土木外文翻译原文和译文

土木外文翻译原文和译文内容摘要：

大学土木工程专业（隧道与城市轨道交通工程方向）毕业设计外文翻译 7 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 重庆交通大学土木工程专业（隧道与城市轨道交通工程方向）毕业设计外文翻译 8 for August. . Comparison of simulated and observed air temperature in Xiluoqi Tunnel in ,simulated values。 2,observed values parison of simulated and observed air temperature inside The Xiluoqi Tunnel in ,simulated values。 2,observed values 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 and the dynamic viscosity )../(102 1 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 3/240 0 mkgd ?? ,content of water and unfrozen water W=3% and W=1%, 重庆交通大学土木工程专业（隧道与城市轨道交通工程方向）毕业设计外文翻译 9 and the thermal conductivity cmW ou ./?? , cmW of ./?? ,heat capacity ckgkJC oV ./? and duf W wC ????? 1 )(,duu W wC ????? 1 )1 2 ( 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 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=3C0 ， and the amplitude is B=12C0 . As for the boundary of R=Ro， we first solve the equations considering R=Ro as the first type of boundary。 that is we assume that T=f(x)? 3%C0 on R=Ro. We find that, after one year, the heat flow trend will have changed in the range of radius between 5 and 25m in the surrounding rock.. Considering that the rock will be cooler hereafter and it will be affected yet by geothermal heat, we appoximately assume that the boundary R=Ro is the second type of boundary。 that is， we assume that the gradient value，obtained from the calculation up to the end of the first year after excavation under the first type of boundary value, is the gradient on R=Ro of T. Considering the surrounding rock to be cooler during the period of construction， we calculate 重庆交通大学土木工程专业（隧道与城市轨道交通工程方向）毕业设计外文翻译 10 from January and iterate some elapses of time。