Many of the attempts made over the past six decades to find a universal system for assessing expansiveness of soils using soil index data have failed to follow the basic principles of soil mechanics. By overcoming most of these limitations Gourley and Schreiner (1993a) developed a new procedure that allows comparison of intrinsic expansiveness of soil samples prepared to have stable micro-fabric and consistent stress history. In this research, the same procedure is used on twenty-seven natural clayey soil samples of varying geological, geomorphological and geographical origin obtained from Kenya, Sudan, Eritrea and South Africa. Each of these samples was tested for Atterberg limits, volume change behaviours and soil suction. Statistical analysis was conducted on different soil parameters derived from these tests to obtain a significant relationship with their intrinsic expansiveness using measured swell. The analysis confirmed that most of the significant relationships obtained contain swell index, C*5' showing the identicalness of the soil properties responsible for volume change behaviour of both saturated and unsaturated clayey soils. Depending on the cost and the significance, the analysis recommended three major models that can be used as a screening system in the assessment of intrinsic expansiveness. For any soil it is possible to obtain preliminary information regarding its intrinsic expansiveness using the cheapest of the recommended models that needs liquid and plastic limit tests and hydrometer analysis, which are the routine tests of geotechnical site investigation. A more detailed assessment can be achieved by including only t he shrinkage test. The most reliable assessment needs addition of consolidation test with the unloading stage. All of the models allow obtaining information regarding the intrinsic expansiveness of soils as early as site investigation stage for successful engineering design. Moreover, they are anticipated to promote worldwide exchange of information regarding these problematic soils. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2004.

Includes bibliographies / 1 v. (various pagings) : / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (D.E.)--University of Adelaide, 1991

Thesis (Ph.D.) -- University of Texas at Arlington, 2008.

Os Vertissolos apresentam alto potencial para a produção agrícola e para estocar carbono. No entanto, diversos aspectos sobre sua gênese, fundamentais para qualidade e sustentabilidade do solo, permanecem incompreendidos. As várias lacunas sobre suas características particulares estão relacionadas ao incomum teor de alumínio trocável; a manifestação de feições morfológicas e vérticas em uma matriz inorgânica dominada por fases cauliníticas; e a preservação e estoque de carbono em condições climáticas de semiárido e temperado. Dessa forma, os objetivos deste estudo foram (i) investigar a gênese de um Vertissolo ácido, bem como os fatores e mecanismos da geração dessa acidez, (ii) compreender o papel dos interestratificados no desenvolvimento das feições vérticas em Vertissolo com predomínio de caulinita na fração argila, e (iii) investigar os fatores e mecanismos que promovem a gênese de Vertissolos Ebânicos sob diferentes condições climáticas no Brasil. Amostras de seis perfis de Vertissolos foram utilizadas, sendo quatro Ebânicos e dois Háplicos, ambos localizados entre as regiões nordeste, sudeste e sul do Brasil. Análises morfológica, físicas, químicas, mineralógicas e isotópicas foram realizadas. Na modelagem dos difratogramas foi utilizado o programa Newmod. Para identificação dos grupos funcionais orgânicos do solo realizou-se a ressonância magnética nuclear da fração ácido húmico, e a subtração espectral. Todos os Vertissolos apresentaram textura de argilosa a muito argilosa, consistência seca variando de dura a extremante dura e consistência molhada entre muito plástica e muito pegajosa. Os valores de pH variaram entre ácido e alcalino. Foram eutróficos, com predomínio de cálcio no complexo de troca na maioria dos perfis. O teor de carbono reduziu em profundidade, não mascarou o potencial de contração e expansão, e promoveu melhorias na agregação, principalmente nos horizontes superficiais. Houve autigênese de minerais, os minerais primários predominaram nas frações areia e silte, e na fração argila espécies de esmectitas dioctaedrais. Independente da espécie esmectítica e do tipo de vegetação (plantas C3 e/ou C4) houve maior diversidade de grupos funcionais nos horizontes superficiais. O mecanismo de estabilização do carbono nos Vertissolos Ebânicos ocorreu por meio da interação entre as fases inorgânicas e orgânicas, mediada por pontes de cátions polivalentes não metálicos e metálicos, e também por interação eletrostática entre os constituintes inorgânicos e orgânicos. A manifestação das feições morfológicas e vérticas no Vertissolo com predomínio de caulinita na fração argila foi gerada pelos interestratificados caulinita-montmorilonita resultantes da perda da lâmina tetraedral das esmectitas via transformações no estado sólido. A acidez no Vertissolo ácido foi gerada pela hidrólise e dissolução das fases minerais mediados por um clima passado mais úmido e continuado pelo clima atual úmido, sendo os teores de alumínio trocável naturais. Nesse contexto, esse estudo contribui com avanços na gênese, mineralogia e mecanismos de estabilização do carbono no solo, os quais são temáticas relevantes desse milênio e contribui a outras áreas cientificas. / Vertisols have high potential for agricultural production and for carbon stocking. However, several aspects about its genesis, fundamental to soil quality and sustainability, remain misunderstood. The various gaps on its particular characteristics are related to the unusual exchangeable aluminum content; the manifestation of morphological and vertic features in an inorganic matrix dominated by kaolinitic phases; and the preservation and stocking of carbon in semi-arid and temperate climatic conditions. Thus, the aims in this study were to (i) investigate the genesis of an acidic Vertisol, as well as the factors and mechanisms of the acidity generation, (ii) understand the role of the interstratified clay minerals in the development of vertic features in a kaolinitic Vertisol, and iii) investigate the factors and mechanisms that promote the genesis of Pellic Vertisols under different climatic conditions in Brazil. Samples of six profiles of Vertisols were used, being four Pellic and two Haplic, both located between the northeast and southern regions of Brazil. Morphological, physical, chemical, mineralogical and isotopic analyzes were performed. In the modeling of the diffractograms, the Newmod program was used. For the identification of the organic functional groups of the soil, the nuclear magnetic resonance of the humic acid fraction and the spectral subtraction were performed. All the Vertisols presented a texture of clayey to very clayey, dry consistency ranging from hard to extremely hard and wet consistency between very plastic and very sticky. The pH values varied between acid and alkaline. They exhibit high base saturation, with the predominance of calcium in the exchangeable complex in most of the profiles. The carbon content reduced in depth; did not overlap the shrinking-swelling potential; and promoted improvements in aggregation, especially in the upper horizons. There was autigenesis of minerals, primary minerals predominated in the sand and silt fractions, and in the clay fraction species of dioctahedral smectites. Regardless of the smectic species and the type of vegetation (C3 and/or C4 plants), there was a greater diversity of functional groups in the superficial horizons. The mechanism of carbon stabilization in the Pellic Vertisols occurred through the interaction between inorganic and organic phases, mediated by bridges of non-metallic and metallic polyvalent cations, and by electrostatic interaction between inorganic and organic constituents. The manifestation of the morphological and vertic features in the kaolinitic Vertisol was generated by the interstratified kaolinite-montmorillonite resulting from the loss of the tetrahedral sheet of smectites by solid-state transformations. The acidity in the acid Vertisols was generated by the hydrolysis and dissolution of the mineral phases mediated by a humid past climate and continued by the current humid climate, being the exchangeable aluminum contents natural. In this context, this study contributes to advances in the genesis, mineralogy, and mechanisms of soil carbon stabilization, which are relevant themes of this millennium and contribute to other scientific areas.

Os Vertissolos apresentam alto potencial para a produção agrícola e para estocar carbono. No entanto, diversos aspectos sobre sua gênese, fundamentais para qualidade e sustentabilidade do solo, permanecem incompreendidos. As várias lacunas sobre suas características particulares estão relacionadas ao incomum teor de alumínio trocável; a manifestação de feições morfológicas e vérticas em uma matriz inorgânica dominada por fases cauliníticas; e a preservação e estoque de carbono em condições climáticas de semiárido e temperado. Dessa forma, os objetivos deste estudo foram (i) investigar a gênese de um Vertissolo ácido, bem como os fatores e mecanismos da geração dessa acidez, (ii) compreender o papel dos interestratificados no desenvolvimento das feições vérticas em Vertissolo com predomínio de caulinita na fração argila, e (iii) investigar os fatores e mecanismos que promovem a gênese de Vertissolos Ebânicos sob diferentes condições climáticas no Brasil. Amostras de seis perfis de Vertissolos foram utilizadas, sendo quatro Ebânicos e dois Háplicos, ambos localizados entre as regiões nordeste, sudeste e sul do Brasil. Análises morfológica, físicas, químicas, mineralógicas e isotópicas foram realizadas. Na modelagem dos difratogramas foi utilizado o programa Newmod. Para identificação dos grupos funcionais orgânicos do solo realizou-se a ressonância magnética nuclear da fração ácido húmico, e a subtração espectral. Todos os Vertissolos apresentaram textura de argilosa a muito argilosa, consistência seca variando de dura a extremante dura e consistência molhada entre muito plástica e muito pegajosa. Os valores de pH variaram entre ácido e alcalino. Foram eutróficos, com predomínio de cálcio no complexo de troca na maioria dos perfis. O teor de carbono reduziu em profundidade, não mascarou o potencial de contração e expansão, e promoveu melhorias na agregação, principalmente nos horizontes superficiais. Houve autigênese de minerais, os minerais primários predominaram nas frações areia e silte, e na fração argila espécies de esmectitas dioctaedrais. Independente da espécie esmectítica e do tipo de vegetação (plantas C3 e/ou C4) houve maior diversidade de grupos funcionais nos horizontes superficiais. O mecanismo de estabilização do carbono nos Vertissolos Ebânicos ocorreu por meio da interação entre as fases inorgânicas e orgânicas, mediada por pontes de cátions polivalentes não metálicos e metálicos, e também por interação eletrostática entre os constituintes inorgânicos e orgânicos. A manifestação das feições morfológicas e vérticas no Vertissolo com predomínio de caulinita na fração argila foi gerada pelos interestratificados caulinita-montmorilonita resultantes da perda da lâmina tetraedral das esmectitas via transformações no estado sólido. A acidez no Vertissolo ácido foi gerada pela hidrólise e dissolução das fases minerais mediados por um clima passado mais úmido e continuado pelo clima atual úmido, sendo os teores de alumínio trocável naturais. Nesse contexto, esse estudo contribui com avanços na gênese, mineralogia e mecanismos de estabilização do carbono no solo, os quais são temáticas relevantes desse milênio e contribui a outras áreas cientificas. / Vertisols have high potential for agricultural production and for carbon stocking. However, several aspects about its genesis, fundamental to soil quality and sustainability, remain misunderstood. The various gaps on its particular characteristics are related to the unusual exchangeable aluminum content; the manifestation of morphological and vertic features in an inorganic matrix dominated by kaolinitic phases; and the preservation and stocking of carbon in semi-arid and temperate climatic conditions. Thus, the aims in this study were to (i) investigate the genesis of an acidic Vertisol, as well as the factors and mechanisms of the acidity generation, (ii) understand the role of the interstratified clay minerals in the development of vertic features in a kaolinitic Vertisol, and iii) investigate the factors and mechanisms that promote the genesis of Pellic Vertisols under different climatic conditions in Brazil. Samples of six profiles of Vertisols were used, being four Pellic and two Haplic, both located between the northeast and southern regions of Brazil. Morphological, physical, chemical, mineralogical and isotopic analyzes were performed. In the modeling of the diffractograms, the Newmod program was used. For the identification of the organic functional groups of the soil, the nuclear magnetic resonance of the humic acid fraction and the spectral subtraction were performed. All the Vertisols presented a texture of clayey to very clayey, dry consistency ranging from hard to extremely hard and wet consistency between very plastic and very sticky. The pH values varied between acid and alkaline. They exhibit high base saturation, with the predominance of calcium in the exchangeable complex in most of the profiles. The carbon content reduced in depth; did not overlap the shrinking-swelling potential; and promoted improvements in aggregation, especially in the upper horizons. There was autigenesis of minerals, primary minerals predominated in the sand and silt fractions, and in the clay fraction species of dioctahedral smectites. Regardless of the smectic species and the type of vegetation (C3 and/or C4 plants), there was a greater diversity of functional groups in the superficial horizons. The mechanism of carbon stabilization in the Pellic Vertisols occurred through the interaction between inorganic and organic phases, mediated by bridges of non-metallic and metallic polyvalent cations, and by electrostatic interaction between inorganic and organic constituents. The manifestation of the morphological and vertic features in the kaolinitic Vertisol was generated by the interstratified kaolinite-montmorillonite resulting from the loss of the tetrahedral sheet of smectites by solid-state transformations. The acidity in the acid Vertisols was generated by the hydrolysis and dissolution of the mineral phases mediated by a humid past climate and continued by the current humid climate, being the exchangeable aluminum contents natural. In this context, this study contributes to advances in the genesis, mineralogy, and mechanisms of soil carbon stabilization, which are relevant themes of this millennium and contribute to other scientific areas.

This research takes a multidisciplinary approach to comprehensively investigate the material and mechanical properties as well as pore water chemistry of the Bearpaw shale. This made it possible to characterize how these properties relate to the mechanical strength of this material. The results of this research challenge our ideas of the hydrogeology and of the geological history of the region. Core samples of the Bearpaw Formation and the overlying glacial till were collected from a field site in southern Saskatchewan, Canada. A combination of laboratory tests including multi-staged oedometer tests, constant rate of strain oedometer tests, specialized triaxial swell tests, along with pore water chemistry and finite element modelling were used to meet the following objectives: (1) To investigate the material properties and compression behaviour of the Bearpaw in addition to assessing disturbance due to specimen size; (2) Examine the time dependent behaviour of the Bearpaw and the transferability of time rate models developed for soft soils to stiff soils; (3) Examine the swelling potential and behaviour of the Bearpaw Formation and the influence of boundary conditions on this behaviour, while assessing the applicability of the swell concepts developed for compacted materials to a naturally swelling clay material; and (4) Constrain the depositional age of the till overlying the Bearpaw Shale. Contrary to what is seen in soft soils, smaller sized specimens were found to reduce disturbance, and produce more accurate and consistent results. Creep was found to follow the same laws as it does in soft soils, calling into question whether the use of preconsolidation pressure to predict geological history in stiff clays is appropriate. There was significant variation in the observed swell pressures of samples of the same size and depth. Finally, the glacial till at site was found to belong uniquely to the Battleford Formation and ranges in age from 22,500 to 27,500 years which is much younger (over 100,000 years younger) than previously believed. / Thesis (Ph.D, Geological Sciences & Geological Engineering) -- Queen's University, 2010-01-29 01:34:14.071

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Thesis (Ph. D.)--University of Adelaide, Dept. of Soil Science. / Copies of author's previously published articles inserted. Includes bibliographical references (leaves 173-196).

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