| With the implemetion of western development strategy and the revitalization of the northeast china, qinghai-tibet railway, qinghai-tibet highway, west-east gas transmitting project, as well as the west line project of the south north water transfer and other series of major projects construction started, there will be more and more tunnel projects in cold region. At present, different degree of freezing damages exsits in cold regions tunnel both domestic and abroad. These freezing damages have a disproportionate influence on the driving safety, structural stability, lowing the service life and increasing tunnel maintenance costs. These freezing damages is a common problem and cause driving safty problems, for this reason, freezing forcast is important in tunnel in the cold region. To analyse the forcast of the freezing damage, it is necessary to get the The boundary condition of temperature inside the tunnel at first, the same as the distributions of air temperature. It is common to get the air temperature inside the tunnel by two mesurement: one is observation on site directly. Though it is accurate and reliable, the expense is bigger, and the observation result lags behind the design, that means the result is usually obtained in tunnel construction or after construction complete. So it is not able to guide the design. The other is analyzed by the caculating heat convection of air and adjacent rock inside the tunnel, this method is able to guide the design of tunnel project and cost less, but the key point is wether the establishment of the reliable heat convection heat convection model is able to forcast the air temperature distribution of tunnel in cold regions accurately. Therefore, it is quite neccesary and urgent issue to study the regularities of air-temperature distribution of tunnel in cold regions, not only its high academic and theoretical value but also important practical engineering guide significance.With national natural science foundation "freezing cold region prediction model and optimum design theory" project as a base, utilizing the basic theory of heat transfer and computational fluid dynamics and considering the coupling influence of air in the channel and tunnel surrounding rock, the paper deduces control equation of hydrokinetics, calculates the formulas and makes secondary development program applying C language on FLUENT as a basis. Based on materials of fenghuoshan tunnels, the paper analyzes the nonlinearity of air which is under different conditions of flow state, length, air-temprature, flow rate, the initial temperature of surrounding rock and cross-sectional size and the coupled convection heat and sums up the infulence of distribution of temperature of surrounding rock which goes along its height , its surrounding, and its axis according to length, air-temprature, flow rate, the initial temperature of surrounding rock and cross-sectional size of tunnels in cold regions, providing the theory base and reference of design, construction and study of tunnels in cold regions.The following conclusion can be drawn through comprehensive analysis:①Air flow state in tunnels in cold regions——laminar and turbulence has a great infulence of distribution of temperature of tunnel surrounding rock and tunnel axial and height. E.g. in the laminar fluid flow condition, the annual average temperature of the cross section of tunnel entrance and exit is the same as or higher than the tunnel inside. in the turbulence flow fluid condition, the annual average temperature diminishes from entrance to exit, And there exsits mutation between the cross-section of entrance and exit and other cross-section. Therefore, the caculation depend on the actual corresponding air flow state in tunnels in cold regions designs.②Tunnels length in cold regions——There is a great infulence of distribution of temperature of height and surrounding of tunnel axial when the length of tunnels in cold regions is 250m,500m,1338m,3000m,6500m,10000m. E.g. the annual average temperature dismisses generally along the length, highest in the entrance cross-section, lowest in the exit cross section. The longer the tunnel is, the more obvious the trend is along the length, and the mutation of the annual average temperature is smaller between the cross-section of entrance and exit and other cross-section. Therefore, the caculation depend on the actual in tunnels in cold regions designs.③The air-temperature of tunnels in cold regions——There is a great infulence of distribution of temperature on surrounding rock and the height and surroungding of tunnel axial and height when the annual average temperature of the tunnel adit is -4℃,-2℃,0℃,2℃,4℃. E.g. when the annual average temperature is -4℃at the tunnel adit, the air has a dismission along the length, highest at the entrance cross-section, lowest at the exit cross-section. In the other 4 conditions, it is higher in the middle than the entrance and exit cross-section, when the annual average temperature is -2℃and 0℃, it is lower in the entrance cross-section than exit cross-section, wthile dismisses along the length in the middle. When the annual average temperature is 2℃and 4℃, it is higher in the entrance cross-section than exit cross-section, wthile dismisses along the length in the middle. In these 5 conditions, there exsits mutation between the cross-section of entrance and exit and other cross-section. Therefore, the caculation depend on the actual annual average temperature in tunnels in cold regions designs.④Air flow rate of tunnels in cold regions——There is a great infulence of distribution of temperature of height and surrounding of tunnel axial when monthly minimum flow is 1m/s,4m/s,6m/s,8m/s. E.g. the air in the tunnel has a dismission trend along the length, highest in the entrance cross-section, lowest in the exit cross section, and there exsits mutation between the cross-section of entrance and exit and other cross-section. While the bigger the flow is, the less the annual average temperature changes in the middle cross-section.Therefore, the caculation depend on the actual air flow in tunnels in cold regions designs.⑤Tunnels surrounding rock's initial temperature in cold regions——There is a great infulence of distribution of temperature of height and surrounding of tunnel axial when the tempreture is -4℃,-2℃,-1℃,0℃,2℃,4℃. E.g. the tempreture in the tunnel has a dismission trend along the length, highest in the entrance cross-section, lowest in the exit cross section, while the higher the ground temperature is, the less the annual average temperature changes in the rear cross-section in tunnel. Therefore, the caculation depend on the actual initial temperature of the surrounding rock in tunnels in cold regions designs.⑥The sizes of cross-section in cold regions——There is a great infulence of distribution of temperature of height and surrounding of tunnel axial when the area is 30m2,50m2,75m2,100m2,120m2. E.g. the tempreture in the tunnel has a dismission trend along the length, highest in the entrance cross-section, lowest in the exit cross section and there exsits mutation between the cross-section of entrance and exit and other cross-section. Therefore, the caculation depend on the actual tunnel section area in tunnels in cold regions designs. |
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