A new horizontal permeability test is proposed. The apparatus for the permeability test has been developed on the basis of the consolidation cell devised by Rowe and Barden. (1966). The size of the soil specimen is 20cm in diameter and 6.7cm thick. A rubber jack is placed over the spacer disc and is fed with water connected with the constant pressure supply line through a valve in the cell cover, applying to the soil specimen a uniform pressure up to approximately 5kgf/cm2. Vertical compression of the specimen is indicated by a hollow stainless steel spindle attached to the rubber jack and passing through the cell cover. The compression is measured by means of a dial gauge mounted on a bracket on the cover. Two slits are opened, diametrically opposite, on the side of the oedometer ring. Water under constant pressure is supplied through the side slits and fed into the soil specimen to establish steady seepage across it in the horizontal direction. The seepage thus obtained makes it possible to compute the coefficient of horizontal permeability at the end of each loading. The vertical permeability of a clay specimen cut to the initial size of 15cm in diameter and 4 cm in thickn'ess was measured also in a Rowe-type consolidometer capable of flowing water vertically through the specimen under a constant head. Direct measurement of the vertical permeability was made at the end of each loading of the consolidation test. Under relatively low consolidation pressures the seepage quantities both in the vertical and horizontal directions are approximately of the same maguitude, while with increase in the applied vertical pressure the flow in the vertical direction decreases more markedly than that in the horizontal direction. Therefore, it is considered that as consolidation proceeds the soil structure become more oriented in the horizontal direction, causing water to flow more readily in the horizontal direction and resulting in more distinct anisotropic permeability. Comparison was made between the values of the coefficient of permeability determined from the proposed permeability tests and from the oedometer tests. The values from the former were significantly greater than those from the latter. It is also noted that the coefficient of permeability increases as the size of specimens increases.
