Dynamic Horizontal Displacement Evaluation Method of Tunnel Shield Tunnel Based on MSD Method for Basement Side Tunnels

The impact of pit excavation on the surrounding environment is closely related to the deformation characteristics of the surrounding enclosure structure. However, most existing methods rely on calculating pit unloading stress based on the Mindlin solution, which does not adequately account for the dynamic deformation characteristics of the enclosure structure at different excavation stages and is difficult to apply for real-time assessment. This paper presents a new calculation method based on the mobilizable strength design (MSD) approach to dynamically predict the horizontal displacement of the shield tunnel adjacent to the excavation pit. By introducing dynamic evaluation of the horizontal displacement of the enclosure structure, the applicability of the traditional MSD method is enhanced. The paper compares and analyzes the differences between this method, the modified MSD (MMSD) method, the MSD method, and measured data from actual pit excavation cases. The results demonstrate that the proposed method more accurately reflects the deformation characteristics of the enclosure structure at different excavation stages and its dynamic impact on the horizontal displacement of the shield tunnel. The spatial distribution of horizontal displacement in the enclosure structure under zoned excavation is analyzed, revealing the coupling relationship between the deformation characteristics of the enclosure structure and the tunnel’s deformation response. The findings of this study provide valuable references for the safety assessment and protective measures of shield tunnels during pit excavation.