积沙对铁路道碴层反射率的影响研究

青藏铁路建成后，随着全球气温的升高及人类活动的影响，青藏高原地表沙化正在呈现加速发展的趋势，地表积沙入侵路基，填堵和覆盖青藏铁路道碴层，影响了青藏铁路道碴层的反射率。为此开展了积沙对于铁路道碴层反射率影响的研究。为此本文将测量碎石层等粗糙表面的反射率的方法进行了改进，使其适用于测量混有流动性材料（如积沙等）的粗糙表面（如铁路道碴层等）的反射率。结果表明：随着铁路道碴层模型积沙覆盖率的增大，铁路道碴层的反射率先减小后增大，当积沙完全覆盖道碴层时，其反射率达到最大。并将该测试方法与ASTM-E1918A标准测试方法进行对比分析发现，在天气晴朗、无云、无雾霾且太阳辐射入射量瞬时强度变化<20W·m^-2时，两种测试方法计算非常接近，其测量差值0~0.002，综合分析认为在测量带有流动材料的反射率时，采用本测试方法方便可靠。但积沙对道碴层的热流平衡影响有待进一步研究。

Study of the effect of sand cover on the albedo of railway ballast layer

After the construction of the Qinghai-Tibet Railway,with the influence of global warming and human activities,the desertification is accelerated on the Tibet Plateau,Because of the invasion of sand,some ballast layers are filled and covered along the railway,and thus the albedo of the ballast layers are changed.Therefore,the effect of sand cover on the albedo of the railway ballast layer are studied in this paper.The results showed that with the increase of the sand cover ratio,the albedo of the railway ballast layer model first decreases,then increases.When the railway ballast layer was completely covered by sand,its albedo reached the maximum.By comparing the used method and the ASTM-E1918A method,it is found that when the variation of solar intensity is less than 20 W · m-2 in sunny days with no clouds and no haze,the results from the used method are very close to those from the ASTM-E1918A method,with a differences of about 0 ～0.002.Based on comprehensive analysis it is believed that used method is more convenient and reliable in measuring the albedo of unstable materials.However,the effect of sand cove on the heat balance of ballast layers still needs further to be study.