Deformation and mechanical characteristics of tunnel-slope systems with existing anti-slide piles under the replacement structure of pile-wall

The planning of mountain tunnels aims to avoid intersecting with landslide-prone areas. However, it is often unavoidable for mountain tunnels to traverse sloped terrain, thereby creating a tunnel-slope system. During the construction of tunnels traversing sloped terrain, disasters such as slope sliding and tunnel collapse frequently occur as a result of tunnel excavation. In order to provide theoretical reference for deformation control and disaster prevention of tunnel-slope systems, taking the left portal of Yangguang Tunnel as a case study, deformation and mechanical characteristics of tunnel-slope systems that incorporate existing anti-slide piles within the context of a replacement structure of pile-wall were studied. A replacement structure of pile-wall was proposed to prevent the sliding of reinforced slopes caused by tunnel excavation. The on-site monitoring data showed that the horizontal displacement of the slope caused by pile cutting and tunnel excavation is 17.7 mm, which proved the reliability of the replacement structure proposed. Under the reinforcement of the replacement structure of pile-wall, tunnel excavation only causes compression deformation of first lining, but the pipe-roof will experience overall sliding deformation. The plastic loosening zone and the disturbance zone of surrounding rock on the deep side of the tunnel are 1.23 times and 3.24 times of the diameter of the tunnel respectively, which are much larger than the loosening zone of the shallow buried side and the tunnel non-biased section. It indicated that the surrounding rock of the deep side of the tunnel is the key area affecting the stability of the tunnel-slope systems. The proposed the replacement structure of pile-wall, as well as the deformation and mechanical characteristics of tunnel-slope systems under its reinforcement, could provide insights for deformation control and disaster prevention of tunnel-slope systems.