Sand control project is the main way used for the protection of the Qinghai-Tibet Railway from sand damage.However,sand-control practice will result in sand deposition inevitably.Currently,the effect of sandy sediments on the surface heat exchange is unclear.Therefore,utilizing net radiometer with four components and adopting the methods of synchronization contrast observation and laboratory tests in the test field of Honglianghe River sand-damaging sections of Qinghai-Tibet Railway,the variation of heat exchange was studied after the ground surface was covered with sandy sediments produced by the sand-control projects of Qinghai-Tibet Railway.The study found that after the ground surface was covered with sandy sediments produced by the sand-control projects of Qinghai-Tibet Railway,the surface albedo increased.The annual average albedo on the surface of sandy sediments was 0.05 higher than that of the surface without sandy sediments.The surface upward shortwave radiation increased with the annual average value of the upward shortwave radiant flux density,the daily total value of the annual average and yearly total value of the upward shortwave radiation on the surface of sandy sediments 8.56 W/m2,0.74 MJ,269.99 MJ higher respectively than those of the surface without sandy sediments.The surface net radiation decreased with the annual average value of the net radiant flux density,the daily total value of the annual average and yearly total value of the net radiation on the surface of sandy sediments 12.49 W/m2,1.08 MJ,393.47 MJ lower respectively,compared with those of the surface without sandy sediments.These variations resulted in the reduction of the heat source on the surface of sandy sediments.Further,the heat transmitted to the underground through sediment deposition was reduced due to the weak thermal conductivity of sand layer,which is beneficial to the prevention of permafrost from degradation in the section of sand-control of the railway.%作为青藏铁路防沙的主要方式,工程防沙必然会引起积沙,积沙对地表热交换的影响目前仍不清楚.为此,在青藏铁路红梁河沙害路段试验场,利用四分量净辐射传感器,通过野外同步对比观测结合室内测试等方法,对青藏铁路工程防沙积沙后地表辐射变化进行研究.发现青藏铁路工程防沙积沙后,地表反照率增大,积沙地表的年平均反照率比无积沙地表增加0.05;地表向上的短波辐射增大,积沙地表向上的短波辐射通量密度年平均值、年平均日总值、年总值分别高出无积沙地表8.56 W/m2、0.74 MJ、269.99 MJ;地表净辐射减少,与无积沙地表相比,积沙地表的净辐射通量密度年平均值、年平均日总值、年总值分别降低12.49 W/m2、1.08 MJ、393.47 MJ.导致积沙地表的热量来源减少,同时,由于沙层的热传导性能弱,通过积沙传导到地下的热量减少,从而有利于铁路沙害防治路段多年冻土的保护.
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