ABSTRACT:

Rock bursts are frequently encountered during the construction of deep-buried tunnels of Jinping II hydropower station, Southwest China. Investigation on the possibility of rockburst prediction during TBM and D&B advancing is necessary in order to guide the construction of tunnels and protect personnel and TBM equipments from rock bursting accidents. A real-time movable microseismic monitoring system was installed to predict rockbursts ahead of the tunnel faces. The tempo-spatial distribution evolution of microseismic events prior to and during rock bursting occurrence were recorded and analyzed in detail. The clustering of microseismic events prior to rockburst is found to be the significant indicator of rockbursting in deep rock tunneling. The successful prediction of rock bursts proved that microseismic monitoring is essential in the assessment and mitigation of rockburst hazard, minimizing the damage of equipment and personnel. Results from present study can be valuable for construction management and safety assessment of other rock engineering in high geostress.

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 eta/. 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 overexcavation, primary support failure and construction delays, which will cause significant economic loss.

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