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Geotechnical investigation for Katse dam, Lesotho
117A
Surface Structures Geological factors of importance in surface structures See also: 932022, 932085 932352 Foundation design in karst terrain Destephen, R A; Wargo, R H Bull Assoc Engng Geol V29, N2, June 1992, P165-173 Karst terrains have highly variable rock surfaces, highly degraded zones, and solution cavities. Differential settlement and sudden or ongoing subsidence are possible. Even the most thorough site investigation may not reveal all the potential hazards. Where major construction is proposed on karst, risks of future subsidence should be defined so the acceptable risk level can be decided upon. Geologic and site development risk factors can be used to provide a qualitative risk assessment and different design alternatives considered. 932353 Geology of dam spillways Woodward, R C Engng Geol V32, N4, July 1992, P243-254 Most major dam projects include some type of spillway. The overall economics and layout of a project can be affected by the extent to which it is necessary to provide concrete lining and energy dissipating structures in the spillway and whether spillway construction spoil can be used as structural rockfill. Good quality rock requiring no lining is likely to be suitable for rockfill, poor quality rock will not. The decision to omit the concrete lining and energy dissipating structures should only be taken after detailed assessment of site geology, the possible erosion mechanisms, severity of discharge conditions, and operational characteristics of the spillway. 932354 Problems in highway construction in Magnesian Limestone Buist, D S; Ineson, P R Highways Transp V39, N4, April 1992, P23-26 Engineering projects in Magnesian limestone may encounter joints, fissures, or gulls whose nature and extent cannot always be identified during site investigation. This can lead to slope instability or loss of integrity of the carriageway. Such occurrences during construction of the A617 Pleasley Bypass in Derbyshire are described. Cut slope angles were selected on the basis of RQD, but with special attention where open fissures or gulls were found. Carriageway fissures were filled or capped with concrete slabs, gulls were excavated and their loose fills replaced with compacted subbase. 932355 Engineering geology and its applications to the selection of sanitary waste sites on the Witwatersrand, South Africa Warwick, D W; Geldenhuis, S J J Proc 6th International Congress International Association of Engineering Geology, Amsterdam, 6-10 August 1990, Symposia P175-181. Publ Rotterdam: A A Balkema, 1990 Procedures leading to the establishment of two waste sites are described. The Witwatersrand is underlain in much of the southern part by Malmani dolomite, and thus the sites were chosen where this rock was covered by dolerite sills. Drilling
and packer tests were required to demonstrate the dolerite was sufficiently impermeable to prevent leachate pollution of the groundwater reservoir in the dolomite. As well as fulfilling customary environmental requirements, it was necessary to prove the reserves of on-site cover soil and to provide operating plans. 932356 Appropriate waste disposal and evaluation of colatamin!ted sites. Some keys to managed protection of groundwater and land Knight, M J Proc 6th International Congress International Association of Engineering Geology Amsterdam, 6-10 August 1990, Symposia P325-335. Publ Rotterdam: A A Balkema, 1990 Landfill disposal rationale is summarized and several case studies presented to illustrate important points. A tabular above-ground design was used to stabilise domestic solid waste landfill involving aerobic free-leaching processes. Recycling of stabilised leachate was considered advantageous. Fluoride bearing aluminium waste, premixed with gypsum to reduce activity and minimise leachate production, was successfully disposed in deeply weathered, clay-rich strata, without groundwater contamination. The principles involved in evaluation of contaminated sites prior to remedial work are discussed. 932357 Geoteclmical investigation for Katse dam, Leeotho Brackley, I J A; Wallace, S; GaUiers, R M; Lephoma, M Proc Tenth Regional Conferencefor Africa on Soil Mec&mics and Foundation Engineering and the Third International Conference on Tropical and Residual Soils, Museru, 23-27 September 1991 V1, P331-342. Publ Rotterdam: A A Balkema, 1991 A 180m high double arch dam on the Malibamatso River is part of the Lesotho Highlands Scheme. It is founded on horizontal basalt flows of thickness 0.3-45m. The rock is strong, of low compressibility and with welded flow contacts. Some geological anomalies however exist: a continuous horizontal fracture in the thickest flow with implications for abutment stability, large stress relief joints parallel to the river valley, and weak autobrecciated layers below the foundation elevation of the dam. The basalt often contains large amounts of clay minerals, which may affect its durability.
Base courses
and pavements
See also: 932088 932358 Review of two European design methods for geotextile reinforced unpaved roads Little, P H Highways Transp V39, N8, Aug 1992, P19-22 Geotextile reinforced unpaved roads have been designed on a range of bases from empirical to numerical analysis. Two design approaches are critically examined. The main method used in the UK is based on the membrane effect. This approach has shortcomings when trying to predict effect of reinforcement at low rut depth. The Dutch design method is essentially that of strain compatibility between the aggregate layer and the gcotcxtile, with tensile forces generated in the gcotcxtile which restrain deformation of the aggregate.
© 1993 Pergamon Press Ltd. Reproduction not permitted
Surface Structures Geological factors of importance in surface structures See also: 932022, 932085 932352 Foundation design in karst terrain Destephen, R A; Wargo, R H Bull Assoc Engng Geol V29, N2, June 1992, P165-173 Karst terrains have highly variable rock surfaces, highly degraded zones, and solution cavities. Differential settlement and sudden or ongoing subsidence are possible. Even the most thorough site investigation may not reveal all the potential hazards. Where major construction is proposed on karst, risks of future subsidence should be defined so the acceptable risk level can be decided upon. Geologic and site development risk factors can be used to provide a qualitative risk assessment and different design alternatives considered. 932353 Geology of dam spillways Woodward, R C Engng Geol V32, N4, July 1992, P243-254 Most major dam projects include some type of spillway. The overall economics and layout of a project can be affected by the extent to which it is necessary to provide concrete lining and energy dissipating structures in the spillway and whether spillway construction spoil can be used as structural rockfill. Good quality rock requiring no lining is likely to be suitable for rockfill, poor quality rock will not. The decision to omit the concrete lining and energy dissipating structures should only be taken after detailed assessment of site geology, the possible erosion mechanisms, severity of discharge conditions, and operational characteristics of the spillway. 932354 Problems in highway construction in Magnesian Limestone Buist, D S; Ineson, P R Highways Transp V39, N4, April 1992, P23-26 Engineering projects in Magnesian limestone may encounter joints, fissures, or gulls whose nature and extent cannot always be identified during site investigation. This can lead to slope instability or loss of integrity of the carriageway. Such occurrences during construction of the A617 Pleasley Bypass in Derbyshire are described. Cut slope angles were selected on the basis of RQD, but with special attention where open fissures or gulls were found. Carriageway fissures were filled or capped with concrete slabs, gulls were excavated and their loose fills replaced with compacted subbase. 932355 Engineering geology and its applications to the selection of sanitary waste sites on the Witwatersrand, South Africa Warwick, D W; Geldenhuis, S J J Proc 6th International Congress International Association of Engineering Geology, Amsterdam, 6-10 August 1990, Symposia P175-181. Publ Rotterdam: A A Balkema, 1990 Procedures leading to the establishment of two waste sites are described. The Witwatersrand is underlain in much of the southern part by Malmani dolomite, and thus the sites were chosen where this rock was covered by dolerite sills. Drilling
and packer tests were required to demonstrate the dolerite was sufficiently impermeable to prevent leachate pollution of the groundwater reservoir in the dolomite. As well as fulfilling customary environmental requirements, it was necessary to prove the reserves of on-site cover soil and to provide operating plans. 932356 Appropriate waste disposal and evaluation of colatamin!ted sites. Some keys to managed protection of groundwater and land Knight, M J Proc 6th International Congress International Association of Engineering Geology Amsterdam, 6-10 August 1990, Symposia P325-335. Publ Rotterdam: A A Balkema, 1990 Landfill disposal rationale is summarized and several case studies presented to illustrate important points. A tabular above-ground design was used to stabilise domestic solid waste landfill involving aerobic free-leaching processes. Recycling of stabilised leachate was considered advantageous. Fluoride bearing aluminium waste, premixed with gypsum to reduce activity and minimise leachate production, was successfully disposed in deeply weathered, clay-rich strata, without groundwater contamination. The principles involved in evaluation of contaminated sites prior to remedial work are discussed. 932357 Geoteclmical investigation for Katse dam, Leeotho Brackley, I J A; Wallace, S; GaUiers, R M; Lephoma, M Proc Tenth Regional Conferencefor Africa on Soil Mec&mics and Foundation Engineering and the Third International Conference on Tropical and Residual Soils, Museru, 23-27 September 1991 V1, P331-342. Publ Rotterdam: A A Balkema, 1991 A 180m high double arch dam on the Malibamatso River is part of the Lesotho Highlands Scheme. It is founded on horizontal basalt flows of thickness 0.3-45m. The rock is strong, of low compressibility and with welded flow contacts. Some geological anomalies however exist: a continuous horizontal fracture in the thickest flow with implications for abutment stability, large stress relief joints parallel to the river valley, and weak autobrecciated layers below the foundation elevation of the dam. The basalt often contains large amounts of clay minerals, which may affect its durability.
Base courses
and pavements
See also: 932088 932358 Review of two European design methods for geotextile reinforced unpaved roads Little, P H Highways Transp V39, N8, Aug 1992, P19-22 Geotextile reinforced unpaved roads have been designed on a range of bases from empirical to numerical analysis. Two design approaches are critically examined. The main method used in the UK is based on the membrane effect. This approach has shortcomings when trying to predict effect of reinforcement at low rut depth. The Dutch design method is essentially that of strain compatibility between the aggregate layer and the gcotcxtile, with tensile forces generated in the gcotcxtile which restrain deformation of the aggregate.
© 1993 Pergamon Press Ltd. Reproduction not permitted