Study on Deformation Mechanism of Soft Rock Tunnel Under Seepage and Mechanical Response of Prestressed Anchor Cable

In complex hydrogeological environments, balancing groundwater recharge and discharge in tunnels is challenging, and disasters caused by seepage damage frequently occur. Therefore, it is urgent to study the disaster mechanism of tunnels under seepage conditions and propose effective support measures. This study conducts tunnel seepage tests under different support conditions in a typical soft rock tunnel, the Haidong Tunnel, located in the complex geological environment of Yunnan Province, China, by introducing the tendency and inclination of laminar structures in the physical modeling tests. The results indicated that the primary cause of surrounding rock failure is that the original support cannot effectively stabilize the excavated surrounding rock, leading to plastic deformation in the shallow surrounding rock and developing a series of cracks that propagate deeper. The penetration of these cracks accelerates the formation of seepage channels and exacerbates the deformation, failure, and collapse of layered surrounding rock under seepage pressure. The prestressed anchor cable can better compensate for the radial stress reduction caused by excavating the surrounding rock at the free surface by mobilizing the stress of the deep surrounding rock and forming a stress superposition area. This effectively controls the development of the plastic zone and prevents seepage failure. In the field test, the prestressed anchor cables reduced the deformation of the surrounding rock from 1211 mm to below 280 mm, optimizing the load distribution on the support structure, and helping to prevent the deformation and seepage-induced damage risks in the initial support of the layered rock tunnel.