Investigating the use of Reliability-calibrated Partial Factors in Tunnel Design

Variability is prevalent in rock engineering conditions. This renders commonly used deterministic design approaches with empirical factors of safety unsuitable for objectively quantifying safety. Instead, probabilistic reliability based design (RBD) can objectively do so with probabilities of failure. However, due to the unfamiliarity of RBD to practicing engineers, 'partial factors' are calibrated which allow deterministic analyses to achieve designs of predefined probabilities of failure. This dissertation investigates the application of calibrated partial factors in tunnel liner design, and its possible inclusion in a coherent design code format. The dissertation concludes that partial factors calibrated from RBD can be applied in design of tunnel liners. However, due to the lack of data collected in rock engineering, development of a design code cannot be currently undertaken. In addition, it is only realistically feasible for simple tunnel construction and support sequences, suggesting that the application of RBD is best done on case-by-case basis.M.A.S