工程方面的外文文献翻译--严寒地区隧道围岩冻融状况分析的导热与对流换热模型(编辑修改稿)

工程方面的外文文献翻译--严寒地区隧道围岩冻融状况分析的导热与对流换热模型(编辑修改稿)内容摘要：

the thermal conductivity， and  the dynamic viscosity of air flow, we calculate the thermal conductivity and kinematic viscosity using the formulas PCａ and. The thermal parameters of the surrounding rock are determined from the tunnel site. 2 . Determination of the initial and boundary conditions .Choose the observed monthly average wind speed at the entry and exit as boundary conditions of wind speed， and choose the relative effective pressure p=0 at the exit ( that is， the entry of the dominant wind trend) and ]5[2 2/)/1( vdkLp  on the section of entry ( that is， the exit of the dominant wind trend )， where k is the coefficient of resistance along the tunnel wall, d = 2R， and v is the axial average speed. We approximate T varying by the sine law according to the data observed at the scene and provide a suitable boundary value based on the position of the permafrost base and the geothermal gradient of the thaw rock materials beneath the permafrost base. 3 A simulated example Using the model and the solving method mentioned above， we simulate the varying law of the air temperature in the tunnel along with the temperature at the entry and exit of the Xiluoqi Tunnel .We observe that the simulated results are close to the data observed[6]. The Xiluoqi No .2 Tunnel is located on the Nongling railway in northeastern China and passes through the part beneath the permafrost base .It has a length of 1 160 m running from the northwest to the southeast, with the entry of the tunnel in the northwest， and the elevation is about 700 m. The dominant wind direction in the tunnel is from northwest to southeast, with a maximum monthlyaverage speed of 3 m/s and a minimum monthlyaverage speed of 1 .7 m/s . Based on the data observed，we approximate the varying sine law of air temperature at the entry and exit with yearly averages of 5℃， ℃ and amplitudes of ℃ and ℃ respectively. The equivalent diameter is 5 .8m， and the resistant coefficient along the tunnel wall is the effect of the thermal parameter of the surrounding rock on the air flow is much smaller than that of wind speed， pressure and temperature at the entry and exit， we refer to the data observed in the Dabanshan Tunnel for the thermal parameters. Figure 1 shows the simulated yearlyaverage air temperature inside and at the entry and exit of the tunnel pared with the data observed .We observe that the difference is less than 0 .2 `C from the entry to exit. Figure 2 shows a parison of the simulated and observed monthlyaverage air temperature inside (distance greater than 100 m from the entry and exit) the tunnel. We observe that the principal law is almost the same， and the main reason for the difference is the errors that came from approximating the varying sine law at the entry and exit。 especially , the maximum monthlyaverage air temperature of 1979 was not for July but for August. 4 Prediction of the freezethaw conditions for the Dabanshan Tunnel 4 .1 Thermal parameter and initial and boundary conditions Using the elevation of 3 800 m and the yearlyaverage air temperature of 3℃ , we calculate the air density p=0 .774 kg/m3 .Since steam exists In the air, we choose the thermal capacity with a fixed pressure of air ),./( 0 CkgkJC p  heat conductivity )./( 02 CmW and the dynamic viscosity )../( 6 smkg After calculation we obtain the thermal diffusivity a= 1 .3788 sm /10 25 and the kinematic viscosity， sm / 25 . Considering that the section of automobiles is much smaller than that of the tunnel and the automobiles pass through the tunnel at a low speed， we ignore the piston effects， ing from the movement of automobiles， in the diffusion of the air. We consider the rock as a whole ponent and choose the dry volumetric cavity 3/2400 mkgd  ,content of water and unfrozen water W=3% and W=1%, and the thermal conductivity cmW ou ./ , cmW of ./ ,heat capacity ckgkJC oV ./ and duf W wC  1 )( , duu W wC  1 )( According to the data observed at the tunnel site， the maximum monthlyaverage wind speed is about 3 .5 m/s， and the minimum monthlyaverage wind speed is about 2 .5 m/s .We approximate the wind speed at the entry and exit as )/]()7(0 2 [)( 2 smttv  , where t is in month. The initial wind speed in the tunnel is set to be .0),0(),)(1(),0( 2  rxVRrUrxU a The initial and boundary values of temperature T are set to be where f(x) is the distance from the vault to the permafrost base， and R0=25 m is the radius of domain of solution T. We assume that the geothermal gradient is 3%， the yearlyaverage air temperature outside tunnel the is A=3 C0 ， and the amplitude is B=12 C0 . As。