock frature (more or less associated with rock ejection), (ii) the failure mechanism of rockmass ejection induced by seismic energy propagation and (iii) rock collapse mechanism induced by the shock of the earthquake. Hoek et al. (1986) considered rockburst was the result of surrounding rockmass shear damage in high stressed areas. Wang et al. (2003) proposed that rockburst was the result of synthetic actions by a variety of factors such as geological structures, surrounding rockmass strength, attitude of stratum, stress state of surrounding rock, deformation characteristics and underground engineering arrangements, etc. They considered that the essential mechanism of rockburst was pressure cracking damage. Rockburst prediction
1 INTRODUCTION
With the rapid growth and development of the world’s population and economics, increasing requirements of energy sources is needed. Many large-scale hydropower stations are being constructed to satisfy this aim. In particular, along with the increasing of energy sources exploiting in China, more and more large-scale hydroelectric projects such as Xiluodu, Baihetan and Jinping hydropower stations have been or are being constructed in the southwest of China (Xu et al. 2010). Many deep-buried tunnels and underground powerhouses among these projects were, are or will be excavated. Therefore, safe and economic tunneling has been a challenging topic in the tunnel construction because of complex geological conditions such as faults, fractures, caverns and high in-situ stress. Lots of rockbursts have occurred during continuous excavation of these tunnels in the past years. Rockburst can not only seriously threatens the safety of workers and mechanical equipments, but also it can induce many problems such as over-excavation, primary support failure and construction delays, which will cause significant economic loss. With the increase of engineering buried-depth, scale and in-situ stress level, rockburst and its corresponding disasters will dramatically augment
remains one of the most complicated problems in rock mechanics worldwide. So far, no acceptable and mature theory and method stood for predicting rockburst.
