| With the rapid development of the national economy,the people have higher requirements for the living environment after solving the basic needs of clothing,food,housing and transportation.Urban waterlogging and overflow pollution are one of the main factors affecting the living environment.The storage reservoir project can effectively solve the above problems.The main structure of the storage reservoir is all underground,which is a typical super large and ultra deep foundation pit project.The core of deep foundation pit engineering is foundation pit support engineering.This deep foundation pit engineering selects concrete internal support structure +diaphragm wall.Previous studies on the support structure in foundation pit mostly studied the support effect of foundation pit from the aspects of internal support spacing,number of lanes,thickness of retaining structure,depth of soil,etc.There are few studies on the influence of other factors on the effect of foundation pit support.This paper mainly studies the internal support structure of deep foundation pit and discusses the relevant factors affecting the effect of internal support.The main research contents and specific conclusions of this paper are as follows:（1）This paper summarizes the previous research results and problems of internal support in foundation pit,analyzes the types and application scope of internal support structure in foundation pit,expounds the deformation theory of foundation pit,and discusses the calculation and analysis theory of internal support.（2）The three-dimensional numerical simulation of the whole process of foundation pit excavation and support is carried out by using the geotechnical finite element analysis software.The simulation results are compared with the field monitoring data.The simulation results of horizontal displacement of diaphragm wall,surface subsidence and support axial force are basically consistent with the monitoring data,the reliability of the three-dimensional finite element numerical simulation results of foundation pit is proved（3）In the three-dimensional numerical simulation,after changing the connection between the horizontal inner support and the column from rigid connection to hinge,the change of surface subsidence displacement around the foundation pit and horizontal displacement deformation of underground diaphragm wall is very small,the change is less than 1mm;The axial force of support in the foundation pit changes greatly,which is reduced by about 26%.It can be shown that the change of the connection between the horizontal inner support and the column from rigid connection to hinged connection has no great impact on the deformation control of the foundation pit and the safety of the foundation pit.（4）In the three-dimensional numerical simulation,when the foundation pit is excavated in layers,it is appropriate to over excavate.When it does not exceed the bottom of the inner support section,compared with the excavation to the top of the inner support beam,the maximum ground surface subsidence displacement increases by 11.5%,and the maximum horizontal displacement of the diaphragm wall increases by 5.6%.It can be shown that over excavation will reduce the support effect of foundation pit,but they are far less than the early warning value of foundation pit deformation,which is not enough to affect the deformation control and safety of foundation pit.（5）In the three-dimensional numerical simulation,the preloaded axial force applied to the concrete internal support components has a great impact on the horizontal displacement of the foundation pit diaphragm wall,which is reduced by20.5%,and has little impact on the surface subsidence around the foundation pit,which is reduced by 5.7%.It can be shown that applying pre axial force to concrete internal support members can effectively improve the effect of internal support and restrain the deformation of foundation pit.Figure [53] table [8] reference [55]... |
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