Rectangular closed diaphragm walls (RCDW) has recently been used as a new type of liquefaction mitigation foundation; however, the mechanisms of liquefaction mitigation have scarcely been studied. This paper proposes a 3D nonlinear solid-fluid fully coupled effective stress numerical model in the OpenSees software to study the liquefaction mitigation mechanisms of RCDW. Data from centrifuge tests of an RCDW in a gently sloping liquefiable deposit are used to validate the predictive capabilities of the state-of-the-art numerical tool. The numerical model captures the soil and RCDW seismic responses well. The validated model was applied to investigate the effectiveness and mechanism of RCDW liquefaction mitigation under earthquake motions with different peak accelerations. The numerical results show that the RCDW can mitigate liquefaction in the soil core during small earthquakes and delay liquefaction triggering during moderate and major earthquakes. The RCDW mitigates soil liquefaction by (1) restraining shear strain in the soil core; (2) working as a cutoff wall against water migration from the near field toward the soil core, thereby enhancing the effect of liquefaction mitigation; and (3) resisting liquefaction-induced lateral spreading, which decreases the damage caused by large deformation. Moreover, (4) RCDW displacements are reduced by the support from the enclosed soil, which mitigates displacement of the superstructure. This understanding of the RCDW mechanism in liquefaction mitigation will help to improve the design of RCDW foundations in liquefiable ground.

矩形封闭式隔板墙（RCDW）最近已被用作新型的液化缓解基础。但是，关于液化缓解机制的研究很少。本文在OpenSees软件中提出了一个3D非线性固液完全耦合有效应力数值模型，以研究RCDW的液化缓解机理。来自RCDW在缓慢倾斜的可液化沉积物中的离心测试数据可用于验证最新数字工具的预测能力。数值模型很好地捕获了土壤和RCDW地震响应。应用验证的模型研究了在不同峰值加速度下地震作用下RCDW液化减缓的有效性和机理。数值结果表明，RCDW在小地震作用下可减轻土心液化，在中，大地震作用下可延缓液化触发。RCDW通过（1）抑制土心中的剪切应变来减轻土壤液化；（2）用作隔水墙，以防止水从近场向土壤核心的迁移，从而增强缓解液化的作用；（3）抵抗液化引起的横向扩展，减少了大变形引起的破坏。此外，（4）通过封闭土壤的支撑减少了RCDW位移，从而减轻了上层建筑的位移。对RCDW缓解液化的机理的理解将有助于改善可液化土地中RCDW基础的设计。