Mechanism Analysis and Prevention Study on Rock Burst of the Surrounding Rock in Long-big Diversion Tunnel
|Disaster Prevention and Reduction Engineering and Protective Engineering
|rock burst marble unloading experiments mechanism finite element technique influencing factor prevention and cure
Underground engineering will be highly developed in the 21st century. Some tunnels will be designed and constructed in deep strata, high stress field and under the sea, which provide vast space for rock burst which is one of the worst geology calamities in tunnel construction in the world. Once rock burst erupted, it can damage equipments in the room of hydroelectric station, traffic tunnel and mining gallery. Rock burst will threaten engineers’ personal security. Therefore, strengthening the discuss of the mechanism, forecast and prevention of rock burst not only can promote the development of geology calamity, but also have benefits to the society and economy.This thesis mainly discusses marble surrounding rock of in diversion tunnel of the Jinping hydroelectric station. The paper analyses the influencing factor, mechanism, and numerical calculation method of rock burst. Chief work and conclusions are summarized as the following:(1) The paper discusses the influencing factors to probability of rock burst, such as ground stress, lithologic characters, rock mass structure, embedded depth, etc. Influencing factors are reduced to two types: stress state of rock and lithologic character of rock.(2) Destructive mechanics characters of rock are analyzed by normal triaxial unloading experiments under different unloading modes. The results indicate that unloading experiments are accord with the actual stress state of rock burst. The paper keeps eyes on macro destructive characters under unloading experiments of keeping axis stress increasing. The broken nicks are scanned by electronic microscope, and the microcosmic characters are analyzed. Then mechanism of rock burst is educed.(3) Setting out from the point of view on numerical analysis, calculative elements of rock burst are discussed by using finite element technique. The paper also advances the calculative method of considering effect of excavation of tunnel. The stress of excavating round tunnel is calculated. Theoretical results are used to contrast it., which indicates that considering effect of excavation of tunnel can reflect the instance of stress collecting of tunnel sufficiently, and the calculation of simulating excavation can reflect the actual stress distribution of surrounding rock of the tunnel. On the side of forecasting the intensity, depth, and width of rock burst, this method of calculation provides degree of accuracy which is better than others.