A fluidização é definida como a suspensão de partículas de um solo granular devido à ação de um fluxo ascendente, que cria uma força de arrasto suficiente para suportar o peso próprio das partículas, produzindo uma zona fluidizada. Neste trabalho são discutidos os mecanismos e os conceitos envolvidos na fluidização de solos arenosos com a utilização de jatos de água, que futuramente podem ser associados a novas tecnologias de instalação de ancoragens de plataformas de petróleo offshore. O estudo foi baseado em ensaios realizados em câmaras de calibração retangulares, com paredes em acrílico, preenchidas com areias de granulometria distintas, compactadas com densidade relativa de 50% e 100%. O sistema de jateamento consiste basicamente em uma bomba centrífuga que succiona a água armazenada em um reservatório e a conduz, através de um circuito hidráulico, à extremidade de tubos metálicos verticais, responsáveis pelo jateamento de água. Foram utilizados tubos com diferentes diâmetros e diversas velocidades de saída do jato. Iniciado o jateamento, tem-se a formação de um leito fluidizado, com formato côncavo e interface bem definida com a zona não fluidizada. O jato de água penetra certa profundidade no interior do leito fluidizado até ser defletido, no sentido ascendente, carregando partículas de areia que são depositadas ao redor da zona fluidizada. Após a formação de uma geometria fluidizada máxima, os tubos são reposicionados em uma nova profundidade. A fluidização ao longo da profundidade apresenta comportamento definido, com uma geometria inicialmente estável, que alcança uma condição de instabilidade em determinada profundidade, até sofrer sucessivos fechamentos, formando uma cavidade submersa fluidizada. Esta cavidade diminui de tamanho com o aumento da profundidade e a fluidização do solo deixa de ocorrer para certa profundidade de saída do jato. Os parâmetros principais que comandam a geometria da zona fluidizada aberta são a velocidade de saída e o diâmetro do jato, em conjunto com o tamanho das partículas do solo. Não foi observada influência da densidade relativa de compactação da areia na geometria fluidizada final. As dimensões geométricas são função do número densimétrico de Froude, cujo emprego permite a determinação de equações empíricas que descrevem o comportamento da geometria fluidizada aberta. O conjunto de ensaios de laboratório possibilitou determinar os parâmetros de controle dos mecanismos de fluidização em areias e a influência destes parâmetros no comportamento do solo fluidizado. / Fluidisation occurs when a granular soil is subjected to an upward fluid flow which creates a drag force sufficient to support the weight of the particles, producing a fluidised zone. In the present work a discussion is made on the mechanisms and concepts controlling the fluidised process produced by upflow washing in granular materials, aiming at the installation of offshore platform anchors. The study was carried out in laboratory rectangular calibration chambers filled with sand at relative densities ranging from 50% to 100%. The upflow washing was produced by a centrifuge pump that sucks water from a reservoir and conducts the water through a hydraulic system to the extremity of a vertical metalic tube, producing the water jet flow. Tubes with different diameters and fluid velocities have been used. The mechanism initiates with the formation of an open fluidised zone having a characteristic shape and distinct boundaries. The fluid penetrates up to a given depth and is deflected towards the surface. Once a stabilized zone is produced, the jet is lowered to another depth and the process is repeated. The shape of the fluidised zone changes with increasing jet depth from an open and stable approximately ellipsoidal form to an unstable spouted profile, and then to a submerged fluidised cavity. The shape of the cavity reduces with increasing depth. Parameters controlling the geometry of an open fluidised zone are fluid velocity and inside diameter of jet, together with diameter soil particles. There has been no influence of relative density in the geometry of the fluidised zone. In fact, this geometry is expressed by densimetric Froude number. The present work was usefull in demonstrating the parameters controlling fluidisation by upflow washing.

The Sandy River (OR) is a coastal tributary of the Columbia River and has a steep hydroshed 1316 square kilometers which is located on the western side of Mount Hood (elevation range 3 m to 1800 m). The system exhibits highly variable flow: Its average discharge is ~40 m3/s, and the highest recorded discharge was 1739 m3/s in 1964. In this study I model the geomorphic sensitivity of an 1800m reach located the downstream of the former Marmot Dam, which was removed in 2007. The hydro-geomorphic response to major flood has implications for system management and aquatic life. Studying hydro-geomorphic change requires a systematic approach. Here, I define flows and flood hydrographs for specified return interval based on the observed hydrologic record, and then examine potential hydro-geomorphic changes using a numerical model. A Pearson Type III distribution is used to calculate 100, 75, 50, 25, 10, and 2 year return periods. Extreme event hydrographs are derived by fitting derived and observed flood hydrographs to the gamma distribution curve. Sediment transport and geomorphology are then modeled numerically with Nays2DH, a solver that is part of iRIC software. Because the model is computationally intensive, I model the domain with five different spatial grid resolutions, to find proper grid resolution. The grid resolutions used are 1.5 m, 2 m, 3 m, 4 m, and 5 m. We choose 4 m as optimum grid resolution, based on the convergence of model results. The model is run for extreme event hydrographs with six above return periods. For result visualization and analysis, we focus on flow properties and bed elevation at peak flow and at the end of each event. For both times for each event, important flow and sediment transport parameters are visualized for the entire domain in plane form and eight cross-sections at 200 m intervals. Finally, we divide the geomorphic response into areas of erosion and deposition. Linear regression analyses of mean values of erosion and deposition at peak flow for all extreme events yield R2 of 0.981 for erosion and 0.986 for deposition. The mean erosion and deposition depth at the end of the events is modeled by nonlinear regression with correlation coefficient of 0.965 for erosion and 0.998 for deposition. The regression models provide direct understanding of impacts of different floods on the geomorphic response of the river domain. examination of the model as a whole suggest that the amount of erosion and deposition in the bed and banks is a function of channel geometry, bank and bed geology, riparian area condition and strongly depend on the amount of flow through the channel.

Sandy soils make up more than 205,000 ha in the coastal area of the North Central region of Vietnam. Thua Thien Hue province lying in the south of this region has predominantly sandy soils that cover almost 47,000 ha out of the 84,000 ha of cultivated land. Most of the population lives in the coastal area and people’s livelihoods are largely dependent on crop farming in these inherently poor soils. The objectives of this study were to provide extensive information on the soil and organic resources (including agricultural and aquatic sources) in the coastal area of Thua Thien Hue province, to assess the fertilization capacity of various organic materials when applied at different rates to soils for different crops and to make a diagnosis of the balance of main plant nutrients within the farms to assess possible risks of depletion in soils or of release to the environment. Soil characteristics were measured from a survey of 300 cultivated plots in seven villages scattered in the coastal area. All these light-textured soils are acidic and are very poor in organic C. Consequently, the cation exchange capacity is very low. Soil properties are linked significantly to the different cropping patterns. Farmers in the studied area use wide diversify of organic materials for various purposes. Very large variations in the content of major elements (C, N, P, K, Ca, and Mg) are observed in the organic samples. Crop yield and soil fertility increased following the rate of farmyard manure and organic amendment application. Organic amendments brought higher profit for rice and peanut growers in coastal sandy area. The highest fertilization efficiency was observed for pig manure in case of growing rice and peanut and goat manure for sweet potato. The most frequently used species of aquatic plants by local farmers are Najas indica, Vallisneria spiralis, Potamogeton malaianus plus various algae species. Najas Indica and Hydrilla verticillata showed the highest fertilization capacity. At farm level, the N, P, K balances in 10 studied farms were positive. More detailed N-P-K balances in 9 field plots indicated that N balance was largely positive for rice and sweet potato plots. P imports exceeded P exports in all studied plots, whereas K balance was always negative in 4 cropping systems.

Spatial patterns as well as temporal dynamics of soil moisture have a major influence on runoff generation. The investigation of these dynamics and patterns can thus yield valuable information on hydrological processes, especially in data scarce or previously ungauged catchments. The combination of spatially scarce but temporally high resolution soil moisture profiles with episodic and thus temporally scarce moisture profiles at additional locations provides information on spatial as well as temporal patterns of soil moisture at the hillslope transect scale. This approach is better suited to difficult terrain (dense forest, steep slopes) than geophysical techniques and at the same time less cost-intensive than a high resolution grid of continuously measuring sensors. Rainfall simulation experiments with dye tracers while continuously monitoring soil moisture response allows for visualization of flow processes in the unsaturated zone at these locations. Data was analyzed at different spacio-temporal scales using various graphical methods, such as space-time colour maps (for the event and plot scale) and binary indicator maps (for the long-term and hillslope scale). Annual dynamics of soil moisture and decimeterscale variability were also investigated. The proposed approach proved to be successful in the investigation of flow processes in the unsaturated zone and showed the importance of preferential flow in the Malalcahuello Catchment, a datascarce catchment in the Andes of Southern Chile. Fast response times of stream flow indicate that preferential flow observed at the plot scale might also be of importance at the hillslope or catchment scale. Flow patterns were highly variable in space but persistent in time. The most likely explanation for preferential flow in this catchment is a combination of hydrophobicity, small scale heterogeneity in rainfall due to redistribution in the canopy and strong gradients in unsaturated conductivities leading to self-reinforcing flow paths.

The purpose of this study is to investigate the efficiencies of bioremediation of sandy beach contaminated by crude oil. In this study, we used two lab-scale tanks, tank-A and tank-B, to simulate a sandy beach contaminated by crude oil. In the experiments, we added the bioreagents and oleophilic fertilizers (Inipol EAP 22®) in order to enrich crude oil degradation of sandy beach. The crude oil was degraded by nature culture in tank-A, while the crude oil was degraded by the mixed culture of several pure strains¡]MO-1, KS-1, DS-4, PF-4, PH-2, B-1, TF and XY-2¡^. We divided the experiment into five stages in this study. In conclusion, we found that the oleophilic fertilizers could increase both of the growth rate of oil degradation bacteria and crude oil biodegradation rate. However, a part of the fertilizers might flow into the ocean due to idal current. The addition of mixed culture could help to improve the biodegradation rate of sandy beach contaminated by crude oil.

In the past, most research on soil mechanical properties was carried out for cohesionless soils in the fields of civil and geotechnical engineering. Little research has been carried out for mechanical properties of agricultural soil, which are essential for designing soil engaging tools in agriculture. In this study, unconsolidated undrained triaxial compression tests were performed to study the effects of moisture level and confining pressure on a sandy loam soil. The soil specimens tested had three moisture levels, and they were high (27-29% d.b.), medium (19-21% d.b.) and low (9-11% d.b.). The confining pressures used for the triaxial tests were 50, 100, and 150 kPa. Soil specimen was loaded at a strain rate of 1%/min. Measurements from the tests included stress-strain curve, shear strength, Young’s modulus, Poisson’s ratio, angle of internal friction, and cohesion. A model was developed using the Discrete Element Method (DEM) and computed by Particle Flow Code in three dimensions (PFC3D), a common DEM software. The model simulated the triaxial compression tests, and the model specimen was an assembly of 5-mm spherical particles which were defined by a set of micro parameters. During simulations, soil shear strength was monitored under different confining pressures. Through sensitivity analysis, it was found that most of the micro parameters affected the simulated soil shear strengths and the stress-strain behaviours. The most influential micro parameter was particle friction coefficient. This micro parameter was calibrated with the data from triaxial tests for different combinations of soil moisture levels and confining pressures. The calibrated particle friction coefficients varied from 0.2 to 1.0. The calibrations were done through matching the shear strengths between simulations and measurements, and the relative errors ranged between 0 and 6 %. / October 2015

No description available.

No description available.

Increasing levels of nitrate (NO3-) in groundwater have become a major environmental and health concern. In situations where NO3-concentrations in the soil-water system pose an environmental hazard, water table management may be a desirable practice to reduce such pollution. Careful management of N applications is also believed to reduce NO3- levels. / A field experiment was conducted in 1996 and 1997 at St. Emmanuel, Quebec, about 30 km South-West of Macdonald Campus of McGill University, to investigate the effect of water table management (WTM) and N fertilizer combinations on potentially leachable NO3- and denitrification rates in the top soil layer (0--0.15 m). The field was planted with monocrop corn (Zea mays. L) in both years. Treatments consisted of a factorial combination of two water table managements, free drainage (FD) and subirrigation (SI) (about 1.0 m and 0.6 m, respectively, below the soil surface) and two N fertilizer rates, 200 kg ha-1 (N200) and 120 kg ha-1 (N120). / Water table management had a significant effect on reducing NO3 - concentrations in the soil profile. Subirrigation treatment reduced NO3- in the top soil layer by 41% and 15% in 1996 and 1997, respectively. Similarly, NO3 - levels were 50% and 20% lower in N120 compared to N200 treatment. / Climatic conditions (rainfall and temperature) played a large role in regulating denitrification rates. Due to drier and cooler conditions in 1997, denitrification rates were lower compared to 1996, leaving more NO3 - in the soil profile. Following harvest, this high NO 3- concentration may be subject to leaching.

A field subirrigation experiment, using saline-sodic water, was carried out on a loamy sand soil in southwestern Quebec. The experimental field was divided into 16 plots with 4 treatments; saline-sodic water, "fresh" water, controlled drainage and non-irrigated. Each treatment had four replicates. Maize yield, hydraulic conductivity, salt concentration, and salt movement through the soil were recorded in all plots. / No significant difference in maize yield occurred between plots irrigated with saline-sodic or fresh water in any of the three years. Irrigated maize plots yielded approximately 30% more than non-irrigated plots. / Hydraulic conductivity reductions in the saline plots were noted in May 1986, after the first snowmelt. From statistical analysis carried out, it appears that the saline-sodic water had an effect on hydraulic conductivity, significant at the 0.05 level. / From the measurements taken from piezometer stations, located throughout the field, salt concentrations and salt movement through the saturated soil profile were determined. Using salt concentration data from both irrigation water and soil water, an average effective field porosity was calculated with a computer program. The results obtained were within 4% of those obtained in laboratory tests. Moreover, the program was then used to model the salt balance of the soil from May 85 to May 87. Results indicated that most salts were removed with the rainfall and snowmelt of the winter months of 85/86 and 86/87.