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Prize protection
REINFORCEMENT:SOIL STABILISATION on the bearing capacity ratio. It was found that the beating capacity ratio of the sand-geogrid system decreased with an increase in foundation width. However, above a certain foundation width (130-140 mm) a practically constant value of bearing capacity ratio was observed. (Authors)
954198 Strip foundation on geogrid-reinforced clay: behavior under cyclic loading B. M. Das & E. C. Shin, Geotextiles & Geomembranes, 13(10), 1994, pp 657-667. Laboratory model tests to determine the permanent settlement of a surface strip foundation supported by geogddreinforced saturated clay and subjected to allow-frequency cyclic load are presented. In conducting the tests, the foundation was initially subjected to an allowable static load. The cyclic load was then super-imposed over the static load. The variation of the maximum permanent settlement with the intensity of the static load and the intensity of the amplitude of the cyclic load are also presented. (Authors)
954199 Field observations on the load-strain-time behaviour of geogrid reinforcement R. J. Fannin, Canadian Geotechnical Journal, 31(4), 1994, pp 564-569. Field data are reported that describe the load-strain-time relationship of geogrid reinforcement in a reinforced soil structure. The data are for a period exceeding 5 years and reveal a continued strain in the reinforcement, which occurs at nearly constant load. The response of loading is attributed to creep of the polymeric material. A comparison of the field data with laboratory isochronous load-strain curves, from rapid loading creep tests performed at a temperature similar to the mean annual temperature in the backfill soil, show that the curves describe very well the magnitude of creep strains observed in the field. Implications of the load-strain-time performance data are assessed with reference to the use in design of a tensile strength established from the rapid-loading creep test and wide-width strip test. The need to clarify, in design of polymeric reinforced soil structures, between a safe and allowable tensile strength is emphasized. (Author)
954200 Capped with confidence ANON, International Construction, 33(8), 1994, pp 30-33. The use of geosynthetics to cap an old landfill site, provide a base seal for a new extension site, and seal between the old and new site is described. The design had also to allow for safe leachate and gas removal. (J.M.McLaughlin)
954201 Prize protection P. Wheeler, Ground Engineering, 27(10), 1994, pp 24-25. In German landfill projects it is normal to spend more on the geomembrane protection layer than on the geomembrane itself. At Pohlsche Heide near Osnabruck a joint venture of contractors are preparing a 130 000 m 2 area for landfilling. The site is to be filled to a height up to 35 m over an anticipated period of 10-15 years, after which it will be capped and returned to woodland. The site is underlain by mudstone, which provides a natural geological boundary usually required for German landfill sites. The engineered aspect of the liner is formed by first recompacting the top 3m of the mudstone. Excavated mudstone is broken down by crushing and sorting before being placed in ten 300ram thick layers which are recompacted to give a minimum permeability of 1 x 10-Sm/s. Above this a 0.75m thick clay liner is placed in three passes of 250mm, compacted to produce a permeability of 1 x 10t°m/s. The barrier section of the base liner is completed by installing 3mm HDPE geomembrane over the
175A
clay. The protection component is a 2000g/m 3 HDPE needle punched geotextile placed directly on the liner, upon a 450ram thick leachate drainage blanket (8-32mm sized gravel). In normal landfill construction sand is spread out over the HDPE liner to minimise deformation and provide protection. The sand need only be 25ram thick, but this is usually unachievable on site and so a 150mm blanket is spread out. Depomat, a geotextile attached to a 25mm thick mesh of entangled lightweight convoluting monofilaments has now been developed. The mat is laid out on then liner and sand is dry blown into the filament mesh filling it. The 25ram layer is then covered with a polyethylene filter geotextile. The thickness of the convoluting fibre layer provides reliable protection against damage and deformation. (from Author)
954202 Stopping leaks with electronics ANON, International Construction, 33(8), 1994, pp 33-34. Presents a case history illustrating the application of electronic leak detection for geosynthetic linings. The example given is of a copper mine were geosythetic lined containment is used for process water and runoff. A twin layer flexible membrane with leak detection drainage layer between was installed. The conductive HDPE geomembrane used for both primary and secondary liners allowed 100% spark testing for leaks following installation. The spark testing procedure is outlined. (Authors)
954203 An experimental study of the performance of geosynthetic band drains Y. Wasti & T. Hergui, Geotextiles & Geomembranes, 13(10), 1994, pp 669-677. The performance of two basic types of geosynthetic bandshaped/strip drains - a composite drain (core surrounded by a geotextile filter) and a monolithic drain (without a geotextile filter) - has been compared by means of radial consolidation tests. Tests were repeated employing the monolithic drain wrapped in the same filter fabric as the composite drain, a cylindrical porous stone and a sand drain. The results were evaluated to compare the rate and amount of consolidation in each case and to assess the possible effect of clogging on the performance of geosynthetie drains. It was observed that the composite drain performed better than the monolithic drain, especially in the ease of finer soil. Wrapping the monolithic drain with the geotextile filter significantly increased its performance. (Authors)
Soil stabilisation 954204 Method of calculating pile fields and other vertically reinforced soil masses V. G. Fedorovskii & S. G. Bezvolev, Soil Mechanics & Foundation Engineering, 31(3), 1994, pp 94-101. A method is proposed for calculating the stabilization (reinforcement) of bases with layers of highly compressible soils by vertical strengthened elements in the form of ordinary bored, cast in-situ, or auger-injected piles, punch holes, granular drains, etc. Such reinforcement reduces several fold settlement and consolidation time of a weak base and also increases its resistance to horizontal (including dynamic) loads. The soil deformation model in the ARM93 program takes into account nonlinearity under compression and shear as well as dissipation of the initial excess pore pressures initiated by the placement of fill and other preliminary loads. The authors have developed 'COMPGEO', an applications program for solving the main geotechnical problems on a computer. The programs realize adequate nonlinear models
954198 Strip foundation on geogrid-reinforced clay: behavior under cyclic loading B. M. Das & E. C. Shin, Geotextiles & Geomembranes, 13(10), 1994, pp 657-667. Laboratory model tests to determine the permanent settlement of a surface strip foundation supported by geogddreinforced saturated clay and subjected to allow-frequency cyclic load are presented. In conducting the tests, the foundation was initially subjected to an allowable static load. The cyclic load was then super-imposed over the static load. The variation of the maximum permanent settlement with the intensity of the static load and the intensity of the amplitude of the cyclic load are also presented. (Authors)
954199 Field observations on the load-strain-time behaviour of geogrid reinforcement R. J. Fannin, Canadian Geotechnical Journal, 31(4), 1994, pp 564-569. Field data are reported that describe the load-strain-time relationship of geogrid reinforcement in a reinforced soil structure. The data are for a period exceeding 5 years and reveal a continued strain in the reinforcement, which occurs at nearly constant load. The response of loading is attributed to creep of the polymeric material. A comparison of the field data with laboratory isochronous load-strain curves, from rapid loading creep tests performed at a temperature similar to the mean annual temperature in the backfill soil, show that the curves describe very well the magnitude of creep strains observed in the field. Implications of the load-strain-time performance data are assessed with reference to the use in design of a tensile strength established from the rapid-loading creep test and wide-width strip test. The need to clarify, in design of polymeric reinforced soil structures, between a safe and allowable tensile strength is emphasized. (Author)
954200 Capped with confidence ANON, International Construction, 33(8), 1994, pp 30-33. The use of geosynthetics to cap an old landfill site, provide a base seal for a new extension site, and seal between the old and new site is described. The design had also to allow for safe leachate and gas removal. (J.M.McLaughlin)
954201 Prize protection P. Wheeler, Ground Engineering, 27(10), 1994, pp 24-25. In German landfill projects it is normal to spend more on the geomembrane protection layer than on the geomembrane itself. At Pohlsche Heide near Osnabruck a joint venture of contractors are preparing a 130 000 m 2 area for landfilling. The site is to be filled to a height up to 35 m over an anticipated period of 10-15 years, after which it will be capped and returned to woodland. The site is underlain by mudstone, which provides a natural geological boundary usually required for German landfill sites. The engineered aspect of the liner is formed by first recompacting the top 3m of the mudstone. Excavated mudstone is broken down by crushing and sorting before being placed in ten 300ram thick layers which are recompacted to give a minimum permeability of 1 x 10-Sm/s. Above this a 0.75m thick clay liner is placed in three passes of 250mm, compacted to produce a permeability of 1 x 10t°m/s. The barrier section of the base liner is completed by installing 3mm HDPE geomembrane over the
175A
clay. The protection component is a 2000g/m 3 HDPE needle punched geotextile placed directly on the liner, upon a 450ram thick leachate drainage blanket (8-32mm sized gravel). In normal landfill construction sand is spread out over the HDPE liner to minimise deformation and provide protection. The sand need only be 25ram thick, but this is usually unachievable on site and so a 150mm blanket is spread out. Depomat, a geotextile attached to a 25mm thick mesh of entangled lightweight convoluting monofilaments has now been developed. The mat is laid out on then liner and sand is dry blown into the filament mesh filling it. The 25ram layer is then covered with a polyethylene filter geotextile. The thickness of the convoluting fibre layer provides reliable protection against damage and deformation. (from Author)
954202 Stopping leaks with electronics ANON, International Construction, 33(8), 1994, pp 33-34. Presents a case history illustrating the application of electronic leak detection for geosynthetic linings. The example given is of a copper mine were geosythetic lined containment is used for process water and runoff. A twin layer flexible membrane with leak detection drainage layer between was installed. The conductive HDPE geomembrane used for both primary and secondary liners allowed 100% spark testing for leaks following installation. The spark testing procedure is outlined. (Authors)
954203 An experimental study of the performance of geosynthetic band drains Y. Wasti & T. Hergui, Geotextiles & Geomembranes, 13(10), 1994, pp 669-677. The performance of two basic types of geosynthetic bandshaped/strip drains - a composite drain (core surrounded by a geotextile filter) and a monolithic drain (without a geotextile filter) - has been compared by means of radial consolidation tests. Tests were repeated employing the monolithic drain wrapped in the same filter fabric as the composite drain, a cylindrical porous stone and a sand drain. The results were evaluated to compare the rate and amount of consolidation in each case and to assess the possible effect of clogging on the performance of geosynthetie drains. It was observed that the composite drain performed better than the monolithic drain, especially in the ease of finer soil. Wrapping the monolithic drain with the geotextile filter significantly increased its performance. (Authors)
Soil stabilisation 954204 Method of calculating pile fields and other vertically reinforced soil masses V. G. Fedorovskii & S. G. Bezvolev, Soil Mechanics & Foundation Engineering, 31(3), 1994, pp 94-101. A method is proposed for calculating the stabilization (reinforcement) of bases with layers of highly compressible soils by vertical strengthened elements in the form of ordinary bored, cast in-situ, or auger-injected piles, punch holes, granular drains, etc. Such reinforcement reduces several fold settlement and consolidation time of a weak base and also increases its resistance to horizontal (including dynamic) loads. The soil deformation model in the ARM93 program takes into account nonlinearity under compression and shear as well as dissipation of the initial excess pore pressures initiated by the placement of fill and other preliminary loads. The authors have developed 'COMPGEO', an applications program for solving the main geotechnical problems on a computer. The programs realize adequate nonlinear models