青藏铁路自动温控通风试验路基观测结果分析

自动温控通风路基(自控路基)是基于通风路基的一种新型工程措施,自控系统通过充分利用冷能,可在很大程度上提升通风路基的降温效能.青藏铁路北麓河试验段自控路基的现场观测资料表明,自控系统实施后,通过暖季对通风管内对流换热作用的限制,路基的传热方式以热传导为主,由此使得通风管内整体升温幅度均小于通风路基,自控路基通风管内温度较通风路基约低1.0℃,且中心温度最低;在自控路基中,路基下3.5 m深度原多年冻土上限附近的地温降温幅度更为显著,在自控措施实施后两年的时间里,通过与通风路基对比发现,两者最高温度在降温过程基本一致的情况下,最低温度差值呈现不断扩大的趋势,观测期内最大差值为0.45℃;路基下3.0～3.5 m位置的热流计算表明,自控路基对应的年均放热热流量约为通风路基的2倍,即从传热角度说明,通过自控系统的实施可以提高通风路基的降温效能1倍左右;同时,自控措施将通风路基有效放热时间增加约40 d,这也是自控路基降温效能表现突出的原因之一.

Analysis on Experiments of the Temperature Controlled Ventilated Embankment of the Qinghai-Tibet Railway

The temperature controlled ventilated embankment (TCVE) is a new engineering measure to take with the duct-ventilated embankment. TCVE improves the cooling efficiency of the duct-ventilated embankment greatly by making full use of cool energy. The field observation data of the Beiluhe temperature controlled ventilated test section of the Qinghai-Tibet Railway show as follows: In the warm seasons,TCVE prevents heat convection between the inside and the outside of the ducts,make heat conduction become the main mode of heat transfer in the embankment,and so decreases the general temperature rising amplitude inside the ducts as compared with the duct-ventilated embankment,thus bringing the temperature inside the ducts 1℃ lower than that of the duct-ventilated embankment and even lower at the centre of the inside of the ducts;comparing to the common duct-ventilated embankment,the cooling effect is even better at the depth of 3.5 m under the ground near the primary permafrost table; after two years of installation of the auto-controlled system,although the peak values of TCVE and the duct-ventilated embankment are basically the same in the coding process,the difference in the lowest temperatures continues to show an increasing tendency and the maximum difference during observation reaches 0.45℃; by calculation of the heat flow at the depth of 3.0～3.5 m under the embankment,the mean annual heat release is found double as that of the common duct-ventilated embankment,and this means that the auto-controlled system can improve the duct-ventilated embankment efficiency by about two times; furthermore,the effective heat release time is prolonged about 40 days,and this is one of the reasons for the good cooling efficiency of TCVE.