Bentonite clay is widely used in barrier systems due to its low hydraulic conductivity and it high swell capacity. Exposure to inorganic solutions can cause significant increases in hydraulic conductivity, due to changes in the surface chemistry and fabric. This phenomenon can be attributed to a reduction in the thickness of the double layer, due to the cation exchange capacity of the clay. The clay can be modified with polymers to render it less susceptible to chemical attack. The treatment process allows the clay to be engineered to enhance specific properties, such as permeability and sorption. In the present study, engineered soils are prepared by sorbing organic polymers to the surface of Na-bentonite. Three classes, cationic, anionic and nonionic polymers are investigated. The sorbents are water-soluble compounds based on the polymerization of acrylamides (PAM). Mixing and sample preparation techniques are developed and discussed. The interaction of the polymeric compounds and the clay mineral surface are evaluated by testing the liquid limit, swell index and specific gravity of the soils. Permeability tests are performed to determine if the polymer treatment enhances the hydraulic performance of the clay when permeated with highly concentrated salt solutions. The effect of permeant, void ratio, initial wetting condition and preparation techniques are found to have a significant affect on the hydraulic conductivity.

Because of its low permeability and high swelling characteristics, bentonite is used in various hydraulic barrier systems and in the manufacturing of Geosynthetic Clay Liners (GCLs). Exposure to inorganic solutions containing elevated concentrations of electrolyte can significantly increase their permeability. To enhance the bentonite's chemical resistance to inorganic solutions, the manufacturers of GCL materials introduced propriety soluble polymeric compounds as an additive to bentonite. The resulting materials are referred to as polymer-treated, chemically-enhanced, or contaminant-resistant clays, and are arguably resistant to a host of inorganic chemicals. In this study, the response of both regular and polymer treated bentonite clays to ordinary tap water and inorganic landfill leachate is evaluated using permeability tests, index tests and x-ray diffraction. The results indicate the high dependence of performance on sample preparation techniques, pre-hydration conditions, and first wetting liquid and, to a lesser extent, polymer treatment. The x-ray diffraction results indicate that the samples reached chemical equilibrium during the permeation process, as demonstrated by a full shift in d-spacing from Na-bentonite to Ca-bentonite. Further, the results show that the cation exchange capacity, the clay plasticity ratio, and the swell index appear to be reliable indicators of the hydraulic compatibility of bentonite permeated with inorganic chemicals

The effect of calcium uptake by hydration and diffusion from an adjacent calcium-rich soil on the performance of a geosynthetic clay liner (GCL) is examined for three cases. In Case 1 the GCL rested directly on a soil with a high calcium (1800 mg/l) concentration in the pore water (called “calcium rich soil” herein). Case 2 involved a GCL resting on 300 mm of soil with a low (200 - 300 mg/l) calcium concentration in the pore water (“foundation soil”) overlying the calcium rich soil. In the third (“control case”), the GCL only rested on the foundation soil. The overburden pressure was 15 kPa. The moisture content of GCL increased to 96%, 86% and 108% in the first 279 days for Cases 1, 2 and 3 respectively. Under isothermal conditions, the GCL moisture content decreased to 80% and 67% for Cases 1 and 2 respectively and increased to 113% for Case 3. After 1100 days, the hydraulic conductivity (k) of the GCL was 4×10-11 m/s for Case 3 but had increased up to about 7×10-11 m/s and 2×10-10 m/s for cases with and without the foundation layer respectively. The results are used to calibrate finite element models. A good correlation was found between k the bulk void ratio (eB) of GCL. Leakage and contaminant transport through 10 mm diameter hole in a geomembrane in a composite liner involving a GCL is examined at a stress of 100 kPa for hydraulic heads of 0.3 or 1 m. When permeated with distilled water, the interface transmissivity (θ) was about 2.3 × 10 11 m2/s. After 800 days of permeation with 0.14M NaCl there was only about 3% increase in the flow despite an order of magnitude increase in GCL permeability near the hole because θ decreased from 2.3×10-11 m2/s to 1.1×10-11 m2/s and controlled the leakage despite the increase in GCL permeability. Numerical modeling demonstrated reasonable agreement with the observed transport. / Thesis (Ph.D, Civil Engineering) -- Queen's University, 2010-09-09 12:20:42.298

<p> The effect of capillary dimensions on the die swell of molten polymers is investigated. Low and high density polyethylene, polypropylene, polystyrene are used to make investigation It is found the die swell decreases vii th L/D. The plot of die swell index (d/D) vs. L/D has the shape of anexponential decay curve. </p> <p> Bagley's decaying equation is used to fit the data. The effect of Deborah number on die swell phenomenon is also studied. 'I'he relationship between the recoverable shear strains of infinitely long capillary and the one with dimensions ratio L/D is obtained. This relationship could be used to estima te the die swell of short capillary from its value at equilibrium and polymer characteristics. </p> / Thesis / Master of Engineering (MEngr)