| The artificial ground freezing method has been widely used in subway tunnel engineering,but the subway tunnels are mostly in urban prosperous areas,the ground frost heave deformation caused by artificial freezing will adversely affect the surrounding environment of the subway tunnel.In general,the freezing tube is designed to be inclined and radial,and it is not strictly horizontal freezing.Therefore,the study of the three-dimensional frost heave deformation of the stratum can truly reflect the actual situation of the project.To this end,this article takes the.construction of the freezing method of theconnection passage in a section of the Shanghai subway as the engineering background,and uses a combination of theoretical analysis and numerical simulation research methods,based on the analysis of the three-dimensional freezing temperature field of the ground,the distribution law of the three-dimensional frost heave deformation of the connection passage during the freezing period is studied.The main research contents and results are as follows:(1)According to the inclined radial layout of the frozen pipe group of the sub way tunnel connection passage,the ABAQUS finite element software is used,comprehensively considering various initial and boundary conditions such as formation temperature,surface convection,and the phase change latent heat process of the soil,a three-dimensional finite element numerical calculation model is established,and the distribution law of the three-dimensional freezing temperature field of the formation during the active freezing period of the connection channel is systematically analyzed,The results show that after the connect passage is actively frozen,the AA section serves as the connect passage freezing weak surface.The thickness of the side freezing wall reaches 2.1m,the top reaches 3.4m,and the bottom is 3.lm.Both have reached the design requirements of the thickness of the freezing wall,which proves that the freezing The arrangement of the pipe group is more reasonable,and the comparison with the temperature drop curve of the actual temperature measurement point on the site verifies the reliability of the finite element numerical analysis of the freezing temperature field.(2)Considering the orthotropic deformation characteristics of frozen soil,the instantaneous frost heave strain component(three-dimensional thermal strain component)generated after the soil temperature reaches the freezing temperature is derived,relying on the secondary development platform of the finite element software ABAQUS,The realization of the three-dimensional frost heave deformation user subprogram of frozen soil,and then use the temperature-displacement sequential coupling method to study the three-dimensional frost heave deformation distribution law of the active freezing period of the connection passage,the results show that for any time surface The maximum vertical frost heaving displacements occur directly above the middle of the connection passage,and as the distance from the connection passage increases,the vertical surface frost heaving displacement also gradually decreases.After the 42 days of active freezing period,The maximum vertical frost heave displacement on the surface of the D-D profile reaches 12.9mm,the maximum vertical frost heave displacements of the surface in sections A-A,B-B and C-C reached 12.2mm,11.1mm and 12.2mm,respectively.The research results of this paper have certain reference value and significance for the numerical simulation of the three-dimensional freezing construction of the subway connection passage stratum,and provide a reference for the actual construction.(3)When considering frost heave deformation as isotropic,and under different cold source conditions,the prediction result is often higher or lower than the actual result,and for the soil body with strong frost heave sensitivity,this prediction difference will be more For notable.Therefore,it is necessary to consider the orthotropic deformation characteristics.Figure 46 table 10 references 69... |
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