根据事故树分析FTA的原理,建造了排桩支护结构体系的事故树图;提出了将专家调查的失事基坑工程统计频率与级差概率相结合的方法来确定底事件的概率的方法;在确定最小割集的基础上,进行了顶事件概率的计算,对于相交的割集通过采用将最小割集中出现的相交和化为不交和的方法–递推化法来实现;最后通过重要度分析评价,对基本事件的重要度进行排序,以便寻求对顶事件发生事故最有影响的潜在因素,并据此进行安全评价报告,指出相应的安全对策及建议。 According to the principle of FTA, an accident tree is constructed and the method of determining the probability of the bottom event is put forward by combining the statistical frequency and step probability of the engineering investigation of cased pit excavation. On the basis of determining the minimum cut set, the calculation of the probability of top event is carried out. For the cut set of the intersection, the method of recursion is adopted by using the method of intersecting and disjoint in the minimum cut set. Finally, Analyze and evaluate the importance of basic events in order to seek the most influential potential event of the top event and conduct a safety assessment report accordingly and indicate corresponding safety measures and suggestions.