Numerical investigation of hydrolysis failure of aggregates in loess via CFD-DEM

Large numbers of aggregates in loess are vital components of the skeleton structure of loess. In this study, a simulation of the water stability of aggregates using coupled computational fluid dynamics and the discrete element method (CFD-DEM) is presented. For the simulation, the "fixed coarse-grid" method of 3D particle flow code (PFC3D) is employed to simulate the particle-fluid coupling. With respect to the degradation law, a customized code was developed using Python, which transformed the hydrolysis of cement into the degradation process for the bond strength between particles via the CFD-DEM model. Under the action of different hydraulic gradients, the rate of hydrolysis of the aggregates increased rapidly with an increase in water pressure, and many piles of particles are denuded from the aggregates, thus causing the destruction of the aggregates. At the same time and under the same water pressure, the rate of hydrolysis of the multi-aggregates was always lower than that of the single aggregate. In addition, the density and porosity of the aggregates would affect, to varying degrees, the water stability.