ABSTRACT
This article presents a simple numerical investigation of ground responses to tunnel-boring machine (TBM) tunnelling with active face support. Unlike other numerical modelling in which a flow inward the excavation chamber was assumed, in this modelling a flow inward the ground surrounding the face was assumed. The later flow is caused by the penetration of slurry (for slurry shield) or foam (for EPB). The effect of soil layering (semi-confined and unconfined aquifers) was also taken into account. The numerical results show that the ground response to TBM tunnelling with active face support can be significantly influenced by soil layering. In a semi-confined aquifer, at a distance larger than approximately three times of tunnel diameter from the face, the excess piezometric heads are the same at any depths. This finding is helpful to improve the solution for the excess pore pressure caused by TBM tunnelling in a semi-confined aquifer proposed by Xu et al. (2019). The existing analytical solution of excess pore water pressure distribution for the case of semi-confined aquifer matches well with the numerical result. It appears that for an unconfined aquifer, contour of the excess pore water pressures is like a radial distribution. The steady state model of piezometric head for the homogeneous soil results in excellent matches with the values derived from the numerical modelling. For a semi-confined aquifer, the ground surface heave was observed. Though the face collapse potential was found for the unconfined aquifer, the displacement around the face was very small.
