Experimental Study on the Permeability of a Soil-Rock Mixture Based on the Threshold Control Method

Abstract

The study of the permeability of soil-rock mixtures is important in supporting theories behind reclamation mechanisms for open-pit mines. To avoid the influence of differences in the spatial distribution of rock within the same sample on the permeability of a soil-rock mixture in laboratory tests, a numerical method for modelling the soil-rock mixture based on the threshold control method was proposed. Through the statistical results of 297 CT (computed tomography) cross sections of soil-rock mixture samples, the threshold values of pores, soils, and rocks are obtained, and a numerical model representing the reactions of the samples to real-world conditions is obtained. A numerical model was used that could vary with different rock block proportions (RBP) and porosities. Based on Darcy's law, it is concluded that macroscopic voids greatly increase the permeability of the sample due to their depth of penetration. The higher the stone content, the closer the permeability will be to the permeability of the rock skeleton. Therefore, during the reclamation process of the open-pit mine, the water-retaining layer below the humus should be compacted, and RBP should be increased to lower permeability and achieve better water retention.