Coupled Discrete Element-Finite Difference Method for Analysing Effects of Cohesionless Soil Conditioning on Tunneling Behaviour of EPB Shield
A computational scheme coupling PFC3D (Particle Flow Code in 3 Dimensions) and FLAC3D (Fast Lagrangian Analysis of Continua in 3 Dimensions) was performed to investigate influences of sand conditioning on the tunneling behaviour of earth pressure balance (EPB) shield in sandy ground. A detailed EPB shield and its near ground were modelled in the PFC3D while the other ground was simulated in the FLAC3D. Decreasing friction coefficients were used to characterize the fluidity improvement of conditioned muck particles. The results indicate that the residence time of muck in the excavation chamber is associated with its position and rotation directions of the spoke. The muck pressure and its difference in front of and behind the cutterhead decrease with the improvement of conditioning degree in a certain conditioning range, and an appropriate soil conditioning scheme can facilitate the control of chamber pressure. In addition, the torque of cutterhead decreases more significantly than the thrust with an improvement of soil conditioning degree within a normal conditioning range.
Keywords: EPB shield, soil conditioning, coupling FLAC3D and PFC3D, muck stress, tunneling parameters