A Model for the Relationship between the Hydraulic Conductivity and Primary Sedimentary Structures of Till

Abstract

An investigation has been made of the relationships between saturated hydraulic conductivity, porosity and micro-structure of undisturbed lodgement till samples. 35 measurements with a constant head laboratory permeameter are the basis for the discussion. All the measurements were made on undisturbed till samples. In order to minimize the effects of soil forming processes and to have the most homogeneous conditions all sampling were made from the C-horizon. The samples have a size of about 300 cm3. Porosity data were derived from capillary pressure curves. A model for how flow direction and long-axis orientations of elongated grains relate to the saturated hydraulic conductivity is presented. For an unsorted sediment such factors as grain size are concluded to be of minor importance for the hydraulic conductivity. The structural properties seem to be a more important factor. This effect can be explained in two ways. Either due to directional relations between sorted lenses and bands which have higher permeability and the flow route through the sample. The other explanation is due to a more continuous pore pattern parallel to the grain orientation. The hydraulic conductivity takes on a directional property, being smaller in directions normal to the structural long-axis orientation than in directions parallel to the orientation. A study of the effective porosity Versus hydraulic conductivity exhibits weak correlation.