The dynamic cone penetrometer in compaction verification on a model road pavement

Compaction verification studies were conducted on a model site during a road construction project. Three compaction plants of different capacities were used on model pavements constructed using loose lifts of lateritic gravel measuring 120, 170, and 220-mm thick. After every two passes of the roller the dynamic cone penetrometer (DCP) test was conducted on the compacted layer alongside the sand replacement test to determine the level of compaction. A correlation was made between the sand replacement and the DCP tests resulting in a calibration equation of the general form log(LC)= kappa-lambda log(DPI) between the DCP penetration rate, DPI, and the level of compaction (LC) achieved as measured by the sand replacement method. kappa and lambda were found to be 2.184 and 0.337, respectively. The level of compaction values was back-calculated across the depth of the pavement using the DPIs. These values indicated that the sand replacement method gives the average degree of compaction over the depth tested whereas the DCP test allows the detection of low-level compaction pockets deeper within the layer.