The soil liquefaction due to earthquakes will usually result in the damage of caisson foundation.Based on the Biot′s dynamic consolidation theory for two-phase media

a coupled FE-FD method is used in this paper to analyze the effective pore water pressure in liquefied seabed caisson foundation.In the numerical analysis

us-pw formulation of dynamic consolidation equation and cyclic elastic-plastic constitutive model is used

and the analytic results have shown that the method performs well in simulating the seabed liquefaction process.The strengthening method to prevent the liquefaction of sand zones by gravel piles was analyzed with the numerical method to suggest how to select the sand zones treated by gravel piles.