Deformation mechanism and collapse treatment of the rock surrounding a shallow tunnel based on on-site monitoring

When tunnels are constructed at shallow depths in areas with poor geological conditions, such as portal sections, valleys and hillsides in regions with granitic bedrock, considerable excavation-induced deformation of the surrounding rock may occur, potentially resulting in tunnel collapses. The main reason for these problems is the lack of understanding of the deformation mechanism and evolution of the soft granitic rock surrounding the tunnel and the adoption of inappropriate construction technology and methods. This article analyzes the deformation mechanism of the rock surrounding a shallow tunnel based on in situ monitoring data as a case study and suggests that certain measures should be taken to effectively control the deformation of the surrounding rock and to minimize the potential for tunnel collapse. The results show that the deformation of the granitic soil surrounding the tunnel can be divided into three stages: the rapid deformation stage, the slow deformation stage and the stabilization stage. Appropriate construction methods should be carefully selected to ensure safety during tunnel excavation in the first stage. To avoid secondary disasters caused by tunnel collapses, three treatment measures may be implemented as part of safety management: enhancing the monitoring of the surrounding rock deformation, adjusting the construction methods and optimizing the support systems. In particular, accurate monitoring data and timely information feedback play a vital role in tunnel construction. Therefore, engineers with considerable engineering experience and professional knowledge are needed to analyze the monitoring data and make accurate predictions of tunnel deformation to ensure that reasonable measures are taken in the process of shallow tunnel excavation.