Evolution of pore structure and hydraulic conductivity of randomly distributed soluble particle mixture

Abstract

The plane strain behavior of particulate mixtures containing soluble particles was investigated by conducting both laboratory tests and numerical analysis. To perform the laboratory experiments, soluble mixtures were prepared using photoelastic disks and ice disks with diameters in the ratios (D-ice disk/D-photoelastic disk) of 0.5 and 0.7, and the evolution of the force chain and pore structure was monitored during the dissolution of the ice disks. Subsequently, numerical analysis was conducted by using the 2-dimensional discrete element method for the soluble mixtures, and it was compared with the experimental results. Additionally, parametric studies were implemented by varying the particle size ratios between the soluble and non-soluble particles and the volumetric fraction of the soluble particles. The results of the laboratory experiments and numerical analysis demonstrate that (1) after the dissolution of the soluble particles, the pore fabric of the specimens changed, resulting in a force chain changes, local void increases, and coordination number decreases; (2) the effects of soluble particles on the macro-behaviors of the mixtures could be divided into 3 zones based on the particle size ratios between the soluble and non-soluble particles and volumetric fraction of soluble particles. These zones were as follows: (Zone 1)with a small total soluble volume, slight decrease in the in situ lateral pressure (K-0), and minor increase in the hydraulic conductivity (k); (Zone 2)with a moderate soluble particle; the dissolution generated a honey-comb particle structure; (Zone 3)the total soluble volume was very large, and the high volumetric fraction of the dissolving particle collapsed the pore structure, decreasing in the in situ lateral pressure (K-0) but increasing the hydraulic conductivity (k). The horizontal stress returned to almost the original level, and the internal arching formation increased significantly with the hydraulic conductivity (k).