Three-dimensional face stability analysis of pressurized tunnels driven in a multilayered purely frictional medium

Abstract

This paper aims at presenting a three-dimensional (3D) failure mechanism for a circular tunnel driven under a compressed air shield in the case of a dry multilayered purely frictional soil. This mechanism is an extension of the limit analysis rotational failure mechanism developed by Mollon et al. (2011a) in the case of a single frictional layer. The results of the present mechanism are compared (in terms of the critical collapse pressure and the corresponding shape of the collapse mechanism) with those of a numerical model based on Midas-GTS software. Both models were found to be in good agreement. Furthermore, the proposed mechanism has the significant advantage of reduced computation time when compared to the numerical model. Thus, it can be used in practice (for preliminary design studies) in the case of a multilayered soil medium.