Research On Optimum Selection Of Supporting Structure For Deep Foundation Pit

Since China’s reform and opening up, construction of city has increased and the ground space is gradually less available. In order to make full use of land resources, underground engineering develop quickly, especially the deep foundation pit engineering which has become an important part of urban construction. Supporting structure is a key in a foundation pit engineering and many engineering accidents is due to the supporting structure caused by the improper selection. In our country, the preferred method of supporting structure of deep foundation pit engineering used to be evaluated by the panel, although this method is simple, but it lacks theoretical basis, so the supporting structure is not optimal and it is buried under the safe hidden trouble. Therefore, developing a system of deep foundation pit supporting structure optimization method is imminent. Combing analytic hierarchy process(ahp) with fuzzy comprehensive evaluation method is an effective method of optimal selection which can overcome the impact of subjective factor to select the optimal supporting structure, making the comprehensive benefit guaranteed.The paper researches the optimal selection of supporting structure a deep foundation pit engineering in Beijing. This paper introduces the features of deep foundation pit supporting structure and summarizes the common supporting structure and briefly describing the applicability of the supporting structure, the common optimization method and the optimal choice should follow the basic principles, through the comparison, the analytic hierarchy process(ahp) and fuzzy comprehensive evaluation method is used to choose the optimal supporting structure. Before the optimization, listing the influencing factors of supporting structure selection and determining the object of study for this two section of the foundation pit engineering. On the basis of the relevant procedures, I choose the primary supporting structure which includes three categories, namely the composite soil nailing wall, the pile anchor supporting, underground continuous wall. At the same time, it is necessary to make evaluation questionnaire and invite dozens of experts who come from China, s first construction engineering company to evaluation which forms some transformation matrix. Finally make the basis of 1-9 scaling method to construct judgment matrix, I establish evaluation model and respectively for each section of the primary supporting structure which is concluded that the two sections of the optimal supporting structure, and the results are consistent with the actual. Finally, using Richard of deep foundation pit software to calculate, the results show that the foundation pit engineering is in a stable state. The paper also use ABAQUS software simulation analysis to carry out on the foundation pit excavation, the results also show that the deformation of supporting structure in a safe range. So the method is reasonable.