Research On Design And Construction Technology Of Internal Support For Large-span Deep Foundation Pit

With the rapid development of national economy,urban land has become increasingly strained5which seriously hinders the development and planning of cities.If the utilization rate of land is improved,it will not only not change the appearance of the original cities,but also make full use of the above ground and underground space.In order to solve the contradiction between urban development and land shortage,Chinese construction engineers have studied underground supporting structures of different forms and functions through a large number of engineering cases and experiments.So far,China's underground structural engineering has been vigorously developed.All kinds of underground rail transit,multi-storey underground parking lots and large unaerground shopping malls are emerging in people's eyes.With the establishment of these large underground structures,the depth of foundation pit excavation is increasing,so the frequency of engineering safety accidents is also increasing.Therefore,in order to reduce the frequency of hidden engineering accidents in the process of deep foundation pit excavation,this paper firstly conducts theoretical analysis on the support theory of deep foundation pit,and then explores the PPP project of Hudaying sewage plant in Hefei city by combining finite element numerical simulation and construction site monitoring.In this paper,MIDAS GTS NX numerical simulation method is used to study the ground settlement around the foundation pit,the bottom heave of the pit and the structural deformation law of the cast-in-place pile as the envelope structure in the excavation process.Due to the limited learning time and content5this paper only studied the influence of changing the pile diameter of the cast-in-place pile on the foundation pit deformation rule,providing reference for later similar projects.The following contents are studied in detail:(1)Through the review of domestic and foreign materials and books,this paper analyzed the design and selection of foundation pit support,smmmarized the way of foundation pit support and different support modes under different circumstances,and analyzed the concrete internal support mode.At the same time,it is also compared with the steel structure support mode.(2)Through three-dimensional numerical simulation of foundation pit excavation,it can be concluded that with the excavation of foundation pit depth,the ground settlement around the foundation pit changes in the shape of "U",and the heave of foundation pit bottom also increases synchronously.The deformation of envelope structure is large above and small below at first,and then small above and large below.(3)Through changing the parameter of pile diameter,it can be found that increasing the diameter of cast-in-place pile has a great influence on the deformation of retaining structure,which not only increases the bearing capacity of retaining pile itself but also increases its stability.Figure[55]table[6]reference[50]...