Numerical Study Of Soil Thermal Field In Horizontal Freezing Shield Portal Reinforced By Cement

Horizontal freezing is used widely,which solve the problem of shield portal in complexstratum. The study of soil thermal field in horizontal freezing shield portal provides scientificbasis for key link of Shield in and out of the hole.With a lot of domestic subway and tunnel arebuilding,the Soil which Shield in consists of a single primary state soil into the complexcharacters of primary state soil,So the study of soil thermal field in horizontal freezing shieldportal becomes necessary.In this paper, with the horizontal soil freezing construction for2﹟tunnel portal of shieldentry Projects in railway station of the second line of Suzhou Metro as an example, Shieldstrengthening modes are Chose, Temperature fields change regularly is acquired by the datafrom the sitemonitoring.Numerical model of freezing temperature field is built for horizontalfreezing shield portal by finite element software, through the measured data and the simulationdata shows that the rationality of the model,and analysis the factors' sensitivity which includedconvection coefficient,heat conductivity,volumetric heat capacity,latent heat of phasechange,cement parameter.Trough the research shows that in terms of freezing effect included the time of frozensoilwall closured, the thickness of frozen soil wall, the average growth speed of frozen soilwall, the average temperature of frozen soil wall,silt reinforced by cement was better than siltyclay reinforced by cement.The time for the release of the latent of Silty clay reinforced bycement was two times as long as the time for the release of the latent of Silt. The thickness ofcup bottom is short tubes length add the length of five times the reamer diameter.The positionwhere the lowest temperature appear is the circular which compose of outer ring of freezingpipes. The Speed of freezing front is smooth curve, the longer the Speed lasts, it slows,andkeeps stable at the end. when convection coefficient and volumetric heat capacity are tow lineardecreasing functions of the freezing effect. The heat conductivity is a linear decreasing functionof the freezing effect. Latent heat of phase change have no effect on freezing effect. When thecement parameter is twelve percent in silty clay,the freezing effect is best. When the cementparameter is sixteen percent in silty soil,the freezing effect is best.