Numerical Simulation Of Earth Pressure Distribution In Head Chamber Of EPB Shield Machine

As the continuous development of urban construction, Metro constructions have been developed in many cities. EPB shield machine has been applied more and more frequently. Unable to real-time observe earth and hydraulic pressure at the excavation face brings difficulty to efficiently control the ground uplift or subside. The relationship between bulkhead pressure and soil and hydraulic pressure at the excavation face needs to be proposed. Therefore, the soil and hydraulic pressure at the excavation face can be real-time forecasted by observing the bulkhead pressure. And then the working state of shield can be regulated by adjusting thrust force of jacks or screw conveyor rotation. Combining with project practice, the nonlinear finite element model of the head chamber of EPB shield is accomplished and the earth pressure distribution in head chamber of shield machine is simulated by finite element method by using ANSYS software. The aim of the paper is to simulate distribution of earth pressure in the head chamber of shield machine by using nonlinear finite element method, to investigate the effect of openings ratio of rotating cutter-head to earth pressure distribution, and to propose the relationship between pressure transportation factor and openings ratio of shield machine.Based on Duncan-Chang nonlinear elastic constitutive model, earth pressure distribution is simulated and earth pressure distribution for different section in the head chamber is obtained. The appropriate earth pressure of excavation face is obtained. The numerical simulation results show that computed bulkhead pressures agree with in-situ measured values. Head chamber models with 32%,52% and 72% openings ratio are modeled. Relationship between pressure transportation factor and openings ratio of shield machine is proposed by using regression analysis.