| Summary: | 碩士 === 國立臺灣大學 === 農業工程學系 === 82 === Because of low permeability, clays are often used as liners or
barriers to prevent pollutants from getting into the nature.
However, after contaminated by organic fluid, permeabilities of
the clays may be changed. In this study, methanol and ethanol
with different concentrations were used as permeant, and sand-
bentonite mixture which was well compacted was the soil used in
the permeability test. Effect of the ratio of bentonite to sand
by mass weight in the mixture on permeability was also studied.
Permeability tests were conducted using a set of automatic
triaxial flexible wall permeameter to avoid side leakage. Test
results show that the permeabilities of the soils using any
concentrations of methanol and ethanol as permeants are
even lower than those using water as the permeant. When the
concentrations of methanol and ethanol are from 40% to 70%, the
permeabilities had a minimum value. When the ratio of bentonite
to sand (B/S) is as low as 10%, and the mixtures are well mixed
and well compacted, the soils are at the optimum conditions in
view of the permeability. Under this condition, the whole sys-
tem is mainly supported by the sand particles. Therefore, the
stability of the system may be insured and the shrinkage of the
system may be effectively controlled. After analyses of
economic efficiency and marginal benefit, it is found that
sand-bentonite mixtures are better than kaolinite when cost
and economic effects are considered. Besides, correlations
between permeability and viscosity, dielectric constant of
the fluid, void ratio of the mixture and B/S, were derived.
Its coefficient of determination is found to be as high as
0.943.
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