深基坑施工风险评估的模糊证据推理方法

Fuzzy witness reasoning-based approach to the risk assessment of the deep foundation pit construction

为了克服既有深基坑施工风险评估方法不能对风险评估结果进行信度评价的局限性,提出了一种将证据推理与模糊集理论相结合的风险评估方法。首先,以《地铁及地下工程建设风险管理指南》为依据,将风险定义为风险事件发生概率与损失程度的乘积并统一用梯形模糊数表示,针对指南中同一风险等级对应多个风险组合值的弊端,通过取有效组合的处理方法,建立风险等级与隶属函数的一一对应关系。然后,将深基坑施工风险事件的风险水平视为反映深基坑整体风险水平的证据,通过对事件风险水平进行置信结构转换及证据融合,得到能够反映不同可信度水平的基坑整体风险评估值。工程实例表明,运用该方法对深基坑施工风险进行评估不但可以反映基坑被评判为某一风险等级的信度,而且能够根据全局权重及置信结构分布较容易地找出影响基坑总体风险水平的关键因素,进而为有针对性地采取风险控制策略提供依据。

The paper is inclined to propose a novel method to make an attempt to determine the reliability of the risk assessment by applying the well-known method for risk assessment in the construction engineering project of the deep foundation pit,which should be incorporated with the evidential reasoning and fuzzy theory for the said risk assessment. For the said purpose,first of all,we would like to propose a trapezoidal fuzzy number based on the content of the corresponding guideline of the risk management in this manner,by taking the level of the risk defined as the product of the consequence severity and the probability of occurrence. And,then,the one-to-one correspondence between the risk levels and the membership functions can be established by choosing the valid combinations to eliminate the drawbacks described in the Guideline in which the same level of the risk is in correspondence with the multiple values at risks. And,next,the risk level of each potential hazardous event can be disclosed in accordance with the assessment of the domain experts,whereas the fuzzy analytic hierarchical process( FAHP) can be taken to set the weight of each potential hazard. And,finally,the risk level of each potential hazard is supposed to be able to provide evidence to reflect the overall risks of the deep foundation pit,so as to convert the risk level of each potential hazard into a form of confidential belief structure,while the overall risk assessment value of a deep foundation pit is supposed to be gained at the different confidence levels through the evidential reasoning by using a novel method. And,in turn,the said method proposed herein can be adopted to evaluate the risk level of the deep foundation pit of underground traffic project of Zhengzhou comprehensive transportation hub in China. And,so,summarizing the conclusion,the proposed method can be taken into application in the following way hereafter:( 1) The result obtained by using the proposed method is by nature a set of risk evaluation data with different degrees of belief,that is,within a given frame of the risk discernment,with each risk grade enjoying its own corresponding reliability. Thus,the drawbacks that the result achieved by the previous methods should be vague and in turn less dependable in reliability and,logically,can be neglected or forsaken;( 2) The proposed method makes an attempt on implementing the fuzzy evidential reasoning under the scenario in which more than 2 continuous fuzzy evaluation grades intersect rather than merely 2 of the adjacent ones;And,( 3) The global weight of the hazard and the extent of irregularity in the belief structure should enjoy 2 determining factors for the evidence fusion. And,so,under condition when the overall risk levels of a deep foundation pit has been given,more attention to the risk assessment should be paid to the hazardous events with the bigger global weight and higher degree of irregularity in the structure given.