The Research On Fuzzy Synthetic Evaluation Of The Safety And Reliability Of The System Of Deep Foundation Pit Bracing

Based on the characteristics of foundation pit bracing project , and having greater uncertainty and more influencing factors during analyzing the reliability of deep foundation bracing system, so this article has made an evaluation of the reliability of deep foundation pit bracing system by using the method of fuzzy synthetic evaluation, and the reliability of deep foundation bracing system should only be studied from the aspect of safety.The main research contents include that after having analyzed the factors which affect the safety and reliability of the system, establish an evaluation system with three layers after combining the monitoring contents, the first layer includes exterior-protected construction, support system and consecutive environment, and the second layer includes the internal force and deformation governed by the above layer, and the third layer includes the reflection of the internal force and deformation, introduce compressive weight and modified identifying method, at the same time, divide the evaluation field to four grades and fuzzy the boundary of each grade, The specific evaluation processes as following:(1) In the actual project of the foundation pit bracing, choice the monitoring contents as the evaluation factors, and establish an evaluation system with three layers.(2) Calculate the characteristic weight of each index by using AHP and then come to compressive weight by combining the numerical weight.(3) Erect the membership functions for each of the four grades including safety, attention, highly attention and danger, confirm the membership grade of each evaluation index according to the monitoring data and then make the judgment matrix.(4) Erect the evaluation model of each layer, the come to the evaluation conclusions by using modified identifying method and combining the traditional identifying method.By practically analyzing a project of foundation pit which is underground diaphragm wall bracing in shenzhen by using the abovementioned theory and method, its feasibility has been validated.