Numerical Computation And Analysis Of Freezing Method In Cross Passage Of Taiyuan Metro Line 2

In view of the relevant engineering experience of the freezing method applied to the subway connecting passage,the freezing method will cause huge changes in the mechanical properties of the surrounding soil after construction.The groundwater in the original soil solidifies,which causes the soil volume to become larger and frost heave occurs.Additional stresses are generated in the connecting passages of the subway,and uneven uplift of the ground surface buildings will cause deformation or collapse of the ground surface buildings in severe cases.Therefore,it is very meaningful to study the mechanism of the disturbance of the soil around the subway connecting channel by the freezing method construction,and its influencing factors.The construction of the connection tunnel is an extremely critical step in the entire subway construction.According to the numerical simulation of the construction process of the connecting passage,the main factors are obtained by comparing with the actual measured data on the site.The most important factors are the buried depth,the thickness of the frozen wall,the temperature field and the excavation of the connecting tunnel.Implement the construction of the three-dimensional calculation model related to the connecting channel,which requires more appropriate strength criteria,parameters and constitutive models,and use FLAC3 D finite element software for numerical simulation analysis.The main research contents and conclusions of this paper are as follows:1.Establish a three-dimensional calculation model for the frozen construction of the connecting passage,use numerical simulation to calculate and analyze the frozen wall,and compare the results of the numerical simulation with the measured data on site to obtain the most reasonable thickness of the frozen wall.2.Study the influence of the buried depth of the connecting channel on the freezing method,which can be obtained by numerical simulation of the different buried depth and thickness of the connecting channel.The smaller the buried depth of the frozen soil curtain,the smaller the overlying load,and the resulting frost heave displacement on the ground The greater the value,the greater the maximum surface deformation and the minimum surface deformation.The displacement of the surface uplift at the central axis is the largest.As the center point spreads to both sides,the value of the surface uplift gradually decreases.3.It can be obtained by studying the influence of the thickness of the frozen soil curtain of the connecting passage on the freezing method.It can be obtained by numerical simulation without the analysis of the thickness of the frozen curtain.The greater the thickness of the frozen soil curtain,the greater the frost heave displacement of the ground surface.The top is the largest.And the decreasing trend is a parabolic decrease.After the excavation of the connecting passage,the most unfavorable position is at the junction of the connecting passage and the tunnel.For the frost heave caused by the freezing method,it is proposed to increase the overlying load of the frozen upper wall and use the load to suppress the frost heave.Reduce the freezing time to reduce the thickness of the freezing wall,thereby frost heaving volume,to ensure safe excavation.4.Study the influence of the different excavation depths of the connecting channel on the freezing method.As the excavation depth continues to increase,the influence on the surface deformation becomes greater and greater.At the same time,the difference between the maximum and minimum surface displacements is also Increase with the increase of excavation depth.Moreover,as the excavation depth continues to increase,the surface deformation trend becomes more and more gentle.