Study on Classification and Influencing Factors of Structure-Type Rockburst

With the development of underground engineering to the depth, complex geological structures are often encountered. Structural rockburst occurs frequently during deep tunnel excavation, which seriously threatens the underground engineering structure stability and security. In order to reveal the occurrence process and mechanism of structure-type rockburst, this kind of rockburst is classified in detail and its influence factors are studied in depth. During the excavation of Jinping II hydropower station, the rockburst cases associated with structure planes were summarized and explained. Direct shear tests were undertaken to explore the influence mechanism of rock type, normal stress and surface roughness on structure-type rockburst. The result indicates that the structure-type rockburst were divided into three categories, namely shear slip rockburst, shear fracture rockburst and splitting bending rockburst. The shear failure of granite joint is more easily to induce rockburst than that of gypsum and marble joints. With the increase in normal stress, the stress drop value increases. Therefore, the energy released by shear failure also increases, resulting in a rise of rockburst tendency. As the surface roughness increases, the shear failure is more serious so that it is likely to trigger a strong rockburst. The research findings are helpful to the prevention and control of structure-type rockburst.