Experimental study on the solar reflectance of crushed rock layer with different sizes

Abstract

A crushed rock layer is often reveted on a cold-region embankment side slope to keep the underlying permafrost layer cool. However, its cooling effect is strongly affected by the solar absorption of this layer. This study proposes a procedure for measuring the albedo of a heterogeneous surface like a crushed rock layer. The albedo of crushed rock layers with different aggregate sizes is measured. It is found that the albedo of the crushed rock layer decreases with the aggregate size and that the albedo of the crushed rock layer is 0.1–0.2 lower than the albedo of the fresh flat rock. This is because the multiple reflections in the inter-aggregate cavity increase the solar absorption of the layer. Painting the crushed rock layer with high-reflective pigments can increase the albedo of the layer about 0.10–0.20, with the greater increase for the layer with the larger aggregate size.