Reliability-based design of tunnel support systems.

摘要

Recent developments of tunnelling technology have led to the construction of many tunnels, not only in rural areas, but also in cities. In particular, tunnel construction in cities requires very high standards of safety, since failure can cause the loss of many human lives as well as damage of properties.;Despite the recent advances in the development of tunnelling methods, it is still difficult to predict the exact properties of the ground where the tunnels are planned to be constructed, due to large uncertainties. Designs that do not take into account the effect of uncertainties could be subject to large error. Consequently, it is very important that uncertainties be accounted for properly in design.;The objective of this study is to propose the use of probabilistic methods to study the effect of uncertainties in the exploration phase, design phase and construction phase of a tunnel project. The outline for each phase is as follows: (1) Exploration phase. Prior to design, rock profiles at a planned site is probabilistically evaluated, based on the information of local experts and borings. (2) Design phase. The reliability of the tunnel supports in soft rock is first examined. The effects of the creep of the rock and bending moment of the lining on the reliability are also evaluated. Next, reliability of the lining in a jointed hard rock is evaluated by first-order second-moment method, based on the distributions of the geometrical properties of the joints. The effect of blasting on the reliability is also examined by linear elastic fracture mechanics. (3) Construction phase. The probabilistic method is presented to predict the long-term deformation of the opening surface during construction. Bayesian approach is used to update the accuracy of the prediction, based on the observed deformation. The reliability of the lining is re-evaluated on the basis of the updated long-term deformation.