Analytical solution for heave of underlying shield tunnel caused by adjacent tunnelling considering shear deformation

Abstract

Excavating a shield tunnel may cause a series of unforeseen adverse impacts on the adjacent underlying in-service tunnels. Therefore, it is significant to reasonably evaluate the influence of the newly excavated tunnel on the existing underlying shield tunnel to ensure safety and applicability of the existing tunnels. In this study, a simplified analytical solution is proposed to rapidly evaluate the responses of an existing underlying tunnel caused by newly tunnel construction. An elastic Timoshenko beam model, considering the shearing deformation of the existing shield tunnel as well as the interaction between adjacent segments, is presented for evaluating the responses of underlying shield tunnel associated with the tunnelling-induced free ground settlement. An equilibrium differential equation, combined with the finite difference analysis, is derived for the responses of the underlying in-service tunnel. The adaptability and reliability of proposed analytical solution is verified in comparison with published measurements. The predicted values were compared with the calculation results of different foundation coefficients. Parametric analyses are showed to evaluate the effects of various factors on the responses of underlying in-service tunnel, including the skew angle, equivalent shear stiffness and bending stiffness of underlying existing tunnel.