Thesis (M.S.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 66-69). Also available on the World Wide Web.

Calcium carbonate precipitation and formation of clog particles inside the leachate collection pipe can cause catastrophic failures in landfill operation. This study focuses on quantifying the effectiveness of electronic scale control to reduce the clog formation within the pipe network. A field scale model (40ft × 20ft) was constructed, featuring side-by-side flow of electronically treated and untreated composite leachate. Data obtained in the first phase of this study indicate that electronic scale control system does not have any statistically significant effect on water quality parameters. The second phase of this study identified calcite (CaCO3) to be the predominant phase present in the precipitates using XRD/XRF diffraction pattern analyzed through a search match calculation program (MATCH! Version 3.2.0) which concur with the previous studies. Furthermore, Rietveld refinement using FullProf Suite confirms that there were no differences between the treated and untreated precipitate based on the phases identified in the respective samples. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection

The process of fluid injection into granular media is relevant to a wide number of applications such as enhanced oil recovery, grouting, and the construction of permeable reactive barriers. The response of the subsurface is dependent on multiple factors such as in-situ stresses, fluid properties, flow rate, and formation type. Based on these conditions a variety of response mechanisms can be initiated ranging from simple porous infiltration to hydraulic fracturing. Currently, the mechanics of fluid injection into competent rock are well understood and can be sufficiently modeled using linear elastic fracture mechanics. Because the grains in rock formations are individually cemented together, they exhibit cohesion and are able to support tensile stresses. The linear elastic method assumes tensile failure due to stress concentrations at the fracture tip. A fracture propagates when the stress intensity factor exceeds the material toughness (Detournay, 1988) However, understanding fluid injection in cohesionless granular media presents a much larger obstacle. Currently, no theoretical models have been developed to deal with granular media displacements due to fluid injection. Difficulty arises from the complexity of fluid rheology and composition used in engineering processes, the strong coupling between fluid flow and mechanical deformation, the non-linear response of subsurface media, and the multi-scale nature of the problem. The structure of this thesis is intended to first give the reader a basic background of some of the fundamental concepts for non-Newtonian fluid flow in granular media. Fluid properties as well as some interaction mechanisms are described in relation to the injection process. Next, the results from an experimental series of injection tests are presented with a discussion of the failure/flow processes taking place. We developed a novel technique which allows us to visualize the injection process by use of a transparent Hele-Shaw cell. Specifically, we will be using polyacrylamide solutions at a variety of concentrations to study non-Newtonian effects on the response within the Hele-Shaw cell. By performing tests at a range of solution concentrations and injection rates we are to be able to identify a transition from an infiltration dominated flow regime to a fracturing dominated regime.

Canada produces about one-third of the global supply of medical radioisotopes. The nuclear power reactors in Ontario, Quebec and New Brunswick have generated about 17 percent of the electricity in the country every year (NWMO, 2010; Noorden; 2013). Since the 1960s, more than 2 million used (or spent) fuel bundles (high-level radioactivity) and 75,000 m³ of low- and intermediate-level radioactive waste have been produced, which is increasing by 2000 to 3000 m³ every year after reducing the processed volume (Jensen et al., 2009). More than 30 countries around the world, including Canada, have proposed construction of very deep geological repositories (DGRs) to store this nuclear waste for design periods 1,000,000 years. DGR concepts under development in Canada (the DGR is likely to be constructed in Ontario) are based on a multi-barrier system (NWMO, 2012). A crucial component of the multi-barrier system is the engineered barrier system (EBS), which includes a buffer, backfill, and tunnel sealing materials to physically, chemically, hydraulically and biologically isolate the nuclear waste. Bentonite-based material has been chosen for this critical use because of its high swelling capacity, low hydraulic conductivity, and for its good ability to retain radionuclides in the case of failed canisters. However, the presence of bentonite-based material in DGRs, surrounded by an aggressive environment of underground saline water, nuclear waste heat decay, and corrosion products under confining stress, may lead to mineralogical changes. Consequently, the physical and physiochemical properties of bentonite-based materials may change, which could influence the performance of bentonite in an EBS as well as the overall safety of DGRs. The objective of this research is to investigate the impact of the underground water salinity, heat generated by nuclear waste, and corrosion products of nuclear waste containers in Ontario on the engineering and micro-/nano-structural properties of bentonite-sand engineered barrier materials. Free-swelling, swelling pressure and hydraulic conductivity tests have been performed on bentonite-sand mixtures subjected to various chemical (groundwater chemistry; corrosion water with iron as a corrosion product) and thermal (heat generated) conditions. Several techniques of micro- and nano-structural analyses, such as x-ray diffraction (XRD), X-Ray microanalysis (DES), surface area and pore size distribution analyses (BET, BJH) and differential gravimetric (TGA and DTG) analyses have also been conducted on the bentonite-sand materials. Valuable results have been obtained for better understanding the durability and performance of the bentonite-sand barrier for the DGR which may be located in Ontario. The obtained results have shown that the groundwater chemistry and corrosion products of the nuclear containers significantly deteriorate the swelling and permeability properties of the tested bentonite-sand barrier materials, while temperature has little or no effect.

The deep geological repository concept is based on “engineered barriers systems (EBS)” that are constructed in the repository and “natural barriers” provided by the surrounding geological environment. The EBS comprises of variety of sub-systems or components, such as the waste form, canister, buffer, backfill, seals, and plugs. Geological disposal is based on the concept of multiple barriers that work together to provide containment. The buffer is made up of densely compacted bentonite or bentonite-sand mix. Bentonite has both mechanical and physico-chemical functions, to fulfill as a barrier material in DGR. The bentonite buffer should hold the containers in place and prevent collapse of the excavation. A plastic deformability of the bentonite is desired to redistribute the stresses that can result from creep in the rock, and prevent transfer of excessive stresses to the canisters. The bentonite buffer must create an impermeable zone around the containers to ensure that the radionuclide released from the vitrified waste is limited by diffusive transport rather than advective transport in groundwater. Another important property of the highly compacted bentonite is its swelling potential. Its swelling potential should be as high as possible, to guarantee the sealing of any cracks occurring in the buffer material or in the storage gallery and thus ensure good imperviousness. Besides its mechanical function, bentonite buffer must sorb escaping radionuclides and thus retard their migration to the geo-environment. The bentonite buffer must retain its mechanical and physico-chemical functions over a span of several hundred thousand years to fulfill its role as a containment barrier in DGR. The bentonite buffer should maintain its physico-chemical and hydro-mechanical integrity on exposure to groundwater. Nuclear power agencies of several countries have identified suitable bentonites for use as buffer in DGR through laboratory experiments and large scale underground testing facilities. Japan has identified Kunigel VI bentonite, South Korea-Kyungju bentonite, China-GMZ bentonite, Belgium-FoCa clay, Sweden-MX-80 bentonite, Spain-FEBEX bentonite and Canada-Avonseal bentonite as candidate bentonite buffer for deep geological repository program. Bentonite from Barmer (Rajasthan State) was identified as suitable buffer for use in Indian deep geological repositories. The influence of moisture and dissolved salt migration on the physico-chemical and hydro-mechanical properties of Barmer bentonite has not been examined. The study is important to understand the clay’s behaviour under deep geological repository conditions, where, the bentonite buffer would come in contact with groundwater. Infiltration of groundwater with variable chemical composition could alter the physico-chemical and hydro-mechanical properties of the clay. The objectives of the thesis are as follows: Examine the influence of permeation of distilled water (DW) and synthetic ground water (SGW) solutions under constant volume condition on suction, physico-chemical and moisture content/dry density characteristics of compacted Barmer bentonite specimens as function of permeation period (maximum permeation period– 30 days). Examine the influence of variation in dry density and gravimetric water content as consequence of DW and SGW solution permeation on swell pressure and unconfined compression strength of Barmer bentonite specimens. Compare experimental swell pressures of re-constituted bentonite specimens with swell pressures predicted by diffuse double layer models. Examine the influence of total dissolved solids (TDS) concentration of permeating solution on the unsaturated permeability of compacted Barmer bentonite specimens. Organization of thesis: After the first introductory chapter, a detailed review of literature is performed in Chapter 2 to review the physicochemical, mineralogical and hydro-mechanical properties of bentonites identified as buffer materials for deep geological repositories of various countries. Based on current understanding and need to perform similar studies with Barmer clay, the chapter develops the scope and objectives of the study. Chapter 3 presents a detailed experimental program of the study. Chapter 4 examines the influence of permeation of distilled water (DW) and synthetic groundwater (SGW) solutions (under constant volume conditions) on the total suction of compacted bentonite specimens at two locations in the clay. The influence of variation in dry density on the moisture migration-suction inter-relations of compacted bentonite specimens is also examined. The associated changes of DW and SGW solution migration under constant volume conditions on the physico-chemical properties, water content and dry density of compacted Barmer bentonite specimens are also examined. The experimental results brought out that matric suction mainly contributed (75 to 92 %) to total suction of the permeated specimens; the permeated specimens experienced reduction in matric suction with increase in gravimetric water content from increase in degree of saturation. Osmotic suction contributed to 10 to 25 % of the total suction of the permeated specimens and was observed to increase with gravimetric water content due to solubilization of salts contained in the voids of the compacted bentonite specimens. The total suction of compacted Barmer bentonite specimen was responsive to the total dissolved solids concentration of the permeating solutions as the specimen permeated with more saline solution (higher TDS value) exhibited lesser total suction. Upon permeation with DW and SGW solutions, the CEC of bentonite was unaltered, while, pH and TDS values were affected. Softening of the bentonite clay occurred from increase in water content and existence of compression zones (material used to seal 1mm gap in relative humidity probe aperture) that in turn facilitated dissipation of swelling stress leading to reduction in dry density values. Chapter 5 examines influence of reduction in dry density and increase in water content on the swell pressure and compression strength characteristics of compacted Barmer bentonite specimens upon DW and SGW solution migration as the results could provide insight into possible deviations from the design properties upon wetting of bentonite buffer by groundwater under deep geological repository conditions. The experimental swelling pressures are also compared with those predicted by Gouy-Chapman diffuse double layer theory. The dry density of 1.6 Mg/m specimens permeated with DW and SGW solutions reduced to 1.59 to 1.36 Mg/m and water contents increased to 18.9 to 27 % on permeation with distilled water and SGW solutions for 30 days. The reductions in dry density and increase in water content caused 30 to 70 % reductions in swell pressures and 31 to 74 % decrease in unconfined compression strength values. Specimens initially compacted to dry density of 1.8 Mg/m, experienced reduction in dry density ranging from 1.79 to 1.52 Mg/m and increase in water content from 18.6 to 24.2 % on permeation of DW and SGW solutions for 30 days. These reductions in dry density and increase in water caused the swell pressures to reduce from 4 to 55 % and unconfined compressive strengths to reduce by 31 to 67 %. Comparison of swell pressures gave -8 to 127 % variations between theoretical (from DDL theory) and experimental values due to errors associated with estimation of surface area and dissolved salt concentrations in pore water. Chapter 6 examines the influence of salinity of permeating solution on the unsaturated permeability of compacted Barmer bentonite specimens. The salinity of permeants was varied by permeating distilled water (DW) and synthetic ground water solutions under constant volume conditions over maximum period of 30 days. Experimental results showed that the saturated permeability coefficients (ksat) of specimens compacted to 1.6 Mg/m, responded to variations in TDS of the permeant. Comparatively, the ksat values of specimens compacted to 1.8 Mg/mwere unaffected by variation in TDS of the permeant. Permeation of DW and SGW solutions decreased the ksat values with time from cation hydration and growth of diffuse ion layers for both, 1.6 and 1.8 Mg/mseries specimens. Increase in gravimetric water content from DW and SGW permeation increased the kunsat values of 1.6 Mg/m specimens from reduction in total suction. Re-orientation of soil structure mobilized larger kunsat values for specimens permeated with SGW solutions than DW at similar total suction. Permeation of DW and SGW solutions had lesser impact on kunsat values of the 1.8 Mg/m specimens in comparison to the 1.6 Mg/m series specimens. Further at both densities, the influence of permeation was more evident at location closer to hydration surface. Chapter 7 summarizes the main findings of this study.