RELIABILITY INDEX ANALYSIS ON ANCHOR-NET-SHOTCRET SUPPORT STRUCTURE OF TUNNEL UNDER NON-SYMMETRICAL CONDITION

Based on the analytical solution of elasticity and plasticity theory of circular tunnel surrounding rocks, the analytical model of reliability index on an anchor-net-shotcrete support structure of a tunnel under a non-symmetrical condition is built. Considered the high non-linearity of functions, the reliability index computation is adopted by the Monte-Carlo and Rosenblueth methods. The calculation results show that the reliability of a support structure is a common action result of surrounding rock, anchor, net and shotcrete. Reliability index decreases with the increase of the variation coefficients of the crustal stress, cohesive force, inner friction angle, thickness of a spraying layer, and the extension strength of an anchor and an anchor-reinforced force. Reliability index increases with the increase of a lateral pressure factor. The reliability index rapidly decreases with the increase of crustal stress.