Comparison And Optimization Design Of Deep Foundation Pit Support Scheme For An Underground Garage

With the rapid development of China's economy and the gradual acceleration of the construction process,more and more urban high-rise buildings,due to site constraints,the underground part of the space occupied by more and more,followed by a larger excavation area of the foundation pit;buried deeper and deeper;its distance from the surrounding buildings is getting closer and closer;construction sites are becoming more and more small.Foundation pit support is becoming more and more important,more and more types of support,as the foundation pit engineering accidents caused by support design become more and more serious,therefore,the choice of reasonable support scheme is becoming more and more important.The supporting design of-foundation pit meets the requirements of strengtn,deformation and stability,and then takes into account the economic benefits and rationality of the project,which requires reasonable selection and optimization design of each feasible scheme.Therefore,reasonable selection of supporting scheme,improvement of engineering quality and reduction of engineering accidents put forward higher requirements for optimization design of foundation pit supporting scheme.In this paper,combined with a large-scale deep foundation pit project,considering the geological and environmental conditions around the foundation pit,through the calculation of different support schemes to determine the optimal form of support,mainly do the following work:(1)This paper expounds the commonly used forms of foundation pit support and their application scope as well as matters needing attention,preliminarily determines the supporting forms to be adopted in this paper,and carries out a detailed discussion on the scheme design and calculation theory.(2)The detailed data of the foundation pit project are collected to determine the soil parameters and the size of the foundation pit,which provide the basis for the subsequent design of the parameters.(3)Through studying the principle of supporting structure scheme optimization,the optimum method suitable for this project,namely AHP,is selected to optimize the original design of supporting scheme.According to the general situation of the foundation pit and the requirement of deformation control,two supporting schemes are put forward initially,that is,1)Underground continuous wall+anchor bolt direct excavation,2)Pile anchor support+slope excavation.(4)A foundation pit model was established by finite element software MIDAS GTS NX.The displacement,internal force,surface subsidence,pit bottom heave,integral stability safety factor and anti-overturning safety factor of the retaining structure under the two kinds of retaining structures in the process of foundation pit excavation are studied.Considering safety and economy,the optimal supporting scheme is determined by AHP model,which provides relevant basis for the construction of the actual project.(5)In this paper,the scheme of dewatering and drainage and the monitoring scheme during the construction of the foundation pit are designed,and the field monitoring data are analyzed and studied,which verifies the correctness of the numerical calculation results and the rationality of the supporting scheme.