No description available.

Made available in DSpace on 2014-06-11T19:28:35Z (GMT). No. of bitstreams: 0 Previous issue date: 2004-11Bitstream added on 2014-06-13T20:58:35Z : No. of bitstreams: 1 mazur_rl_me_guara.pdf: 2192483 bytes, checksum: 24772053abc0675fdf4455448fe4adc3 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Universidade Estadual Paulista (UNESP) / As superligas à base de níquel são aplicadas nos mais diversos e complexos sistemas de engenharia, entretanto há poucos dados sobre o comportamento erosivo destas superligas frente ao impacto de particulas sólidas em um fluxo gasoso. A erosão por partícula sólida é um fenômeno complexo e caracteriza-se pela deformação e remoção de material durante o impacto das partículas, gerando elevadas temperaturas. As superligas à base de níquel Nimonic 80 A e Inconel 600, são materiais que possuem ótimas propriedades mecânicas emelevadas temperaturas, por este motivo, as suas características quanto à erosão em temperatura ambiente, serão medidas e analisadas, em vista da perda das propriedades mecânicas dos aços em temperaturas mais altas durante o impacto das partículas. Os ensaios de erosão foram realizados em um dispositivo do tipo jato de impacto ar-areia, onde as partículas erosivas forma introduzidas em um sistema à alta pressão e aceleradas ao longo de um bocal antes de impactar a superfície do material, permitindo simular os principais parâmetros do desgaste erosivo. Os ensaios realizados apresentaram pequenas diferenças para todosângulos de impacto testados (15°, 30°, 60°, 90°), porém os intervalos de confiança se superpõem para quase todos eles apesar da marcante diferença entre as propriedades mecânicas das superligas Nimonic 80 A e Inconel 600, não sendo possível estabelecer alguma correlação com a resistência à erosâo. / The Ni-base superalloys are applied in several and complexest engineering systems, however there are few data about the erosive behaviour of these superalloys regarding the impact of solid particles in a gaseous flow. The solid particle erosion is a complex phenomenon and it is characerized by the deformation and material removal during the impact of the particles generating high temperatures. The Ni-basesuperalloys Nimonic 80 A and Inconel 600, have excellent mechanical properties in high temperature, by this reason, theirs characteristics in erosion at room temperature, will be measured and analyzed, in view of the losses of the mechanical properties of the steels in higher temperatures during the impact of the particles. The erosion tests have been performed in air-sand jet impingement device, where the erosive particles were introduced in a system with high pressure and accelerated along a nozzle before impact the surface of the material, allowing to simulate the main parameters of the erosion wear. The results showed small differences for all impact angles tested (15°, 30°, 60°, 90°), however the reliable intervals have been superimpsed for almost all of them, in spite of the great differences among the mechanical properties of the superalloys Nimonic 80 A and Inconel 600, it was noto possible to establish some correlation with the erosion resistance.

Made available in DSpace on 2015-03-03T11:52:44Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-06-30Bitstream added on 2015-03-03T12:07:06Z : No. of bitstreams: 1 000805832.pdf: 4937874 bytes, checksum: bcf1424a8c5e4cca59263834d615aa4a (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nivel Superior / Esta dissertação de mestrado apresenta resultados acerca da avaliação da erodibilidade de um solo não saturado localizado em uma área urbana de Bauru-SP afetada por um processo erosivo. O processo erosivo em questão se desencadeou devido a intervenção antrópicas no local sem devidas precauções para amenização do impacto causado, como o desmatamento, impermeabilização do solo e construção de loteamentos residenciais de alto padrão com projetos inadequados e falta de obras de infra-estrutura de drenagem. A avaliação do fenômeno se due por meio de levantamento bibliográfico do tema, principalmente do histórico de informações disponíveis acerca do processo erosivo, observações de campo e ensaios de laboratório: caracterização, erodibilidade através do Inderbitzen e cisalhamento direto, além de ensaios para medida e controle de sucção das amostras, afim de se obter a curva de retenção e valores de comparação através deste parâmetro para os ensaios de erodibilidade. Todos os ensaios foram realizados em amostras de dois locais distintos ao longo do processo erosivo. Os solos da região são residuais de Arenito, caracterizados como areias finas a médias argilosiltosas. Os resultados dos ensaios de erodibilidade através do Inderbitzen mostraram grande quantidade de solo carreada pelo escoamento hídrico superficial, sendo maiores taxas ocorridas no solo do Local A. A perda de solo variou em sua quantidade de acordo com a inclinação da rampa. Assim, quanto maior a inclinação da rampa, maior a quantidade de perda do solo, que demonstra a susceptibilidade deste solo à erosão hídrica em locais com a topografia mais acentuada. Em geral, a maior taxa de erodibilidade ocorreu no tempo de 5 minutos, com uma tendência à estabilização nos tempos seguintes. Essa tendência ocorreu nos diferentes tipos de amostras utilizadas, exceto para a amostra com sucção de 0 kPa, que apresentou o pico de maior perda de... / This master's dissertation reports an assessment of the erodibility of unsaturated soil located in an urban are affected by erosion in Bauru, São Paulo. The erosion process in question was triggered by human interference at the site, which was undertaken without proper precautions to reduce the resulting impact, which included deforestation, sealing of the soil, use of inadequate plans to construct high-end residential subdivisions, and lack of drainage infrastructure. The phenomenon was assessed by a survey of the literature-principally historical information related to the erosion process - field observations, and laboratory tests: characterization, erodibility as assessed by the Inderbitzen and direct shear tests, and tests to measure and monitor soil suction of the samples in order to obtain the soil-water retention curve and comparison values through this parameter for the erodibility tests. All tests were performed on samples from two distinct locations throughout the erosion zone. The soils from the region are remnants of sandstone and are characterized as clay-sit soils with fine to medium sand. The Inderbitzen tests showed a large amount of soil carried away by water flow, with higher rates registered for the soil from Location A. Soil loss varied in quantify according to the slope of the ramp. Consequently, the greater the slope of the ramp, the greater the amount of soil loss, which demonstrates the susceptibility of this soil to erosion resulting from water in places with more pronounced topography. In general, the highest rate of erodibility occurred at 5 min, with a tendency to stability thereafter. This tendency occurred in the different types of samples used, except for the sample with soil suction of 0 KPa, which showed the greatest soil loss at 1 min. This demonstrates the influences of soil suction in the first moments of contact with the water flowing in the Inderbitzen test. The direct shear tests showed that the...

Comprehensive sediment budgets are compiled for a series of pocket shingle beaches in West Dorset backed by massive soft cliffs that degrade in a rapid and complex manner. Studies involve the identification and quantification of sediment (primarily shingle) inputs, transfers, storage and outputs within terrestrial and marine subsystem components. Results are unified within budget and flow models and applied to tackle questions of coastal evolution and management. Research involved mapping and sampling of the ground forming materials in terms of their beach forming potential. Cliff landsliding and recession are analysed using comparisons of historical maps, aerial photos and documentary evidence. A method of quantifying the release, throughput and supply to the beaches of various sediment grades from the eroding cliffs is presented. The volumes and types of sediment at the beach and in the inshore zone are investigated by various profile, intertidal, and offshore surveys. Detailed sampling and sediment analysis of the beaches is undertaken to elucidate beach drift and for attrition assessments through comparisons with cliff inputs. Shingle tracing experiments using aluminium tracers are conducted to study transport and sorting at two contrasting sites over a full spectrum of wave energy conditions. Validated littoral drift volumes and original wave power relationships are developed. Information is compiled to produce budget models for the main beaches. Complex long established links are demonstrated between eroding cliff sources and the shingle beaches that they supply. Chesil Beach is identified as the ultimate shingle sink suggesting that it is not entirely a product of the Holocene transgression as often envisioned, but a component of a Lyme Bay process system and open periodically to inputs of shingle from the west. Adverse impacts arising from various human interventions are highlighted using the models.

Biochar production and application to soil can mitigate climate change and improve soil quality. This thesis investigated the influence of biochar preparation methods and application rates on the hydrological and erosional characteristics of biochars themselves and the soils to which they were applied. Biochar hydrophobicity was influenced by feedstock and decreased with increasing highest treatment temperature (HTT). Biochar did not influence soil wettability and the effect of HTT on biochar porosity was more important for soil water-holding capacity than its effect on hydrophobicity. HTT affected biochar yield, cation exchange-capacity and provision of fungal substrates. HTT also significantly influenced the effect of biochar on soil suction. Smaller feedstock particles produced biochars that were slightly more hydrophobic than those produced from larger particles. The effects of biochar application on the properties of sandy loam were influenced by biochar particle size, because larger particles had less effect on bulk density and had slower water uptake. A low biochar application rate (5 g kg-1) had no effect on the aggregate stability of a silt loam and did not affect the hydrological and erosional response of the soil under simulated rainfall. Application rates of 25 and 50 g kg-1 reduced aggregate stability, which led to surface sealing and overland flow generation occurring more readily. However, there was no more erosion of these soils than those with low or zero biochar content, and the crusts formed by seal drying were much weaker than those formed on soils with low or zero biochar. Biochar was preferentially eroded from the soils, regardless of the application rate used. HTT and particle size can have important implications both for the properties of biochar itself and for its effects on soil properties. However, biochar may only substantially influence soil hydrology and erosion when applied at sufficiently high rates.

Orientador: Roger Augusto Rodrigues / Banca: José Augusto de lollo / Banca: Heraldo Luiz Giacheti / Resumo: Esta dissertação de mestrado apresenta resultados acerca da avaliação da erodibilidade de um solo não saturado localizado em uma área urbana de Bauru-SP afetada por um processo erosivo. O processo erosivo em questão se desencadeou devido a intervenção antrópicas no local sem devidas precauções para amenização do impacto causado, como o desmatamento, impermeabilização do solo e construção de loteamentos residenciais de alto padrão com projetos inadequados e falta de obras de infra-estrutura de drenagem. A avaliação do fenômeno se due por meio de levantamento bibliográfico do tema, principalmente do histórico de informações disponíveis acerca do processo erosivo, observações de campo e ensaios de laboratório: caracterização, erodibilidade através do Inderbitzen e cisalhamento direto, além de ensaios para medida e controle de sucção das amostras, afim de se obter a curva de retenção e valores de comparação através deste parâmetro para os ensaios de erodibilidade. Todos os ensaios foram realizados em amostras de dois locais distintos ao longo do processo erosivo. Os solos da região são residuais de Arenito, caracterizados como areias finas a médias argilosiltosas. Os resultados dos ensaios de erodibilidade através do Inderbitzen mostraram grande quantidade de solo carreada pelo escoamento hídrico superficial, sendo maiores taxas ocorridas no solo do Local A. A perda de solo variou em sua quantidade de acordo com a inclinação da rampa. Assim, quanto maior a inclinação da rampa, maior a quantidade de perda do solo, que demonstra a susceptibilidade deste solo à erosão hídrica em locais com a topografia mais acentuada. Em geral, a maior taxa de erodibilidade ocorreu no tempo de 5 minutos, com uma tendência à estabilização nos tempos seguintes. Essa tendência ocorreu nos diferentes tipos de amostras utilizadas, exceto para a amostra com sucção de 0 kPa, que apresentou o pico de maior perda de... / Abstract: This master's dissertation reports an assessment of the erodibility of unsaturated soil located in an urban are affected by erosion in Bauru, São Paulo. The erosion process in question was triggered by human interference at the site, which was undertaken without proper precautions to reduce the resulting impact, which included deforestation, sealing of the soil, use of inadequate plans to construct high-end residential subdivisions, and lack of drainage infrastructure. The phenomenon was assessed by a survey of the literature-principally historical information related to the erosion process - field observations, and laboratory tests: characterization, erodibility as assessed by the Inderbitzen and direct shear tests, and tests to measure and monitor soil suction of the samples in order to obtain the soil-water retention curve and comparison values through this parameter for the erodibility tests. All tests were performed on samples from two distinct locations throughout the erosion zone. The soils from the region are remnants of sandstone and are characterized as clay-sit soils with fine to medium sand. The Inderbitzen tests showed a large amount of soil carried away by water flow, with higher rates registered for the soil from Location A. Soil loss varied in quantify according to the slope of the ramp. Consequently, the greater the slope of the ramp, the greater the amount of soil loss, which demonstrates the susceptibility of this soil to erosion resulting from water in places with more pronounced topography. In general, the highest rate of erodibility occurred at 5 min, with a tendency to stability thereafter. This tendency occurred in the different types of samples used, except for the sample with soil suction of 0 KPa, which showed the greatest soil loss at 1 min. This demonstrates the influences of soil suction in the first moments of contact with the water flowing in the Inderbitzen test. The direct shear tests showed that the... / Mestre

Low-tech rock structures called gabions are commonly used in dryland stream channels to reduce erosion, slow floodwaters, and increase infiltration. Gabions may also increase water availability for riparian vegetation, and increase the duration of surface flow in ephemeral stream channels. However, their effects on infiltration and recharge are not well-understood. This study tested low-cost methods for easily quantifying the total infiltration induced by gabion construction in an ephemeral stream channel, over the course of a single flow event. We used well-established methods to find point infiltration fluxes from subsurface temperature time-series. Unique to this study, we then upscaled these measurements to the gabion’s entire area of influence using time-lapse photo data, which recorded the onset of flow and the duration of ponding. For a flow lasting ~5 hours, we ran 225 model scenarios, estimating that a single gabion could have increased the total infiltrated volume in the channel reach between it and the next gabion by as much as 255% or as little as 0%, but the most likely scenario is a 10.8% increase. We found the photo data to be invaluable in obtaining these estimates, and in understanding the dynamics of a remote field site. Future work would benefit from more precise measurements of point infiltration fluxes and better records of ponded surface area over time. If these improvements are made and our estimates can be replicated reliably, they would suggest that gabions are a more powerful restoration and management tool than previously understood.

This thesis concerns soil erosion and conservation in Zimbabwe. It is framed in the light of the contemporary heightened concern for the environment generally in Africa and the recent publication of the National Conservation Strategy for Zimbabwe (1987). Soil erosion is an archetypal interdisciplinary problem. This thesis complements and extends understanding of soil erosion and conservation in Zimbabwe via a methodological approach and a scale of analysis which have been under-represented in the literature to date. The research adopts a pluralist, regional political ecology approach (after Blaikie and Brookfield 1987) to soil erosion and conservation in Svosve communal area, combining political-economic understanding with case study analysis of changing social-environmental relationships. Plural problem definitions are constructed through interview and survey techniques, historical analysiso f archival sourcesa nd oral testimonies,a ssessmenot f contemporary policy and planning documents and via sequential air photograph analysis. The researchc hallengesa spectso f the colonial conservationislti terature to date for southernA frica andn ational level modelling of human-environmenrte lationshipsi n Zimbabwe. It presentsa quantitativea ssessmenotf the changei n symptomso f deterioration and in the nature and extent of soil erosion for the case study area. It operationalisesth e concepto f multiple problem definitions with implications for the contemporary model for conservation extension and for improving the role of local development institutions.

The study examines the relationship between the spatial variation in soil erosion and various natural and anthropogenic attributes of the region between the coastal plateau and the Winterberg escarpment of Ciskei. A raster-based geographical information system is derived for four separate study catchments and data on soil erosion and various soil erosion hazard indices are read into a computerised data matrix. The independent variables (soil erosion hazard indices) used in the study are selected on the basis of a review of the literature and on the availability of data in the Ciskei region. Multivariate analyses of the relationship between soil erosion and the various independent variables reveals that the primary variables affecting the spatial variation in soil erosion are land use, dominant soil type, geology, veld type and mean annual precipitation. All of these variables are readily quantifiable at the regional scale for large areas of Ciskei. An erosion hazard assessment model for use in central Ciskei is developed based on the results of the statistical analyses. The model is tested in separate study areas and is shown to provide an efficient method of identifying areas of differing susceptibility to soil erosion. The derived model is simple to operate and has input requirements which are easily met. It can be applied without the aid of computers, or where large areas are to be mapped it is well suited to computerisation

No description available.