66 / 2021-11-16 01:17:46

Stability design for hard rock tunnels under uncertainty using inverse-reliability strategy

hard rock tunnel; stability design; inverse reliability; target reliability index

Abstract—The stability design of hard rock tunnels, as a significant aspect of geotechnical community dominated heavily by the inherent uncertainty in geological analyses, should be correctly implemented to produce meaningful results. With the tremendous development of reliability methods (via the reliability index or probability of failure) used to cope with the uncertainty in a systematic manner, the design standards have an increasing tendency to guarantee stability of geotechnical structures by prescribing a target reliability index. This manifests that the reliability level of a hard rock tunnel is pre-defined as a target to be fulfilled. In such a scenario, an inverse-reliability strategy is proposed to solve the stability problem of hard rock tunnels. The basic idea behind it is to how to back-calculate the engineering parameters involved in the stability design process to ensure the pre-defined level of reliability when knowing the target reliability index. In conformity with this strategy, an inverse first-order reliability method (IFORM) is developed and its solution procedure is also summarized. On this basis, the computational accuracy and efficiency are both verified in identifying the engineering parameters. Further, in view of various levels of the target reliability index, the hard rock tunnel stability design was conducted based on the spalling of the surrounding rock. Using several typical examples of the hard rock tunnel, the feasibility and validity of the developed IFORM are demonstrated, during which the associated sensitivity study and further discussion are also performed. By dint of the presented inverse-reliability strategy, the engineering parameters can be adjusted conveniently, thus providing guidelines which are found to be  in accordance with the practical situations for the stability design of hard rock tunnels.