Reliability analysis of underground excavation in elastic-strain-softening rock mass: Fid-Bau Portal

Reliability analysis of underground excavation in elastic-strain-softening rock mass

Song, Li / Li, Hang-Zhou / Chan, Chin Loong / Low, Bak Kong

Highlights • Deterministic solution of tunnel in strain softening rock mass was obtained. • VBA procedure of the elastic-strain-softening model is created. • Reliability analysis was illustrated based on an elastic strain-softening model. • Reliability-based design of the required support pressure was demonstrated. • The influences of parameters on the reliability of the tunnel were investigated.

Abstract This paper deals with the reliability analysis of a circular tunnel in elastic-strain-softening rock mass. Dilatancy angle which varies with softening parameter in different stress conditions is accounted for. Deterministic and probabilistic analyses of the circular tunnel in elastic-strain-softening rock mass are performed. Computational procedures for the first-order and second-order reliability methods (FORM/SORM) are used in the reliability analyses of the elastic-strain-softening model. The results are in good agreement with those from Monte Carlo simulations incorporating importance sampling. Reliability-based design of the required support pressure for the circular tunnel is efficiently conducted. The effect of positive correlation between compressive strength and elastic modulus of the rock mass on the reliability of the tunnel is discussed. The influence of in situ field stress and support pressure as random variables on the probability of failure of the tunnel is investigated.