自动温控通风路基应用效果分析

EFFECT ANALYSIS OF AUTO-TEMPERATURE-CONTROLLED VENTILATION ROADBED

自动温控通风路基是“冷却路基”的一种有效措施,并经历了青藏铁路北麓河试验段半年多的现场检验。结果表明,对于30,40 cm 两种管径的通风管在实施自动温控系统控温后,分别使原多年冻土上限抬升 0.3,0.7 m,到达最大融化深度的时间均提前 20 d,延长路堤的放热时间约 1个多月,分别降低通风管下部平均地温 1.2 ℃,1.7 ℃,降低路基底部地温 0.5 ℃,0.7 ℃。通过热计算,在进入多年冻土含土冰层热通量最大月份,自动温控通风路基降低热通量约一半左右。通过 2 种管径的降温效果对比,30 cm 管径的降温效果略好于 40 cm 管径的降温效果。自动温控通风路基结构中路堤降温速率大于通风路基的主要原因在于自动温控路基具有降温机制。

Auto-temperature-controlled ventilation roadbed is one of positive engineering measures for cooling roadbed. In the engineering measure, an auto-temperature-controlled system is installed at one or two ends of the vent-duct. The system is composed of air temperature responsive unit and control unit, by which the wind door in ventilation duct can be controlled. When the air temperature reaches the designed value, the wind door can be automatically opened or closed. Through the system the effect of the heat flux in summer can be effectively controlled, and natural cold can be effectively used to cool the roadbed to adjust the temperature of permafrost and ensure the long-term stability of railway. In order to verify its engineering efficiency, the system was installed on two sections of ventilation roadbed with different duct diameters in Beiluhe test section in Qinghai-Tibet railway. Through the field tests from April to October, 2003, with ground temperature comparison between the ventilation roadbeds with and without the system, the test results showed that, with the application of the system with 30 and 40 cm diameter ducts, the artificial permafrost table were raised by 0.3 and 0.7 m, respectively, and the average temperature under tubes were reduced by 1.2°C and 1.7°C, respectively, and the average temperature under roadbed were reduced by 0.5°C and 0.7°C, respectively. The time of reaching maximal thawed depth could be advanced for nearly 20 days, and the time for roadbed giving out heat was extended for more than a month. Through thermal calculation, the thermal flux has been decreased nearly half in a month with maximal thermal flux coming into permafrost. Comparison of the cooling effect in auto-temperature-controlled ventilation roadbeds with different duct diameters indicates that the efficiency of duct with 30 cm diameter is slightly higher than that with 40 cm diameter.