Theoretical analysis on the deformation of existing tunnel caused by under-crossing of large-diameter slurry shield considering construction factors

Abstract

With the expansion of underground space networks, new tunnels especially large-diameter shields under-crossing existing tunnels have been commonly practiced. To obtain a better understanding of the effect of large-diameter slurry shield under-crossing on the existing tunnel and provide a quick and effective tool for evaluating the deformation behaviors of the existing tunnel before construction, in this study a simplified analytical method is proposed. Based on the two-stage method, and considering the characteristics of construction factors such as additional thrust on the shield excavation face of the slurry shield machine, friction force of the shield shell, and grouting pressure of the shield tail, deformation of the existing tunnel caused by the crossing of the large-diameter slurry shield in saturated soil is calculated. The proposed method is verified with field measurement data from a case study. A parametric analysis is conducted to study the influence of typical factors on tunnel responses, including longitudinal bending stiffness, elastic modulus, clearance between two tunnels, and shield crossing angle. The parametric study indicates a significant influence of the crossing angle on maximum settlement and the influence range of settlement of the existing tunnel. Recommendations for safe values of shield crossing clearance are given. The proposed analytical solution can be used as a reference to predict the potential risk of new large-diameter slurry shield crossing on the existing tunnel in engineering practices.