中文摘要：

工程防沙必然会引起积沙，地表积沙后下伏冻土的热状况如何变化目前尚不明确。为此，在青藏铁路多年冻土区红梁河沙害路段实验场，利用热敏电阻温度传感器，通过野外同步对比观测方法，对青藏铁路不同工程防沙措施产生的不同厚度积沙后下伏冻土热状况进行研究。研究发现积沙较厚的外缘阻沙工程与积沙较薄的内缘固沙工程都能使下伏冻土地温降低，季节融化深度减小，活动层变薄，冻结层增厚，冻土上限上升。其中，冻土地温的年平均值最大降幅为0．3℃，上限上升幅度最大达0．4m。分析表明：地表积沙后冻土热状况改变的主要原因是沙层反射率高、热传导性能差；青藏铁路多年冻土路段地表积沙，有利于提高冻土上限，增强路堤稳定性，对类似地带工程有借鉴意义。

英文摘要：

Sand-control engineering practice will result in sand deposition inevitably. How will the thermal regime of underlying permafrost change after the ground surface has been covered with sandy sediments？ No significant conclusions have been drawn currently. Therefore, utilizing thermistor temperature sensors and adopting the synchronization contrast observation method in the test field of Honglianghe san＆damaging sections in permafrost regions along the Qinghai-Tibet Railway, the thermal regime of permafrost lying underneath sand sediments of different thicknesses as the results of different sand-control measures taken along the Qinghai-Tibet Railway was studied. Both san＆block engineering projects situated in the outer-edge area with thick sand sediments and sand-fixing engineering projects situated in the inner-edge area with thin sand sediments were found to be able to make the ground temperature of underlying perma- frost lower,seasonal thawing depths shorter, active layers thinner, freezing layers thicker and permafrost table higher. The maximum annual mean value of the permafrost temperature drop reached 0.3~C and the permafrost table rose by 0.4 m maximally. By mechanism analysis,changes of the thermal regime of permafrost after ground surface being cov- ered with sand sediments were attributed mainly to high reflectivity and poor heat conductivity of sand layers. It is seen that sand sediments on ground surface are beneficial to improve the permafrost table and enhance subgrade stability in permafrost sections of the Qinghai-Tibet Railway. This has reference significance to other projects in similar zones.