Geotechnical Properties of Sand-Bentonite Liner Material Permeated with Calcium Chloride Solution

Abstract

AbstractSand-bentonite mixture is conventionally used as the liner material for waste disposal facilities. Depending upon the nature of waste, a host of chemicals is generated as leachate. The present study focuses on the effect of CaCl2 solutions on an optimised sand-bentonite mixture, which simulates the effect of leachates on geotechnical characteristics of sand-bentonite liner material. The selection of CaCl2 solution as a permeating liquid for sand-bentonite mixture is based on the abundant ions in leachate and by referring works of previous researchers. Sand-bentonite mixtures compacted at OMC and MDD are permeated with 0.1, 0.3 and 0.6 M of solutions of CaCl2 for 7, 14 and 21 days. The geotechnical properties of optimised sand-bentonite mixture permeated with distilled water and 0.1, 0.3 and 0.6 M of solutions of CaCl2 were evaluated. It is observed that liquid limit and plasticity index decrease with increasing permeating time and concentration of chemical. Coefficient of consolidation increases with increasing concentration of solution and permeating time. However, the unconfined compressive strength of the sample decrease with increase in the concentration of chemical and permeating time. Similarly, swelling index is found to be decreased with increasing permeating time and concentration of CaCl2 solution. XRD is performed to identify the composition of the sand-bentonite mixture. The observed chemical changes are correlated to engineering behaviour. The engineering properties of sand-bentonite liner material permeated through CaCl2 solutions of different on centration is attributed to the changes in thickness of diffused double layer due to permeation of the CaCl2 solution.KeywordsCompacted clay linerHigh concentration chemical solutionsGeotechnical properties