Formation mechanism of rockburst in deep tunnel adjacent to faults: Implication from numerical simulation and microseismic monitoring

• Published in: Journal of Central South University Vol. 29; no. 12; pp. 4035 - 4050
• Main Authors: Chen, Yi-yi, Xiao, Pei-wei, Li, Peng, Zhou, Xiang, Liang, Zheng-zhao, Xu, Nu-wen
• Format: Journal Article
• Language: English
• Published: Changsha Central South University 01.12.2022; Springer Nature B.V
• Subjects: Acoustic emission; Damage; Engineering; Excavation; Failure analysis; Failure mechanisms; Failure modes; Fault lines; Faults; Hydroelectric power stations; Lateral stress; Mechanical properties; Metallic Materials; Microseisms; Monitoring; Rock masses; Rockbursts; Simulation; Spatial distribution; Stress ratio; Tunnel construction; Tunnels; near-fault tunnel; 岩爆; 深埋隧洞; 微震监测; formation mechanism; rockburst; 数值模拟; microseismic monitoring; numerical simulation; 破坏机制
• ISSN: 2095-2899; 2227-5223
• DOI: 10.1007/s11771-022-5211-6

Rockbursts were frequently encountered in the construction of deeply buried tunnels at the Jinping-II hydropower station, Southwest China. In those cases, the existence of large structural planes, such as faults, was usually observed near the excavation boundaries. The formation mechanism of the “11·28” rockburst, which was a typical rockburst and occurred in a drainage tunnel under a deep burial depth, high in-situ stress state and complex geological conditions, has been difficult to explain. Realistic failure process analysis (RFPA 3D ) software was adopted to numerically simulate the whole failure process of the surrounding rock mass around the tunnel subjected to excavation. The spatial distribution of acoustic emission derived from numerical simulation contributed to explaining the mechanical responses of the process. Analyses of the stress, safety reserve coefficient and damage degree were performed to reveal the effect of faults on the formation of rockbursts in the deep tunnel. The existence of faults results in the formation of stress anomaly areas between the tunnel and the fault. The surrounding rock mass failure propagates toward the fault from the initial failure, to different degrees. The relative positions and angles of faults play significant roles in the extent and development of surrounding rock mass failure, respectively. The increase in the lateral stress coefficient leads to the aggravation of the surrounding rock mass damage, especially in the roof and floor of the tunnel. Moreover, as the rock strength-stress ratio increases, the failure mode of the near-fault tunnel gradually changes from the stress-controlled type to the compound-controlled type. These findings were consistent with the microseismic monitoring results and field observations, which was helpful to understand the mechanical behavior of tunnel excavation affected by faults. The achievements of this study can provide some references for analysis of the failure mechanisms of similar deep tunnels.