“冷却路基”方法在青藏铁路上的应用

Application of Roadbed Cooling Methods in the Qinghai-Tibet Railway Construction

青藏铁路穿越550 km多年冻土,其中约一半为高温多年冻土,其年平均地温为0^-1℃.青藏铁路是百年大计,必须考虑未来50~100 a的气候变化.在全球变暖的背景下,青藏铁路高温冻土段的建设必须改变单纯依靠热阻(增加路堤高度、采用保温材料等)的消极“保”温方法,而改用“冷却路基”的积极“降”温措施.青藏铁路的建设采用了一整套“冷却路基”的方法:通过遮阳板调控辐射;通过通风管、热管和气冷路堤调控对流;通过“热半导体”材料调控传导;通过这些调控方式的组合,加强冷却效果.这些方法均可有效地降低路基下多年冻土的地温,保证青藏铁路路基的稳定.

About one-half of the permafrost area traversed by the Qinghai-Tibet Railway is warm permafrost with a mean annual ground temperature of 0 --1 ℃, and around 40% is ice-rich perma- frost. The railway is expected to operate over 50- 100 years, therefore, climate change for the next 50- 100 years must be considered seriously. Traditionally, road constructions in permafrost regions rely passively on thermal resistance methods such as increasing embankment height and/or using thermal resistant maferials to protect permafrost under roadbed from thawing. Under the global warming scenario, it is needed to take proactive methods to cool down the roadbed temperatures in order to maintain railv^ay stability. Various roadbed cooling approaches have been adopted in the construction of the Qinghai-Tibet Railway, such as, shading board to reduce solar radiation, ventilated duct, thermosyphon, crushed rock interlayer and revetment to control thermal convection, ＂thermal diode＂ material to control thermal conduction, and the combination of above methods to enhance the cooling effect. Observational data have shown that all these roadbed cooling approaches can ensure the stability of railroad.