| In the northern part of the seasonal frozen soil foundation pit engineering,due to the continuous expansion of the scale,the construction period and the use of the period has undergone great changes,may have to go through the winter.The pile anchor supporting structure is a kind of supporting system,which is supported by the pile,anchor cable and the supporting soil.At present,the design and construction of this supporting type in the face of the overwintering period is still a lack of the necessary attention.Because the soil freezing will appear frost phenomenon,the swelling deformation for retaining structure will have a big security risk.In the actual engineering design and construction must fully consider the effect of frost heave effect of supporting structure,in order to ensure the stability of foundation pit engineering in construction and service stage.Therefore,it is necessary to carry out research on frost heave and deformation under the action of pile anchor supporting structure mechanical characteristics,to improve the structure of the foundation pit design theory and construction method.In order to study on the problem of the influence of foundation pit supporting structure stability of winter frost heave,in this paper,the frost heave on pile anchor bracing of deep foundation pit engineering is simulated by using the finite element software ABAQUS,numerical simulation can be simplified model of practical engineering,accumulate experience and provide reference for future similar foundation pit design.The main works are as follows:(1)According to the domestic and foreign researches on frost theory,summarizing the characteristics and influence factors of soil heave,analyzing the effect of supporting structure of foundation pit heave mechanism,and winter excavation pile anchor supporting structure deformation and damage form,requirements in the design and construction of a real project should fully consider the influence caused by frost heave.(2)Taking a practical foundation pit project as an example,this paper uses ABAQUS finite element software to simulate the overwintering condition of the pile anchor supporting structure.In order to be more close to the actual,firstly,simulation of excavation was carried out,the simulation results of excavation completed is used as the initial conditions of the frost heave of foundation pit supporting structure.(3)The temperature field model is established to simulate the temperature field of the foundation pit.According to the calculation results,the temperature range and the temperature variation of the soil are analyzed,and the accuracy of the temperature field simulation is verified with the actual situation.To establish the model of foundation pit,import the temperature field simulation results,using the method of thermo-mechanical coupling simulation of frost heave effect on foundation pile-anchor supporting system generated.The change of horizontal displacement and axial force of bolt are analyzed.Comparing the simulation results with the actual engineering monitoring data,it is found that the two trends are basically the same.(4)According to the cooling rate and soil moisture content,12 kinds of working conditions are designed.The influence of temperature on the thermodynamic properties of soil is considered under the same conditions that the expansion coefficient and the falling temperature are the same,simulating the 12 kinds of working conditions of temperature field by using ABAQUS finite element software,and the simulation of frost heave effect on foundation pile-anchor supporting system generated by thermo-mechanical coupling.According to the calculation results,the change trend of the horizontal displacement of pile top and the axial force of the anchor rod are analyzed under different soil water content and different cooling rate,and then concluded that the effect of temperature on the thermodynamic properties of soil is greater.The frost heave is more significant on the displacement and stress changed of pile anchor supporting system. |
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