地铁深基坑坍塌事故安全风险分析

为了降低和控制地铁深基坑施工风险,避免在施工过程中造成深基坑坍塌事故,以重庆市某地铁站深基坑开挖为例,进行了深基坑开挖风险评估。建立了深基坑坍塌事故导致人员伤亡的事故树模型,再通过事故树建立层次结构模型,将事故树的结构重要度转化为层次分析法中的判别因子,结合层次分析法的权重计算及排序,对深基坑坍塌事故的致灾因素进行了定性识别和定量分析。结果表明,施工地质条件复杂、设计方案不合理、勘察资料有误等事件为主要致灾因素。在地铁深基坑施工过程中应做好动态监测及日常管理工作,保证勘察设计的准确性与可行性。改进后的模型可为企业施工管理提供理论指导。

Safety risk analysis for the deep foundation pit collapse accidents in the subway construction system

To reduce and control the risk of deep foundation pit construction and avoid such pit collapse of deep foundation pit in the process of construction,the paper has taken a deep foundation pit excavation project of a subway station in Chongqing as a case study sample for the risk assessment. In doing so,it is first of all to analyze the likely causes of such collapse accidents on the construction spot to see such deep foundation pits in the said way. However,the general reasons for causing such collapse accidents can be summarized into 4 sorts: that is,the human factor,the construction technological factor,the environmental and management factors. On the above said bases,we have established a fault tree model of the deep foundation pit collapse accidents in terms of the engineering cases. And,secondly,such basic events are to be identified by the fault tree and then transform the basic likely events into the index layers in the analytic hierarchy process( AHP) so as to build up a hierarchical structure model through the above said fault tree model. Finally,a comparison has to be done by following the order of the structural importance of each basic event in the fault tree. The judgment and evaluation matrix in the analytic hierarchy process has been built up by calculating the weight value of each factor in the target whereas the disaster-causing factors of the foundation pit collapse accidents are to be qualitatively identified and quantitatively analyzed. Among the lots of basic causative events,the chief ones are to be the bedding slide of foundation pit slope,the influence of the surrounding buildings and the disturbance of the construction in the environmental factors. The unreasonable design of the supporting structure,the incorrect geological investigation data and the unreasonable construction organization planning can all be the 2-secondary essential factors,with the improper construction methods and irregular construction advances being the 3-rd level factors. Thus,the results of our study show that an improved and innovated analytic hierarchy process turns to be suitable and applicable for the purpose. And,the given results of the present study can help to lay a scientific basis for the safety management of the foundation pit construction in the subway construction enterprises.