Laboratory investigation of efficiency of conical-based pounders for dynamic compaction

The pounder for dynamic compaction is conventionally built to have a flat b ottom. An innovative idea of using a conical-based pounder to improve the e fficiency of dynamic compaction has been investigated, and the results are presented in this paper. Both a conical-based pounder and a hat-based pound er were used in an extensive programme of laboratory dynamic compaction tes ts. An air pluviation technique was used to prepare dry sand specimens, 60 cm in diameter and 50 cm high, to have initial relative densities of 30% an d 40%. Wet sand specimens with an initial relative density of 60% were prep ared from the dry sand specimens. A total of 14 dynamic compaction tests we re performed. The results of each test include dimensions of the crater, he ave around the crater, and cone penetration resistance at 13 penetration lo cations. It is found from the test results that the efficiency of dynamic c ompaction,vith the conical-based pounder depends on both the grain size cha racteristics and the volume change behaviour of the sand. The conical-based pounder is more effective in the Mai-Liao fine sand,vith 8% fines than in the clean Ottawa medium sand.