Objective The undercrossing construction of new tunnels may have an adverse effect on existing overlying tunnels. Pre-reinforcing the existing tunnel underlying soil can somewhat control tunnel settlement affected by the new tunnel during the undercrossing period. However, current theoretical analysis methods generally assume that the existing tunnel is surrounded by homogeneous soil, failing to fully consider the influence of soil reinforcement on the mechanical response of the existing tunnel. Therefore, further in-depth research on this problem is necessary.

Method Based on the non-homogeneous Winkler foundation model and Euler-Bernoulli beam theory, and incorporating the degradation curve of shear modulus, an interaction analysis method for the new tunnel and the existing overlying tunnel considering soil reinforcement is proposed to reflect the small-strain characteristics of the soil. The effectiveness of the proposed method is validated through an engineering case study from Shenzhen Metro. For the working condition of a newly constructed single line tunnel undercrossing an existing tunnel, three critical influencing parameters—the length of the soil reinforcement zone, the maximum shear modulus of the reinforced soil, and the clearance between the two tunnels—are selected to analyze the effects of each parameter’s value on the existing tunnel mechanical response.

Result & Conclusion  The calculated values obtained from the proposed method show a good agreement with the actual measured project data, validating the applicability of the method. In the practice of tunnel undercrossing construction, corresponding computational analysis should be conducted in advance to select the most reasonable soil reinforcement parameters.