A fractional elastic-viscoplastic (F-EVP) creep model describing the anisotropy of soft soil is established. A nonlinear viscoplastic creep expression is obtained by a fractional derivative and the Laplace transformation, which is extended by the definition of the reference yield surface. On this basis, the anisotropy of soil is considered in the model by a rotating hardening criterion, and the effect of anisotropic parameters on the stress-dilatancy ratio is discussed. The scalar multiplier in the form of stress ratio is described, and a critical friction angle is used to unify the modeling parameter. The validity of the model is examined by the existing triaxial creep results. The results indicate that the rotational anisotropy induces coaxial rotation as the result of the stress-dilatation relationship. The fractional viscoplastic model can reasonably describe the plastic behavior of soil before yielding, and accurately characterize the creep behavior of soil. From the comparison between the test results and the model calculation results, it is found that the model calculation results are basically consistent with the test results.

建立了描述软土各向异性的分数弹性-粘塑性（F-EVP）蠕变模型。通过分数导数和拉普拉斯变换获得非线性粘塑性蠕变表达式，并通过参考屈服面的定义扩展了拉普拉斯变换。在此基础上，通过旋转硬化准则考虑了土体的各向异性，并讨论了各向异性参数对应力-剪胀比的影响。描述了应力比形式的标量乘子，并使用临界摩擦角来统一建模参数。现有三轴蠕变结果检验了模型的有效性。结果表明，由于应力-膨胀关系，旋转各向异性引起同轴旋转。分数粘塑性模型可以合理地描述屈服之前土壤的塑性行为，并准确地表征土壤的蠕变行为。通过测试结果与模型计算结果的比较，发现模型计算结果与测试结果基本一致。