寒区隧道温度场的时空演化规律及温控措施研究

Temporal-Spatial Evolution Laws of Temperature Field in Cold Region Tunnel and Temperature Control Measures

推导寒区隧道围岩—衬砌—气流的非稳态热传导的有限差分方程,通过在建寒区铁路隧道现场实测温度场与计算温度场的对比,验证数值解的准确性。结果表明:隧道贯通后,随着时间的推移,距离衬砌表面一定范围内衬砌和围岩的温度变化曲线呈正弦曲线,与风流温度的相同,而且越往断面径向深处,衬砌和围岩的温度变化越小,相位滞后越大;隧道二衬拱顶处的温度最高,轨面处的温度最低,各测点温度平均值与拱腰处的接近;隧道二衬温度的计算值稍低于实测的平均值,但满足工程使用精度要求;采用硬泡聚氨酯保温材料作为隔热层,可以有效提高寒区隧道衬砌和围岩的温度,且隔热层厚度为0.05m左右时工作效率最高;外贴式和中隔式保温隔热层均能起到良好的保温效果,而外贴式的保温效果更优;考虑到外贴式隔热层便于维护和更换,而中隔式保温层遇水及受挤压均易变形,因此在材料及施工工艺允许的前提下,建议寒区隧道采用外贴式保温隔热层。

The unsteady heat transfer finite difference equations for surrounding rock,lining and air flow of tunnel in cold region were deduced.The accuracy of numerical solution was validated by comparing the field measured temperature field and calculated temperature field of railway tunnel under construction in cold region.The results show that,after the run-through of tunnel,as time goes on,the temperature variation curves of tunnel lining and surrounding rock show sine curve within a certain range from lining surface,which are the same with those of air flow temperature.Moreover,the temperature has smaller change and the phase lag is greater towards the radial depth of section.The temperature at the vault of the secondary lining is the highest and that on rail surface is the lowest.The average temperature of each measuring point is close to that of hance.The calculated value of the temperature of tunnel secondary lining is slightly lower than the measured one,but it still meets the precision requirements for engineering use.Adopting rigid polyurethane foam as the thermal insulation layer can effectively improve the temperature of tunnel lining and surrounding rock in cold region,and the efficiency is the highest when the thickness of thermal insulation layer is around 0.05 m.Both the external mounted and septum types of thermal insulation layers can play good thermal insulation effects,and the effect of external mounted type is better.Considering that the external mounted type is easy to maintain and replace while the septum type is liable to deform with water and extrusion,it is suggested to construct external mounted type of thermal insulation layer for cold region tunnel under the premise of the allowable materials and construction technology.