Abstract: In this study, we perform a series of oedometric tests on saturated sand-clay mixtures with five different sand contents at high pressure using a self-designed high-pressure oedometer. The evolutions of compressibility and permeability and their dependency on mineralogical compositions during compaction process were investigated. Experimental results showed that the compression curve (e-lgP) of the saturated sand-clay mixtures transfers from an exponential function to a hyperbolic function with the increase of sand content. However, the compression curve (e-P) plotted in normal coordinates presents a linear evolution for all the sand-clay mixtures when the consolidation pressure is above 8.1 MPa, and its slope depends on sand content. The concept of optimum sand content is used to describe the minimum void ratio at a certain value of consolidation pressure. The optimum sand content varied continuously from 75% to 30% following the increase of consolidation pressure. Furthermore, it was founded that the relationship among void ratio, consolidation pressure and sand content follows the uniform power function for all the mixtures studied. An exponential correlation is proposed to describe the correlation between the permeability coefficient and void ratio, which can further reveal the influence of sand content on hydraulic conductivity. Overall, the effects of consolidation pressure and sand content on the compressibility and permeability of the sand-clay mixtures were analyzed from the perspectives of skeleton structure and pore features of sand-clay mixture. The correlation between the skeleton structure and sand content of sand-clay mixtures was further confirmed by SEM microphotograph observations.

Key words: sand-clay mixture, compressibility, sand content, pore structure, permeability