Decomposition method for existing tunnel lining displacement induced by undercrossing: a case study

A decomposition method is proposed to divide the field monitoring displacement of tunnel linings into different components induced by dislocation, rotation, and elliptical deformation of the lining rings. Based on this method, a corresponding tunnel lining monitoring plan is also suggested. The key principles of the decomposition are the continuity of longitudinal deformation, the sinusoidal functional relationship between the rotation angle and the longitudinal distance to the cross point, and neglecting the longitudinal joint deformation. The proposed decomposition method was successfully applied to a metro project in China, and the decomposed pattern laws were discussed. The decomposed data indicate that the displacement of the lining ring is primarily influenced by elliptical deformation and dislocation, with elliptical deformation having the strongest impact. Moreover, the z-direction displacement of the existing tunnels linearly increases with the crossing angle, whereas the affected zone decreases nonlinearly. As for the lining ring rotation angle, its maximum value occurs during a 90° undercrossing scenario, and the rotation angles decrease nonlinearly as the crossing angle diminishes. Furthermore, the rotation angle first increases and then decreases as the distance from the crossing center increases. Temporally, the rotation angles follow a pattern of initial increase followed by gradual reduction. Regarding the ellipticity, the ellipticity increases with the crossing angle but decreases with distance from the crossing center. The findings of this study contribute to improved knowledge of tunnel lining displacement composition and monitoring. Future integration of our computational approach with total station monitoring systems could enable real-time monitoring, calculation, and analysis in tunnel engineering applications.