Reliability of tunnel lining design using the Hyperstatic Reaction Method

The reliability analysis of tunnel linings is a challenging task, due to the complex nature of soil-structure interactions, and due to the large uncertainty in soil properties and soil-structure interaction parameters. Usually, numerical models are employed to properly describe structural geometry and soil-structure interactions, rendering reliability solutions computationally expensive. In the past, tunnel reliability was addressed by local point estimate methods, which are very economical in the number of points where the numerical solutions are computed, but which can be quite inaccurate. More recently, surrogate modelling techniques have been employed to alleviate the computational burden, producing global response approximations. In this paper, an alternative procedure is proposed, which consists in the direct coupling between mechanical and reliability solution algorithms. Such direct coupling is viable because the very efficient Hyperstatic Reaction Method is employed to model the soil-structure interactions. Typical concrete tunnel lining is addressed. Solutions are computed for several failure modes of the tunnel lining, also considering that failures can occur at any point along the tunnel perimeter. Solutions for individual failure modes are computed by FORM, and system reliability is computed by different Monte Carlo simulation techniques.