Abstract: Due to the complex construction process, many risk factors and high collapse accident rate of tunnel constructed by drilling and blasting method, the application of traditional fault tree analysis (FTA) method is limited by the probability, the logical relationship, and the fault state of events only considering the binary-state. In this paper, a method for evaluation of collapse possibility of construction tunnel by drilling and blasting method based on T-S fuzzy fault tree is developed to reduce construction risk and provide decision-making basis for prevention. In this method, fuzzy numbers and T-S fuzzy gates are introduced into fault tree analysis. T-S fuzzy gates are used instead of traditional logic gates to describe the relationship between events, which reflects the fuzziness of fault mechanism and event connection, and reduces the difficulty of establishing the fault tree. Fuzzy numbers are used to describe the fault probability and degree of the bottom event, which overcomes the problem that traditional fault tree relies too much on probability and can not consider the influence of the fault state of events. This method not only can calculate the tunnel collapse possibility by using the priori fuzzy possibility of the bottom event and the actual fault degree in construction, but also can guide the risk control work according to the result analysis of bottom event importance. Two engineering examples are analyzed. Results show that the proposed method is more in line with the engineering practice than the traditional fault tree method. It can evaluate the possibility of tunnel collapse more scientifically and rationally and determine the key risk factors. It can be used as a decision-making tool for tunnel construction safety risk analysis and management.

Key words: construction of tunnel drilling and blasting method, collapse possibility, T-S fuzzy fault tree, fuzzy number, T-S fuzzy gate