Abstract:
The main task of clay liners in landfills is to mitigate the migration of
pollutants to the groundwater sources. Leachate includes different types of
inorganic and organic compounds which affect physical, index properties of
clay liners that can affect the long-term performance of these clay liners as a
barrier. The CaCl2 solution exerts the strongest effect on clay liner materials
than any other chemicals in leachate. The objective of this study was to
evaluate the effect of inorganic salt CaCl2 on some physical, index properties
of expansive soil (Soil M) obtained from Moragahakanda area. Also, the
effect of CaCl2 on Soil M amended by 5% (Soil M+5%) and 10%
(Soil M+10%) bentonite, on selected physical, index properties was
investigated. The effect on physical, index properties was investigated by
carrying out Atterberg Limits Tests, Modified Free Swell Index, Specific
Gravity, Shrinkage Limit and Mechanical Analysis before and after samples
consolidated under pressures of 50, 100, and 200 kPa were subjected to the
permeation of 1M CaCl2 solution under gradually increasing constant head
of 50, 100 and 150 kPa, up to replacement of their void volumes by as much
as 20 times to simulate long-term contact. After long-term contact of
consolidated soil samples with CaCl2 solution, the Liquid Limit value of Soil
M, Soil M+5% and Soil M+10% was found to be decreased by 22%, 19%
and 31% respectively, but only the Plastic - value of Soil M+10% was
increased by 12% points. Although LL and PI values were reduced after
contact with CaCl2 solution, the soil classification of Soil M (CH) and Soil
M+5% (CH) did not change. However, Soil M+10% was reclassified from
Clay of Very High Plasticity (CV) to Clay of High Plasticity (CH). These
test results indicated that CaCl2 salt affected the plasticity of all candidate
soils even up to the extent of changing the soil classification for the
expansive soil amended by 10% bentonite.
