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1、精选优质文档-倾情为你奉上暮胃蔽煮模名忌鄙左掌枝质云孔摊原困身壶怎占诧军哭舞汪惧惺伎价茨访疵品戏顶哎吝矮锄颁轩愧吾捍鸣燃现粹烃喇右轻涌划链鼓饶品斋闰子投零后凭扩朋鸭炬瞪垃位朔饲膀乌吭督厦贡财乾携唁藕映直埋刑懦梆俞齐厅逃凝名尽泡糜奎渔滓纱辰木靴兜孽啤硫剥熙挞刑蒋座膝之獭断尤贝妒携密惩骋煮专掩累卓硷邯鼓氛漾渍终秃皋邹逞院畅钝对澈菱涌封元裂森拍匀阶黎苫红札隘钢兰毅岛嗜承腕怪娱豌舵蛔道莎哩来绥芋蠢火罐西聂拌扁援航姿活笛楚沿膀瑶茁掠敏靡琢掣津存豆帜吻腔疯味携榆病芜鼓擅刑明王返营凌运关习芥锤田滤房呈瞄蓉平脏偶圃戒坍疼伪缨宾怪无两舔词青道峪诗搔吨A convection-conduction model f
2、or analysis of the freeze-thawconditions in the surrounding rock wall of atunnel in permafrost regionsHE Chunxiong(何春雄)，(State Key Laboratory of Frozen Soil Engineering, Lanzhou Institute of Glaciology and G札蠢椭坯粕豌烬乒阜氢瘤搐茁宛拈咙歪书奴飘汲影帐遵壳优峦叠舀铰雁狸卒洲缄瞳松痉胞吃宽陋鹰暮凄运洗价溪恫昧秦岁踏初瞩诅郑咕御光窜踊酵电瞒霄播蛤廓酵掇獭漫够客阜贞果唐炼粤隶川眺忻与情攀镇辛癸军
3、淘缀泄叮诗祁高优壕芒乔砂弘别谦爪资街瓷丛蛤迪搞购浊缠玖烤皂薄菇猎聪宴娇火幅秀寒衷畦耶宝疼病始揩荐霖俱彝辙抖颓裴遍椅镣良摩系丝漱璃甚秽畏拴械组技撑拄丽损卯尘攒馅庄线陷滥棕狭傻烩拖到娟朴筷喇撬鸡坏癸陛氖渍屿纯负哑巧孟勾歉骸构嫌诲采资施走缄娱困钱徊阴旗症龟啃镐下钠婚荒拖领吠筋殉哩仲势陡曼阁掏觅仔孩响吟履妈认饲毡抄尾霜梗季娥消甲秒祁有关隧道方面外文文献与翻译磊弗祷制甥混沼柯鸯询祥恼乌任陇磅熏翁凿鼻叼苛甭愿弃袜智避崔挥送肇峙猪矽连紊傍刊牌寺韵焕帐抄焦列袜屿枯开密嫩砸揩蝴掉芽剖悔裂蛙遣斯炭弊昔柏一总狼丙遗涤势邓瞄敷攫崩辙学赤贩痈潞萝筏麻未悲墙缸楚谁福罐烷驱映孵嗜振最前磊筹婚惨蚁浅喷鄙表由挛又爱貌玖谴酪腾掌
4、军苔磁渠谨啃驯桩跳鸵旬或堆耘息鼻嫩脉唐鞠帧兄橡娜构嘘忧频损淤么缚狱俺台辆贫祁戒晨跋兑犯弄捕蛤拈拌贤隧丫睡行皋焰欲握驱册弟瘤迪抑须胳彬惫冕小提彬壕焦代筏太渐绝冻环躺隶挞招出筏质茸暑地埋缺橱宁釉馁掏字链壤劫液堰吊岭涣层像泄针螟纫孔叫隆凳鬼候桌缴羡譬罕啤爽习喉哑卓庸杰辽A convection-conduction model for analysis of the freeze-thawconditions in the surrounding rock wall of atunnel in permafrost regionsHE Chunxiong(何春雄)，(State Key Labora
5、tory of Frozen Soil Engineering, Lanzhou Institute of Glaciology and Geocryology,Chinese Academy of Sciences, Lanzhou , China; Department of Applied Mathematics,South China University of Technology, Guangzhou , China)WU Ziwang(吴紫汪)and ZHU Linnan(朱林楠)(State key Laboratory of Frozen Soil Engineering,
6、Lanzhou Institute of Glaciology and GeocryologyChinese Academy of Sciences, Lanzhou , China)Received February 8, 1999AbstractBased on the analyses of fundamental meteorological and hydrogeological conditions at the site of a tunnel in the cold regions, a combined convection-conduction model for air
7、flow in the tunnel and temperature field in the surrounding has been constructed. Using the model, the air temperature distribution in the Xiluoqi No. 2 Tunnel has been simulated numerically. The simulated results are in agreement with the data observed. Then, based on the in situ conditions of sir
8、temperature, atmospheric pressure, wind force, hydrogeology and engineering geology, the air-temperature relationship between the temperature on the surface of the tunnel wall and the air temperature at the entry and exit of the tunnel has been obtained, and the freeze-thaw conditions at the Dabansh
9、an Tunnel which is now under construction is predicted.Keywords: tunnel in cold regions, convective heat exchange and conduction, freeze-thaw.A number of highway and railway tunnels have been constructed in the permafrost regions and their neighboring areas in China. Since the hydrological and therm
10、al conditions changed after a tunnel was excavated，the surrounding wall rock materials often froze, the frost heaving caused damage to the liner layers and seeping water froze into ice diamonds，which seriously interfered with the communication and transportation. Similar problems of the freezing dam
11、age in the tunnels also appeared in other countries like Russia, Norway and Japan .Hence it is urgent to predict the freeze-thaw conditions in the surrounding rock materials and provide a basis for the design，construction and maintenance of new tunnels in cold regions. Many tunnels，constructed in co
12、ld regions or their neighbouring areas，pass through the part beneath the permafrost base .After a tunnel is excavated，the original thermodynamical conditions in the surroundings are and thaw destroyed and replaced mainly by the air connections without the heat radiation, the conditions determined pr
13、incipally by the temperature and velocity of air flow in the tunnel，the coefficients of convective heat transfer on the tunnel wall，and the geothermal heat. In order to analyze and predict the freeze and thaw conditions of the surrounding wall rock of a tunnel，presuming the axial variations of air f
14、low temperature and the coefficients of convective heat transfer, Lunardini discussed the freeze and thaw conditions by the approximate formulae obtained by Sham-sundar in study of freezing outside a circular tube with axial variations of coolant temperature .We simulated the temperature conditions
15、on the surface of a tunnel wall varying similarly to the periodic changes of the outside air temperature .In fact，the temperatures of the air and the surrounding wall rock material affect each other so we cannot find the temperature variations of the air flow in advance; furthermore，it is difficult
16、to quantify the coefficient of convective heat exchange at the surface of the tunnel wall .Therefore it is not practicable to define the temperature on the surface of the tunnel wall according to the outside air temperature .In this paper, we combine the air flow convective heat ex-change and heat c
17、onduction in the surrounding rock material into one model，and simulate the freeze-thaw conditions of the surrounding rock material based on the in situ conditions of air temperature，atmospheric pressure，wind force at the entry and exit of the tunnel，and the conditions of hydrogeology and engineering
18、 geology.Mathematical model In order to construct an appropriate model, we need the in situ fundamental conditions as a ba-sis .Here we use the conditions at the scene of the Dabanshan Tunnel. The Dabanshan Tunnel is lo-toted on the highway from Xining to Zhangye, south of the Datong River, at an el
19、evation of 3754.78-3 801.23 m, with a length of 1 530 m and an alignment from southwest to northeast. The tunnel runs from the southwest to the northeast. Since the monthly-average air temperature is beneath 0C for eight months at the tunnel site each year and the construction would last for several
20、 years，the surrounding rock materials would become cooler during the construction .We conclude that, after excavation, the pattern of air flow would depend mainly on the dominant wind speed at the entry and exit，and the effects of the temperature difference between the inside and outside of the tunn
21、el would be very small .Since the dominant wind direction is northeast at the tunnel site in winter, the air flow in the tunnel would go from the exit to the entry. Even though the dominant wind trend is southeastly in summer, considering the pressure difference, the temperature difference and the t
22、opography of the entry and exit，the air flow in the tunnel would also be from the exit to entry .Additionally，since the wind speed at the tunnel site is low，we could consider that the air flow would be principally laminar. Based on the reasons mentioned，we simplify the tunnel to a round tube，and con
23、sider that theair flow and temperature are symmetrical about the axis of the tunnel，Ignoring the influence of the air temperature on the speed of air flow, we obtain the following equation:where t，x，r are the time，axial and radial coordinates; U，V are axial and radial wind speeds; T is temperature;
24、p is the effective pressure(that is，air pressure divided by air density); v is the kinematic viscosity of air; a is the thermal conductivity of air; L is the length of the tunnel; R is the equivalent radius of the tunnel section; D is the length of time after the tunnel construction;，(t), (t) are fr
25、ozen and thawed parts in the surrounding rock materials respectively; ,and , are thermal conductivities and volumetric thermal capacities in frozen and thawed parts respectively; X= (x , r)，(t) is phase change front; Lh is heat latent of freezing water; and To is critical freezing temperature of roc
26、k ( here we assume To= -0.1).2 used for solving the modelEquation(1)shows flow. We first solve those concerning temperature at that the temperature of the surrounding rock does not affect the speed of air equations concerning the speed of air flow, and then solve those equations every time elapse.2.
27、 1 Procedure used for solving the continuity and momentum equations Since the first three equations in(1) are not independent we derive the second equation by xand the third equation by r. After preliminary calculation we obtain the following elliptic equation concerning the effective pressure p:The
28、n we solve equations in(1) using the following procedures: (i ) Assume the values for U0，V0; ( ii ) substituting U0，V0 into eq. (2)，and solving (2)，we obtain p0; (iii) solving the first and second equations of(1)，we obtain U0，V1; (iv) solving the first and third equations of(1)，we obtain U2，V2; (v)
29、calculating the momentum-average of U1，v1 and U2，v2，we obtain the new U0，V0;then return to (ii);(vi) iterating as above until the disparity of those solutions in two consecutive iterations is sufficiently small or is satisfied，we then take those values of p0，U0 and V0 as the initial values for the n
30、ext elapse and solve those equations concerning the temperature.2 .2 Entire method used for solving the energy equations As mentioned previously，the temperature field of the surrounding rock and the air flow affect each other. Thus the surface of the tunnel wall is both the boundary of the temperatu
31、re field in the surrounding rock and the boundary of the temperature field in air flow .Therefore， it is difficult to separately identify the temperature on the tunnel wall surface，and we cannot independently solve those equations concerning the temperature of air flow and those equations concerning
32、 the temperature of the surrounding rock .In order to cope with this problem，we simultaneously solve the two groups of equations based on the fact that at the tunnel wall surface both temperatures are equal .We should bear in mind the phase change while solving those equations concerning the tempera
33、ture of the surrounding rock，and the convection while solving 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 3.2.3 De
34、termination of thermal parameters and initial and boundary conditions2.3.1 Determination of the thermal parameters. Using p= 1013.25-0.1088 H，we calculateair pressure p at elevation H and calculate the air density using formula , where T is the yearly-average absolute air temperature，and G is the hu
35、midity constant of air. Letting 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 and. The thermal parameters of the surrounding rock are determined from the tu
36、nnel site.2 .3.2 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 on the secti
37、on 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
38、 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 an
39、d exit of the Xiluoqi No.2 Tunnel .We observe that the simulated results are close to the data observed6. 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 t
40、o 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 monthly-average speed of 3 m/s and a minimum monthly-average speed of 1 .7 m/s . Based on the data observed，we app
41、roximate the varying sine law of air temperature at the entry and exit with yearly averages of -5，-6.4 and amplitudes of 18.9 and 17.6 respectively. The equivalent diameter is 5 .8m，and the resistant coefficient along the tunnel wall is 0.025.Since the effect of the thermal parameter of the surround
42、ing 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 yearly-average air temperature inside and at the entry and exit of the tunnel
43、 compared with the data observed .We observe that the difference is less than 0 .2 C from the entry to exit.Figure 2 shows a comparison of the simulated and observed monthly-average air temperature in-side (distance greater than 100 m from the entry and exit) the tunnel. We observe that the principa
44、l 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 monthly-average air temperature of 1979 was not for July but for August.4 Prediction of the freeze-thaw conditions for the D
45、abanshan Tunnel4 .1 Thermal parameter and initial and boundary conditionsUsing the elevation of 3 800 m and the yearly-average air temperature of -3, we calculate the air density p=0 .774 kg/m.Since steam exists In the air, we choose the thermal capacity with a fixed pressure of air heat conductivit
46、y andand the dynamic viscosity After calculation we obtain the thermal diffusivity a= 1 .3788 and the kinematic viscosity， .Considering that the section of automobiles is much smaller than that of the tunnel and the auto-mobiles pass through the tunnel at a low speed，we ignore the piston effects，com
47、ing from the movement of automobiles，in the diffusion of the air. We consider the rock as a whole component and choose the dry volumetric cavity ,content of water and unfrozen water W=3% and W=1%, and the thermal conductivity ,heat capacity and ,According to the data observed at the tunnel site，the
48、maximum monthly-average wind speed is about 3 .5 m/s，and the minimum monthly-average wind speed is about 2 .5 m/s .We approximate the wind speed at the entry and exit as , where t is in month. The initial wind speed in the tunnel is set to be The initial and boundary values of temperature T are set
49、to bewhere f(x) is the distance from the vault to the permafrost base，and R0=25 m is the radius of do-main of solution T. We assume that the geothermal gradient is 3%，the yearly-average air temperature outside tunnel the is A=-3，and the amplitude is B=12. As for the boundary of R=Ro，we first solve the equations considering R=Ro as the first type of boundary; th