Shaking Table Test on Seismic Response of Coral Sand Foundation Reinforced by Vibroflotation Compaction

The foundation treatment of coral islands is becoming more and more serious. Shaking table tests were carried out on coral sand foundation reinforced by vibroflotation and loose coral sand foundations not reinforced by vibroflotation. The responses of excess pore pressures and accelerates were collected and analyzed. The results indicated that the excess pore pressures of vibroflotation-reinforced coral sand foundation continued to increase until the end of excitation when experienced 0.1g seismic simulation, while these of the unreinforced loose foundation raised rapidly at 3~4 s and kept stable until the excitatory input ended. In the whole seismic simulation process, the excess pore pressure of a reinforced foundation is always smaller than that of an unreinforced one. Vibroflotation can effectively reduce the development of excess pore pressure in coral sand foundations under seismic input. The excess pore pressure of the coral sand foundation reinforced by vibroflotation decreased by 37.2%~67.3% under 0.1g seismic simulation compared with the unreinforced loose condition. Moreover, the coral sand foundation reinforced by vibroflotation can effectively reduce the amplification effect of acceleration. The amplification coefficient after vibroflotation reinforcement is 78.1%~91.1% of that of the unreinforced foundation.