Laboratory experiment study on response of vibroflotation compaction of coral sand

The treatment of the hydraulic fill coral sand ground starts to attracted a lot of attentions with the development of marine island reef engineering. By using self-developed laboratory vibroflotation instruments, vibroflotation tests on of saturated coral sands ground are conducted to analyze dynamic response regularity during vibro-compaction, such as dynamic pore water pressure and horizontal earth pressure. The characteristics of settlement and relative density are also investigated. The results indicate that loose coral sands can be improved to medium density after two times of double-point vibro-compaction; meanwhile, the most obvious effect to relative density appears at the point where vibrator works, and the middle or deeper areas are better improved than the surface areas. The maximal excess pore water pressure appears at the stage of vibrator penetration. The excess pore water pressure starts to attenuate at the beginning of vibration retention. A significant descend of excess pore water pressure happens when vibrator starts to lift. The peak excess pore water pressure of the second penetration is obviously smaller than that of first penetration. The excess pore water pressure ratio contours exhibits parallel distribution during vibro-compaction. The shallow horizontal earth pressure of coral sands shows an increase with both penetration and extraction of vibrator, while the deep horizontal earth pressure presents a decrease.