Experimental study on dynamic response of hammer in underwater tube dynamic compaction stone column

A series of model tests on underwater tube dynamic compaction gravel pile are conducted. The effects of hammer shape, tamping energy, single filling amount and soil strength on the installation and performance of the stone column are studied. The changes in the peak acceleration, compaction settlement and column density during compaction are analyzed. The experimental results show that the peak acceleration during compaction with the new conical hammer is close to that of the traditional flat-bottom hammer, but the time history decreases, which shows a development characteristic of first increasing oscillation and then rapidly decreasing. A fitting formula has been established for the normalized maximum impact force of the rammer during compaction, with respect to the parameters such as compaction coefficient, tamping energy soil strength and single filling amount, which can be used to predict the maximum impact force of underwater tube dynamic compaction stone column on different foundation strengths.