Enlarging a large-diameter shield tunnel using the Pile–Beam–Arch method to create a metro station

Abstract

It is an effective approach to enlarge a large-diameter shield tunnel using the Pile–Beam–Arch (PBA) method to construct a metro station, especially when traditional excavation methods cannot be used because of the narrow roads and dense buildings. Based on the structural characteristics of a metro station, FLAC3D is used to build a three-dimensional model and to analyse the mechanical performance of structurally critical joints and their effect on the settlement of the ground surface. The critical joints include segment joints, connections between blocks of key segments, connections between longitudinal beams and segments, and connections between primary linings and segments. The results show that the calculated stress in the structure does not exceed the strength during the enlarging process. A control standard for the project is also presented based on a comparison between the results of the numerical simulation and the control reference of a Beijing metro station. The numerical analysis result is used to guide the construction. Based on the in-situ monitoring data, the feasibility of the expansion method is verified, as is the accuracy of the numerical simulation.