青藏铁路多年冻土区热棒的施工技术

青藏铁路要穿越550 km长的多年冻土区,其中年平均地温>-1.0℃的高温多年冻土路段275 km,高含冰量冻土类型路段长221 km.为确保路基工程的整体稳定,部分地段采用了热棒处理措施.热棒路基利用自然能源,在温差作用下驱动内部制冷工质的汽液两相对流循环,通过蒸发段蒸发吸热作用降低周围冻土温度,增加冻土本身的冷储量,提高热稳定性,保护多年冻土.热棒技术是一种有着广阔应用前景的新技术,尤其是在全球气温升高大环境下,其作用更为明显.针对热棒的工作原理和施工技术进行了系统的总结分析,实践证明,热棒能够很好的防止多年冻土的融沉、冻胀病害,已在青藏铁路、公路多年冻土区路基试验段取得重要的阶段成果,以后将会在多年冻土区施工中逐步推广应用.

The Construction of Two-Phase Closed Thermosyphon in Qinghai-Tibet Railway Permafrost Regions

The full length of the Qinghai-Tibet Railway(QTR) is 1 142 km,of which 550 km cuts across permafrost regions,275 km in warm(0~1.0 ℃) permafrost regions and 221 km in ice-rich permafrost regions.To protect permafrost from thawing,the two-phase closed thermosyphon is applied.The two-phase closed thermosphon,of which the upside(condensation part) has a radiator,the downside(evaporation part) is embedded into permafrost and the middle part is thermal-insulating,with special liquid(such as ammonia,freon,etc.) inside,can utilize effectively the natural energy resource.It can change the liquid into vapour through convective circulation under temperature difference.The evaporation part can absorb heat and then lower the temperature of permafrost,increasing the cold energy to protect the permafrost and keeping heat stability.The two-phase closed thermosphon is a new engineering technique that has wide application foreground in permafrost regions,especially,under the condition of global warming.In this paper the operational principle and engineering techniques of the two-phase closed thermosphon are summed up and analyzed.Practice demonstrates that the two-phase closed thermosphon can prevent and reduce thawing and frost heaving,which can apply widely in permafrost regions.In the Qinghai-Tibet railway and highway testing sections the two-phase closed thermosphon has shown its great advantage.It is expected that it will be applied more widely in permafrost regions from now on.