Anisotropic hydraulic conductivity and critical hydraulic gradient of a crushed sandstone-mudstone particle mixture

This paper describes the development of a modified instrument used to measure the anisotropic hydraulic conductivity of coarse soils. Then, based on this modified instrument, horizontal and vertical hydraulic conductivities and critical hydraulic gradients of a crushed sandstone-mudstone particle mixture are measured. Using this data, we investigate the effects of particle size on the anisotropic hydraulic conductivity. The testing results indicate that the anisotropic hydraulic conductivity coefficient, which is defined as the logarithm value of the ratio of the horizontal hydraulic conductivity to the vertical conductivity, ranges from 0.079 to 0.358. This means the horizontal hydraulic conductivity is 1.20 to 2.28 times to that of the vertical conductivity. The anisotropic coefficient decreases as the uniformity coefficient increases. Meanwhile, the critical hydraulic gradient increases with an increase in fine particle content.