| The artificial freezing construction method is often used in the subway tunnel contact channel construction.Construction of subway contact channel under the soft and water-rich stratum of coastal area using artificial freezing method has the characteristics of support stability,great water retention,great strength and small pollution.During the construction of the channel,the mechanical properties of frozen soil will change,resulting in frost heave.Ground surface building,built tunnels and underground pipelineswill be affected by frost heave.The structure may cause cracks,and may be damaged in severe cases.In order to control the impact of frost heave on buildings and earth’s surface,it is necessary to studythe law of the temperature field of the frozen wall with the freezing time and the scope of impact of frost heave deformation in the coastal area.In this paper,combined with horizontal freezing engineering example of Sancha Street Station ~ Baihu Ting Station interval contact channel of the Fuzhou Metro Line 1,through the method of the typical physical and mechanical performance test of subway surface in Fuzhou subway station,the three-dimensional numerical simulation of ABAQUS finite element method and the freezing construction site monitoring,the temperature field and displacement field during the construction of artificial freezing are simulated and the distribution of the temperature field and the numerical size and the distribution of displacement field are studied.And the results are compared with the measured results.The results verify the reliability of the finite element simulation results,indicating that the three-dimensional numerical simulation of the freezing construction can predict the temperature field and displacement field of the similar engineering and provide the design reference and experience for the freezing project.The main research contents and conclusions:1.Through the typical test of physical and mechanical properties of Fuzhou metro station surface soil layer,the change law of basic physical mechanics parameters of soil under the condition of normal temperature and frozen state were studied.The physical parameters such as soil density,water content,thermal conductivity(Including frozen soil thermal conductivity),specific heat capacity and the mechanical parameters such as the frozen soil elastic modulus,uniaxial compressive strength,frost heave rate and frost heave force and other were obtained.2.Combined with engineering examples,three-dimensional finite element numerical model for the freezing construction of contact channel by using the obtained physical and mechanical parameters is created.Considering the influence of thermal conductivity varies with temperature and latent heat of frozen soil,the law of distribution and development of temperature field,the law of the distribution of displacement field and the frost heave deformation degree and its influence on surface in artificial freezing process were studied.3.The temperature changes with time of the subway contact channel artificial freezing construction was on site monitoring.By observing the freezing effect of the workface,combined with monitoring feedback data,the development and distribution of the frozen curtains during the construction of artificial freezing were analyzed,the results show that the design of the freezing scheme is reasonable and the freezing effect is good.4.The results of three-dimensional finite element numerical simulation are compared with the engineering measured results,and the numerical simulation results and engineering measured results are plotted as freezing time-temperature curves.Then the curve fit well shows that the numerical simulation results are close to the engineering measured results,and the three-dimensional numerical simulation can provide reference and experience for artificial freezing design and construction. |
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