中文摘要：

波浪循环荷载通过堤身和砂质土置换层传递给软土地基,在软土地基中产生循环动应力,使软黏土发生不排水强度弱化现象,严重影响格型钢板桩防波堤承载性能。结合工程算例,基于动力有限元法建立考虑软土循环弱化效应的格型钢板桩防波堤三维弹塑性动力分析模型,对软土地基在循环荷载作用下最大孔压增长规律以及不排水强度弱化特性进行研究。建立格型钢板桩-软土地基系统动力稳定性分析方法,对格型钢板桩-软土地基系统的破坏模式、稳定性以及沉降变形特性进行分析。结果表明：最大孔隙水压力主要分布在格体周围软土层,主、副格仓底部及部分桩-土接触部位的不排水强度发生明显弱化。考虑软土地基循环弱化效应时,格型钢板桩-软土地基系统的稳定性安全系数显著降低。建议在实际工程中应考虑软土地基循环弱化效应对格型钢板桩防波堤稳定性的影响。

英文摘要：

Cyclic stress generated in soft foundation after cyclic wave loading is transferred to the intercalated soft layer through embankment and the backfilled sand layer. The strength of saturated soft clay degrades and soil loses bearing capacity. A 3D elasto-plastic dynamic model of steel sheet pile considering post-cyclic undrained strength degradation is developed using the dynamic finite element method. The maximum excess pore pressure and post-cyclic strength degradation of the intercalated soft layer are investigated. A method for dynamic stability analysis of steel sheet pile-soft foundation system is proposed to investigate the failure mode, stability and settlement of steel sheet pile-soft foundation system. The results show that the maximum excess pore pressure is generated in soft clay around the cell. Post-cyclic strength degradation occurs at the bottom of the main cell, arc cell and some soil-pile interaction areas. Safety factors of stability of steel sheet pile-soft foundation system decrease significantly with considering post-cyclic strength degradation of soft foundation. It is suggested that the post-cyclic strength degradation should be considered in practical design.