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Civil-Comp Proceedings
ISSN 1759-3433
CCP: 105
PROCEEDINGS OF THE NINTH INTERNATIONAL CONFERENCE ON ENGINEERING COMPUTATIONAL TECHNOLOGY
Edited by:
Paper 100

Probabilistic Instability Assessment of Tunnels Constructed in Rock Masses

J.M. Mayoral and R. Rivas

Instituto de Ingeniería, UNAM, México

Full Bibliographic Reference for this paper
J.M. Mayoral, R. Rivas, "Probabilistic Instability Assessment of Tunnels Constructed in Rock Masses", in , (Editors), "Proceedings of the Ninth International Conference on Engineering Computational Technology", Civil-Comp Press, Stirlingshire, UK, Paper 100, 2014. doi:10.4203/ccp.105.100
Keywords: risk analysis, fractured rock, performance, tunnelling, tunnel stability, state limit of failure, state limit of service.

Summary
This paper introduces a numerical analysis framework with the aim of establishing the probability of tunnel faces, walls and crown instability in medium to strongly fractured rock masses. The proposed approach is an enhancement of a methodology proposed for tunnels built in fine-grained cemented soils to be extended to rock masses, seeking to unify the revision of both state limits of failure and service. Initially, the strength and deformability parameters are established based on the Hoek and Brown approach. This required solving an optimization problem to obtain extreme rock strength parameters, expressed in terms of cohesion, friction angle and its associated deformation parameters. Then, the bivariable point estimate method, coupled with tridimensional finite difference models is used to compute the factors of safety spatial distribution, probabilities of failure at the face and around the tunnel, reliability indexes, and ground movements. This approach is applied to a typical 8.7m external diameter tunnel section, assumed to be constructed in the dacitic-andesitic rock mass formation found in the northwest Mexico City surroundings.

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