Abstract: Suffusion refers to the phenomenon that the movable fine particles in internally unstable soil migrate through the pore channels under seepage flow. The constitutive model, which describes the transition of the deposited fine particles to the fluidized fine particles in the pore fluid, determines the reliability of numerical analysis results. Currently, there are many constitutive models for suffusion based on constant hydraulic conditions, but the models considering the effect of hydraulic fluctuation are still lacking. First, the meso-mechanism of fine particle migration under different hydraulic conditions was summarized, and the particularity of the fine particle migration mechanism under fluctuating hydraulic conditions was highlighted. Then, based on the meso-mechanism, a constitutive model for suffusion was developed by using the volumetric exchange rate of deposited fine particles to fluidized fine particles. The model can consider the combined effect of the interstitial flow velocity, the variation rate of interstitial flow velocity, as well as the hydraulic action time. Based on a set of parameters, the model well reproduced the fine particle erosion process under various hydraulic loading paths in the existing experimental studies, demonstrating the effectiveness of the model.

Key words: suffusion, hydraulic condition, constitutive model, fine particle loss, erosion rate