Authors: Qing Lü Chin Loong Chan Bak Kong Low
Publish Date: 2012/07/14
Volume: 46, Issue: 4, Pages: 821-833
Abstract
This paper presents a practical procedure for assessing the system reliability of a rock tunnel Three failure modes namely inadequate support capacity excessive tunnel convergence and insufficient rockbolt length are considered and investigated using a deterministic model of groundsupport interaction analysis based on the convergence–confinement method CCM The failure probability of each failure mode is evaluated from the firstorder reliability method FORM and the response surface method RSM via an iterative procedure The system failure probability bounds are estimated using the bimodal bounds approach suggested by Ditlevsen 1979 based on the reliability index and design point inferred from the FORM The proposed approach is illustrated with an example of a circular rock tunnel The computed system failure probability bounds compare favorably with those generated from Monte Carlo simulations The results show that the relative importance of different failure modes to the system reliability of the tunnel mainly depends on the timing of support installation relative to the advancing tunnel face It is also shown that reliability indices based on the secondorder reliability method SORM can be used to achieve more accurate bounds on the system failure probability for nonlinear limit state surfaces The system reliabilitybased design for shotcrete thickness is also demonstrated
Keywords: