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Abstract:
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The present study aimed at critically looking at the current practice of the
installation of compacted clay liner using bentonite enhanced sand (BES).
The application of bentonite is currently the most accepted practice for
lining purposes. The ideal bentonite sand combination, which satisfies the liner
requirements is 20% bentonite and 80% sand, was selected as one of the liner
materials for the investigation of development of desiccation cracks. Locally
available sundried marine clay and its combination with bentonite were also
included in the study. The desiccation tests on liner materials were conducted for
wet/dry cycles to simulate the seasonal variations. Digital image processing
techniques were used to measure the crack intensity factor (CIF), a
useful and effective parameter for quantification of desiccation cracking.
The repeatability of the tests could be well established, as the variation in CIF values
of identical samples had a very narrow range of 0 to 2%. The studies on the
development of desiccation cracks showed that the CIF of bentonite enhanced
sand mixture (BES) was 18.09%, 39.75% and 21.22% for the
first, second and third cycles respectively, while it was only 9.83%, 7.52% and
4.58% respectively for sun dried marine clay (SMC). Thus the locally available,
alternate liner material suggested, viz SMC, is far superior to BES, when
subjected to alternate wet/dry cycles. Further, the improvement of these liner materials when amended with randomly distributed fibre reinforcements was also investigated. Three types of
fibres ,namely nylon fibre, polypropylene monofilament and polypropylene fibre
mesh were used for the study of fibre amended BES and SMC.The influence of
these amendments on the properties of the above liner materials is also studied.
The results showed that there is definite improvement in the properties of the liner
materials when it is reinforced with discrete random fibres. The study also proved
that the desiccation cracks could be controlled with the help of fibre
reinforcement. |