Abstract
This study demonstrates a three-dimensional numerical simulation of earth pressure balance (EPB) shield tunnelling using a coupled discrete element method (DEM) and a finite difference method (FDM). The analysis adopted the actual size of a spoke-type EPB shield tunnel boring machine (TBM) consisting of a cutter head with cutting tools, working chamber, screw conveyor, and shield. For the coupled model to reproduce the in situ ground condition, the ground formation was generated partially using the DEM (for the limited domain influenced by excavation), with the rest of the domain being composed of FDM grids. In the DEM domain, contact parameters of particles were calibrated via a series of large-scale triaxial test analyses. The model simulated tunnelling as the TBM operational conditions were controlled. The penetration rate and the rotational speed of the screw conveyor were automatically adjusted as the TBM advanced to prevent the generation of excessive or insufficient torque, thrust force, or chamber pressure. Accordingly, these parameters were maintained consistently around their set operational ranges during excavation. The simulation results show that the proposed numerical model based on DEM–FDM coupling could reasonably simulate EPB driving while considering the TBM operational conditions.
Highlights
The versatility of an earth pressure balance (EPB) shield has led it to become the most popular type of tunnel boring machine (TBM) for use in various ground conditions around the world [1,2]
The shield model is inserted up to the depth of the bulkhead wall, because unless the chamber is filled with prestressed balls, abrupt settlement at the discrete element method (DEM)-finite difference method (FDM) boundary will occur, and the coupling will be broken
This section discusses the applicability of the proposed model and the numerical analysis results for the measured torque and thrust force, the monitored chamber pressure, the discharged volume and discharge rate of particles, and the surface settlement
Summary
The versatility of an earth pressure balance (EPB) shield has led it to become the most popular type of tunnel boring machine (TBM) for use in various ground conditions around the world [1,2]. DEM represents a straightforward approach to modeling ground behavior and, could be applied to collecting real-time TBM data concerning the dynamic interaction of the soil and structure during shield tunnelling [22,23,24,25]. A spoke-type TBM (diameter, 6.14 m) comprising a cutter head with cutting tools, working chamber, screw conveyor, and shield is imported into the model.
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