PERFORATION STRENGTH OF GEOSYNTHETICS AND SPHERICITY OF COARSE GRAINS- A NEW APPROACH

Perforation of a geomembrane by the coarse grains in the drainage laye r of a composite liner for a landfill would be a serious environmental problem. Therefore, the geomembrane is generally protected against pe rforation by a geotextile. Several laboratory tests already exist for designing the geotextile. Some of them use coarse grains as penetrator s, others replace them by artificial geometrically defined penetrators . The first method has the disadvantage of not being reproducible whil e the second method lacks any correlation between the morphology of th e stones and the form of the penetrators. A method of correlating the form of the penetrators with that of the stones has been established ( Antoine, 1995). It is based on the measurement of the angularity and b luntness of the bumps on the stones. These measurements were made by a nalysing digitised pictures. A probability analysis using the Beta law has been used to define the angles and bluntness characterising a 'da ngerous' stone and an 'average' stone. Then, steel penetrators were ma nufactured with these characteristics. Puncture tests have been run wi th these artificial penetrators to compare the efficiency of some prot ection geotextiles. Other tests using stones as penetrators have then been performed to verify the effectiveness of the simulation of the co arse grains. It seems that the correlation found is valid, but that an other parameter, describing the more general form of the stone around the bump, is necessary to explain the differences in behaviour. (C) 19 97 Elsevier Science Ltd.