| In recent years,safety accidents caused by construction projects emerge in endlessly,especially in the process of deep foundation pit excavation and enclosure,the surrounding buildings and structures cracking,inclining and even collapsing caused by foundation pit settlement and deformation occur frequently.Therefore,the scientific design and disaster prevention and control work of construction such as deep foundation pit are particularly important.Generally speaking.there are many unfavorable conditions in the construction of deep foundation pit excavation,and the surrounding environment is complex.The support design of deep foundation pit based on strength control is difficult to meet the requirements of stability and deformation of deep foundation pit under complex environment,and it is gradually changing to deformation control.Therefore,it is necessary to study the displacement changes of supporting structure and surrounding important buildings in the process of foundation pit excavation,verify and analyze the design results of foundation pit,demonstrate the reasonable safety of support design,optimize the support scheme,and put forward effective engineering measures,so as to ensure the safety of foundation pit construction in advance.This paper starts from the background of sand bar area along the river plain,expounds the great significance of foundation pit engineering for the safety guarantee of construction projects in this area,and briefly introduces the current research status and main methods at home and abroad,and elaborates the contents,characteristics,optimization design theory and main calculation methods of deep foundation pit engineering design,and fully compares several common methods for deep foundation pit selection Based on the advantages and disadvantages of the foundation pit support scheme and the applicable scope,the geological conditions and surrounding environment of the proposed site are comprehensively considered.In this paper,taking a deep foundation pit project in Suzhou as an example,MIDAS / GTS NX software is used to simulate the deformation of retaining structure and adjacent buildings in the process of foundation pit construction,and the field monitoring data are compared and analyzed,and the variation law of soil displacement outside the foundation pit is discussed.According to the actual situation of the foundation pit,select the more appropriate specific parameters of the supporting structure,draw up the support design scheme,reasonably divide the construction condition sequence of the excavation process of the foundation pit,carry out the simulation in different conditions,study the internal force and deformation of the support structure under different conditions,calculate the support structure,and obtain the stability analysis of the whole support system.From the calculation results,the design of foundation pit support scheme is reasonable,and the displacement and stability check calculation can meet the requirements of the current code.The results show that: the foundation pit support scheme is reasonable,the finite element calculation results are basically consistent with the measured results.The results of the deep foundation pit supporting structure and the simulation of the excavation process of the deep foundation pit prove that the finite element analysis can truly reflect the actual state of the deep foundation pit excavation process.In the process of deep foundation pit excavation,the controlling deformation is the key.The deformation here mainly refers to the displacement of retaining structure caused by various factors such as soil pressure,water pressure and load pressure.Since the retaining structure is the key to support the stability of soil around the pit,its deformation and displacement will cause displacement and deformation of surrounding soil,buildings and structures,underground pipeline Gallery,etc.especially for tunnel construction,subtle soil deformation will cause chain effect and great harm,Therefore,deformation control has become the first element of deep foundation pit construction.In view of the fact that the deformation law is mainly related to the construction scheme and the control distance,the finite element model should be established for the design scheme of the supporting structure of the deep foundation pit to simulate and analyze the displacement field of each excavation stage of the deep foundation pit.The influence of the stiffness of the retaining structure,the number of layers of the internal support and the horizontal spacing of the internal support on the excavation deformation of the foundation pit is studied.The results show that the thickness of diaphragm wall,the number of layers of internal support and the transverse spacing of internal support have influence on the deformation of foundation pit,and the layout of internal support has obvious influence on the deformation of foundation pit,Based on the analysis and summary of the influence of supporting structure on excavation deformation of foundation pit,the optimization measures for deformation control during the design and construction of deep foundation pit are proposed,which provides reference for the design and construction of similar deep foundation pit engineering.Figure [101] table [17] reference [57]... |
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