已有震害研究表明，震后边坡会因持续变形而破坏，且伴随着土体强度逐渐降低的现象，即土的循环软化行为。因此，有必要研究考虑循环软化的非线性动力本构模型以用于复杂条件下地震边坡稳定性分析。在已有的非线性动力本构模型基础上，提出了考虑循环软化的处理方法。同时，在FLAC3D平台上实现了本构模型二次开发，并通过了理论公式与已有文献中试验数据的验证。结果表明：计算出的骨干曲线与理论公式一致，且计算出的动剪切模量比及阻尼比与试验数据吻合较好，能够克服Hardin-Drnevich模型和Davidenkov模型在较大应变处（>0.01%）过高地估算阻尼比的缺陷；考虑了循环软化后，计算出的剪切强度有明显降低，且当遇到骨干曲线剪应力可以连续地过渡到软化后的主干曲线上，模型的收敛性较好。所开发的本构模型可为大应变条件下软土场地及边坡地震灾害评估提供支持。

Catastrophic failure of slopes often results from cyclic softening, i.e. onset of significant strains or strength loss in soils during earthquakes. Therefore, it is necessary to study the nonlinear dynamic constitutive model considering cyclic softening in order to analyze the stability of seismic slope under complex conditions. On the basis of existing nonlinear dynamic constitutive models, a method to deal with the cyclic softening is proposed. A secondary development of the constitutive model is implemented into the FLAC3D platform, and the proposed procedure is verified by the theoretical formulation and the experimental data available in the references. It is shown that the calculated backbone curve is consistent with the theoretical formula, and the calculated dynamic shear modulus ratio and damping ratio are in good agreement with the experimental data. When the shear strain is larger than >0.01%, the modified model describes better the damping ratio-shear strain relationship than Hardin-Drnevich model and Davidenkov model. If the cyclic softening is taken into account, the calculated shear strength is significantly reduced, and the convergence of the model is improved when the shear stress of the backbone curve can be continuously transferred to the softening main curve. The developed constitutive model can provide support for the seismic disaster assessment of soft soil site and slope under large strain condition.