Study Of Rockburst Of Drainage Tunnels In Jinping Ⅱ Hydropower Station

The rockbusrst problems involve multi-fields such as hydropowerproject, mine exploitation, tunnel projects of railway and roadway and so on. It causes serious economic losses and casualties every year, and becomes a major disaster in the field of industrial safety.JinpingⅡhydropower station is located in a high geostress region of South-West China. Since the excavation of drainage tunnel, more than 110 rockbursts were recorded. These rockbursts activities have severe influence on the construction progress and safety of the personnel and equipments. To be better understanding the mechanism and prediction of rockburst of hard rock, the related problems of rockburst are studied in the dissertation. Based on theory analysis, using numerical simulation technology, and combining results of experiment research and field monitoring with characterization of rockburst, the rockburst in the drainage tunnel is studied systematically. The main research works are as following:(1) The rockburst in the drainage tunnel is mainly partial strain rockbust, fault-control while joint-control rockbust are infrequent. The break styles include spalling, bending, exploding, and collapsing. The strain rockburst occurred frequently in the layer with deep overburden, high in-situ stress, and intact rock mass. Fault and joint often influence the character of rockburst.(2) In response to the nature of the unloading since excavating of the underground, a series of rock experiment are carried out. The results illustrate that:the marble in the drainage tunnel has a characteristic elastic-brittle property, and the nature is influenced by loading velocity, unload velocity and failure confining pressure. If the energy in the rock which due to the change of the equipment attach the limitation energy of the rock self, the rock specimen will break.(3) Combining the results of the experiment research, field monitoring and numerical simulation, the energy change path in the tunnel wall are proposed, which has two patterns, release and release-accumulation. Based on the theory of the limitation of the energy in rock and the change of the energy when the excavating, the mechanism of rockburst preparation and development is proposed.(4) The influence on the rockburst by buried depth, side pressure coefficient, fault structure, joint structure, formation lithology, excavation shape, construction method, support action, strength degradation of rock mass have been analyzed. Based on the study conclusion mentioned above, some valuable laws are derived.(5) Based on the elastic energy release character of rock mass, combining the pre-existing rock burst criterion, the multi-criteria of rockburst are proposed, which considered the request of the rock mechanics, brittleness, integrity of rock mass, energy accumulating capability, energy release ability, and the index of the rock burst. Based on the multi-criteria of rockburst, the probability of rockburst in the residual drainage tunnel was analyzed and predicted. The results illustrate that:SK09+869～SK08+000 section will occurⅢlevel rockburst, SK08+000～SK07+000 section will occurⅡlevel rock burst and the others section will occurⅠlevel. Finally, the treatment measures of rockburst were presented.