Abstract
In order to evaluate the shear strength parameters of an anionic polymer-added bentonite-sand mixture that was permeated with tap water, Proctor compaction tests and direct shear tests were performed on the mixture with a bentonite content of 15% by mass. The polymer content in the polymer-bentonite mixture was chosen as 0.5, 1, 2, 5, 10, 15 and 20% by mass, respectively. According to the results, maximum dry unit weight (Vdmax) first decreased as the polymer content was increased to 1% and then, increased. Vdmax of 20% polymer-added mixture and the mixture without polymer addition was measured as 17.55 and 17.28 kN/m3, respectively. Test results indicated that cohesion (c) increased and internal friction angle (ø) decreased due to polymer addition. 2% polymer addition caused an increase of 42 kPa in c but a decrease of 4.2° in ø. As the polymer content increased, maximum shear strength of the mixture (τmax) increased. τmax increased from 171.8 to 197.8 kPa as the polymer content was increased from 0 to 2%. As a result, 2% anionic polymer-added bentonite-sand mixture provided sufficient increase in the shear strength of the mixture.
Highlights
Bentonite-sand mixtures are preferred to be used as barriers in waste containment areas by minimizing leachate advection through the ground soil layers
They added a copolymer with a content of 0.025, 0.05 and 0.1% by mass to the mixtures, respectively and the results showed that cohesion increased and internal friction angle decreased as the polymer content increased. [4] conducted direct shear tests on polyurethane organic polymer-polypropylene fiber-sand mixtures
The powdered anionic polymer that was added to a granular, sodium bentonite-poor graded sand mixture with a bentonite content of 15% by mass, resulted in an increase in the cohesion (c) and a decrease in the internal friction angle (ø)
Summary
Bentonite-sand mixtures are preferred to be used as barriers in waste containment areas by minimizing leachate advection through the ground soil layers. [1] conducted direct shear and unconfined compression tests on bentonite-river sand mixtures with 5, 10 and 20% bentonite content by mass, respectively. The results of these tests showed that the unconfined compressive strength, the cohesion and the Young’s modulus all increased with an increase in the bentonite content, while the angle of internal friction decreased. Cohesion decreased and internal friction angle increased for the mixtures with a silt content of 50 and 70%. They added a copolymer (poly methyl methacrylate) with a content of 0.025, 0.05 and 0.1% by mass to the mixtures, respectively and the results showed that cohesion increased and internal friction angle decreased as the polymer content increased. Test results showed that polymer addition up to 4% by mass caused almost 2 times increase in the shear strength of the untreated sand
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