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通过测量平均粒径为1,2,3和5 cm的天然碎石层的反射率,以揭示影响碎石层反射率的主控因子。为了提高碎石层的反射率,将不同粒径骨料均匀涂上高反射率材料,并将实测碎石层表面的反射率与采用ASTM E1918A规范计算结果进行对比。研究发现:ASTM E1918A规范计算值是文中模型的一个特例。当太阳辐射瞬时强度值变化小于20 W/m2,模型计算的反射率与ASTM E1918A计算值的偏差在0.00~0.03。由于碎石层表面粗糙度,其反射率总比新鲜碎石平面的反射率低0.10~0.25,且随着骨料粒径的增大,天然碎石层的反射率逐渐降低。因为从表面散射反射的光子重新回到表面的概率增大,加剧了碎石孔隙间的多重反射,从而降低了反射率。经喷涂高反射率材料后,可将碎石层反射率从0.262提高至0.433,提高幅度在0.10~0.20。提高碎块路基的反射率可以有效地降低路基边坡温度,有利于保护冻土路基的稳定性。
The reflectance of the natural crushed-stone layer with an average particle size of 1, 2, 3 and 5 cm was measured to reveal the dominant factor that affects the reflectance of the crushed-stone layer. In order to improve the reflectivity of the gravel layer, the different particle size aggregates were uniformly coated with high reflectivity materials, and the reflectivity of the surface of the measured gravel layer was compared with that calculated by the ASTM E1918A specification. The study found that the calculated value of ASTM E1918A is a special case of the model. When the change in instantaneous solar radiation intensity is less than 20 W / m2, the difference between the model calculated reflectance and the calculated value of ASTM E1918A is between 0.00 and 0.03. The reflectivity of the gravel layer is always 0.10 ~ 0.25 lower than that of the fresh gravel, and the reflectivity of the natural gravel layer decreases with the increase of the aggregate size. Since the probability of photons scattered back from the surface returning to the surface increases, the multiple reflections between the pores of the gravel are aggravated, reducing the reflectivity. After spraying high reflectivity materials, the gravel layer reflectivity can be increased from 0.262 to 0.433, an increase of 0.10 to 0.20. Raising the reflectivity of the crushed subgrade can effectively reduce the temperature of the subgrade slope, which is beneficial to the stability of the frozen subgrade.