Evaluation of road subsurface drain performance by geophysical methods

Infiltrated water from precipitation runoff and freeze-thaw cycles is a detrimental climatic factor affecting pavement stability. To collect and remove excess free water from pavements, road subsurface drains in the form of underdrains and edgedrains are extensively used. One objective of this study was to evaluate the performance of road subsurface drain systems by estimating water contents in pavement and subgrade via two geophysical methods. At three road locations in the State of Georgia, volumetric water contents were calculated from the results of ground penetrating radar (GPR) and low-frequency electromagnetic induction (EM). Water contents were estimated assuming that pavement materials, subgrade characteristics, and water ionic concentration were constant throughout each site area. Thus, contour maps of infiltrated water content in each finite ground volume were prepared. The majority of pavement sections where road subsurface drains were clogged or damaged showed high water contents and vice versa. These results suggest the effectiveness and quickness of geophysics to capture the variability of infiltrated water content during site investigations. Copyright ASCE 2008.