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Crushed aggregate-bentonite mixtures as backfill material for repositories of low- and intermediate-level radioactive wastes
48A 862072 Crushed aggregate-bentonite mixtures as backfill material for repositories of low- and intermediate-level radioactive wastes Holopainen, P Engng Geol V21, N3j4, June 1985. P239-245
862076 Experience from preparation and application of till/bentonite mixtures Pusch. R; Alstermark, G
Backfill materials consisting of three components, crushed rock aggregate,finely ground rock aggregate and bentonite, were studied. To determine the optimum percentages of the crushed and ground aggregate, a series of permeability tests were conducted. The mixture containing 29% of ground and 71% of crushed rock material was chosen as ballast material, its hydraulic conductivity being approximately O.OOOOlm/s.
Clay-based layers which serve to minimize infiltration of surface water into waste piles are a promising concept. since their hydraulic conductivity can be kept so low that the net effect of cyclic drying and wetting under Swedish climatic conditions will not lead to water penetration. Problems may arise, however, from physico/chemical processes as well as from swelling. as one example demonstrates.
862073 Effect of leaching on the integrity of a natural clay Yong, R N; Elmonayeri, D S; Chong, T S
862077 Water flow in a natural rock fracture as a function of stress and sample size Raven. K G; Gale, J E
Engng Geol V21, N3i4. June 1985, P377-382
Engng Geol V21, N3/4, June 1985, P279-299
Int J Rock Mech Min Sci V22, N4, Aug 1985, P251-261
Leaching can effect the strength of a natural clay substrate and lead to the failure of pond containment, especially if the clay material constitutes the liner system for the containment pond. The integrity of the clay in the face of five different types of leachates is studied by examining the creep characteristics of the clay. The resultant effects are evaluated in terms of (1) soil fabric/structure reinforcement or degradation, and/or (2) changes in the relationships established between soil particles and chemical pore fluid. The integrity of the clay is seen to be severely conditioned by factors producing the initial soil structure state, the chemistry of the leachate, local boundary conditions,and time.
The results of a laboratory study to evaluate the normal stresspermeability relation of natural fractures and how this relation is affected by changes in sample size and cyclic loading are reported. Five granite cores, each containing part of the same natural fracture, oriented perpendicular to the core axis, were tested. Fracture flow rate was found to decrease with increasing sample size and with each additional loading cycle. The data indicate that the smaller fracture surfaces may be characterized by a few asperities unevenly distributed over the sample, while the larger fracture surfaces may be typified by a greater number of more variable height asperities more evenly distributed over the sample.
862074 Physical and chemical behaviour of clay-based barriers under percolation with test liquids Simons, H; Reuter, E Engng Geol V21, N3/4. June 1985, P301-310
A research and development project is being carried out at the University of Braunschweig, West Germany, in which the permeability and durability of clayey liners for waste deposits are investigated. Results of long-term permeability tests with different aggressive test liquids are shown and sample behaviour is explained. The test liquids were analysed before and after percolation of the liner materials. Leaching or absorption effects can thus be recognized. After percolation, the liners are mineralogically investigated in order to obtain additional information on ion exchange processes, by comparison with water analyses, and on the long-term durability of the liner materials. The different analytical methods used are presented and important results are discussed.
862075 Some aspects of sandwiched soil cover design for toxic waste repositories Sailie, L Engng Geol V21. N3/4, June 1985, P321-326
Environmentalists favour ‘dry’ waste management systems in preference to the more common practice of shallow land burial. With the former, sandwiched soil covers are usually employed. A double barrier concept for the sandwiched construction, comprising of hydraulic and capillary barriers, is presented and discussed. The critical matrix potentials of the two barrier materials appear to have significant influence on the performance of the dual barrier system. 0
862078 Relationship of the degree of interconnection to permeability in fracture networks Long, J C S; Witherspoon, PA J Geophys Res V90, NB4, 10 March 1985, P3087-3097
Examination of how the degree of interconnection affects both magnitude and nature of fracture permeability. The effect of the degree of interconnection was investigated by numerically simulating flow in fracture networks where fracture size and density varied inversely, while the product of these two parameters was held fixed. Directional permeabilities of a number of such networks were determined, and the hydraulic behaviour of each fracture system was compared to that of an ideal porous medium. The permeability of the rock matrix between the fractures was assumed to be low enough to be negligible. Results show that as fracture length increases, the degree of interconnection increases. So, for a given fracture frequency as measured in a borehole, the permeability of the system increases as fracture length is increased. and density is proportionally decreased. 862079 Permeability of unconsolidated sands and porous rocks Gangi, A F J Geophys Res V90. NB4, IO March 1985, P3099-3104
Data from earlier work of Krumbien and Monk who derived an empirical relationship between the permeability of unconsolidated sand and mean and standard deviation of grain size has been re-analysed to express the permeability in terms of mean diameter. This is a more physical approach as the permeability depends upon the number of pores of particular sizes. It is expected that the pore size distribution function is more closely related to the grain size distribution function by number than to the grain size distribution function by weight. The results may be applied to porous rocks if Berg’s semi-
1986 Pergamon Press Ltd. Reproduction
not permitted
862076 Experience from preparation and application of till/bentonite mixtures Pusch. R; Alstermark, G
Backfill materials consisting of three components, crushed rock aggregate,finely ground rock aggregate and bentonite, were studied. To determine the optimum percentages of the crushed and ground aggregate, a series of permeability tests were conducted. The mixture containing 29% of ground and 71% of crushed rock material was chosen as ballast material, its hydraulic conductivity being approximately O.OOOOlm/s.
Clay-based layers which serve to minimize infiltration of surface water into waste piles are a promising concept. since their hydraulic conductivity can be kept so low that the net effect of cyclic drying and wetting under Swedish climatic conditions will not lead to water penetration. Problems may arise, however, from physico/chemical processes as well as from swelling. as one example demonstrates.
862073 Effect of leaching on the integrity of a natural clay Yong, R N; Elmonayeri, D S; Chong, T S
862077 Water flow in a natural rock fracture as a function of stress and sample size Raven. K G; Gale, J E
Engng Geol V21, N3i4. June 1985, P377-382
Engng Geol V21, N3/4, June 1985, P279-299
Int J Rock Mech Min Sci V22, N4, Aug 1985, P251-261
Leaching can effect the strength of a natural clay substrate and lead to the failure of pond containment, especially if the clay material constitutes the liner system for the containment pond. The integrity of the clay in the face of five different types of leachates is studied by examining the creep characteristics of the clay. The resultant effects are evaluated in terms of (1) soil fabric/structure reinforcement or degradation, and/or (2) changes in the relationships established between soil particles and chemical pore fluid. The integrity of the clay is seen to be severely conditioned by factors producing the initial soil structure state, the chemistry of the leachate, local boundary conditions,and time.
The results of a laboratory study to evaluate the normal stresspermeability relation of natural fractures and how this relation is affected by changes in sample size and cyclic loading are reported. Five granite cores, each containing part of the same natural fracture, oriented perpendicular to the core axis, were tested. Fracture flow rate was found to decrease with increasing sample size and with each additional loading cycle. The data indicate that the smaller fracture surfaces may be characterized by a few asperities unevenly distributed over the sample, while the larger fracture surfaces may be typified by a greater number of more variable height asperities more evenly distributed over the sample.
862074 Physical and chemical behaviour of clay-based barriers under percolation with test liquids Simons, H; Reuter, E Engng Geol V21, N3/4. June 1985, P301-310
A research and development project is being carried out at the University of Braunschweig, West Germany, in which the permeability and durability of clayey liners for waste deposits are investigated. Results of long-term permeability tests with different aggressive test liquids are shown and sample behaviour is explained. The test liquids were analysed before and after percolation of the liner materials. Leaching or absorption effects can thus be recognized. After percolation, the liners are mineralogically investigated in order to obtain additional information on ion exchange processes, by comparison with water analyses, and on the long-term durability of the liner materials. The different analytical methods used are presented and important results are discussed.
862075 Some aspects of sandwiched soil cover design for toxic waste repositories Sailie, L Engng Geol V21. N3/4, June 1985, P321-326
Environmentalists favour ‘dry’ waste management systems in preference to the more common practice of shallow land burial. With the former, sandwiched soil covers are usually employed. A double barrier concept for the sandwiched construction, comprising of hydraulic and capillary barriers, is presented and discussed. The critical matrix potentials of the two barrier materials appear to have significant influence on the performance of the dual barrier system. 0
862078 Relationship of the degree of interconnection to permeability in fracture networks Long, J C S; Witherspoon, PA J Geophys Res V90, NB4, 10 March 1985, P3087-3097
Examination of how the degree of interconnection affects both magnitude and nature of fracture permeability. The effect of the degree of interconnection was investigated by numerically simulating flow in fracture networks where fracture size and density varied inversely, while the product of these two parameters was held fixed. Directional permeabilities of a number of such networks were determined, and the hydraulic behaviour of each fracture system was compared to that of an ideal porous medium. The permeability of the rock matrix between the fractures was assumed to be low enough to be negligible. Results show that as fracture length increases, the degree of interconnection increases. So, for a given fracture frequency as measured in a borehole, the permeability of the system increases as fracture length is increased. and density is proportionally decreased. 862079 Permeability of unconsolidated sands and porous rocks Gangi, A F J Geophys Res V90. NB4, IO March 1985, P3099-3104
Data from earlier work of Krumbien and Monk who derived an empirical relationship between the permeability of unconsolidated sand and mean and standard deviation of grain size has been re-analysed to express the permeability in terms of mean diameter. This is a more physical approach as the permeability depends upon the number of pores of particular sizes. It is expected that the pore size distribution function is more closely related to the grain size distribution function by number than to the grain size distribution function by weight. The results may be applied to porous rocks if Berg’s semi-
1986 Pergamon Press Ltd. Reproduction
not permitted