Identification of potential high-stress hazards in deep-buried hard rock tunnel based on microseismic information: a case study

Rockbursts, stress-induced collapse, and spalling often occur in the excavation process of deep-buried hard rock tunnel, which affect the stability thereof. The early identification of these potential high-stress hazards during tunnel excavation can provide reliable basis for the selection of preservative and controlled measures. During the excavation of a deep-buried hard rock tunnel in southwest China (a railway tunnel with a maximum burial depth over 2000 m), rockbursts, stress-induced collapse, spalling, and cracking occurred frequently. In this study, the microseismicity of various high-stress hazards in the genesis process of the tunnel was analysed. The difference of microseismicity characteristics of these high-stress hazards was revealed. A matter-element extension mathematical model was established to quantify the microseismicity of the rock mass during tunnel excavation. Based on microseismic (MS) information, an identification method of potential high-stress hazards in deep-buried hard rock tunnels was established. The method was then applied to a real case, and reliability analysis thereof performed. Thirty test case samples were selected for reliability analysis and case verification. Through practical application, it is found that 90% samples were identified correctly. The results show that the identification method of potential high-stress hazards in the deep hard rock tunnel constructed in this study is both applicable and reliable, and can identify potential high-stress hazard types in the process of tunnel excavation by using MS information.