Abstract:

Rockburst is one of the primary geological disasters faced by deepburied hardrock tunnels, which severely threatens the life of siteconstruction personnel, affects the construction schedule, and increases the protection cost. To deal with the highfrequency and highstrength rockburst occurring in the Qinling water diversion tunnel of the Hanjiang rivertoWeihe river water diversion project in Shaanxi, China, the geological characteristics, rock mechanical characteristics, and actual occurrence of rockburst in the Qinling tunnel are investigated. Rockburst monitoring and earlywarning works, focusing on microseismic monitoring for more than 13 km of continuous tunnel sections, are conducted. Furthermore, a mobile 24h continuous microseismic monitoring system is constructed, and a rockburst rating evaluation system based on microseismic energy is established. After continuous exploration and comparison, a simple quantitative discrimination method of "microseismic energy as the main, frequency and concentration as the auxiliary" is developed, which remarkably improves the legibility of data and the utilization efficiency of monitoring results. The results show that the comprehensive warning accuracy of rockburst reaches 90%. Moreover, no major accidents caused by rockburst casualties occurred until smooth penetration, effectively guaranteeing the progress and safety of the project.

Key words: tunnel, rockburst, microseismic monitoring, early warning