Hydraulic conductivity of bentonite-sand mixtures

The use of bentonite alone or amended with natural soils for construction o f liners for water-retention and waste-containment facilities is very commo n. The importance of bentonite content in reducing the hydraulic conductivi ty of liners is well recognised. The study illustrates the role of the size of the coarser fraction in controlling the hydraulic conductivity of the c lay liner. It has been shown that at low bentonite contents the hydraulic c onductivity of the liner varies depending on the size of the coarser fracti on apart from clay content. At a given clay content, the hydraulic conducti vity increases with an increase in the size of the coarser fraction. But wh en the clay content is more than that which can be accommodated within the voids of the coarser fractions, the hydraulic conductivity is controlled pr imarily by clay content alone. Four different methods of predicting hydraul ic conductivity of the liners are presented. Using two constants, related t o the liquid limit, the hydraulic conductivity can be predicted at any void ratio.