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.

Sediment Fabric and Anisotropy of Hydraulic Conductivity in Sandy Till, Wisconsin, U.S.A.

“…Haldorsen et al (1983) found that the hydraulic conductivity of some till units is controlled more by structural properties such as sorted sediment zones and fractures than by grain size distribution. Nyborg (1989Nyborg ( , 1990 measured the hydraulic conductivity of 35 oriented samples of till taken from a drumlin in western Sweden using a permeameter. He determined the hydraulic conductivity of small (about 300 cm3) samples and found a statistical association between grain orientation and hydraulic conductivity.…”

Subglacial deformation: evidence from microfabric studies of particles and voids in till from the upper Ürümqi river valley, Tien Shan, China

“…Hart, 1994; Benn, 1995; Hooke and Iverson, 1995; Truffer and others, 2000), and studies of till microfabric provide information about this process. Microfabrics defined by elongate clay and sand particles in tills have been studied by Harrison (1957), Gravenor and Meneley (1958), Ostry and Deane (1963), Evensen (1971), Kujansuu (1976), Johnson (1983) and Nyborg (1989), among others. In some studies, microfabrics have been used as indicators of subglacial deformation (Menzies and Maltman, 1992; Van der Meer, 1993; Menzies and others, 1997) or to differentiate till types (Van der Meer, 1990).…”