Stability analysis of a pressurized tunnel face in a spatially varying sand using the statical approach of limit analysis

Abstract

This paper presents a probabilistic study of the face stability of a pressurized tunnel driven in spatially random sand using numerical lower bound limit analysis in conjunction with a random field. The spatial variation of the soil properties is represented within the finite element mesh of the lower bound approach by the Karhunen-Loève expansion. Monte Carlo simulations are carried out to determine the critical collapse loads for selected ranges of the statistical characteristics of the random field. The results obtained using the present approach are presented and compared to those reported in literature. It appears that the lognormal distribution can be used to characterize the critical collapse load, when the input random field is lognormal. The proposed method has the advantage of automatically seeking the critical limit load, although it is computationally more expensive than the kinematical approach based on a rigid block mechanism by Mollon et al. (2011a). © 2013 Taylor & Francis Group, London.