Over the past years, levee failures during floods have caused significant losses of lives and properties in the nation. Majority of these failures were induced by seepage through granular foundation soils underneath the top soil on which the levees were built. One of methods to mitigate this phenomenon includes the treatment of the granular soil deposits with an engineered fluid delivered by permeation (permeation grouting), resulting in a less pervious deposit. Since the conventional cement-based suspensions and chemical solutions may cause groundwater contamination due to long term reaction with groundwater, clay suspension such as bentonite suspension can be an alternative in terms of environmental friendliness and long-term safety. Moreover, the suspensions, after being permeated, are expected to be stable in the pore space due to the thixotropic nature of bentonite. The main challenge in this approach is being able to permeate a concentrated suspension through the pores of a granular material. To achieve a significant reduction in the hydraulic conductivity, concentrated bentonite suspensions should be used; however, concentrated suspensions can have low mobility, resulting in a low penetration depth and little practical application. The main objective of this study is to investigate the permeation of concentrated bentonite suspensions by controlling their rheological properties. The first portion of this research focuses on measuring the rheological properties of the various engineered bentonite suspensions over time. The second point of focus of this research is the parameters affecting the flow of the bentonite suspensions through granular soils, and the final focal area is determining the hydraulic performance of the grouted granular soils. In order to achieve these objectives, an experimental program was developed in this research. First, rheological tests were performed with the bentonite suspensions with and without various concentrations of sodium pyrophosphate (SPP); SPP is an ionic additive that is used to reduce the initial yield stress and viscosity of bentonite suspensions. A stress controlled test with the vane geometry produced rheological parameters with a minimal disturbance. Suspensions were stored in sealed cups and tested at various times to measure the long term thixotropic changes in yield stress and viscosity. Second, the various concentrations of the bentonite suspensions were injected at a constant pressure through clean sands which were prepared at various conditions (relative density, fine contents, and grain size) in order to investigate soil and suspension parameters affecting the flow of the bentonite suspensions. The results from these experimental tests were utilized to develop a groutability criterion of bentonite suspensions for practical purposes. Finally, the saturated hydraulic conductivity of the treated soils was measured using falling and rising head method. The traditional concept of “clay void ratio” was re-examined. The results from this study showed that the modified bentonite suspensions could be used as an alternative grout in permeation grouting to improve hydraulic performance of the permeable granular soils. / text

No description available.

In this thesis, a smectite rich bentonite ore deposit from Porto Santo Island (Portugal) was characterized and then applied to prepare clay-biopolymer nanocomposite material. Natural clay sample is mainly composed of Fe rich smectite, having also feldspar, calcite and magnetite-maghemite minerals. Both montmorillonite from the clay source repository (SWy-2) and the Porto Santo bentonite were used for the nanocomposite synthesis. An exocellular polysaccharide – scleroglucan was used as a biopolymer. The X-ray diffraction and transmission electron microscopy results show that smectite is well dispersed in the scleroglucan matrix with partial exfoliation. The study of various experimental parameters reveal that only the scleroglucan/clay mineral mass ratios determine the level of the clay sheets’ dispersion in the polymer matrix. Compared to SWy-2, the Porto Santo bentonite shows a smaller degree of dispersion within the polymer matrix, but nevertheless its potential outstanding mechanical properties could be of interest for further studies.

Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2002. / Includes bibliographical references. Also available in electronic version. Access restricted to campus users.

Th. doct.-ing.--Génie chim.--Toulouse--I.N.P., 1985. N°: 388.

The deformation behavior of unsaturated soil has been the subject of numerous experimental and theoretical investigations. However, this phenomenon is not fully understood. Problems, such as the adoption of the proper stress variables, reduction of suction inducing collapse, suction effect on soil stiffness, rate dependency and air trapped within the soil under rainfall infiltration still need additional studies. In the present studies, an elasto-viscoplastic model for unsaturated soil is used based on two stress variables: 1) the skeleton stress is adopted as the stress variable; 2) suction is incorporated into the constitutive model to describe the collapse behavior. In addition, to investigate the multiphase behavior of unsaturated soil, a three-phase coupled model has been proposed based on the Theory of Porous Media (TPM) and finite deformation theory. Van Genuchten type of equation is employed as a constitutive equation between the saturation and the suction. Three-dimensional multiphase simulations are carried out to reproduce the behavior of unsaturated soil during monotonic loading triaxial tests under drained and undrained conditions for water and air. Compared with experimental results and the simulated results, it is seen that the proposed formulation is very suitable to describe the mechanical behaviors of unsaturated soil. Cyclic behavior of unsaturated soil has attracted much attention during the past few years. An elasto-viscoplastic cyclic model for saturated soil is extended for modeling of unsaturated soil. Based on finite deformation theory, three-dimensional multiphase analyses for unsaturated soil under cyclic loading are presented. The simulations are verified with cyclic triaxial tests on unsaturated silty clay under undrained for water and air conditions. It shows that the proposed multiphase formulation can be used to simulate the behaviors of unsaturated soil under cyclic loading. The high expansiveness of bentonite is another significant problem in unsaturated soil mechanics. In this research, an elasto-viscoplastic model for unsaturated expansive soil has been developed. An evolutional equation is adopted for describing the absorption of water into interlayer of clay platelets. In addition, the internal compaction effect caused by swelling of clay unit is expressed with the expansion of overconsolidation boundary surface and static yield surface. Based on the model, one-dimensional finite element analysis is conducted to study the development of swelling pressure. Compared with experimental results and simulated results, it is found that the proposed model can reproduce the effects of dry density and initial water content on swelling behavior. Using the proposed swelling model, two-dimensional swelling behaviors of the waste barrier are simulated. / Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第13775号 / 工博第2879号 / 新制||工||1425(附属図書館) / 25991 / UT51-2008-C691 / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 岡 二三生, 教授 松岡 俊文, 准教授 木元 小百合 / 学位規則第4条第1項該当

Submitted by Maria Medeiros (maria.dilva1@ufcg.edu.br) on 2018-09-12T12:56:27Z No. of bitstreams: 1 DANIELA DE LOURDES ANJOS COUTINHO SIMÕES ANDRADE - TESE (PPGEP) 2009.pdf: 2248344 bytes, checksum: 28a93ae4236853f59fe35037c2ab6f28 (MD5) / Made available in DSpace on 2018-09-12T12:56:27Z (GMT). No. of bitstreams: 1 DANIELA DE LOURDES ANJOS COUTINHO SIMÕES ANDRADE - TESE (PPGEP) 2009.pdf: 2248344 bytes, checksum: 28a93ae4236853f59fe35037c2ab6f28 (MD5) Previous issue date: 2009 / A proposta deste trabalho foi preparar nanocompósitos de polipropileno/compatibilizante/bentonita, pelo método de intercalação na fusão, utilizando como carga uma argila sódica comercial Argel, fornecida por uma indústria local, purificada e modificada organicamente com um sal quaternário de amônio empregando diferentes métodos de preparação. Ao longo do trabalho foram utilizadas duas matrizes e dois tipos de compatibilizantes: PP H103, PP H401, Polipropileno modificado com anidrido maleico (PP-g-MA) e Copolímero de etileno e álcool vinílico (EVOH), respectivamente. As argilas foram caracterizadas por difração de raios-X (DRX), espectroscopia de infravermelho (FTIR) e análise termogravimétrica (TG) visando determinar o método de preparação mais eficiente para obtenção das argilas organofílicas. Uma vez determinado o melhor procedimento para organofilização, na segunda parte deste estudo, avaliou-se o efeito do tipo e teor de argila organofílica, bem como o tipo e teor de compatibilizante nas propriedades de filmes de polipropileno. De acordo com os resultados preliminares deste estudo, há uma indicação de que os filmes de nanocompósitos PP/PP-g-MA/argila organofílica, contendo 1% de argila organofílica e 15% de polipropileno modificado com anidrido maléico (PP-g-MA) podem ser promissores para o mercado de embalagens e poderão em um futuro próximo serem usados como um novo produto por empresas nacionais. / The purpose of this work is to prepare nanocomposites of polypropylene/compatibilizer/bentonite, by melting intercalation, with a commercial sodium clay – Argel – as filler. This clay was organically purified and modified by different methods, with a quaternary ammonium salt. The clays were characterized by X-Ray diffraction (XRD), infrared spectroscopy (FTIR) and thermogravimetric analyses (TG) to determine the most efficient preparation method. Before that, in the second stage of this study, the influence of the type and contend of organoclay in the properties of the polypropylene films was measured; the same was done for the compatibilizer. The preliminary results indicate that the nanocomposites film with 1% of organoclay and 15% of polypropylene grafted with maleic anhydride show promise as packing materials and may be used, in the near future, as a new product by the national industry.

In this thesis, a smectite rich bentonite ore deposit from Porto Santo Island (Portugal) was characterized and then applied to prepare clay-biopolymer nanocomposite material. Natural clay sample is mainly composed of Fe rich smectite, having also feldspar, calcite and magnetite-maghemite minerals. Both montmorillonite from the clay source repository (SWy-2) and the Porto Santo bentonite were used for the nanocomposite synthesis. An exocellular polysaccharide – scleroglucan was used as a biopolymer. The X-ray diffraction and transmission electron microscopy results show that smectite is well dispersed in the scleroglucan matrix with partial exfoliation. The study of various experimental parameters reveal that only the scleroglucan/clay mineral mass ratios determine the level of the clay sheets’ dispersion in the polymer matrix. Compared to SWy-2, the Porto Santo bentonite shows a smaller degree of dispersion within the polymer matrix, but nevertheless its potential outstanding mechanical properties could be of interest for further studies.

Deep geological disposal is a method of managing high level, long-­‐lived nuclear waste. It is a concept that many countries are exploring for the possibility of managing nuclear waste generated from power production. For deep geological disposal to be viable then areas where problems may surface have to be explored. Bentonite clay has been proposed as the material to be used for the backfill of the repositories. Its swelling properties ensure that it will expand to plug the bore holes that will be made for the waste, its impermeable nature restricts contact between groundwater and the waste package and its stability on a geological timescale all make it desirable as a backfill material. This project looks at the role that colloids formed from the bentonite clay could have in facilitating radionuclide transport away from a nuclear waste repository. Several radionuclides (Eu(III), U(VI), Th(IV) and Am(III)) have been considered in this research, and information from these studies will be used in the BELBaR project’s outputs, which will eventually support a disposal safety case. Ternary systems of 152Eu(III), bulk bentonite and EDTA ([Eu] = 7.9 x 10-­‐10 M; pH = 6.0 – 7.0) have been studied. Without EDTA, there was slow uptake in a two-­‐stage process, with initial rapid sorption of Eu(III) (96%), followed by slower uptake of a smaller fraction (3.0 % over a period of 1 month). The reversibility of Eu(III) binding was tested by allowing Eu(III) to sorb to bentonite for 1 – 322 days. EDTA was added to the pre-­‐equilibrated Eu bentonite systems at 0.01 M. A dissociation rate constant of approximately 4.3 x 10-­‐8 s-­‐1 (values in the range 2.2 x 10-­‐8 – 1.0 x 10-­‐7 s-­‐1) for pre-­‐equilibration times ≥ 7 days was measured. Eventually, the amount of Eu(III) remaining bound to the bentonite was within error of that when EDTA was also present prior to contact (4.5 % ± 0.6). Eu interactions with colloidal bentonite were studied, and the dissociation rate constant measured by a resin competition method. A dissociation rate of 8.8 x 10-­‐7 s-­‐1 and a range of 7.7 x 10-­‐7 – 9.5 x 10-­‐7 s-­‐1 were measured. For both bulk and colloidal bentonite slow dissociation was observed for Eu(III), but there was no evidence for ‘irreversible’ binding. The interactions of 232U(VI) with bentonite colloids ([U] = 5.43 x 10-­‐10 M; pH = 8.8 ± 0.2) have been studied using a resin ion exchange competition technique. The reversibility of the interaction was studied by allowing U(VI) to sorb to bentonite colloids for periods from 1 – 35 days. A fraction of the U(VI) was removed from the solution instantaneously (28-­‐50 %), and after 3 days, the amount of U(VI) remaining on the bentonite colloids was 17-­‐ 25%. With time, the amount of U(VI) retained by the bentonite colloid is reduced further, with a first order dissociation rate constant of 5.6 x 10-­‐7 s-­‐1. Whilst the dissociating fraction was small (24% (+34; -­‐12 %)), complete dissociation was not observed. Although slow dissociation was observed for U(VI), there was no convincing evidence for ‘irreversible binding’ of the radionuclide by the colloid. The interactions of 228Th(IV) ([Th] = 3.79 x 10-­‐12 M; pH = 8.8 ± 0.2) and 241Am(III) ([Am] = 3.27 x 10-­‐9 M; pH = 8.8 ± 0.2), with bentonite colloids have been studied using an ion exchange competition technique. Th(IV) was not fully associated with the bentonite colloids, and filtration showed that the uptake after 1 week was 78.3% (± 2.7%). Am(III) was weakly associated to the bentonite colloids, the uptake after 1 week was 20.1 % (± 5.2 %). Cellulose phosphate was added to the radionuclide/bentonite colloid systems (1 g for Th(IV), 0.2 g for Am(III)), an amount that was sufficient to retain the radionuclide when no bentonite colloids are present. A fraction of the Th(IV) is initially removed by the Cellphos (75-­‐93 %), and after 7 days the amount of Th(IV) remaining on the colloids is 1 -­‐ 3 %. Over the time of the experiment, the amount of Th(IV) retained by the bentonite colloid appears to remain level and the amount bound to the bentonite colloid at the end of the experiment is 2.1 % ± 0.88 % which is within experimental error of the steady state equilibrium of the system. A fraction (48-­‐94 %) of the Am(III) is also initially removed by the Cellphos, after 7 days the8amount of Am(III) remaining on the colloids is 1.2 – 9.3 %. However, after 35 days of contact time with the cellulose phosphate it appears that Am(III) is released back into the system, preventing dissociation rates from being calculated in this case. Studies of the association of Eu(III) to the clay colloids and its subsequent dissociation in this thesis follow similar trends to those described elsewhere in the literature (Missana et al. (2008), Bouby et al. (2011)). The Eu/bentonite colloid dissociation rate calculated here (8.8 x 10-­‐7 s-­‐1 (± 9.1 x 10-­‐7 s-­‐1)) is within error of the dissociation rates for trivalent ions estimated by Wold (2010) (Am(III) 5.6 x 10-­‐7 s-­‐1 Cm(III) 1.7 x 10-­‐6 s-­‐1). The U(VI) studies in this thesis show a dissociation rate of 5.6 x 10-­‐7 s-­‐1 (± 4.2 × 10-­‐7) which is within error of the U(VI) dissociation rate estimated by Wold (2010) (8.3 X 10-­‐7 s-­‐1). Reliable dissociation rates could not be obtained from the Am(III) and the Th(IV) studies in this thesis, other studies (e.g. Bouby et al. (2011) showed signs of irreversible binding of Th(IV) to bentonite colloids, however, no irreversible binding was observed in this thesis. Am(III) did not appear to be a close analogue of Eu(III) in these systems. All of the isotopes studied in this thesis showed no evidence of irreversible binding to bentonite or bentonite colloids. As such, the role that bentonite colloids will have in the facilitated transport of radioisotopes away from a repository is likely to have only a limited impact, at most, on the environmental safety case.

The overall goal of this research is concerned with understanding the effects of bentonite on the external corrosion of bare mild steel well casing. Na-bentonite is mainly used in enormous amounts in drilling processes, so it used as the main electrochemical environment surrounding the casing at different condition. The major part of the current study was divided into 3 stages; the first stage is constant current cathodic protection (CP) with a range of 0.0 (Open Circuit Potential) to 200mA.m-2 was applied respectively to protect bare mild steel buried vertically inside the bentonite layer contains 45% (w/w) 0.5 M NaCl Solution. This study was attempted to investigate the polarisation potential distribution over depth. The second stage is polarisation potential with a range of OCP to -1.15V/SCE was applied to protect mild steel exposed to 0.5M sodium chloride solution containing different concentration of bentonite, namely 0.0%, 1.0 and 10.0% (w/w). The third stage was concerning with the ZnCl2 added at 500ppm and 1000ppm to the bentonite as cathodic inhibitor to investigate its effects on the corrosion process of mild steel. CP at 0.0mV (OCP) and -1.15 V against saturated calomel electrode (SCE) were applied for this experiment. Weight loss, visual observation, Open Circuit Potential (OCP), cathodic protection and linear polarisation resistance (LPR) techniques were employed for this study. Optical microscope, Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray analysis (EDX), and X-Ray diffraction (XRD) analysis are illustrated to study, examine and analyse the films that formed on the metal surface. It is demonstrated that the corrosion rate produced from LPR measurement data was fairly lower than that obtained by experimental weight loss data. Low corrosion rate was recorded for the specimens immersed in 0.5NaCl solution, containing bentonite compared to that were obtained for solution free of bentonite. Magnesium hydroxide and calcium carbonate were the main chemical compounds that detected on the metal surfaces when cathodic protection (CP) was applied at -1.15V vs. SCE. It was confirmed that, the addition of ZnCl2 at two different concentration, 500ppm and 1000ppm has reduced the current density applied to a considerable value. This was ascribed to the formation of compacted and uniform film on the protected surface. The examination of the specimens using EDX and XRD has shown the formation of zinc containing compounds. Small amount of NaCl in the form of halite for both concentrations was also detected.