Design And Application Of Optimization Model For Supporting Scheme Of A Deep Foundation Pit

In the stability analysis of deep foundation pit,randomness and fuzziness appear in its uncertainty.The design parameters with the characteristics of random variables are the main manifestation of randomness,and the instability state with the characteristics of judgment criteria is the main manifestation of fuzziness.The characteristics of fuzzy random are consistent with the characteristics of support scheme optimization,which is easy to be applied to the selection of foundation pit support scheme.However,due to the complexity of foundation pit support engineering and the subjectivity of decision-makers,the conventional optimization method is insufficient.Therefore,it is necessary to refine the scheme selection and reduce the impact of adverse factors on the whole optimization process.This paper expounds the theory and establishes the model.Based on the case-based reasoning theory,a large number of similar foundation pit supporting engineering cases are collected and sorted out,the case base is established,the entropy weight rough set theory is introduced to calculate the weight value,and the primary selection model is established.AHP method and fuzzy mathematics theory are introduced to form the evaluation system of the scheme and complete the establishment of the final selection model of the scheme.In this paper,a deep foundation pit project of an underground garage in Nanchang city is selected as an example to apply the optimization model of foundation pit support scheme.In the application stage of model primary selection,the feasible alternatives are selected by searching the similarity between the target case and the case base case.Through the application of the final model,the final scheme is selected from the alternatives,and the scheme is put on the ground,and the finite element analysis of its design and excavation impact is carried out to further verify the feasibility of the model and complete the application of the whole model.The main conclusions are as follows:(1)According to the weight calculation of retaining structure and support system,the weight of foundation pit depth is 0.151 and 0.181 respectively,which is the highest compared with other indexes.It shows that the depth has a great influence on the selection of foundation pit support scheme,and further verifies the scientific effectiveness of the method.(2)Based on the engineering case,the model is applied.After using the model,combined with the actual situation,it is found that if the anchor rod support is used,it will exceed the red line of the land,so the final scheme is modified,and the concrete internal support is selected to complete the final selection of the scheme.(3)Compared with the fuzzy comprehensive evaluation method,it increases the case base,explores its learning ability,makes it intelligent,and refines the scheme primary selection,weakening the subjective influence of only relying on expert scoring.Compared with case-based reasoning method,the first three similarity ranking schemes are selected,and then fuzzy comprehensive evaluation is carried out to reduce the error rate and improve its effectiveness.