Abstract: Seismic active earth pressure is the primary load for retaining wall design in high earthquake-intensity areas. Based on the relative position relationship among water table, crack depth and wall heel, this study firstly presented three mechanical models of seismic active earth pressure on retaining walls in unsaturated soils with cracks, which corresponded separately to high/medium/low water tables. The pseudo-dynamic method was then employed to calculate the seismic effect of sliding soils behind a retaining wall. The solution of seismic active earth pressure on inclined retaining walls for changing water table was derived by adopting mechanical principles of unsaturated soils and the limit equilibrium method. The iterative steps to be easily conducted were provided, and the proposed solution was compared with the results of theoretical analysis and the shaking table test available in the literature. Finally, the influences of water table, crack depth and unsaturated soil characteristics on the seismic active earth pressure coefficient were discussed. The results show that the proposed solution well considers the effects of water table, crack depth and unsaturated soil characteristics, which can be degraded to the classical earth pressure equation. Additionally, it agrees well with the existing theoretical solution and measured data of the shaking table test. Consequently, the proposed solution has an important theoretical significance and good application prospect. The influences of water table, crack depth, matric suction, suction distribution and suction angle on the seismic active earth pressure are all apparent. In order to optimize the seismic design of a retaining wall, engineering measures should be taken to maintain stable existence of matric suction, suction distribution, low water table and small crack depth.

Key words: seismic active earth pressure, unsaturated soils, pseudo-dynamics method, water table behind a retaining wall, soil crack