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Investigation of the relation between fissure flow and degree of contact area by an electric analogue model
IIA 861078 Effect of electrolyte solutions on the unsaturated hydraulic conductivity of a sodic clay soil Scotter, D R Aust J Soil Res V23, N2, 1985, P301-307 The effect of infiltrating gypsum or sodium chloride solutions or distilled water on the hydraulic conductivity of a heavy clay at matrix potentials -0.5 to -8kPa has been examined. Percolation with gypsum solution led to a fourfold increase in conductivity relative to distilled water. Substituting sodium chloride solution did not change the enhanced conductivity but replacing either of the salt solutions with distilled water caused conductivity to fall, although not to its initial level. Mechanisms for the conductivity changes are discussed.
861079 Hydraulic conductivity of natural clays permeated with simple liquid hydrocarbons Fernandez, F; Quigley, R M Can Geotech J I:22, N2, May 1985, P205-214 Clay or clayey soil barriers are increasingly used for waste impoundment. Their hydraulic conductivity (k) is influenced by the physicochemical properties of the permeating fluid. Laboratory tests on a natural soil compacted and permeated with pure hydrocarbons showed a wide range of values of k. For water wetted soil samples, k did not increase for simple water-insoluble aromatics (benzene, xylene, cyclohexane), but for water soluble alcohols there was a 10 fold increase. Sequential permeation of water wetted samples by alcohols then simple aromatics gave values of k with a 1000 fold increase over the alcohol value. Attempts are made to explain these phenomena by considering the size of the clay-permeant double layer and its effect on micro- and macro-porosity.
861080 Internal stability of granular filters Kenney, T C; Lau, D Can Geotech J V22, N2, May 1985, P215-225 A granular material exhibits lack of internal stability when it cannot prevent loss of its own small particles due to disturbing forces such as seepage or vibration. Factors affecting seepage loss of small particles from a cohesionlcss granular filter include the density of the compacted material, particle size distribution and the severity of the disturbing forces. Results are presented for seepage tests on a number of stable and unstable materials. A method for evaluating the potential for grading instability, based on the shape of the grain size distribution curve, has been proposed from analysis of test results. It is, however, suggested that laboratory evaluation of filter materials is still desirable.
861081 Osmosis: a cause of apparent deviations from Darcy's law. Note Olscn, H W Can Geotech J V22, N2, May 1985, P238-241 Previous examples of non-Darcy flow behaviour in soils are reexamined. This review of the existing evidence shows that osmosis can cause intercepts in the flow rate-hydraulic gradient relationships which are consistent with observed deviations from Darcy's law at very low gradients. It is suggested that the natural cause of osmosis in the laboratory samples could be chemical reactions such as those involved in ageing effects. It is still necessary to establish whether geochemical causes of osmosis in nature are rare, or regular but unrecognised.
861082 Hydraulic conductivity of two prototype clay liners Day, S R; Daniel, D E J Geotech Engng Div ASCE Vl11, N8, Aug 1985, P957-970 Prototype clay liners were constructed from clays of high and low plasticity. Hydraulic conductivity (k) was determined by ponding the liners and measuring the seepage rate. Field permeability tests were also made using ring infiltrometers. Hydraulic conductivity was measured in the laboratory on laboratory compacted samples and on undisturbed samples taken from the liners. Laboratory k values were approximately 1000 times less than field measurements. Ring infiltrometer tests gave scattered k values, but their average was close to the overall field measurement. It is concluded that laboratory tests do not use a volume large enough to be representative of the whole material, that is they do not contain the largest pores located between clods of clay or in tiny cracks or zones of poor compaction.
861083 Investigation of the relation between fissure flow and degree of contact area by an electric analogue model Tselentis, G A J Hydrol V78, N3/4, June 1985, P325-330 Hydraulic properties of fissured rocks will change under conditions of increasing effective stress and thus increasing rockrock contact area. Using a simple electric analogue model, where electrically conductive paper represents a fissure and holes cut therein represent contact areas, the above relationship has been examined. Fissure discharge was seen to decrease with increasing contact area and to be dependent upon the way in which the contact area is distributed.
861084 Scaling the exponential soil-water diffusivity for soils from Ghana Laryea, K B; Abenney-Mickson, S J Hydrol V79, NI/2, 10 July 1985, P95-106 Horizontal infiltration experiments were carried out on six tropical soils from the savannah and forest regions of Ghana. Soil-water diffusivities were calculated according to Bruce and Klute (1956) then fitted with an exponential regression equation to determine the values of the 'universal' constants proposed by Reichardt et al (1972), Miller and Bresler (1977) and Brutsaert (1970). Values of these constants did not agree with those suggested by Brutsaert and Reichardt, thus negating the universality concept proposed by these authors.
861085 Investigation of the permeability behaviour of rock of varying strength by means of packer tests (In German) Heitfcld, K H; Krapp, L Proc 6th National Rock Mechanics Symposium, Aachen, 3-4 April 1985 P45-54. Publ Essen: German Society.for Soil Mechanics and Foundation Engineering, 1985 Many improvements have been made in the acquisition and interpretation of data from packer tests to determine the permeability of rock masses. Problems arise with rocks of variable strength. Weak rocks crack at low pressure and material is eroded from seepage channels. These problems are illustrated and discussed with reference to marly Neogenc rocks at a Cretan dam site.
861079 Hydraulic conductivity of natural clays permeated with simple liquid hydrocarbons Fernandez, F; Quigley, R M Can Geotech J I:22, N2, May 1985, P205-214 Clay or clayey soil barriers are increasingly used for waste impoundment. Their hydraulic conductivity (k) is influenced by the physicochemical properties of the permeating fluid. Laboratory tests on a natural soil compacted and permeated with pure hydrocarbons showed a wide range of values of k. For water wetted soil samples, k did not increase for simple water-insoluble aromatics (benzene, xylene, cyclohexane), but for water soluble alcohols there was a 10 fold increase. Sequential permeation of water wetted samples by alcohols then simple aromatics gave values of k with a 1000 fold increase over the alcohol value. Attempts are made to explain these phenomena by considering the size of the clay-permeant double layer and its effect on micro- and macro-porosity.
861080 Internal stability of granular filters Kenney, T C; Lau, D Can Geotech J V22, N2, May 1985, P215-225 A granular material exhibits lack of internal stability when it cannot prevent loss of its own small particles due to disturbing forces such as seepage or vibration. Factors affecting seepage loss of small particles from a cohesionlcss granular filter include the density of the compacted material, particle size distribution and the severity of the disturbing forces. Results are presented for seepage tests on a number of stable and unstable materials. A method for evaluating the potential for grading instability, based on the shape of the grain size distribution curve, has been proposed from analysis of test results. It is, however, suggested that laboratory evaluation of filter materials is still desirable.
861081 Osmosis: a cause of apparent deviations from Darcy's law. Note Olscn, H W Can Geotech J V22, N2, May 1985, P238-241 Previous examples of non-Darcy flow behaviour in soils are reexamined. This review of the existing evidence shows that osmosis can cause intercepts in the flow rate-hydraulic gradient relationships which are consistent with observed deviations from Darcy's law at very low gradients. It is suggested that the natural cause of osmosis in the laboratory samples could be chemical reactions such as those involved in ageing effects. It is still necessary to establish whether geochemical causes of osmosis in nature are rare, or regular but unrecognised.
861082 Hydraulic conductivity of two prototype clay liners Day, S R; Daniel, D E J Geotech Engng Div ASCE Vl11, N8, Aug 1985, P957-970 Prototype clay liners were constructed from clays of high and low plasticity. Hydraulic conductivity (k) was determined by ponding the liners and measuring the seepage rate. Field permeability tests were also made using ring infiltrometers. Hydraulic conductivity was measured in the laboratory on laboratory compacted samples and on undisturbed samples taken from the liners. Laboratory k values were approximately 1000 times less than field measurements. Ring infiltrometer tests gave scattered k values, but their average was close to the overall field measurement. It is concluded that laboratory tests do not use a volume large enough to be representative of the whole material, that is they do not contain the largest pores located between clods of clay or in tiny cracks or zones of poor compaction.
861083 Investigation of the relation between fissure flow and degree of contact area by an electric analogue model Tselentis, G A J Hydrol V78, N3/4, June 1985, P325-330 Hydraulic properties of fissured rocks will change under conditions of increasing effective stress and thus increasing rockrock contact area. Using a simple electric analogue model, where electrically conductive paper represents a fissure and holes cut therein represent contact areas, the above relationship has been examined. Fissure discharge was seen to decrease with increasing contact area and to be dependent upon the way in which the contact area is distributed.
861084 Scaling the exponential soil-water diffusivity for soils from Ghana Laryea, K B; Abenney-Mickson, S J Hydrol V79, NI/2, 10 July 1985, P95-106 Horizontal infiltration experiments were carried out on six tropical soils from the savannah and forest regions of Ghana. Soil-water diffusivities were calculated according to Bruce and Klute (1956) then fitted with an exponential regression equation to determine the values of the 'universal' constants proposed by Reichardt et al (1972), Miller and Bresler (1977) and Brutsaert (1970). Values of these constants did not agree with those suggested by Brutsaert and Reichardt, thus negating the universality concept proposed by these authors.
861085 Investigation of the permeability behaviour of rock of varying strength by means of packer tests (In German) Heitfcld, K H; Krapp, L Proc 6th National Rock Mechanics Symposium, Aachen, 3-4 April 1985 P45-54. Publ Essen: German Society.for Soil Mechanics and Foundation Engineering, 1985 Many improvements have been made in the acquisition and interpretation of data from packer tests to determine the permeability of rock masses. Problems arise with rocks of variable strength. Weak rocks crack at low pressure and material is eroded from seepage channels. These problems are illustrated and discussed with reference to marly Neogenc rocks at a Cretan dam site.