Experimental study on underwater rammed stone column.

• A new underwater rammed stone column (RSC) is proposed to improve soft marine clay. • A series of model tests are conducted to evaluate the bearing capacity of RSC. • Bearing capacities of RSCs are better than those of traditional stone columns (TSCs). • The load transfer mechanism and failure mode of RSCs and TSCs are revealed. An underwater rammed stone column (RSC) is proposed in this paper to improve the bearing capacity of the coastal marine clay. The main idea of this technology is to drill a hole into the seabed from the sea surface with protection from a large steel pipe and then use a rammer to compact the aggregates into the seabed to form the RSC composite foundation. A series of model tests were conducted to validate the installation method and evaluate the bearing capacities of RSC. The test results showed that the bearing capacities of RSCs are much better than those of the traditional stone columns (TSCs) with the ultimate bearing capacity of maximum improving 77.6% for the full-length columns and 65.3% for the floating columns. The effective length of the RSCs was 6 times column diameter and most of the load is born by the top sections of RSCs with a length of 3 times column diameter. The bulging failure occurs in TSC and RSC with the maximum bulging position at approximately 1.5 times column diameter from the column head. [ABSTRACT FROM AUTHOR]