| Summary: | 碩士 === 國立臺灣大學 === 環境工程研究所 === 84 === Because of its low permeability, compacted clay is often used
as liners in landfills. Under certain conditions clays may be
subject to organic contamination, resulting in the change in
hydraulic conductivity. This study tries to explore the
dissolution of kaolinite in the presence of oxalic acid in
terms of hydraulic conductivity of compacted kaolinite and
bentonite-field soil mixtures. Compaction test was performed by
the standard Proctor methods, and flexible-wall permeameter was
used. Specimens werefirst permeated with 0.01 N CaCl2 until a
stable hydraulic conductivity was observed and the oxalic acid
was then introduced. Batch dissolution results show that both
increasing surface protonation and decreasing surface
protonation enhance thedissolution rate, and the dissolution
rate was affected by the concentration of oxalic acid.
Furthermore, the dissolution of kaolinite is surface
controlled. Permeability test results show that in the
kaolinite and bentonite-field soil mixtures systems, with the
introduction of oxalic acid, hydraulic conductivities slightly
decrease. The decrease is attributed to the dissolution of
clods, which in turn clogged the soil pores and reduced the
hydraulic conductivity. With the ratio of bentonite to field
soil 12 %, the hydraulic conductivity is close to 10-8 cm/sec.
In the mixtures, field soil forms the load-supporting framework
and bentonite acts as a seepage barrier, and the mixture was
not influenced by permeating with oxalic acid.
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