基坑锚杆脱粘风险的事故树分析

Debonding risk analysis of anchors in excavation engineering based on fault tree

根据事故树分析原理,构造了基坑锚杆支护结构脱粘的事故树图;提出了将专家统计的失事基坑工程频率与级差概率相结合来确定基本事件概率;在确定最小割集的基础上,进行了顶事件概率的计算;最后通过敏感性分析,对各基本事件的敏感性进行排序,揭示基本事件对于顶事件的贡献程度.分析结果表明,基坑锚杆支护结构脱粘的概率为0.180 64;土层锚杆脱粘失效对锚固段长度最为敏感;"预应力施加过早过大"、"砂浆配比不合理"、"灌浆方式不合理"、"浆体密实度不足"、"锚固体表面积过小"、"荷载过大"等几个基本事件的敏感系数排序靠前,在基坑锚杆的设计与施工过程中,必须引起足够重视.

According to analysis theory of fault tree, the fault tree diagram of retaining structure system with anchors is established, and the method put forward to combine wrecking foundation trench project statistical frequency inquired by experts and differential probability to determine probability method of the bottom event. Based on confirming minimum cutset, the probability of top events is calculated. In the end, through sensitivity analysis, sensibilities of various basic events are sequenced to reveal contribution degree from basic events to the top event. It is shown from the analytic result that the debond probability of foundation trench bolting structure is 0.180 64 and the earth anchor debond invalidation is sensitive to length of the anchorage segment. basic events such as＆quot;too early and oversize application of pre-stress＆quot;, ＆quot;unreasonable mixture ratio of mortar＆quot;, ＆quot;unreasonable grouting mode＆quot;,＆quot;insufficient mortar compactness＆quot;, ＆quot;less anchorage surface area＆quot;, ＆quot;oversize load＆quot;, etc moved to the top. During design and construction process of earth anchor, attention to these problems has to be paid.