Trenching

After the flexible test items were declared “failed”, trenches were cut in the transverse direction in the pavement. The purpose of the trenches was to conduct posttraffic investigation into the failure mechanism of the pavement structure. The trenching involved removal of the P-401 AC layer, the P-209 crushed stone base, and the P-154 subbase layer to reveal the subgrade interface and subsequent subgrade layers below. The final trench dimensions were 60 feet (18.3 m) long (across the width of the test pavement), 4 feet (1.22 m) wide, and the depth varied depending on the test section. Tests and measurements were performed on the various layers of the pavement structure. After the completion of testing, the trench walls were cleaned to clearly expose the layer interfaces. Measurements of the pavement layer interface profiles were made relative to a horizontal string line to quantify the contribution of each component layer to the total pavement rutting and upheaval.