Reliability Analysis of Tunnels

Abstract

he increasing world-wide activity m the construction of tunnels necessitates the investigation of the reliability of tunnels under different construction conditions. Those reliability studies should primarily serve to assess practical design rules, for example, partial safety factors. In addition, tunnel bodies experience a pronounced nonlinear behavior during construction. The reliability analysis of such complex structures requires approximate techniques in the mechanical and/or probabilistic models. There are two categories of methods which can handle the reliability of complex nonlinear structures; namely, direct and indirect methods. In the first group lie FORM/SORM in conjunction with FEM and the adaptive conditional expectation method (ACEM) in conjunction with FEM, while in the second group lies any efficient reliability method like FORM/SORM in conjunction with FEM via a response surface method. The use ofFORM/SORM in conjunction with FEM requires full access to the finite element code in order to efficiently evaluate the gradients of the response quantities with respect to the basic random variables. Unfortunately, the evaluation of these gradients may be very difficult or impossible especially in the vicinity of the critical point.