Numerical Analysis For Frost Deformation Of The Subway Station Entrances Side-walls

With the rapid development of economy,the city scale uninterrupted growth.In this form,the development of rail transit in China has progressed a lot.Subway station as the Urban Rail Transit Hubs whose security concerns the normal operation of the subway,the safety of passengers and state property.Therefore,it is particularly important to ensure its security and stability.Due to the temperture in mountain is lower than it in plain,so when the subway station located in the Mountainous Area,it is more vulnerable to suffer frost heaving damage.In view of the above,making the Ming Tombs Subway Station of Changping as the engineering background in this paper.Do the research with the way of the theoretical analysis and the simulation into the change rule of temperture field of soil that around subway station,when the subway station operation in winter.And compared with the temperture field of natural soil.On this foundation,the author calculated horizontal frost-heave force and horizontal frost-heave displacement of the subway station entrance side-walls by thermal-mechanics coupling.Through the analysis on the result of calculation,the distributing of horizontal frost-heave force and horizontal frost-heave displacement along the side-walls is obtained.The main content of this paper is as follow:(1)The author studied and deducted the fundamenttal formulate of temperture field,fluid field and stress field of frozen soil.The factors(total water content,dry density,unfrozen water content)that influence heat exchange coefficient(thermal conductivity,volumetric heat capacity)and mass transfer coefficient of soil(hydraulic conductivity,differential water capacity)were discussed in detail.The author studied the method to determine the each parameters.(2)Analysed the change of temperature gradinet and the density of isothermal in different location of soil around subway station and natural soil,when the subway station operation in winter.The effects of different initial soil water content on temperture field and frozen depth was studied.(3)According to the thermal-mechanics coupling theory and the relation between temperture and unfrozen water content,formula of thermal expansion cofficient of saturated soil in closed system was deducted in theory,the original formula was improved.And then the formula was used in numerical calculation,and the result is as accurate as measured data.(4)Analysed the distributing of horizontal frost-heave force and horizontal frost-heave displacement along the side wall Analysed effects of different initial soil water content on forst deformation of side-walls and the change rule of horizontal frost-heave force with freezing time.At last,the author contrasted different structuring forms of entrances forst deformation.(5)The results of both measured and simulated were compared and analysed,confirmed the factors that influence the distribution rules of horizontal frost-heave force along depth include cooling condition of soil(double direction freezing,unidirectional freezing),structural style of building and groundwater depth.