High moisture within pavements accelerates pavement deterioration. Ensuring water is kept out of these pavement layers increases life and saves maintenance costs. A high-speed moisture survey technique employed overseas, utilising ground penetrating radar combined with video and laser LIDAR, was used on a range of roads in the lower North Island.
A unique moisture damage index was developed for use in New Zealand to enable the identification of high moisture levels at three different depths (top; middle; bottom) in 2m increments along the road using results from the ground and air coupled radar. In the free viewer software the road cross section can also be displayed to determine the rut depth, ditch depths, cross fall and high lip, which aid in determining the most appropriate improvement in drainage.
The New Zealand trial of the moisture detection equipment showed higher rutting in road sections with high moisture, while low moisture was detected in areas of nil or low rutting. Ten test pits measuring moisture at top, middle and bottom depths showed the moisture detection survey conducted seven months earlier was correct in the assessment of high and low moisture for 80% of the time.
Keywords: drainage, ground penetrating radar, laser scanner, moisture, monitoring, water content