Three-dimensional lattice Boltzmann simulation of the permeability of soil-rock mixtures and comparison with other prediction models

With the discrete element method and the proposed virtual slicing technique for three-dimensional discrete element model, random pore-structural models of soil-rock mixtures (SRMs) are constructed and voxelized. Then, the three-dimensional lattice Boltzmann method (LBM) is introduced to simulate the seepage flow in SRMs on the pore scale and the influences of rock content, rock size, relative density on the simulated permeability of SRMs are comprehensively investigated. Finally, several theoretical models are introduced to predict the permeability of SRMs, and comparison is made between the results given by these prediction models and the numerical results obtained in this study. The results show that the permeability of SRMs presents a gradually increasing trend with the increase of rock content, and the rate of increase is also getting larger. When the other conditions remain unchanged, the permeability of SRMs decreases with the increase of relative density. When the rock content is lower than a threshold value, the permeability decreases as the rock size increases; however, this trend gets reversed when the rock content exceeds the threshold value. The permeability values of SRMs simulated with the LBM are lower in different levels than those calculated with the HS model, EMA model, and Zhou model, but most of them are very close to those predicted by the Daigle model.

Automated summary

This study investigates the effects of rock content, rock size, and relative density on the permeability of soil-rock mixtures using the discrete element method and lattice Boltzmann method. The results show that the permeability of soil-rock mixtures increases with rock content and decreases with relative density. Additionally, the permeability values obtained with the LBM are lower than those predicted by some theoretical models, but closer to those from the Daigle model.