An analytical model to predict the limit support pressure on a deep shield tunnel face

摘要

The support pressure acting on a tunnel face is critical for the stability of the ground during shield tunnelling. This paper presents a multi-arch model to predict the limit support pressure (LSP) acting on a tunnel face for deep shield tunnelling in dry cohesionless soils based on the limit equilibrium method. The model consists of the upper end-bearing arch, the middle friction arch, the stability zone, and the lower wedge. A formula for calculating the height of the friction arch zone H was derived, in which the ranges of the parameters were suggested based on the results of existing model tests. Then, the rationality and effectiveness of the new model were verified by comparison with model tests, existing theoretical methods and numerical simulations. Finally, the effects of a series of parameters on the LSP were also discussed. The results show that the soil internal friction angle phi, the soil-cutterhead friction angle delta, and the soil volume bulking factor a (when alpha > 0.04) have significant effects on the LSP acting on the tunnel face. This study provides a significant reference for evaluating the stability of a tunnel face for deep shield tunnelling in dry cohesionless ground.