Creep modelling of soft soil based on the fractional flow rule: Simulation and parameter study

•Formulated a novel creep model for soft soil based on the fractional flow rule.•Demonstrated the advantage and availability of suitable kernel function for the proposed model through numerical analysis.•Proved the accuracy and efficiency of the proposed model for depicting full-stage creep behaviors of soft soil.•Established the physical significance of model parameters which is highly related to the applied stress. The creep deformation of soft soil is a critical factor in geotechnical design of engineering facilities built on soft soil foundations. In this study, a novel fractional creep model for soft soil is developed by introducing the Almeida fractional derivative into the classic elastic-viscoplastic model. A series of numerical analyses are conducted to determine the kernel function of the proposed model with the best performance, and the good agreement between the model predictions and test results is observed. With the advantage of introducing the fractional flow rule, the fractional creep model exhibits higher accuracy and convenience than conventional models as fewer material parameters and state variables are required. Furthermore, a parameter study reveals that the fractional order directly relates to the stress level, and the different deformation patterns of soft soil under low and high stresses could be reflected by the tendency of the order.