Microscopic mechanism regarding permeability anisotropy of kaolin-montmorillonite mixed clays

A series of experiments are conducted by using the triaxial permeameters to study the influences of the incorporation ratio of bentonite and the effective consolidation stress on permeability anisotropy, and the corresponding microscopic mechanisms are investigated. The results show that: (1) When the bentonite is added, the permeability coefficient and permeability anisotropy of the mixed soil decrease significantly, but with the increasing incorporation ratio of bentonite, the permeability anisotropy tends to be stable because the effective pore proportion ratio tends to remain constant. (2) With the increasing effective consolidation stress, the permeability anisotropy of the mixed soil increases. When the effective consolidation stress increases, both the effective pore area ratio and the effective pore proportion ratio increase, which indicates that the ratio of vertical to horizontal effective pore areas is increasing. (3) Considering the influences of the incorporation ratio of bentonite and the effective consolidation stress comprehensively, if intending to quantitatively analyze the impact of these two factors from the perspective of microscopic analysis, it is recommended to use the effective pore proportion ratio as the parameter of microstructure.