Fuzzy Fault Tree Analysis of Failure Probability of SMW Retaining Structures in Deep Excavations

Traditional fault tree analyses use single probability to represent each basic event. However, it is unrealistic to evaluate the occurrence of a top event by using a crisp value without considering inherent uncertainty and imprecision each basic event has. The fuzzy set theory can be used to deal with this kind of phenomenon. A triangular fuzzy number is introduced to represent the failure probability of a basic event. Fuzzy fault tree algorithm is developed by the lambda-cut method. The fuzzy failure probability of SMW retaining structures in deep excavations is calculated by a fuzzy fault tree. Main basic events affecting the occurrence probability of the top event are verified by a sensitivity analysis, which can be applied in the risk analysis of SMW retaining structures in deep excavations. Compared with the traditional fault tree analysis, the fuzzy fault tree method can get the failure possibility distribution of SMW retaining structures in deep excavations.