青藏铁路沿线风沙堆积对多年冻土环境影响的实验研究

Desertification in Tibet Plateau is taking an increasing trend. Sand accumulation resulted from desertification will exert great influences on permafrost environment by changing the interaction between ground surface and air, and finally destory the original equilibrium state of permafrost. Furthermore, it could also affect the roadbeds' stability by burying or filling the existed measures along the Qinghai-Tibet Railway. However, both of the influences processes and their mechanism is not clear so far and needed to be studied furhter. This project will conduct in-depth and systemic research on the influences of sand accumulation on permafrost environment through various methods, which are widely used both in research fields of desert, meteorology and cryopedology, including field investigations, in-situ observation and laboratory testing and so on. Firstly, the influences of sand sediments on surface energy balance of permafrost would be revealed by field investigations. Secondly, the the influences of sand accumulation thickness on ground temperature of underlying permafrost would be clarifed by in-situ obsevations, which would be conducted synchronously over artificially established test sites. Thirdly, the influences of sand accumulation on roadbeds' stability would be revealed by means of laboratory testing of freezing-thawing cycles. The expected research results could not only enrich the theoretical system both for desertification investigation and permafrost degradation research in alpine regions, but also could provide scientific foundation for sand damage controlling and roadbed protection in Tibetan Plateau. Therefore, it has great significance to throey and in practice.

青藏高原沙漠化问题日益严重，由此产生的风沙堆积物通过改变地-气相互作用，对敏感和脆弱的下覆多年冻土环境产生影响，破坏冻土系统平衡，进而影响青藏铁路沿线路基的稳定性，其影响过程和机理都亟待开展研究。本项目拟通过沙漠、大气和冻土等多学科交叉研究，利用野外调查、定位监测和室内冻融循环模拟等手段，深入和系统研究风沙堆积对多年冻土环境影响过程和机理。通过野外微气象观测，揭示风沙堆积对冻土地表能量平衡的影响；通过建立人工试验场，对不同厚度风沙堆积物下覆冻土地温定位观测资料的分析和比较，阐明冻土环境对积沙厚度变化的响应机制；通过室内冻融模拟试验，揭示积沙对冻土路基降温效果的影响。本项研究不仅可以丰富高寒区沙漠化和冻土退化研究理论体系，也能为高原沙害防治和冻土路基保护提供科学依据，具有重要的理论和实践意义.

青藏高原沙漠化问题日益严重, 由此产生的风沙堆积物通过改变地-气相互作用, 对敏感和脆弱的下覆多年冻土环境产生影响, 破坏冻土系统平衡, 进而影响青藏铁路沿线路基的稳定性, 目前国内外针对积沙对冻土环境影响问题的研究并没有明确的结果. 本项目以青藏铁路沿线风沙问题较为严重的红梁河地区为典型区, 利用野外调查、定位监测和室内冻融循环模拟等手段, 系统研究了风沙堆积对多年铁路沿线冻土环境的影响过程和机理. 野外定位监测和室内模拟实验表明, 积沙地表的中上层年均地温低于天然地表, 积沙越厚, 年均地温越低. 总体来看，积沙在暖季对近地表的降温幅度大于积沙在冷季对近地表的增温幅度，在一定程度上延缓了季节冻土的融化. 冻融循环模拟结果表明, 青藏铁路沿线积沙填埋块石路基会减弱块石层的降温效果, 导致块石路基的“主动冷却”效果减弱或消失. 随着时间的推移, 这将严重威胁到青藏铁路路基稳定和安全运营. 本项目研究成果丰富了高寒区沙漠化和冻土退化研究的理论体系, 并为高原沙害防治和冻土路基保护提供了科学依据, 具有重要的理论意义和实践价值.