Turfgrass establishment on sand-based rootzones is routinely accomplished by using sod produced on a fine-textured native soil. As a result, soil layering occurs, potentially causing initial reduction in water infiltration, rooting, aeration, and overall turfgrass quality. This research was aimed at determining the feasibility of applying sand over existing native soil to produce hybrid bermudagrass (Cynodon dactylon [L.] Pers. x C. transvaalensis Burtt-Davy) sand-based sod. Factors evaluated were visual quality and scalping. Treatments were harvested and transplanted to a sand-based research green where handle-ability, tensile strength, and infiltration were also evaluated. Results indicate aerify and topdress treatments showed higher quality pre-harvest. Control and 25 mm treatments were best in terms of harvesting, handle-ability, and sod tensile strength. Infiltration data indicated no significant differences between treatments. These outcomes along with further analysis could provide sod producers with a valuable product for use on sand-based rootzones.

Yes / The principal aim of this paper is to investigate the effect of sand grading, surface morphology, and content on the rheological properties—that is, yield stress and plastic viscosity—of fresh mortar. Mortars were produced from four different types of sand at two volumetric cement-sand ratios of 1/0.9 and 1/0.6. Each blend was prepared with five water-cement ratios of 0.60, 0.55, 0.50, 0.45, and 0.40. The rheometer was used to determine yield stress and plastic viscosity parameters of each cement paste and mortar. Test results show that the relative yield stress and plastic viscosity of mortar to cement paste is inversely proportional to the excess paste thickness up to low values, below which the surface texture of sand particles becomes significant.

Sand movement is one of the many environmental problems facing humans in the dry and semi-dry areas of the world. This study has investigated the observed changes in sand dune coverage compared to predictions, and has also assessed the impact of sand movement on human activity in the north western coastal region of Libya. The study used three methods. The first was a statistical model proposed by Bagnold, which correlates wind shear velocity with particle size, in order to predict likely sand movement. It was found that 60% of sand grains within the study area have a diameter of less than 0.25 mm, making them liable to be moved by the wind speeds recorded, particularly from March until September, and mostly in a northerly direction. The sand in the western part of the study area had a greater predicted rate of sand transport compared with the sand in the eastern part, which was related to its origin. The second method involved the analysis of satellite images for four different years; from 1986 to 2003. The land cover in the study area was found to have changed over this time. Sand dune area cover had increased, and there were other changes particularly a decline in forest. The third method was the use of a questionnaire (the respondents being land owners), which showed that there was notable loss of crop production (by about a quarter) due to sand movement, and that land owners mostly used afforestation to help control the sand movement in the region. The observed sand movement did not match the predictions based solely on sand grain size and wind speed, and climatic analyses showed no convincing trends which could explain increased sand movement except perhaps an increase in wind gusts. The thesis concludes that the overriding determinant in greater sand movement over the period studied was the loss of forest from the area due to human impacts, which farmers are having to compensate for by planting trees locally to reduce sand movement.

No description available.

The goal of this work is to develop and characterize a manufacturing process that is able to create metal matrix composites with complex cellular geometries. The novel manufacturing method uses two distinct additive manufacturing processes: i) fabrication of patternless molds for cellular metal castings and ii) printing an advanced cellular ceramic for embedding in a metal matrix. However, while the use of AM greatly improves the freedom in the design of MMCs, it is important to identify the constraints imposed by the process and its process relationships. First, the author investigates potential differences in material properties (microstructure, porosity, mechanical strength) of A356 — T6 castings resulting from two different commercially available Binder Jetting media and traditional 'no-bake' silica sand. It was determined that they yielded statistically equivalent results in four of the seven tests performed: dendrite arm spacing, porosity, surface roughness, and tensile strength. They differed in sand tensile strength, hardness, and density. Additionally, two critical sources of process constraints on part geometry are examined: (i) depowdering unbound material from intricate casting channels and (ii) metal flow and solidification distances through complex mold geometries. A Taguchi Design of Experiments is used to determine the relationships of important independent variables of each constraint. For depowdering, a minimum cleaning diameter of 3 mm was determined along with an equation relating cleaning distance as a function of channel diameter. Furthermore, for metal flow, choke diameter was found to be significantly significant variable. Finally, the author presents methods to process complex ceramic structure from precursor powders via Binder Jetting AM technology to incorporate into a bonded sand mold and the subsequently casted metal matrix. Through sintering experiments, a sintering temperature of 1375 °C was established for the ceramic insert (78% cordierite). Upon printing and sintering the ceramic, three point bend tests showed the MMCs had less strength than the matrix material likely due to the relatively high porosity developed in the body. Additionally, it was found that the ceramic metal interface had minimal mechanical interlocking and chemical bonding limiting the strength of the final MMCs. / Ph. D.

No description available.

Este trabalho teve como objetivo traçar um panorama do gerenciamento dos processos das indústrias de fundição ferrosa no estado do Rio Grande do Sul que utilizam areias de fundição, com ênfase nas alternativas buscadas por estas empresas quanto à minimização, recuperação e destinação final dada às areias usadas. Esta avaliação foi feita enfocando desde a recepção das areias virgens, armazenamento, preparação da mistura para fabricação dos moldes e machos, até o descarte nos setores de desmoldagem e retirada dos fundidos, recuperação e reutilização das areias no próprio processo ou descarte, e a procura de possibilidades de reúso em outros processos. No gerenciamento dos processos foram abordadas ainda, questões relativas às emissões geradas durante o manuseio, armazenamento, mistura, operações de moldagem e macharia, bem como no resfriamento e desmoldagem. Procurou-se relacionar o gerenciamento ambiental adequado dos processos acima mencionados ao licenciamento ambiental e à existência de certificação ambiental. O trabalho iniciou com pesquisa no Banco de Dados da FEPAM, sendo verificado o número de fundições no estado, elaborados e enviados questionários para essas empresas, utilizando-se o método survey. Os resultados obtidos possuem uma boa representatividade, considerando resposta de 85% dos mesmos. Através dos resultados verificou-se que, apesar de 81% das empresas descartarem as areias geradas em aterros industriais licenciados pelo FEPAM, somente uma delas está procurando alternativas de reúso das areias geradas. Também verificou-se que não há uma preocupação com a minimização da geração desses resíduos. O licenciamento ambiental no Rio Grande do Sul é hoje a única ferramenta através da qual é possível exigir das empresas a adequação de suas atividades de forma a não impactar o meio ambiente. Quanto às demais questões ambientais relacionadas aos processos envolvendo areias, a percepção das empresas ainda é bastante incipiente. / This work aimed to present a preliminary evaluation of foundry sand processes management in Rio Grande do Sul state, Brazil, with emphasis in alternatives related to sand reduce, regeneration e final destination. This evaluation was made with focuse since sands reception, their storage and preparation, till the discharge in the shakeout system, regeneration e their reuse. It also aims to relate the proper waste management to environmental license as well to the existence of environmental certification. Attempt was made to verify if the companies, in regard of their costs with new sand and molding sand disposal in specialized landfills, as well as to the requirements of environmental agency, are working in sense of seeking and implant new recycling technologies and reuse of used sands. In adition to that, it was verified if it would exist a relation between environmental license and/or certification with the sand used correct management and proper foundry sand destination. Or still, within the approach of cleaner technologies and best available techniques if the alternatives for recycling sand into their own processes or reuse in other process are being pursuited. Within the sand management, it was still approached questions related to emissions generated during handling, storage, mixing, molding and coremaking, as well as cooling and shaking. This work was developed inicially through research on FEPAM, the environmental state agency, database, where it was verified the number of foundry industries in Rio Grande do Sul state, being elaborated and sent to the companies, questionnaires using the survey method. The gotten results have good representation considering that 85% of the questionnaires had been answered.Through the gotten results it was verified that, although 82% of the companies discharge used sands in licensed landfills, in accord with regulamentation, only one of them is seeking for reuse alternatives out of the process. It also was verified that there isn’t any concernig about reducing the sand generation. The environmental licence here in Rio Grande do Sul is in fact, the only way to make the companies adequate their installations aiming at environmental protection. To the other questions related to the processes using sands, the companies perception are very incipient.

Este trabalho teve como objetivo traçar um panorama do gerenciamento dos processos das indústrias de fundição ferrosa no estado do Rio Grande do Sul que utilizam areias de fundição, com ênfase nas alternativas buscadas por estas empresas quanto à minimização, recuperação e destinação final dada às areias usadas. Esta avaliação foi feita enfocando desde a recepção das areias virgens, armazenamento, preparação da mistura para fabricação dos moldes e machos, até o descarte nos setores de desmoldagem e retirada dos fundidos, recuperação e reutilização das areias no próprio processo ou descarte, e a procura de possibilidades de reúso em outros processos. No gerenciamento dos processos foram abordadas ainda, questões relativas às emissões geradas durante o manuseio, armazenamento, mistura, operações de moldagem e macharia, bem como no resfriamento e desmoldagem. Procurou-se relacionar o gerenciamento ambiental adequado dos processos acima mencionados ao licenciamento ambiental e à existência de certificação ambiental. O trabalho iniciou com pesquisa no Banco de Dados da FEPAM, sendo verificado o número de fundições no estado, elaborados e enviados questionários para essas empresas, utilizando-se o método survey. Os resultados obtidos possuem uma boa representatividade, considerando resposta de 85% dos mesmos. Através dos resultados verificou-se que, apesar de 81% das empresas descartarem as areias geradas em aterros industriais licenciados pelo FEPAM, somente uma delas está procurando alternativas de reúso das areias geradas. Também verificou-se que não há uma preocupação com a minimização da geração desses resíduos. O licenciamento ambiental no Rio Grande do Sul é hoje a única ferramenta através da qual é possível exigir das empresas a adequação de suas atividades de forma a não impactar o meio ambiente. Quanto às demais questões ambientais relacionadas aos processos envolvendo areias, a percepção das empresas ainda é bastante incipiente. / This work aimed to present a preliminary evaluation of foundry sand processes management in Rio Grande do Sul state, Brazil, with emphasis in alternatives related to sand reduce, regeneration e final destination. This evaluation was made with focuse since sands reception, their storage and preparation, till the discharge in the shakeout system, regeneration e their reuse. It also aims to relate the proper waste management to environmental license as well to the existence of environmental certification. Attempt was made to verify if the companies, in regard of their costs with new sand and molding sand disposal in specialized landfills, as well as to the requirements of environmental agency, are working in sense of seeking and implant new recycling technologies and reuse of used sands. In adition to that, it was verified if it would exist a relation between environmental license and/or certification with the sand used correct management and proper foundry sand destination. Or still, within the approach of cleaner technologies and best available techniques if the alternatives for recycling sand into their own processes or reuse in other process are being pursuited. Within the sand management, it was still approached questions related to emissions generated during handling, storage, mixing, molding and coremaking, as well as cooling and shaking. This work was developed inicially through research on FEPAM, the environmental state agency, database, where it was verified the number of foundry industries in Rio Grande do Sul state, being elaborated and sent to the companies, questionnaires using the survey method. The gotten results have good representation considering that 85% of the questionnaires had been answered.Through the gotten results it was verified that, although 82% of the companies discharge used sands in licensed landfills, in accord with regulamentation, only one of them is seeking for reuse alternatives out of the process. It also was verified that there isn’t any concernig about reducing the sand generation. The environmental licence here in Rio Grande do Sul is in fact, the only way to make the companies adequate their installations aiming at environmental protection. To the other questions related to the processes using sands, the companies perception are very incipient.

Este trabalho teve como objetivo traçar um panorama do gerenciamento dos processos das indústrias de fundição ferrosa no estado do Rio Grande do Sul que utilizam areias de fundição, com ênfase nas alternativas buscadas por estas empresas quanto à minimização, recuperação e destinação final dada às areias usadas. Esta avaliação foi feita enfocando desde a recepção das areias virgens, armazenamento, preparação da mistura para fabricação dos moldes e machos, até o descarte nos setores de desmoldagem e retirada dos fundidos, recuperação e reutilização das areias no próprio processo ou descarte, e a procura de possibilidades de reúso em outros processos. No gerenciamento dos processos foram abordadas ainda, questões relativas às emissões geradas durante o manuseio, armazenamento, mistura, operações de moldagem e macharia, bem como no resfriamento e desmoldagem. Procurou-se relacionar o gerenciamento ambiental adequado dos processos acima mencionados ao licenciamento ambiental e à existência de certificação ambiental. O trabalho iniciou com pesquisa no Banco de Dados da FEPAM, sendo verificado o número de fundições no estado, elaborados e enviados questionários para essas empresas, utilizando-se o método survey. Os resultados obtidos possuem uma boa representatividade, considerando resposta de 85% dos mesmos. Através dos resultados verificou-se que, apesar de 81% das empresas descartarem as areias geradas em aterros industriais licenciados pelo FEPAM, somente uma delas está procurando alternativas de reúso das areias geradas. Também verificou-se que não há uma preocupação com a minimização da geração desses resíduos. O licenciamento ambiental no Rio Grande do Sul é hoje a única ferramenta através da qual é possível exigir das empresas a adequação de suas atividades de forma a não impactar o meio ambiente. Quanto às demais questões ambientais relacionadas aos processos envolvendo areias, a percepção das empresas ainda é bastante incipiente. / This work aimed to present a preliminary evaluation of foundry sand processes management in Rio Grande do Sul state, Brazil, with emphasis in alternatives related to sand reduce, regeneration e final destination. This evaluation was made with focuse since sands reception, their storage and preparation, till the discharge in the shakeout system, regeneration e their reuse. It also aims to relate the proper waste management to environmental license as well to the existence of environmental certification. Attempt was made to verify if the companies, in regard of their costs with new sand and molding sand disposal in specialized landfills, as well as to the requirements of environmental agency, are working in sense of seeking and implant new recycling technologies and reuse of used sands. In adition to that, it was verified if it would exist a relation between environmental license and/or certification with the sand used correct management and proper foundry sand destination. Or still, within the approach of cleaner technologies and best available techniques if the alternatives for recycling sand into their own processes or reuse in other process are being pursuited. Within the sand management, it was still approached questions related to emissions generated during handling, storage, mixing, molding and coremaking, as well as cooling and shaking. This work was developed inicially through research on FEPAM, the environmental state agency, database, where it was verified the number of foundry industries in Rio Grande do Sul state, being elaborated and sent to the companies, questionnaires using the survey method. The gotten results have good representation considering that 85% of the questionnaires had been answered.Through the gotten results it was verified that, although 82% of the companies discharge used sands in licensed landfills, in accord with regulamentation, only one of them is seeking for reuse alternatives out of the process. It also was verified that there isn’t any concernig about reducing the sand generation. The environmental licence here in Rio Grande do Sul is in fact, the only way to make the companies adequate their installations aiming at environmental protection. To the other questions related to the processes using sands, the companies perception are very incipient.

Liquefaction is a phenomenon in which soil loses a large percentage of its shear resistance due to increased pore water pressure and flows like a liquid. Undrained cyclic loading conditions during earthquakes cause liquefaction of soils, which can lead to catastrophic failures such as bearing capacity failures, slope failures and lateral spreads. The concepts and mechanisms of liquefaction were studied extensively by many researchers. Though the factors affecting the liquefaction response of soils during earthquakes are well documented in literature, there are still some gray areas in understanding the individual and combined effects of factors like frequency, gradation, fines content and surcharge pressure on the initiation of liquefaction. The objective of this thesis is to study the influence of ground motion, soil and site parameters on the initiation of liquefaction in saturated sand beds through laboratory shaking table model tests and numerical studies. Shaking table tests are carried out using a uniaxial shaking table on sand beds of 600 mm thickness. The initiation of liquefaction was observed and identified by measuring the pore water pressure developed during the sinusoidal cyclic loading. Free field liquefaction studies are carried out on sand beds to study the influence of ground motion parameters, namely, input acceleration and frequency of shaking on liquefaction. These studies revealed that acceleration is one of the important parameters that can affect the initiation of liquefaction in sands. Increase in acceleration reduces the liquefaction resistance of sand and a small increase in acceleration can trigger liquefaction. Frequency of shaking did not affect the initiation of liquefaction at lower frequencies but a threshold frequency which triggered instant increase in the excess pore pressures is observed. Liquefaction caused slight initial amplification followed by de-amplification of accelerations due to the stiffness reduction in soils during liquefaction, the effect being more pronounced in the top layers of the sand bed. Pore water pressure ratios during dynamic loading decreased with depth below the surface of the sand bed due to the low initial effective vertical stress and upward transmission of pore pressure during undrained loading. Shaking table tests are carried out to study the influence of soil parameters such as relative density, thickness of dry overlying sand layer and gradation. Relative density of sand can influence the liquefaction potential of sand to a great extent, about 10% increase in relative density bringing down the probability of liquefaction by about 50%. With the increase in height of dry overlying sand layer, liquefaction potential has decreased nonlinearly. Change in grain size altered the pattern of liquefaction and pore pressure development and it is observed that the liquefaction in finer sands is influenced by the frequency of shaking to a larger extent. Surcharge pressure from building loads increased the liquefaction potential and heavier structures got liquefied at lower pore water pressure ratios. Significant post-liquefaction de-amplification was observed in sand beds with surcharge pressure. Parametric numerical analyses are carried out using finite difference program FLAC (Fast Lagrangian Analysis of Continua) with FINN model to measure pore water pressures in the sand bed. Results from numerical analyses with change in the acceleration, surcharge pressure and thickness of dry overlying layer agreed well with the experimental results. However, effect of frequency in numerical studies did not match with the experimental observations, because of the inherent boundary effects in the experimental models. Results from this thesis provided important insights into the development of pore water pressures in sand beds during cyclic loading events, apart from enhancing the understanding towards the effect of various ground motion, site and soil parameters on the initiation of liquefaction in sand beds.