抄録
A series of permeability tests on high-quality undisturbed sand samples was performed using a triaxial cell. The high-quality undisturbed sand samples were recovered by the in-situ freezing sampling method from four sites. The effects of anisotropy, confining stress, void ratio and relative density on permeability were investigated. Next, the effects of the physical properties of the undisturbed samples on the permeability coefficient were evaluated. The coefficient of permeability of the high-quality undisturbed samples was also compared with those estimated from Creager's proposal and Hazen's equations, using the soil gradation characteristics of the undisturbed samples. Based on the test results, the following conclusions were noted. (1) For the sands tested, the coefficient of permeability in the horizontal direction (H-specimen) was found nearly equal or only slightly larger than that in the vertical direction (V-specimen). The maximum difference of the coefficient of permeability between the H and the V-specimens was only about 70%. (2) The permeability of the sands was slightly influenced by the confining stress, such that the permeability decreased with increasing confining stress. A small decrease in the permeability due to the increase in confining pressure, can be interpreted to be caused by the minute decrease in the void ratio caused by an increase in the confining stress. (3) No relationship between the void ratio/relative density and the permeability coefficient, which is observed for all types of sand, was found. (4) A good correlation between the coefficient of permeability and the percent fines content of in-situ sandy soils was noted. Although the data was limited, a simple tentative equation was proposed to relate the coefficient of permeability and the fines content. (5) It is possible to estimate the coefficient of permeability of sandy soils roughly for design purposes, both from Hazen's equations and Creager's proposal, in the range of D10 larger than 0.5 mm or D20 larger than 0.1 mm, respectively.
