| With the advancement of all kinds of construction projects,more and more deep foundation pit projects appear,and engineering accidents caused by foundation pit collapse are common.Therefore,in order to improve the safety of foundation pit construction in engineering,it is often necessary to improve the control requirements of displacement and settlement of supporting structure and surrounding.But in the actual construction,the change of different loads makes the deformation of foundation pit change constantly,so the axial force of steel support is also changing.In particular,the steel support has small stiffness and the connection with the support is movable.When the support is subject to stress relaxation or plastic deformation due to temperature change and other reasons,the loss of axial force is likely to occur,and serious safety accidents such as support falling off will occur [1-2].Because the construction time of deep foundation pit is longer than that of general foundation pit,the axial load of steel support is constantly lost in the construction of deep foundation pit.In order to solve this problem,the steel support axial force servo system is used in the construction of deep foundation pit.The steel support axial force servo system is an adaptive device for the change of the steel support axial force.Through real-time monitoring,the support axial force is extracted and adjusted continuously through the hydraulic system.Therefore,the change range of the axial force of the support in the deep foundation pit can be stabilized in a certain range,so as to control the deformation of the foundation pit and ensure the safety of the foundation pit.Based on the construction of deep foundation pit of a subway station,this paper studies the effect of supporting axial force servo system in deep foundation pit support through field monitoring and simulation analysis.The main research contents and conclusions are as follows:(1)This paper summarizes the characteristics of the steel support axial force servo system and its practical application status.(2)Based on the theoretical calculation method and the field monitoring results,the foundation pit supporting system without steel supporting axial force servo system is analyzed theoretically and numerically according to the excavation construction characteristics of the foundation pit.The calculation results show that the steel supporting axial force servo system can effectively control the deformation of the foundation pit supporting structure.(3)Based on the investigation of the monitoring data such as the displacement of the supporting structure,the vertical displacement of the foundation bottom and the ground settlement,the occurrence and change rule of the displacement of the supporting system and the axial force of the support during the construction of the foundation pit are analyzed.On this basis,the effect of the axial force servo system of the steel support on reducing the deformation of the support,the surface settlement and the top displacement of the support structure in the process of excavation is further demonstrated.(4)In order to understand the effect of the axial force servo system of steel support in the support system,combined with the field monitoring results,the numerical simulation method is used to model the foundation pit support system assuming that the axial force servo system of steel support is not set according to the excavation construction characteristics of the foundation pit.The calculation results show that the simulation results can reasonably reflect the axial force servo system of steel support not set The influence of the support system of the system on the excavation process of the foundation pit is further clarified.The axial force servo system of steel support can effectively improve the stability of the support structure.Through the adjustment of the axial force in the simulation condition,the setting of the axial force servo system of steel support is simulated.The mechanism of restricting the deformation of the foundation pit is that the change of the axial force is effectively constrained.(5)Based on the purpose of application of steel support axial force servo system in foundation pit supporting engineering,the influence of supporting axial force servo system,system loading position,construction load range,construction load and other factors on supporting structure deformation,soil pressure distribution and surrounding ground deformation is mainly investigated through simulation analysis The structure design and construction have provided certain theoretical basis. |
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