Study On The Stability Of Soft Soil Deep Foundation Pit Support System

The development of urban speeds up in recent years. It is a trend to develop and utilizethe underground space. With the underground space develop, a lot of foundation pitengineering has arisen. There are many support patterns in foundation pit engineering, suchas deep mixing cement-soil pile, steel sheet pile retaining wall, bored piles retaining wall,diaphragm wall, SMW method, soil nailing wall, inverse arch wall. Different areas useddifferent foundation pit supporting forms. The selection is more carefully in the thick softsoil area.The research object of this article is jinghui square foundation pit engineering injiaxing. First, studying the general situation, site engineering geological conditions anddesigning scheme of foundation pit supporting by collecting data; Secondly, conductinginformation monitoring of foundation pit construction process, and summarizing ofmonitoring results. Finally, simulating a typical section with finite difference method FLAC3D, which is commonly used in geotechnical engineering. The main research results in thearticle are as follows:(1) As the earth excavation of foundation pit, the displacement of foundation pit sidesoil increased, After completion of the floor construction, the deformation is stable,furthermore, the maximum deformation is within a reasonable range. The maximumsettlement of road is13.9mm after the construction is completed. Underground water levelfluctuates in a small range and finally be stable. The results show that the SMW pile withprestressed type steel support and churning mixing stiffening piles is very effective inconstrained deformation of foundation pit in soft soil area, SMW pile can effectively sealwater and the combined supporting structure has less impact on the environment.(2) In soft soil area, the stiffening pile prestressed decay soon. The first line ofstiffening pile attenuation is obvious. The actual construction demonstrated that byincreasing prestressed and repeating tension can effectively reduce the stress loss, andcontrol the deformation of foundation pit.(3) Both monitoring results and the simulation results show that after the completion ofexcavation，the position of maximum displacement of foundation pit soil is in the excavation surface above1-2m.(4) The simulation results of excavation without support show that the excavationimpact in the range of2times excavation depth environment.(5) Using FLAC3D for numerical simulation，then to analyse the different between themonitoring results and the simulation results of deep soil displacement and axial force ofstiffening pile. The two results are consistent. It is indicated that the division of the grid, theselection of the structural unit, as well as the value of material parameters are reasonable.The results can provide reference for the similar foundation pit design and construction offuture. At the same time it also validates the rationality of the design.