Experimental Study On Anisotropic Permeability Characteristics Of Sandstone-mudstone Particle Mixture

Taken the characteristics of anisotropic seepage into account, an anisotropy permeation apparatus for sandstone-mudstone particle mixture was developed. With the test equipment, anisotropic permeability of the compacted sandstone-mudstone particle mixture is studied by indoor experments. Based on the results of exprements, the effects of the proportion of sandstone-mudstone particle, gradation, dry density on anisotropy permeability characteristics were discussed. The mechanism of anisotropic seepage characteristic of the mixture sample of sandstone-mudstone particle was illustrated. By numerical simulation method, the influence of the anisotropic permeability on saturation line, seepage field distribution, stability of the homogeneous earth dam has been studied. The specific contents and conclusions are as follows:(1) Based on Darcy’s law and the constant head permeability test method, a anisotropy permeation apparatus for sandstone-mudstone particle mixture was developed. The sample of the test instrument is designed as a rectangular parallelepiped. To facilitate preparating samples of permeability characteristics in both horizontal and vertical directions, front and rear covers and superstructure is designed to be freely opened and closed. Rationality, reliability and applicability of anisotropic permeability apparatus has been clear validated in several ways: tightness, water flow orientation, instrument size, sidewall leakage, the location of the manometer-type tube, saturated methods.(2) With the test equipment, anisotropic permeability of the compacted sandstone-mudstone particle mixture is studied by indoor experments. Penetration test under the conditions of different proportion of sandstone-mudstone particle, gradation, dry density. Based on the results of exprements, the effects of permeability potential, particle size distribution fractal dimension, the percentage content of the shale particles, dry density of the sample, the characteristic particle size on the permeability coefficient and critical gradient has been discuessed.(3) Use the concept of the anisotropy coefficient, the compacted sample’s anisotropic permeability characteristics of the sandstone-mudstone particle mixture was analysed. Results show that the horizontal permeability is1.59times greater than the vertical permeability coefficient, anisotropic permeability characteristics is significant.(4) According to the characteristics of the shape of the sandstone and mudstone particles and sample preparation methods,"staggered joints wall" model of the tabular grain and "series parallel" penetration model of uneven density distribution samples were proposed. The mechanism of anisotropy permeability is explained by the two models.(5) Based on saturated-unsaturated theory, the influence of the anisotropic permeability on saturation line, seepage field distribution, stability of the homogeneous earth dam has been studied. The necessity of taking the anisotropic permeability characteristicis into account is demonstrated.