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Specimens of a glacial till and a silty clay, compacted at molding water contents corresponding to optimum water content or greater, have been tested in triaxial apparatus. The migration of water, due to capillary forces acting between partially saturated samples placed at different molding water contents and densities, has been investigated experimentally, and typical results are reported. Experimental studies of air permeability in partially saturated soils and water permeability in both partially saturated and saturated soils are described. The air permeability is shown to range over five log cycles as the degree of saturation is increased and becomes negligible as the suction, μa − μw, approaches zero. The validity of Darcy's law is confirmed by performing water permeability tests at different back pressures. If the soil is completely saturated, there is no evidence of a “threshold gradient” or a nonlinear relationship between velocity and hydraulic gradient as reported by some investigators. Coefficients of permeability as determined by direct measurement are compared with values calculated from triaxial consolidation test data, and the lack of agreement is discussed briefly on a theoretical basis.
permeability, capillarity, soil (material), glacial till, silt (material), clay, triaxial test, air permeability, water permeability, saturation, Darcy's law, hydraulic gradient, consolidation, embankments, seepage
Matyas, E. L.
Assistant professor, University of Waterloo, Waterloo, Ontario