Simplified Analytical Calculation for the Influence of Tunnel Excavation on Overlying Existing Pipelines

Abstract

[Objective] When a shield tunnel passes under existing pipeline, it can cause settlement and deformation of the existing pipelines. Therefore, it is necessary to study the force and deformation of the overlying existing pipelines caused by tunnel excavation through theoretical calculations. [Method] Based on a two-stage method, a simplified calculation method for predicting the deformation response of overlying existing pipelines due to tunnel excavation is proposed. The method first utilizes the Loganathan function to obtain the free vertical displacements of the surrounding soil mass caused by tunnel excavation. These displacements are then applied to the axis of the existing pipelines. The existing pipelines are simplified as infinitely long beams supported on the Vlazov foundation model. Considering the influence of lateral soil mass on the pipeline, the analytical solution for pipeline longitudinal deformation is obtained using the finite difference method. [Result & Conclusion] The proposed simplified calculation method is compared with actual engineering monitoring data from existing literature, validating the rationality. A comparison with the results from the degraded Vlazov foundation model and Winkler foundation model validates that the proposed simplified calculation method is closer to measured data. An increase in the ground loss ratio and tunnel excavation radius leads to increased settlement and bending moments in existing pipelines. Increasing the angle between the new tunnel and existing pipelines reduces pipeline settlement but increases bending moments.

Keywords

• metro tunnel
• existing pipeline
• analytical solution