Statistical Analysis of Factors Influencing Segmental Joint Opening in a Soft Soil Tunnel

The opening degree of longitudinal joints in the segmental lining of cross-passages in soft soil strata directly affects structural safety during tunnel construction. This study utilizes field monitoring data from the F-capping segment of Ring 30 in the Guangzhou–Nanzhou Intercity Railway Connecting Tunnel. Employing multivariate linear regression analysis, it investigates the variation patterns in longitudinal joint opening in connecting tunnel segments under changes in earth pressure, water pressure, axial force, and reinforcement stress. The fitted results for joint opening are compared with field monitoring data, demonstrating good agreement. The results indicate that axial force and reinforcement stress exert minimal influence on longitudinal joint opening in soft soil sections. Conversely, hydrostatic pressure and earth pressure exhibit moderate linear correlations with joint opening: opening increases with rising hydrostatic pressure and decreases with increasing earth pressure. These findings, based on short-term monitoring data from a single ring during construction, provide preliminary theoretical and empirical support for understanding joint behavior in site-specific soft soil conditions. Further validation is required for generalized early warning systems.