The influence of grain-size and sediment sorting on the hydraulic conductivity of some Swedish tills

Porosity, grain-size distribution and sorting were studied in relation to hydraulic conductivity of 44 undisturbed till samples from three different sites in western Sweden. In addition, grain roundness and roughness of ten of the samples was studied. The results show that neither the porosity nor the grain parameters are sufficient to describe the hydraulic properties of till. In spite of the relatively uniform texture, hydraulic conductivity varied considerably from sample to sample, from about 10(-9) m/s up to more than 10(-5) m/s. The results should be regarded as confirmation of the crucial role of structure in determining the hydraulic conductivity of till. Grain sorting, and above all grain orientation, which in turn is connected to layering, lamination and fissility structures, are among the most important factors for determining hydraulic conductivity and anisotropy of till. There appears to be no relationship between the hydraulic conductivity and the parameters roughness, sphericity and mean grain size. In the same way the total porosity of the studied tills is more or less independent of the grain size but somewhat correlated to grain sorting.