No description available.

Thesis (M. Sc.)--University of Hong Kong, 2005.

Orientador: José Humberto Barcelos / Banca: Cláudio Antonio de Mauro. / Banca: Silvio Carlos Bray. / Banca: Antonio Giacomini Ribeiro. / Banca: Luiz Nishiyama. / Resumo: A região ocupada pelo bioma Cerrado, no Triângulo Mineiro, a partir das últimas três décadas, vem experimentando um acelerado processo de expansão agrícola/pecuária. A crescente necessidade hídrica para este desenvolvimento implicou a construção de inúmeros pequenos reservatórios superficiais de água dentro dos canais de drenagem em bacias de até 3ª ordem. Este tipo de ocupação antrópica, normalmente feita sem um conhecimento adequado tanto do meio físico como das técnicas construtivas, vem contribuindo para o surgimento de diversos problemas ambientais. Este trabalho apresenta o estudo sobre esta ocupação dentro deste bioma, realizado em uma superfície de 2918,89 km2, pertencente à folha de Tupaciguara-MG, em escala regional de 1:100.000. Inicialmente, foi produzido um levantamento de campo sobre os aspectos construtivos empregados para a confecção destes pequenos reservatórios. Em paralelo, foi desenvolvido um estudo sobre o conjunto de atributos do meio físico, adotando-se os procedimentos de mapeamento geotécnico e tendo como base a proposta metodológica de ZUQUETTE (1987 e 1993), representado em 6 documentos cartográficos básicos. A seguir, procedeu-se à análise e sistematização dos documentos cartográficos produzidos na fase anterior, resultando em dois novos documentos cartográficos (carta de declividade generalizada e carta de predisposição à erosão). A caracterização geotécnica dos materiais inconsolidados, realizada a partir de ensaios de laboratório, possibilitou a determinação da textura, massa específica dos sólidos, limites de consistência, compactação e permeabilidade. Finalmente, a análise conjunta de todos os documentos produzidos nas fases anteriores gerou a carta de avaliação geoambiental, que indica as potencialidades e as limitações para este tipo de ocupação no ambiente...(Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The region occupied by the environment of the "Brazilian Cerrado", a typical vegetation from the west of Minas Gerais State which is called "Triângulo Mineiro", since the last three decades, has been experiencing a quick process of agricultural and cattle raising expansion. The increasing hydric necessity for this developing led to the construction of many small superficial water dams inside the draining channels for bays until the 3rd order. This type of human occupation, usually done without an appropriate knowledge from either the physical medium or the constructive techniques, has been contributing for the appearance of several environmental problems. This work presents the studies about the occupation inside this environment, which is done over an area of 2918,89 km2, belonging to the chart of "Tupaciguara-MG", using a regional scale of 1:100000. Initially, it was done a field research about constructive issues applied for the construction of these small dams. As a parallel work, it was developed a study about the set of features of the physical medium, using the procedures of geotechnical charting and based upon the methodological proposal of ZUQUETTE (1987 and 1993), presenting 6 basic cartographic documents. Afterwards, it was done the analysis and systematization of the cartographic documents developed on the former phase and the result was two new cartographic documents (general sloping chart and erosion tendency chart). The geotechnical description of the unconsolidated materials, which was done using laboratory tests, made possible the determination of the texture, specific solid masses, consistence limits, compactation and permeability. Finally, the analysis of all the documents together produced on the former phases generated the geoenvironmental evaluation chart that indicates the possibilities and limitations for this specific environmental occupation...(Complete abstract click electronic access below) / Doutor

published_or_final_version / Applied Geosciences / Master / Master of Science

No description available.

With the aim to achieve a better understanding of the time- and rate-dependent behaviour of unsaturated clays, particularly stiff natural clays, a critical review of the literature and a program of laboratory testing were carried out as part of this research. With emphasis on examining the effect of suction on viscous response, mainly primary and secondary consolidation (creep), stress-relaxation, and rate-dependency, a series of conventional multi-stage loading (MSL) oedometer tests, long-term single-stage loading (SSL) oedometer tests, and advanced constant-rate-of-strain (CRS) oedometer tests were carried out on natural and corresponding reconstituted specimens of a stiff clay namely, London Clay, retrieved from a site in the Isle of Sheppey, UK. The results obtained provide a significant contribution to the existing database and address important knowledge gaps highlighted from the literature review. The experimental studies performed included; a) An investigation of the effect of water reservoir surface roughness on the cavitation mechanism and performance of a newly designed high-capacity tensiometer (HCT), with regard maximum sustainable suction (smax) and maximum duration of measurements (tmax). b) An examination of the influence of soil suction on the primary and secondary consolidation of natural and reconstituted London Clay from a set of MSL and SSL oedometer tests. c) Characterisation of the stress-relaxation behaviour of the reconstituted London Clay subjected to suction and strain-rate variations from a set of CRS oedometer tests in an in-house designed suction-monitored cell. d) An examination of the coupled effects of suction and strain-rate on one-dimensional (1D) stress-strain response of reconstituted London Clay. Based on the experimental findings, the validity of the empirical relationships proposed in the literature for correlating time- and rate-dependency coefficients was examined and necessary modifications were proposed. The main experimental findings can be outlined as: - The mechanism of cavitation in tensiometers is indeed influenced by the surface roughness of the water reservoir. The new approach for expanding the range and duration of suction measurements for a newly designed HCT, based on hydrophilic coating of the reservoir walls, sounds promising. - The compression index (Cc) and creep index (Cαe) and the ratio α = Cαe/Cc for Sheppey London Clay are stress- and suction-dependent. The hypothesis of constant α for natural clays, as suggested by Mesri et al. (1994), is therefore rejected. - The volumetric creep deformations of unsaturated stiff clays appear to be relatively simply modelled by a creep law based on a power function. - A coupled effect of suction and strain-rate on 1D compression response was identified. At a constant suction, the higher the strain-rate, the higher the apparent preconsolidation pressure (σ'p). Similarly, at a constant strain-rate, the higher the suction, the higher the σ'p. - The values of relaxation coefficient (Rα) differ in saturated and unsaturated states. However, a clear relationship between Rα and suction was not found. The Rα = Cαe/Cc relationship, suggested by Yin et al. (2014) for saturated soft clays, appears, with an approximation, to be valid for the unsaturated stiff London Clay in the range of applied vertical stresses and soil suctions in this study. - The process of stress-relaxation in unsaturated clays is highly influenced by factors such as soil suction, pre-relaxation strain, stress, and strain-rate.

Resumo: Em um país de grande extensão territorial como o Brasil, são comuns faixas de dutos com muitas centenas e até milhares de quilômetros. Eles atravessam lugares com diversidade morfológica, rios, ambientes da costa marinha e áreas metropolitanas. A partir do momento em que o duto é instalado, este passa a sofrer influência do ambiente e também causar impacto ao mesmo, como vazamentos, e pesquisas têm interesse nestas questões porque estas envolvem a integridade dos dutos e comprometem o abastecimento dos derivados de petróleo. Neste contexto, este trabalho visa analisar a pressão da cobertura e uso da terra em faixas dos dutos Rio - Belo Horizonte, localizadas em três municípios do Estado do Rio de Janeiro, no período de 1986 a 2005, com a utilização de técnicas de geoprocessamento. Para a identificação e avaliação das pressões dos impactos humanos nas faixas de dutos, foram utilizados dados multitemporais e técnicas de detecção de mudanças. As análises de uso e ocupação da terra consideraram as relações dos sistemas de relevo em áreas de influência dos dutos. A partir destas primeiras análises, um índice de pressão antrópica (IPAd) foi proposto para analisar de forma conjunta as classes de uso e ocupação da terra. O mapa de IPAd e o mapa de variação de IPAd, possibilitaram a identificação de áreas de maior e menor pressão antrópica à faixa de dutos, bem como a variação desta pressão ao longo do período analisado. / Abstract: In a country with a great territorial extension as Brazil, pipelines with a lot of hundreds and even thousands of kilometers are common. They cross morphologic diversity places, rivers, coastal marines environments and metropolitan areas. After their installation, the pipelines suffer environmental influence that can cause impacts on them, as emptying, and some researchers have interest in these questions because it involves the pipeline integrity and compromise the supplying of oil derivates. In this context, this work aim to analyze the pressures of land use and land cover on Rio - Belo Horizonte pipelines strip, located in three municipal districts of Rio de Janeiro State, during 1986 to 2005, with geoprocessing techniques. To identify and evaluate the pressures of human impacts on the pipelines strip, multi-temporal datasets and change detection techniques were used. The analyses of land use and land cover considered the relationships of relief systems in some areas of pipeline influence. From these first analyses a pressure human index (IPAd) was proposed for pipelines strip, objecting an integrated study form between land cover and land use classes. The IPAd map and IPAd variations map, enabled the identification of areas with high and low pressure human for pipelines strip, as well as a variation of the pressures over the analyzed period. / Orientador: Paulina Setti Riedel / Coorientador: Mara Lúcia Marques / Banca: Cenira Maria Lupinacci da Cunha / Banca: Diana Sarita Hamburger / Mestre

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1981. / Vita. / Bibliography: leaves 232-235. / by Mark Hing Chuen Chan. / Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1981.

The research presented in this thesis focuses on the spatial variability of the Keswick and Hindmarsh Clays within the Adelaide city area. Keswick Clay is locally significant since many of Adelaide's multi-storey buildings are founded directly on it, and internationally significant, since it has been shown by Cox (1970), that this clay exhibits remarkably similar properties to those of the well-documented London Clay. The assessment of the small-scale variability of the undrained shear strength of these clays is based on measurements obtained using the electrical cone penetration test (CPT), and a micro-computer based data acquisition system, designed specifically for this study. A significant feature of the data acquisition system is that it enables measurements to be obtained at intervals of 5 mm, both reliably and efficiently. The development of the data acquisition system is discussed, and the accuracy of its measurements is examined. The small-scale variability of the undrained shear strength of the Keswick Clay is based on more than 200 vertical CPTs, performed within an area of 50 X 50 metres at a site located in the Adelaide city area. The CPTs were spaced at lateral intervals varying between 0.5 and 5 metres, with each vertical CPT extending to a typical depth of 5 metres. In addition, the small-scale horizontal spatial variability of the Keswick Clay is examined using an electrical cone penetrometer driven horizontally into the face of an embankment, again located within the Adelaide city area. The accuracy of the CPT measurements is examined, and discussion is given of the shortcomings associated with a commonly used technique, by Baecher (1982), for estimating the random measurement error associated with various test procedures. The assessment of the large-scale spatial variability of the undrained shear strength of the Keswick and Hindmarsh Clays is founded on a data base of geotechnical engineering properties, compiled from a number of consulting engineering practices and government instrumentalities. The data base, known as KESWICK, contains approximately 160 site investigations, 380 boreholes, and 10,140 measurements obtained from a number of different laboratory and in situ tests. In addition, KESWICK is used to establish generalised trends and bounds, associated with the various geotechnical engineering design properties contained within the data base. The techniques of random field theory and geostatistics are used to quantify, model and predict the spatial variability of the Keswick and Hindmarsh Clays. These techniques are compared with one another in order to assess the suitability and shortcomings of each, when applied to the study of the spatial variability of geotechnical engineering materials. Furthermore, a number of specifically-written computer programs, which were developed to enable the various spatial variability analyses to be performed, are discussed. It is demonstrated that the lateral undrained shear strength of the Keswick Clay, within the Adelaide city area, exhibits a nested structure; that is, one which is the compound effect of several genetic sources of spatial variation. In addition, it is shown that this nested structure can be adequately modelled by means of a spherical semivariogram model. The nested structure is used, together with the kriging estimation process, to provide preliminary estimates of the undrained shear strength of the Keswick Clay, within the Adelaide city area. The analyses demonstrate that the nested model and the kriging process provide a useful facility for generating preliminary estimates of the strength of the clay. Finally, the significance of the spatial variability of the undrained shear strength of clay soils is examined, with reference to the design of embankments and pile foundations. It is demonstrated that the correlation distance can greatly influence the design of each of these geotechnical systems. / Thesis (Ph.D.)--Dept. of Civil and Environmental Engineering, 1995.

University of Macau / Faculty of Science and Technology / Department of Civil and Environmental Engineering