The Research On The Deformation Characteristics Of Supporting Structure Of Deep Foundation Pits Under Top-down Excavation

With the development of our modern society.The acceleration of population and city-process,especially the construction to the big city,make a great needed to the land.Due to the nervous land using,the ground land can no longer satisfy people’s growing demand.At the same time of seeking for high-rise building,people have been explore new area in underground which made foundation got rapid development.Due to the complex construction environment of the city,and the strict requirements of the deformation,which made the traditional pit engineering methods a more and more restrictions.Popularization of top-down method,which could adapt to small working place or intensively surroundings and complex underground pipe network,provided a good solution to the deep foundation pit.Because of the compactness and strong stiffness of diaphragm wall,the top-down method can try its best to deduce the settlement of structure and the outside soil.But at the same time,this method needed the more strict process of engineering because of the complicated technology of the method.Therefore,the research of the Supporting structure deformation before the pit engineering would be especially important.And the research could be a well guide for the similar excavation engineering.It is researched in the paper of the deep foundation pit of the new traffic in Hefei.By using the MIDAS/GTS three-dimensional finite element software to research the deformation of the retaining structure in different excavation depths and conditions.The mainly contents are following:(1)First of all,the characteristics of the foundation pit engineering is briefly introduced,including research and development status both at home and abroad.Then reviewed the top-down method,including advantages and disadvantages of the methods,the construction principle and classification of it.Elaborated the roughly development status and existing problems at present stage of the top-down method.Then finally introduced the research skills and contents of this paper.(2)Briefly introduces several types of pit supporting and focus on the supporting structure of the wall.Then summarized the characteristics and deformation-law of theretaining structure of foundation pit project.Overviews the various factors affecting to the deformation of foundation pit and introduced the design theory of retaining structure.(3)Introduces the hefei new traffic building engineering geological conditions and supporting method,and made reasonable selection of the material parameters.using the MIDAS/GTS three-dimensional finite element software to build model of the excavation of the building,to simulate the whole construction process of foundation pit excavation through the different excavation condition.(4)Built a three-dimensional model to calculated the deep lateral horizontal of the wall,the horizontal lateral and vertical settlement of crown beam,and combined The results of numerical simulation with the monitoring data.And finally drawn the conclusion of these three.(5)The result of the numerical simulation and the data showed that,the curve of the lateral displacement of the wall went a bow shade,which both the hand and down-side small but the middle-side got a rise.The maximum deformation occurred in central position of the excavation-depth.Both horizontal sides displacement direction toward the inside of the foundation pit,and fluctuated as the support structure applying.The settlement of crown beam displacement deformation keep a down trend.