Research on the Pre-Grouting Effect of Open TBM Tunnel

When a TBM passes through fault fracture zones with surface gullies, machine jamming accidents are prone to occur, leading to longer processing times and higher costs. To ensure the safety of TBM excavation through the gully fault section and avoid situations such as the collapse of the tunnel face, machine jamming, and equipment "falling head", surface pre-grouting reinforcement technology is commonly used to address the fractured zones of gully-related fault sections. This article focuses on the problem of machine jamming during the TBM construction of a tunnel in Xinjiang, where is a fault fracture zone with gullies on the surface. The effects of pipe shed grouting and surface grouting on the stability of surrounding rock are compared and analyzed through numerical simulation. The economic benefits of the two grouting methods were examined. The results show that: When a TBM passes through fault fracture zones with surface gullies, surface pre-grouting reinforcement technology can be employed. The slurry can better fill the surrounding rock’s cracks and improve the surrounding rock’s integrity and bonding degree. The effectiveness of surface pre-grouting reinforcement and filling of rock fractures was verified through drilling and ultrasonic testing. Surface pre-grouting construction has a significant advantage over pipe shed grouting in terms of the construction period. However, when TBM uses pipe shed grouting for escape, there is a higher risk of rock collapse, which poses a higher danger to both construction personnel and TBM machines. Considering both economic feasibility and technical difficulty, surface pre-grouting should be used to prevent TBM jamming accidents when the tunnel is buried at a depth of 70 m. The research can provide reference for similar engineering.