Research on Rapid Tunnel Entry Construction Technology for Four-Lane Tunnels with Shallow Cover and Unbalanced Load in Weak Surrounding Rock

For shallow-buried tunnels in weak surrounding rock, methods such as the Cross Diaphragm (CRD) method, the Center Diaphragm (CD) method, and the Double-sided Wall Pilot Tunnel method are commonly used for tunnel entry construction. These conventional methods require the installation of numerous temporary supports, which significantly impact the progress of tunnel construction to a certain extent. Based on the Yanfeng Tunnel project, this paper innovatively proposes a combined construction method of “Double-sided Wall + Bench Cut Method.” A simulation model considering three-dimensional terrain information is established to conduct a comprehensive analysis of the construction impact on the entire structure throughout the process. The results indicate that this tunnel entry method can effectively control the displacement of the surrounding rock, ensuring safe tunnel entry while accelerating the construction progress. This provides a reference and guidance for similar projects.