Perforation strength of geosynthetics and sphericity of coarse grains: A new approach

Perforation of a geomembrane by the coarse grains in the drainage layer of a composite liner for a landfill would be a serious environmental problem. Therefore, the geomembrane is generally protected against perforation by a geotextile. Several laboratory tests already exist for designing the geotextile. Some of them use coarse grains as penetrators, others replace them by artificial geometrically defined penetrators. The first method has the disadvantage of not being reproducible while the second method lacks any correlation between the morphology of the 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 bluntness of the bumps on the stones. These measurements were made by analysing digitised pictures. A probability analysis using the Beta law has been used to define the angles and bluntness characterising a 'dangerous' stone and an 'average' stone. Then, steel penetrators were manufactured with these characteristics. Puncture tests have been run with these artificial penetrators to compare the efficiency of some protection geotextiles. Other tests using stones as penetrators have then been performed to verify the effectiveness of the simulation of the coarse grains. It seems that the correlation found is valid, but that another parameter, describing the more general form of the stone around the bump, is necessary to explain the differences in behaviour. (C) 1997 Elsevier Science Ltd.