Theory and procedure for measuring the albedo of a roadway embankment

Abstract

The construction of roadway embankments in permafrost regions modifies the pre-existing ground surface, possibly increasing the solar absorption of the embankment. Measuring the albedo of the embankments is crucial to understand the degree of the construction-induced thermal disturbance and to cool the permafrost in the roadbed. While there are existing standards for measuring the albedo of a curved surface, these standards cannot be adpated to the albedo of an embankment. This study develops a theoretical model for measuring the albedo of a roadway embankment. The albedo of an embankment prototype is estimated by successively covering a target surface with a white mask, a black mask, and the embankment prototype and recording the diffuse reflections and the global horizontal radiation accordingly. The albedo of a typical embankment is about 0.05 to 0.08 lower than a flat surface that has the same surface material as the embankment, suggesting that an embankment absorbs more sunlight than its adjacent ground surface and its pre-existing ground surface. The embankment-albedo measuring procedure is compared with the ASTM E1918-06, with a focus on minimizing the errors of the measurements.