Impact of Unsaturated Flow on Pavement Edgedrain Performance

Abstract

Water movement in pavement sections that included an edgedrain trench was investigated by means of numerical simulations that explicitly included unsaturated water flow. Most of the resulting water movement from infiltration in response to simulated rainfall events occurred under unsaturated conditions, that is, under negative water pressures. Fully saturated conditions and positive pressures most often only occur in the drainage trench bottom. Drainage efficiency was shown to depend on the base course and edgedrain backfill material properties and configuration. The saturated hydraulic conductivity of the base course was shown to not be a reliable indicator of drainage efficiency. The performance of the edgedrain trench depends on whether water directly enters the trench through a shoulder crack, or has to first move through the adjacent base course to reach the trench. In the latter case, the trench backfill material can serve as a restriction to flow to the trench even if the material has a very large saturated hydraulic conductivity.