Study on Deformation Control of Large Deformation Tunnel in Soft Rock across Faults

This study focuses on the area of large deformation of soft rocks across the fault in Dongmachang China to investigate support methods for fractured surrounding rocks Negative Poisson's Ratio (NPR) anchor cable support. The research employs field monitoring, 3D physical model experiments, and numerical simulations. The results show that: (1) the maximum settlement displacement of the Dongmachang Tunnel section with original support can reach about 476 mm and has an upward trend, the limit of initial branch intrusion is 41.2 cm, and the width of invert joint is 5–50 mm; (2) the dynamic impact experiment of NPR anchor cable shows that the NPR anchor can withstand several impacts, the maximum cumulative impact deformation within the range of constant resistance is 500–1,000 mm, and the impact resistance is strong; and (3) NPR anchor cable can effectively control the large deformation disaster of surrounding rock in the fault fracture zone of Dongmachang Tunnel, basically ensuring that the deformation of the surrounding rock is below 300 mm, and the control effect is good. These findings suggest that NPR anchor cables are effective for controlling large deformations in tunnels constructed through soft rock across faults and provide a scientific basis for implementing new support systems for other similar tunnels.

At present, the international support of deep-buried underground engineering still takes the new Austrian method as the mainstream, but the core idea of the new Austrian method is passive support, which often cannot effectively support the deep-buried soft rock with high stress and large deformation. This paper takes the anchor cable with high preload (350 kN) as the core and the excavation compensation method proposed by Academician He Manchao as the starting point, and innovatively supports the deep-buried soft rock large deformation tunnel, which provides a new idea for the support of other deep-buried underground projects. Although this paper studies the support effect of negative Poisson’s ratio (NPR) cable compensation mechanics from the perspectives of laboratory test, physical model experiment, and numerical simulation, because the tunnel has not yet been started, it has not been studied from the perspective of field application. The support effect of NPR anchor cables on surrounding rock in the fracture zone needs further study.