Stability analysis of TBM tunnel under unfavorable geological conditions of large dip faults

Based on the Dali I section of the Central Yunnan Diversion Dali Tunnel Project, an indoor model test of TBM traversing faulted geological conditions under high ground stress was carried out using the self-developed miniature TBM tunneling integrated test system to study the impact of faulting on the stability of TBM tunnels under high ground stress, analyze and summarize the change of stress and strain in the surrounding rock of the tunnel and the tunnel damage phenomenon, and reveal the disaster-causing mechanism of faulted geological jamming. The research results show that the TBM tunneling process first produces cracks in the surrounding rock at the upper part of the tunnel, and then a small drop in the vault when the TBM bores into the intersection of the two materials. The pressure on the surrounding rock in front of the palm face is mainly in the range of 0.43D～0.50D (D is the diameter of the hole), with the maximum increase of 1.19 times in the pressure on the surrounding rock. The internal rock displacement above the tunnel vault has four distinct phases of change with TBM tunneling. The closer the upper surrounding rock is to the tunnel contour line, the greater the deformation. When TBM passes through the fault interface, the deformation rate of the surrounding rock is the highest. The impact range on the internal displacement of the surrounding rock is mainly within 1.21D in front of the palm and 1.50D above it. The impact range of the fault is about 1.73H (H is the horizontal projection length of the fault interface), which is mainly caused by the loose sliding of the surrounding rock above the fault interface, and it is also easy to cause TBM jamming, Therefore, it is advisable to carry out advanced treatment at the fault interface during construction to reduce the risk of TBM operation.