Tunnels crossing fault zones are common in railway engineering, water conservancy engineering and highway engineering. Engineering geological disasters induced by crossing fault fracture zones account for more than 50% of the total number of tunnel disasters in China. Ensuring the safety and stability of tunnels crossing fault zones is the top priority in the development of tunnel engineering in China. Based on the engineering background of Tabaiyi Tunnel, this paper explores the effective support measures of surrounding rock under the influence of fault fracture zone. In order to solve the problem of large deformation of soft rock in Tabaiyi Tunnel, this paper first explores the main controlling factors of large deformation by carrying out on-site point load test, in-situ stress test and indoor mineral composition analysis test. Then, according to the deformation mechanism of Tabaiyi Tunnel, a high pre-tightening force and long-short NPR anchor net support scheme is proposed. According to the excavation compensation theory, the high pre-tightening force of NPR anchor cable is used to compensate the stress of tunnel surrounding rock. Through numerical simulation and field monitoring, it is shown that the tunnel can effectively reduce the large deformation of surrounding rock under the influence of fault fracture zone under the high pre-tightening force and long-short NPR anchor net support scheme. The research results can provide reference for tunnel support crossing fault zone.

After more than 1000 years of unloading effects, the roof of Beishan Cave 168 at Dazu Rock Carvings is riddled with intersecting cracks, posing significant structural stability problems. At present, the cave roof is temporarily supported by materials like steel plates and pipes, but cracks continue to spread, and the steel plates are severely corroded, leaving the cave at risk of instability and collapse. Emergency reinforcement and protection are urgently needed. Due to the cultural importance of the site, the reinforcement process must minimize disturbance, necessitating continuous monitoring throughout construction. This paper uses numerical simulation to analyze the deformation mechanism under existing support conditions, guiding the placement of monitoring points. Monitoring data from the entire construction process are analyzed to evaluate the engineering treatment. The results provide valuable insights for monitoring and protecting similar structured grotto roofs.