Made available in DSpace on 2014-06-11T19:32:19Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-12-06Bitstream added on 2014-06-13T20:03:41Z : No. of bitstreams: 1 oliveira_ffg_dr_rcla.pdf: 4610872 bytes, checksum: 45e52968a1567896d83779b200a2257f (MD5) / Este trabalho objetiva identificar analiticamente os impactos ambientais negativos e determinar, a partir de modelos empíricos, em escala de 1:25.000, os graus de vulnerabilidade ambiental existentes no litoral sul do Estado do Rio Grande do Norte. Os resultados dos impactos foram obtidos mediante a proposição de metodologias de geoprocessamento específicas para cada impacto. A distribuição das diferentes classes de vulnerabilidade ambiental foi determinada a partir de modelamentos por álgebra de mapas. Os impactos ambientais analisados configuram-se nos campos de dunas, manguezais, faixas de praia e remanescentes florestais de Mata Atlântica. Quanto às dunas, o mapeamento indicou que 48,24% da área têm uma magnitude de impacto classificada como muito fraca. Contudo, o que preocupa é que os locais onde a magnitude do impacto é muito forte são exatamente as áreas com maior vulnerabilidade ambiental. Atualmente o maior avanço da carcinicultura ocorre em áreas que não são de manguezais, mas em sistemas ambientais associados. As faixas de praia podem se diferenciar quanto ao seu comprometimento ambiental, pois a capacidade de suporte aos impactos desses ambientes varia em função de suas características geoambientais. Apesar de os fragmentos florestais de Mata Atlântica apresentarem predominância de áreas muito irregulares (60,39%), muito pequenas (64,08%), com proporção de borda de 54,34%, má distribuição de sua densidade (setor sul) e circundados por cana-de-açúcar e áreas campestres (72,04%), eles ainda são responsáveis pelo controle geossistêmico e ecológico da área. Quanto à vulnerabilidade ambiental, verificou-se de que mais de 80% da área é classificada como de baixa e moderada vulnerabilidade. Isso mostra que, de acordo com o método aplicado e com os... / This study aims to identify analytically the negative environmental impacts and determine, based on empirical models, on a scale of 1:25,000, the existing degree of environmental vulnerability in the south coast of Rio Grande do Norte. The results of the impacts were obtained by the proposition of geoprocessing methodologies specific to each impact. The distribution of different classes of environmental vulnerability were determined from models for map algebra. The environmental impacts analyzed, are configured in the fields of dunes, mangroves, beach strips and areas of Mata Atlantica. Refering to the dunes, the mapping indicated that 48.24% of the area has a magnitude of impact rated as very small. However, the problem is that the locations where the magnitude of impact is very strong are the areas with greater environmental vulnerability. Currently the largest improvement in shrimp farming occurs in areas that are not mangrove, but in associated environmental systems.The beach strips may differ as to its environmental commitment, because the ability to support the impacts of these environments varies with geo-environmental characteristics. Although the present Mata Atlantica forest fragments shows predominance of very irregular areas (60.39%), very small (64.08%), with proportion of edge of 54.34%, bad distribution of density (southern sector) and surrounded by sugar cane fields and grassland (72.04%), they are still responsible for controlling geosystems and ecological area. Refering to the environmental vulnerability, we have concluded that more than 80% of the area is classified as low-and moderate vulnerability. This shows that, according to the method used and results achieved, most of the area is in balance. However... (Complete abstract click electronic access below)

Made available in DSpace on 2014-06-11T19:32:19Z (GMT). No. of bitstreams: 0 Previous issue date: 2002-11-08Bitstream added on 2014-06-13T19:47:12Z : No. of bitstreams: 1 nogueira_fr_dr_rcla.pdf: 6690879 bytes, checksum: d442517932963e0eff714639dec3f0ee (MD5) / O objetivo desta pesquisa foi a construção de um modelo conceitual e operacional para o gerenciamento municipal de riscos ambientais associados a escorregamentos em áreas de ocupação subnormal. Para tanto, foram adotadas duas vertentes metodológicas: (1) a revisão crítica de ampla bibliografia temática compilada, tendo como parâmetro a aplicabilidade à gestão municipal brasileira; e (2) à luz da teoria, a avaliação dos acertos e das dificuldades da prática pública de gerenciamento de riscos associados a escorregamentos nos municípios visitados ou acompanhados pelo pesquisador. Apresentam-se, ao longo do texto, conceitos e instrumentos operacionais úteis para técnicos e gestores públicos. No capítulo 6, os resultados da pesquisa estão sintetizados na forma de diretrizes e de um modelo para o gerenciamento de riscos ambientais associados a escorregamentos em áreas ocupadas por favelas e loteamentos irregulares, aplicáveis às diferentes realidades ambientais e urbanas do país. / The goal of this research was the construction of a conceptual and operative model for the local management of environmental risks associated with landslides in areas of subnormal urbanization. To achieve this goal, two methodological perspectives were adopted: (1) a critical revision of the broad thematic bibliography assembled, having its application to the Brazilian municipal management as a framework; (2) the use of theoretical approaches to evaluate accomplishments and difficulties experienced by public managers of landslide risks in some Brazilian cities. Throughout the paper, concepts and operative tools for technicians and public sector managers are presented. The chapter 6th. presents the synthesis of the products organized as directives and a model for management for environmental risks associated to landslides in sites occupied by slums and illegal settlements. These models are meant to be applicable to diverse environmental and urban realities of the country.

Orientador: Kenitiro Suguio / Banca: Omar Yazbek Bitar / Banca: Celso Santos Carvalho / Banca: Flavio Farah / Banca: Leandro Eugenio da Silva Cerri / Resumo: O objetivo desta pesquisa foi a construção de um modelo conceitual e operacional para o gerenciamento municipal de riscos ambientais associados a escorregamentos em áreas de ocupação subnormal. Para tanto, foram adotadas duas vertentes metodológicas: (1) a revisão crítica de ampla bibliografia temática compilada, tendo como parâmetro a aplicabilidade à gestão municipal brasileira; e (2) à luz da teoria, a avaliação dos acertos e das dificuldades da prática pública de gerenciamento de riscos associados a escorregamentos nos municípios visitados ou acompanhados pelo pesquisador. Apresentam-se, ao longo do texto, conceitos e instrumentos operacionais úteis para técnicos e gestores públicos. No capítulo 6, os resultados da pesquisa estão sintetizados na forma de diretrizes e de um modelo para o gerenciamento de riscos ambientais associados a escorregamentos em áreas ocupadas por favelas e loteamentos irregulares, aplicáveis às diferentes realidades ambientais e urbanas do país. / Abstract: The goal of this research was the construction of a conceptual and operative model for the local management of environmental risks associated with landslides in areas of subnormal urbanization. To achieve this goal, two methodological perspectives were adopted: (1) a critical revision of the broad thematic bibliography assembled, having its application to the Brazilian municipal management as a framework; (2) the use of theoretical approaches to evaluate accomplishments and difficulties experienced by public managers of landslide risks in some Brazilian cities. Throughout the paper, concepts and operative tools for technicians and public sector managers are presented. The chapter 6th. presents the synthesis of the products organized as directives and a model for management for environmental risks associated to landslides in sites occupied by slums and illegal settlements. These models are meant to be applicable to diverse environmental and urban realities of the country. / Doutor

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published_or_final_version / Applied Geosciences / Master / Master of Science

The purpose of this study is to improve site investigation in geotechnical engineering via the evaluation and development of statistical approaches for characterizing the spatial variability of soil properties and the development of site investigation simulation software for educational use. This study consists of four components: statistical characteristics, data measurement, simulation, and educational training. Statistical measures of spatial variability of soil properties were examined for three different geographical areas where soil formation processes differ to assess the influence on the spatial variability of soils. Statistical measures of spatial variability were also calculated for a case history where blasting was used as a method of soil improvement to evaluate the effects of man-made changes to soil structure. The concept of spatial aliasing was employed to estimate the maximum allowable sampling interval for field data as a function of the spatial correlation properties. Once a maximum statistically allowable sampling interval is determined for a specific soil property, the minimum statistically required number of soundings / borings is calculated to perform an economical site investigation at a specific site. A simple and efficient simulation technique was proposed to generate correlated, multi-dimensional simulations of soil properties. Based on limited data, the proposed simulation technique generated accurate and correlated simulations of soil properties that are consistent with the observed or proposed correlation structures of soil properties. Lastly, a geotechnical site investigation simulation program with a wide variety of in situ and laboratory tests was developed to allow students to plan and perform a comprehensive site investigation program. The simulation generates an input file based partly on the statistical characteristics of the spatial variability of soil properties analyzed in this study and partly on traditional values. Spatial variability in soil properties is modeled via correlated random fields, interpolation, and a decomposition method to yield realistic geotechnical data. Via the simulation, students are able to obtain experience and judgment in an essential component of geotechnical engineering practice. The four components of this research (statistical characteristics, data measurement, simulation, and educational training) focus on the improvement of site investigation performance in geotechnical engineering, thereby improving reliability analysis in geotechnical practice.

Photocopy of typescript. / Digitized by Kansas State University Libraries

The phenomenon known as the ‘arching effect’ occurs when a portion of granular mass yields relative to an adjacent stationary region. The movement is resisted by shearing stresses which act to reduce the pressure on the yielding support and increase the pressure on the adjacent stationary supporting zones. Arching is widely observed in both natural and man-made structures such as piled embankments, tunnelling, and above mine works and sinkholes. In this research the arching effect is recreated in the increased gravity environment of a geotechnical centrifuge where the pressure distribution across both the yielding and supporting soil masses is measured and the resulting soil displacements observed. A motor driven ‘trapdoor’ apparatus was built inside a plane strain container to model the yielding support. Both the trapdoor and an adjacent support were instrumented to measure the force (and derived pressure) distribution. Soil and trapdoor displacements are determined by analysis of digital images taken in-flight through a Perspex wall of the container. One method of increasing soil shear strength and its resistance to deformation is the reinforcement of soil with randomly distributed discrete fibres. The degree of improvement has been shown to be directly related to the fibre content in the soil, the fibre aspect ratio, orientation and mechanical properties. In this research the effect of fibre reinforcement on the arching process and resulting deformation is examined by variation of fibre parameters such as fibre aspect ratio and volumetric content of fibre. The influence of fibre and model scale effects were investigated by conducting a modelling of models exercise whereby trapdoor scale and effective stress were varied whilst maintaining a constant cover depth to structure width ratio, and compaction effort. The results were compared directly with those obtained for unreinforced soil trapdoor tests in order to determine the extent of improvement offered by fibre-reinforcement.

The interpretation of measurements from the cone penetration test is still predominately based on empirical correlations, which can be attributed to the lack of understanding of penetration mechanisms, that involve severe stress-strain and shear dilatancy close to the probe. Even so, it remains one of the most widely used in-situ tools for site characterisation, and several methods for displacement pile design have been developed using CPT data. This research investigates the response of penetrometers and the behaviour of layered soils during installation of probes using geotechnical centrifuge modelling and cavity expansion analysis. Two series of centrifuge tests were performed in stratum configurations of silica sand in a half-cylindrical axisymmetric model, allowing the observation of the induced soil deformation through a Perspex window. The variations of penetration resistance and soil deformation with penetration depth, soil density, stress level and soil layering are examined from the results of the centrifuge tests. The quantified soil displacements and the resulting strains in the axisymmetric model have provided an effective approach for investigation of penetration mechanisms with soil element trajectories, strain paths and rotations of principal strain rate. The effects of layering on both resistance and soil deformation are shown with dependence of the relative soil properties and profiles. The results presented also serve as a base for applications of cavity expansion solutions, back analyses and further studies. Analytical solutions for cavity expansion in two concentrically arranged regions of soil are developed using a non-associated Mohr-Coulomb yield criterion for large strain analysis of both spherical and cylindrical cavities. The solutions are validated against finite element simulations and a detailed parametric study of the layered effects on the pressure-expansion curves is performed. To apply the proposed solutions to penetration problems, a simplified combination approach is suggested to eliminate the discrepancy between concentric layering and horizontal layering. The analytical study of penetration in two-layered and multi-layered soils is therefore achieved, with comparisons to elastic solutions and numerical simulations provided. The back analyses based on the resistance and soil deformation emphasise the influences of small-strain stiffness, soil-probe interface friction angle, and relative density/state parameter. The correlation between the cone tip resistance and the pile bearing capacity is also discussed, and the scale effects are examined through the ground surface effect and the layering effect by the developed cavity expansion solutions. The penetration mechanisms are summarised from the aspects of soil stress-strain history, particle breakage, soil patterns, and penetration in layered soils. The layered effects emphasised in this research indicate that the penetration resistance is strongly dependent on the soil properties within the influence zones above and below the probe tip, and also related to the in-situ stress gradient along the penetration path. It is also suggested that correlations from calibration chamber tests using uniform soil and a constant stress field may not be suitable for direct interpretation of CPT data. Finally, the averaging technique for pile design is suggested based on the transition curve of tip resistance in layered soils with consideration of the scale effects.

Cone penetration testing (CPT) is one of the most versatile devices for in situ soil testing. With minimal disturbance to the ground, it provides information about soil classification and geotechnical parameters. Several researchers have used different numerical techniques such as strain path methods and finite element methods to study CPT problems. The Discrete Element Method (DEM) is a useful alternative tool for studying cone penetration problems because of its ability to provide micro mechanical insight into the behaviour of granular materials and cone penetration resistance. This study uses three-dimensional DEM to simulate the cone penetration testing of granular materials in a calibration chamber. Due to the geometric symmetry of this study a 90 degree segment of the calibration chamber and the cone penetrometer was initially considered followed by a 30 degree segment to allow for the simulation of smaller particle sizes and to reduce computational time. This research proposes a new particle refinement method, similar to the mesh refinement of finite-element modelling, in the sense that a large number of small particles were brought into contact with the cone tip, while the large particles were distanced further away from the cone, to reduce computational time effectively. Using a radius expansion method for sample preparation and assigning a constant mass to each particle in the sample was found to reduce computational time significantly with little influence on tip resistance. The effects of initial sample conditions and particle friction coefficient were found to have an important influence on the tip resistance. In addition, prohibiting particle rotation was found to increase tip resistance significantly compared to when the particles were permitted to rotate freely. Particle shape in this study was simulated by replacing the spheres with simple two-ball clumps and was found to have an important effect on the tip resistance. DEM simulations of biaxial tests were conducted to investigate the effect of initial sample conditions, particle shape and particle friction coefficient on the stress-strain behaviour of granular materials. All the above mentioned parameters were found to have a significant effect on the stress-strain behaviour of granular materials. Biaxial test simulations were also conducted to obtain basic granular material properties to derive analytical CPT solutions from continuum mechanics principles. Some of the DEM simulation results were found to be in good agreement with the analytical solutions that used a combined cylindrical-spherical cavity expansion method. Particle crushing was simulated during the cone penetration tests by replacing a broken particle with two new equi-sized smaller particles with mass conserved. The results showed considerable reduction in the tip resistance for the crushing model compared to the non-crushing model and this reduction increased as the confining stress increased.