Tanit Chalermyanont and Surapon Arrykul

pp. 313 - 323

Abstract

Sand is a pervious material in nature. Mixing sand with appropriate bentonite contents yields sandbentonite mixtures having low hydraulic conductivity that can be used as hydraulic containment liners. In
this study, compaction tests were conducted to determine the optimum water content and maximum dry unit
weight of compacted sand-bentonite mixtures. Direct shear and hydraulic conductivity tests were conducted
to assess the shear strength parameters and hydraulic conductivity of compacted sand-bentonite mixtures.
Test results indicate that hydraulic conductivity of mixtures decreases about four orders of magnitude when
mixed with 5% bentonite or more. Mixing sand with bentonite, however, results in a decreased shear strength
of the mixtures due to the swell of bentonite when soaked with water. For the mixtures with bentonite content
varying from 0 to 9%, the hydraulic conductivity of the mixtures decreases from 3.60×10^-5 to 4.13×10^-9 cm/s;
while the corresponding friction angle and swell ranges from 49 to 22 degrees and 0.85 to 10.32%, respectively. In addition, the compacted sand-bentonite mixture with 3% bentonite content could achieve low
hydraulic conductivity of 1×10^-7 cm/s which is a regular requirement for hydraulic containment liners, while
still having relatively high shear strength.

Keywords

• sand-bentonite mixture
• hydraulic conductivity
• liners