Abstract: A perfect anisotropic permeability model is helpful to guide the drainage and grouting scheme of underground buildings during construction and operation period. To study permeability anisotropy model, mixed kaolinite-montmorillonite clays were used in a series of permeation experiments by triaxial permeameter, and the development of anisotropic permeability model was attempted from both macroscopic and microscopic perspectives. The results show that: as the amount of bentonite increases, the small pores increase, but the large pores decrease; as the consolidation stress increases, all pores decrease, and the maximum pore size decreases. Macroscopically there is no correlation between the void ratio considering the liquid limit void ratio and the permeability anisotropic ratio, which indicates that the void ratio e and liquid limit void ratio are not the key parameter determining the permeability anisotropy ratio. The permeability anisotropy model expressed by microscopic parameters indicates that it is not only feasible to explore the permeability anisotropy model from the microscopic point, but also to reveal the essence of permeability anisotropy. In all microscopic models, the permeability anisotropy model expressed by pore indexes – is well correlated, which can reflect changes in larger pores.

Key words: mixed clay, permeability anisotropy model, macroscopic parameter, microscopic parameter, pore index