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Made available in DSpace on 2015-03-26T13:28:04Z (GMT). No. of bitstreams: 1 texto completo.pdf: 4571311 bytes, checksum: d283703263efe3572fa1ac4afa57f8c4 (MD5) Previous issue date: 2008-02-26 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / This research addresses the application of a technique to a soil from the Southeast of Brazil and representing significant portion of the Brazilian territory in order to produce new products herein named modified soils. This conversion was based on the manipulation of the soil chemical and mineralogical compositions in order to change its geotechnical behavior. The laboratory testing program encompassed the following steps: (i) chemical, mineralogical and geotechnical characterization of the soil; (ii) development of chemical and mineralogical procedures for soil modification; (iii) chemical and geotechnical characterizations of the modified soils. Based on the testing data, conclusions are as follow: (i) good performance of the developed procedures for soil modification, which can be applied to field conditions after minor adjustment; (ii) the applied treatments produced significant variation in the chemical soil parameters, specially in the CEC; (iii) the treatments were responsible for significant geotechnical chances in the soil plasticity and compaction parameters, and for minor changes in the soil unconfined compression strength, hydraulic conductivity, compressibility and shear strength determined through triaxial tests. / Nesta pesquisa, buscou-se aplicar a um solo de ocorrência significativa na região Sudeste e em parte expressiva do território brasileiro uma técnica para a sua conversão em novos produtos, aqui denominados de solos modificados . Essa técnica teve por base a modificação das composições química e mineralógica do solo em estudo, com intuito de alterar os seus padrões de comportamento geotécnico. O programa de estudo de laboratório abrangeu: (i) caracterizações química, mineralógica e geotécnica do solo em estudo; (ii) desenvolvimento de processos capazes de promover alterações nas propriedades químicas e mineralógicas, com vistas à produção de solos modificados ; (iii) caracterizações química e geotécnica dos solos modificados . Com base nos resultados obtidos, pode-se concluir que: (i) os métodos desenvolvidos para a modificação do solo em estudo mostraram-se adequados para as finalidades previstas, bem como apresentaram a vantagem de poderem ser, com pequenas adaptações, implementados em trabalhos de campo; (ii) os tratamentos provocaram mudanças significativas nos parâmetros químicos, em especial na CTC do solo; (iii) os tratamentos conferiram ao solo analisado mudanças geotécnicas significativas nos seus parâmetros de plasticidade (redução do LL e LP) e de compactação (aumento do peso específico aparente seco máximo e queda no teor ótimo de umidade) e, em menor escala, nos de resistência à compressão não-confinada, condutividade hidráulica, compressibilidade e resistência ao cisalhamento determinada em ensaios triaxiais.

During a survey of black cotton soil zones of Karnataka, indigenously stabilized black cotton soil deposits were encountered in Belgaum, Bijapur, Bagalkot and Gadag Districts of Karnataka. These modified black cotton soils have low swelling and negligible shrinkage tendencies. Owing to their low volume change potential on moisture content changes, these soils are widely preferred in earth construction activities. The exact origin of these modified black cotton soil deposits is not known. According to anecdotal references, these soils were prepared by mixing unknown proportions of wood ash, organic matter and black cotton soil and allowing them to age for unknown periods of time. As wood-ash was apparently used in their preparation, these modified black cotton soils are referred to as ash-modified soils (AMS) in the thesis. The practice of preparing ash-modified soils is no longer pursued in black cotton soil regions of Karnataka and the available supply of this indigenously stabilized soil is being fast depleted. Also, attempts have not been made to characterize the physico-chemical and engineering properties of AMS deposits of Karnataka. Given the widespread utilization of ash-modified soils in black cotton soil areas of Karnataka, there is a need to understand their physico-chemical and engineering behaviour and the physico-chemical mechanisms responsible for their chemical modification. Swelling and shrinkage of expansive soil deposits are cyclic in nature due to periodic climatic changes. Chemically stabilized black cotton soil deposits are also expected to experience cyclic wetting and drying due to seasonal climatic changes. The impact of cyclic wetting and drying on the swelling behaviour of natural expansive soils is well-documented. However, the impact of alternate wetting and drying on the swelling behaviour of admixture stabilized expansive soils (these include natural - ash-modified soils and laboratory - lime stabilized black cotton soils) has not been examined. Such a study would be helpful to assess the long term behaviour of admixture stabilized soils in field situations. To achieve the above objectives, experiments are performed that study: 1.The physico-chemical and engineering properties of ash-modified soils from different Districts of Karnataka. The physico-chemical and engineering properties of natural black cotton soil (BCS) specimens from locations adjacent to ash-modified soil deposits are also examined to understand and evaluate the changes in the engineering characteristics of the ash-modified soils due to addition of admixtures. 2. Identify the physico-chemical mechanisms responsible for the chemical stabilizationof ash-modified soils. 3.The influence of cyclic wetting and drying on the wetting induced volume changebehaviour of admixture stabilized black cotton soils, namely, ash-modified blackcotton soils and lime stabilized black cotton soils.