Simplified Calculation Method for Existing Tunnel Settlement Caused by Shield Under-passing Based on Timoshenko-PasternakModel

Objective It is aimed to tackle the inefficient accuracy of traditional Euler-Bernoulli beam and Winkler foundation model in calculating settlement induced by shield under-passing existing tunnels. Method Based on the Timoshenko beam theory and Pasternak foundation theory, the Timoshenko-Pasternak model, which simultaneously considers the soil shear effect and the tunnel overall shear deformation, is introduced. Settlement control equations for shield under-passing existing tunnels are derived and solved using finite difference method to obtain settlement calculation results. These results are then compared in detail with finite element numerical simulation solutions, actual engineering monitoring data, and theoretical solutions from traditional Euler-Bernoulli-Winkler model. Result & Conclusion Research results show that the Euler-Bernoulli-Winkler model tends to underestimate settlement values and overestimate settlement trough width and segment opening amount for existing tunnels. Additionally, it fails to calculate the segment misalignment amount of existing tunnels. In contrast, the calculation results from Timoshenko-Pasternak model are more consistent with the numerical simulation and actual monitoring values. The model can accurately estimate settlement, settlement trough width, and segment opening amounts for existing tunnels, and provides reliable calculation results for tunnel segment misalignment. The findings are of significant practical value, offering a reliable reference for engineeringapplications.