Analysis of Loose Surrounding Rock Deformation and Slope Stability at Shallow Double-Track Tunnel Portal: A Case Study

A low-clearance tunnel portal in the shallow-buried, joint-developed, broken, and loose surrounding rock slope deposit may cause safety issues during construction. In this study, Guanyin Mountain Tunnel of Chong-Ai expressway was taken as a case characteristics broken rocks, their low clearance, shallow buried bias were comprehensively studied. The three-dimensional numerical model section constructed by Rhino, AutoCAD, FLAC 3D software, whole construction process simulated. Under conditions deformation, surface settlement, stability at with small clear distance center diaphragm (CD) method circular reserved core soil following conclusions are drawn. During simulated excavation tunnel, maximum settlement is 10.74 mm, which meets requirement specification. When left excavated, deformation right arch shoulder should be carefully considered. value can reach 14.314 mm. After excavation, rate large, initial support installed time. Since stratum strongly weathered, uplift bottom large gradually decreases along axial direction. foot plastic areas prone to tensile damage. Therefore, it imperative strengthen inverted weathered stratum. sequence adopts excavating first then more conducive ensuring stability.