【正文】 ng those equations concerning the temperature of the air flow, and we only need to smooth those relative parameters at the tunnel wall surface .The solving methods for the equations with the phase change are the same as in reference [3]. Determination of thermal parameters and initial and boundary conditions Determination of the thermal parameters. Using p= H， we calculate air pressure p at elevation H and calculate the air density ? using formula GTP?? , where T is the yearlyaverage absolute air temperature，and G is the humidity constant of air. Letting PC be the thermal capacity with fixed pressure, ? 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 重慶交通大學(xué)土木工程專 業(yè)（隧道與城市軌道交通工程方向）畢業(yè)設(shè)計(jì)外文翻譯 7 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。 X= (x , r)， ? (t) is phase change front。 p is the effective pressure(that is， air pressure divided by air density)。 T is temperature。 f? , u? and fC , uC are thermal conductivities and volumetric thermal capacities in frozen and thawed parts respectively。 then return to (ii)。用此模型對(duì)大興安嶺西羅奇 2 號(hào)隧道的洞內(nèi)氣溫分布進(jìn)行了模擬計(jì)算，結(jié)果與實(shí)測(cè)值基本一致 。在洞壁表面上方程系數(shù)的光滑化 .另 外，帶相變的溫度場(chǎng)的算法與文獻(xiàn) [3]相同 . 2. 3 熱參數(shù)及初邊值的確定 熱參數(shù)的確定方法 : 用 p= 計(jì)算出海拔高度為 H 的隧道現(xiàn)場(chǎng)的大氣 壓強(qiáng)，再由 GTP?? 計(jì)算出現(xiàn)場(chǎng)空氣密度 ? ，其中 T為現(xiàn)場(chǎng)大氣的年平均絕對(duì)溫重慶交通大學(xué)土木工程專 業(yè)（隧道與城市軌道交通工程方向）畢業(yè)設(shè)計(jì)外文翻譯 16 度， G為空氣的氣體常數(shù) .記定壓比熱為 PC ,導(dǎo)熱系數(shù)為 ? ，空氣的動(dòng)力粘性系數(shù)為 ? .按??PC?ａ 和???? 計(jì)算空氣的導(dǎo)溫系數(shù)和運(yùn)動(dòng)粘性系數(shù) .圍巖的熱物理參數(shù)則由現(xiàn)場(chǎng)采樣測(cè)定 . 初邊值的確定方法 :洞曰風(fēng)速取為現(xiàn)場(chǎng)觀測(cè)的各月平均風(fēng)速 .取卞導(dǎo)風(fēng)進(jìn)曰的相對(duì)有效 氣壓為 0，主導(dǎo)風(fēng)出口的氣壓則取為 ]5[2 2/)/1( vdkLp ??? ，這里 k為隧道內(nèi)的沿程阻力系數(shù)， L 為隧道長(zhǎng)度， d 為隧道端面的當(dāng)量直徑， ? 為進(jìn)口端面軸向平均速度 .進(jìn)出口氣溫年變 化規(guī)律由現(xiàn)場(chǎng)觀測(cè)資料，用正弦曲線擬合，圍巖內(nèi)計(jì)算區(qū)域的邊界按現(xiàn)場(chǎng)多年凍土下限和地?zé)崽荻却_定出適當(dāng)?shù)臏囟戎祷驕囟忍荻?. 3 計(jì)算實(shí)例 按以上所述的模型及計(jì)算方法，我們對(duì)大興安嶺西羅奇 2號(hào)隧道內(nèi)氣溫隨洞曰外氣溫變化的規(guī)律進(jìn)行了模擬計(jì)算驗(yàn)證，所得結(jié)果與實(shí)測(cè)值 [6]相比較 ,基本規(guī)律一致 . 西羅奇 2 號(hào)隧道是位十東北嫩林線的一座非多年凍土單線鐵路隧道，全長(zhǎng)1160 m ,隧道 近西北一東南向，高洞口位于西北向，冬季隧道主導(dǎo)風(fēng)向?yàn)槲鞅憋L(fēng) .洞口海拔高度約為 700 m , 月平均最高風(fēng)速約為 3m/s,最低風(fēng) 速約為 ，我們將進(jìn)出口氣溫?cái)M 合為年平均分別為 5C0 和 ，年變化振幅分別為 和 C0 的正弦曲線 .隧道的當(dāng)量直徑為 m,沿程阻力系數(shù)取為 數(shù)對(duì)計(jì)算洞內(nèi)氣溫的影響 遠(yuǎn)比洞口的風(fēng)速、壓力及氣溫的影響小得多，我們這里參考使用了大坂山隧道的資料 . 圖 1 給出了洞口及 洞內(nèi)年平均氣溫的計(jì)算值與觀測(cè)值比較的情況，從進(jìn)口到出口，兩值之差都小于 . 圖 2 給出了洞內(nèi) (距進(jìn)出口 l00m以上 )月平均氣溫的計(jì)算值與觀測(cè)值比較的情況，可以看出溫度變化的基本規(guī)律完全一致，造成兩值之差的主要原因是洞口氣溫年變化規(guī)律之正弦曲線的擬合誤差，特別是 1979 年隧道現(xiàn)場(chǎng)月平均最高氣溫不是在 7 月份，而是在 8 月份 . 重慶交通大學(xué)土木工程專 業(yè)（隧道與城市軌道交通工程方向）畢業(yè)設(shè)計(jì)外文翻譯 17 圖 1. 比較 1979 年 在 西羅奇 周家山 2 號(hào)隧道 仿真試驗(yàn)與 觀察的 空氣溫度 .