• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 13
  • 9
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 31
  • 14
  • 14
  • 11
  • 11
  • 9
  • 8
  • 7
  • 6
  • 5
  • 5
  • 5
  • 5
  • 4
  • 4
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Mätning av hydraulisk konduktivitet med Lewis metod : En utvärdering av tillförlitligheten och användbarheten hos en enkel metod för mätning i olika jordarter

Eriksson, Daniel January 2016 (has links)
The purpose of this study was to evaluate Lewis (2016) simple method to determine hydraulic conductivity in soil samples. This was conducted by comparing Lewis method to a slug-test, Guelph permeameter and calculations from grain size analysis in order to find out if the method is a reliable source for measuring hydraulic conductivity. Other parameters to compare is time consumption, cost effectiveness and area of use. Four different samples were used in the testing, a sand, two tills and pyrite ash (which is a rest product from manufacturing sulfite pulp). The results indicated that measurements in the homogenic sand all methods was in a good range of each other, while in the more heterogenic till the slug-test and Lewis method was close and the calculations from grainsize analysis was much lower. Only grainsize analysis was performed on the pyrite ash and the results was similar to Lewis method. This study shows that Lewis method works well as a reliable source for K measurements and is less time consuming than all the other methods. The material required for the method can be obtained in a hardware store.
12

A Comparative Study to Calculate Hydraulic Conductivity in Ultisols on an East Tennessee Hillslope

Lawson, Sydney A 01 May 2015 (has links)
This study compares four different methods to measure hydraulic conductivity (K) at two sites on the East Tennessee State University Valleybrook Campus. It compares the K values to each other, to the different K values between the two sites, and to United States Department of Agriculture (USDA) K values. Two field methods, Well Bail Test and Auger Hole Test, and two lab methods, Constant Head Permeameter Test and Grain Size Distribution Test (GSD), were performed on the clay rich Ultisol soils on an East Tennessee hillslope in the Valley and Ridge Physiographic Province. One site was located close to a monitoring well and the other on the floodplain of an existing stream. The Hazen, Alyamani & Sen, and Slichter methods were used to compute K from the GSD Test. The Alyamani & Sen, Slichter, and permeameter methods produced similar K values ranging from 9.52 x 10-6 to 1.25 x 10-3 cm/sec. These are similar to the USDA K values ranging from 9.17 x 10-4 to 2.82 x 10-4 cm/sec. The Hazen method overestimated K and ranged from 8.10 x 10-3 to 1.09 x 10-1 cm/sec. The Well Bail Test yielded a lower K value (ranging from 8.16 x 10-9 to 1.19 x 10-8 cm/sec) than the USDA values as expected for water flow in deeper soil horizons at a depth of 8.50 meters. Comparing these values helped to better understand the difference between various methods to compute the hydraulic conductivity.
13

Hydrostratigraphy and Groundwater Migration within Surficial Deposits at the North Lakes Wetland, Hillsborough County, Florida

LaRoche, Jason J. 27 June 2007 (has links)
A wetland in west-central Florida was studied to characterize the local hydrostratigraphic configuration of surficial deposits overlying more-permeable limestones and conceptualize groundwater recharge. Eight continuous cores were drilled through the surficial deposits and partially into the underlying limestone. A total of 111 samples were extracted from the cores for laboratory sediment analyses and testing. The surficial deposits are roughly eight meters thick and made up of upper and lower clean-sand hydrostratigraphic layers (S1 and S3, respectively) separated by a low-permeability layer of clayey sand (S2). Also, a discontinuous low-permeability layer of clayey sand (S4) lies between S3 and the top of limestone. Equivalent hydraulic conductivity values for the S2 and S4 clayey layers (0.01 and 0.1 m/day respectively) are significantly less than those of the S1 and S3 sand layers (2 and 1 m/day respectively).Significant confinement between the surficial and Upper Floridan aquifers by means of a laterally extensive dense-clay unit immediately above the limestone is consistently reported elsewhere in the region, but was not encountered within the wetland. Partial confinement is apparently the result of low-permeability layers within the surficial deposits alone. Results of ground-penetrating radar and vertical head difference measurements suggest the presence of buried sinkhole features which perforate the low-permeability S2 layer and create preferred pathways for flow or karst drains. Comparison of results between laboratory sediment testing and a site-scale aquifer performance test (APT) suggest that the primary mechanism for drainage during the APT was by vertical percolation through the S2 layer while flow through karst drains was minimized. In this case, calculated leakances based on laboratory sediment testing are most accurate in approximation of effective leakance.It is predicted that as water table stages rise within the wetland, effective leakance will increase as flow toward karst drains becomes the more dominant mechanism for drainage. As a result, calculated leakances based on direct laboratory sediment testing are a decreasingly accurate approximation of effective leakance.
14

Soil Air Permeability and Saturated Hydraulic Conductivity: Development of Soil Corer Air Permeameter, Post-fire Soil Physical Changes, and 3D Air Flow Model in Anisotropic Soils

Chief, Karletta January 2007 (has links)
Air permeability (ka) is a viable alternative to water- and texture-based methods to rapidly map saturated hydraulic conductivity (Ksat). The ability to measure this important hydraulic property without the use of more cumbersome and time-consuming methods may provide a practical approach to generate more complete data to describe hydrologic conditions. This study presents the development of an air permeameter which is suitable for desert soils. The Soil Corer Air Permeameter (SCAP) is compatible with a standard soil corer and employs digital components to measure flowrates under low-pressure gradients to improve accuracy, ease of use, and portability. SCAP allows for the extraction of undisturbed soil samples for laboratory analysis, providing direct comparisons of ka with other soil physical and hydraulic properties. The applicability of a regression equation to estimate Ksat from field-measured ka using SCAP was examined in unburned and burned soils. Ex situ field ka and laboratory Ksat measurements were compared and air to water permeability (ka/kw) ratios were calculated to determine structural changes due to water saturation. The study also characterized changes in permeability due to fire in woodland-chaparral and coniferous soils. For soils that could be extracted with minimal structural changes, results show ka and Ksat measurements for unburned and burned soils were within the 95% confidence intervals of a ka-Ksat regression developed for agricultural soils. However, correlations for in situ ka measurements in some burned soils showed a decrease in accuracy and may be attributed to soil anisotropy. A three-dimensional steady-state finite element air flow model was developed using FEMLAB 3.0A to consider the effects of anisotropy on in situ ka measurements. Results show that anisotropic conditions can introduce an error as high as a factor of 2 especially for air permeameters with high diameter to height (D/H) ratios, however, the error is much smaller than the anisotropy ratio. If anisotropy is important to characterize, it was shown that paired measurements of in situ and ex situ ka can be used to infer the anisotropy ratio.
15

Assessment controls on reservoir performance and the affects of granulation seam mechanics in the Bredasdorp Basin, South Africa.

Schalkwyk, Hugh Je-Marco January 2006 (has links)
<p>The Bredasdorp Basin is one of the largest hydrocarbon producing blocks within Southern Africa. The E-M field is situated approximate 50 km west from the FA platform and was brought into commission due to the potential hydrocarbons it may hold. If this field is brought up to full producing capability it will extend the lifespan of the refining station in Mosselbay, situated on the south coast of South Africa, by approximately 8 to 10 years. An unexpected pressure drop within the E-M field caused the suite not to perform optimally and thus further analysis was imminent to assess and alleviate the predicament. The first step within the project was to determine what might have cause the pressure drop and thus we had to go back to cores drilled by Soekor now known as Petroleum South Africa, in the early 1980&rsquo / s.</p> <p><br> <br /> </br>Analyses of the cores exposed a high presence of granulation seams. The granulation seams were mainly subjected within sand units within the cores. This was caused by rolling of sand grains over one another rearranging themselves due to pressure exerted through compaction and faulting, creating seal like fractures within the sand. These fractures caused these sand units to compartmentalize and prohibit flow from one on block to the next. With advance inquiry it was discovered that there was a shale unit situated within the reservoir dividing the reservoir into two main compartments. At this point it was determined to use Petrel which is windows based software for 3D visualization with a user interface based on the Windows Microsoft standards. This is easy as well as user friendly software thus the choice to go with it. The software uses shared earth modeling tool bringing about reservoir disciplines trough common data modelling. This is one of the best modelling applications in the available and it was for this reason that it was chosen to apply within the given aspects of the project A lack of data was available to model the granulation seams but with the data acquired during the core analyses it was possible to model the shale unit and factor in the influences of the granulation seams to asses the extent of compartmentalization. The core revealed a thick shale layer dividing the reservoir within two sections which was not previously noted. This shale layer act as a buffer/barrier restricting flow from the bottom to the top halve of the reservoir. This layer is thickest at the crest of the 10km&sup2 / domal closure and thins toward the confines of the E-M suite. Small incisions, visible within the 3 dimensional models could serve as a guide for possible re-entry points for future drilling. These incisions which were formed through Lowstand and Highstand systems tracts with the rise and fall of the sea level. The Bredasdorp Basin consists mainly of tilting half graben structures that formed through rifting with the break-up of Gondwanaland. The model also revealed that these faults segregate the reservoir further creating bigger compartments. The reservoir is highly compartmentalized which will explain the pressure loss within the E-M suite. The production well was drilled within one of these compartments and when the confining pressure was relieved the pressure dropped and the production decrease. As recommendation, additional wells are required to appraise the E-M structure and determine to what extent the granulation seems has affected fluid flow as well as the degree of sedimentation that could impede fluid flow. There are areas still containing untapped resources thus the recommendation for extra wells.</p>
16

Estudo do comportamento hidráulico, mecânico e químico de barreiras hidráulicas verticais, compostas por solo residual, bentonita e cimento sob ação de substâncias agressivas / Study of the hydraulic, mechanic and chemical behavior of verticals hydraulic barriers composed by sandy soil, bentonite and cement under aggressive substances’ action

Lemos, Rosemar Gomes January 2006 (has links)
Este estudo tem como objetivo analisar os comportamentos hidráulico, mecânico e microestrutural de misturas compostas, por solo residual arenito Botucatu e bentonita sódica, com e sem adição de cimento, quando permeadas por água (H2O), soda cáustica (NaOH), na concentração de 5% e ácido sulfúrico (H2SO4) na mesma concentração para sua possível utilização em barreiras de contenção de contaminantes do tipo slurry wall. O arenito, solo areno-siltoso característico da região de São Leopoldo/ RS, compõe a matriz das misturas, sendo que a bentonita sódica confere a estas características impermeabilizantes, imprescindíveis às barreiras hidráulicas de contenção. O cimento, além de fazer com que a mistura adquira resistência, interfere na reatividade da barreira, mediante os contaminantes utilizados. A estimativa da eficiência destas misturas baseou-se na comparação entre os valores do coeficiente de condutividade hidráulica, resistência à compressão simples e parâmetros de compressibilidade determinados através dos ensaios de compressão confinada, apresentados nos ensaios com e sem contaminação, conjuntamente com a análise microestrutural das misturas nas mesmas situações. Foram feitas análises químicas por Difração de Raios-x, Microscopia Eletrônica de Varredura (SEM) e Análise Química Elementar (EDS) visando à explicação ordinária das causas microestruturais que levam as misturas a determinado comportamento sob percolação de contaminantes. Na busca do efeito de cada componente sobre o comportamento final de determinada mistura, houve a necessidade de realizar análises químicas e microscópicas individuais, também sob interferência ou não de substâncias agressivas. A partir deste estudo foi possível inferir que a mistura solo-cimentobentonita, é adequada à utilização como barreira vertical quando o contaminante for ácido sulfúrico, por no mínimo 20 semanas, já que a eficiência da mesma foi comprovada pela realização de ensaios no permeâmetro de parede rígida, considerado adequado para este tipo. O uso da mistura solo bentonita para barreiras verticais pode ser emergencial visto que quando o contaminante for soda cáustica a mistura resiste por 4 dias. / The objective of this study is to analyze the hydraulic, mechanical and micro-structural conduct of composite mixtures of Botucatu residual soil and sodic bentonite, with and without cement addition, when permeated by water (H2O), caustic soda (NaOH) in a concentration of 5% and sulfuric acid in the same concentration to their possible utilization in contention of contaminant barriers of the slurry walls type. The sandy soil constitutes part of the matrix of the mixtures. The sodic bentonite confers to these mixture essential waterproof characteristics of hydraulic barriers of containment. The cement interferes on the barrier reactivity moreover add resistance to the mixture by the contaminants that were utilized. The efficiency estimation of these mixtures was established by comparison between hydraulic conductive coefficient, unconfined compression strength and one dimensional compressibility presented on the tests with or without contamination, with the mixture micro-structural and chemical analysis on the same situations: X-ray diffraction, scanning electronic microscopy, Elemental Chemical Analysis (EDS), they want to explain the micro-structural causes that make the mixtures to determinate behavior by percolating of contaminants. Searching the effect of all components about the final behavior of determined mixture there was the necessity to carry out chemical and microscopically individual analysis also by aggressive or non-aggressive substances interference. After completed the study, it is possible to affirm that the soil-cement-bentonite mixture, is good for using as a vertical barrier when the contaminant is sulfuric acid, based on the results of rigid wall permeameter, adequate for this kind of mixture. The use of soilbentonite mixture as vertical barrier for caustic soda could be done just in emergency cases and for a short period of time, once that after some time the barrier reduces drastically its efficiency.
17

Estudo do comportamento hidráulico, mecânico e químico de barreiras hidráulicas verticais, compostas por solo residual, bentonita e cimento sob ação de substâncias agressivas / Study of the hydraulic, mechanic and chemical behavior of verticals hydraulic barriers composed by sandy soil, bentonite and cement under aggressive substances’ action

Lemos, Rosemar Gomes January 2006 (has links)
Este estudo tem como objetivo analisar os comportamentos hidráulico, mecânico e microestrutural de misturas compostas, por solo residual arenito Botucatu e bentonita sódica, com e sem adição de cimento, quando permeadas por água (H2O), soda cáustica (NaOH), na concentração de 5% e ácido sulfúrico (H2SO4) na mesma concentração para sua possível utilização em barreiras de contenção de contaminantes do tipo slurry wall. O arenito, solo areno-siltoso característico da região de São Leopoldo/ RS, compõe a matriz das misturas, sendo que a bentonita sódica confere a estas características impermeabilizantes, imprescindíveis às barreiras hidráulicas de contenção. O cimento, além de fazer com que a mistura adquira resistência, interfere na reatividade da barreira, mediante os contaminantes utilizados. A estimativa da eficiência destas misturas baseou-se na comparação entre os valores do coeficiente de condutividade hidráulica, resistência à compressão simples e parâmetros de compressibilidade determinados através dos ensaios de compressão confinada, apresentados nos ensaios com e sem contaminação, conjuntamente com a análise microestrutural das misturas nas mesmas situações. Foram feitas análises químicas por Difração de Raios-x, Microscopia Eletrônica de Varredura (SEM) e Análise Química Elementar (EDS) visando à explicação ordinária das causas microestruturais que levam as misturas a determinado comportamento sob percolação de contaminantes. Na busca do efeito de cada componente sobre o comportamento final de determinada mistura, houve a necessidade de realizar análises químicas e microscópicas individuais, também sob interferência ou não de substâncias agressivas. A partir deste estudo foi possível inferir que a mistura solo-cimentobentonita, é adequada à utilização como barreira vertical quando o contaminante for ácido sulfúrico, por no mínimo 20 semanas, já que a eficiência da mesma foi comprovada pela realização de ensaios no permeâmetro de parede rígida, considerado adequado para este tipo. O uso da mistura solo bentonita para barreiras verticais pode ser emergencial visto que quando o contaminante for soda cáustica a mistura resiste por 4 dias. / The objective of this study is to analyze the hydraulic, mechanical and micro-structural conduct of composite mixtures of Botucatu residual soil and sodic bentonite, with and without cement addition, when permeated by water (H2O), caustic soda (NaOH) in a concentration of 5% and sulfuric acid in the same concentration to their possible utilization in contention of contaminant barriers of the slurry walls type. The sandy soil constitutes part of the matrix of the mixtures. The sodic bentonite confers to these mixture essential waterproof characteristics of hydraulic barriers of containment. The cement interferes on the barrier reactivity moreover add resistance to the mixture by the contaminants that were utilized. The efficiency estimation of these mixtures was established by comparison between hydraulic conductive coefficient, unconfined compression strength and one dimensional compressibility presented on the tests with or without contamination, with the mixture micro-structural and chemical analysis on the same situations: X-ray diffraction, scanning electronic microscopy, Elemental Chemical Analysis (EDS), they want to explain the micro-structural causes that make the mixtures to determinate behavior by percolating of contaminants. Searching the effect of all components about the final behavior of determined mixture there was the necessity to carry out chemical and microscopically individual analysis also by aggressive or non-aggressive substances interference. After completed the study, it is possible to affirm that the soil-cement-bentonite mixture, is good for using as a vertical barrier when the contaminant is sulfuric acid, based on the results of rigid wall permeameter, adequate for this kind of mixture. The use of soilbentonite mixture as vertical barrier for caustic soda could be done just in emergency cases and for a short period of time, once that after some time the barrier reduces drastically its efficiency.
18

Estudo do comportamento hidráulico, mecânico e químico de barreiras hidráulicas verticais, compostas por solo residual, bentonita e cimento sob ação de substâncias agressivas / Study of the hydraulic, mechanic and chemical behavior of verticals hydraulic barriers composed by sandy soil, bentonite and cement under aggressive substances’ action

Lemos, Rosemar Gomes January 2006 (has links)
Este estudo tem como objetivo analisar os comportamentos hidráulico, mecânico e microestrutural de misturas compostas, por solo residual arenito Botucatu e bentonita sódica, com e sem adição de cimento, quando permeadas por água (H2O), soda cáustica (NaOH), na concentração de 5% e ácido sulfúrico (H2SO4) na mesma concentração para sua possível utilização em barreiras de contenção de contaminantes do tipo slurry wall. O arenito, solo areno-siltoso característico da região de São Leopoldo/ RS, compõe a matriz das misturas, sendo que a bentonita sódica confere a estas características impermeabilizantes, imprescindíveis às barreiras hidráulicas de contenção. O cimento, além de fazer com que a mistura adquira resistência, interfere na reatividade da barreira, mediante os contaminantes utilizados. A estimativa da eficiência destas misturas baseou-se na comparação entre os valores do coeficiente de condutividade hidráulica, resistência à compressão simples e parâmetros de compressibilidade determinados através dos ensaios de compressão confinada, apresentados nos ensaios com e sem contaminação, conjuntamente com a análise microestrutural das misturas nas mesmas situações. Foram feitas análises químicas por Difração de Raios-x, Microscopia Eletrônica de Varredura (SEM) e Análise Química Elementar (EDS) visando à explicação ordinária das causas microestruturais que levam as misturas a determinado comportamento sob percolação de contaminantes. Na busca do efeito de cada componente sobre o comportamento final de determinada mistura, houve a necessidade de realizar análises químicas e microscópicas individuais, também sob interferência ou não de substâncias agressivas. A partir deste estudo foi possível inferir que a mistura solo-cimentobentonita, é adequada à utilização como barreira vertical quando o contaminante for ácido sulfúrico, por no mínimo 20 semanas, já que a eficiência da mesma foi comprovada pela realização de ensaios no permeâmetro de parede rígida, considerado adequado para este tipo. O uso da mistura solo bentonita para barreiras verticais pode ser emergencial visto que quando o contaminante for soda cáustica a mistura resiste por 4 dias. / The objective of this study is to analyze the hydraulic, mechanical and micro-structural conduct of composite mixtures of Botucatu residual soil and sodic bentonite, with and without cement addition, when permeated by water (H2O), caustic soda (NaOH) in a concentration of 5% and sulfuric acid in the same concentration to their possible utilization in contention of contaminant barriers of the slurry walls type. The sandy soil constitutes part of the matrix of the mixtures. The sodic bentonite confers to these mixture essential waterproof characteristics of hydraulic barriers of containment. The cement interferes on the barrier reactivity moreover add resistance to the mixture by the contaminants that were utilized. The efficiency estimation of these mixtures was established by comparison between hydraulic conductive coefficient, unconfined compression strength and one dimensional compressibility presented on the tests with or without contamination, with the mixture micro-structural and chemical analysis on the same situations: X-ray diffraction, scanning electronic microscopy, Elemental Chemical Analysis (EDS), they want to explain the micro-structural causes that make the mixtures to determinate behavior by percolating of contaminants. Searching the effect of all components about the final behavior of determined mixture there was the necessity to carry out chemical and microscopically individual analysis also by aggressive or non-aggressive substances interference. After completed the study, it is possible to affirm that the soil-cement-bentonite mixture, is good for using as a vertical barrier when the contaminant is sulfuric acid, based on the results of rigid wall permeameter, adequate for this kind of mixture. The use of soilbentonite mixture as vertical barrier for caustic soda could be done just in emergency cases and for a short period of time, once that after some time the barrier reduces drastically its efficiency.
19

Assessment controls on reservoir performance and the affects of granulation seam mechanics in the Bredasdorp Basin, South Africa

Schalkwyk, Hugh Je-Marco January 2006 (has links)
Magister Scientiae - MSc / The Bredasdorp Basin is one of the largest hydrocarbon producing blocks within Southern Africa. The E-M field is situated approximate 50 km west from the FA platform and was brought into commission due to the potential hydrocarbons it may hold. If this field is brought up to full producing capability it will extend the lifespan of the refining station in Mosselbay, situated on the south coast of South Africa, by approximately 8 to 10 years. An unexpected pressure drop within the E-M field caused the suite not to perform optimally and thus further analysis was imminent to assess and alleviate the predicament. The first step within the project was to determine what might have cause the pressure drop and thus we had to go back to cores drilled by Soekor now known as Petroleum South Africa, in the early 1980’s. Analyses of the cores exposed a high presence of granulation seams. The granulation seams were mainly subjected within sand units within the cores. This was caused by rolling of sand grains over one another rearranging themselves due to pressure exerted through compaction and faulting, creating seal like fractures within the sand. These fractures caused these sand units to compartmentalize and prohibit flow from one on block to the next. With advance inquiry it was discovered that there was a shale unit situated within the reservoir dividing the reservoir into two main compartments. At this point it was determined to use Petrel which is windows based software for 3D visualization with a user interface based on the Windows Microsoft standards. This is easy as well as user friendly software thus the choice to go with it. The software uses shared earth modeling tool bringing about reservoir disciplines trough common data modelling. This is one of the best modelling applications in the available and it was for this reason that it was chosen to apply within the given aspects of the project A lack of data was available to model the granulation seams but with the data acquired during the core analyses it was possible to model the shale unit and factor in the influences of the granulation seams to asses the extent of compartmentalization. The core revealed a thick shale layer dividing the reservoir within two sections which was not previously noted. This shale layer act as a buffer/barrier restricting flow from the bottom to the top halve of the reservoir. This layer is thickest at the crest of the 10km² domal closure and thins toward the confines of the E-M suite. Small incisions, visible within the 3 dimensional models could serve as a guide for possible re-entry points for future drilling. These incisions which were formed through Lowstand and Highstand systems tracts with the rise and fall of the sea level. The Bredasdorp Basin consists mainly of tilting half graben structures that formed through rifting with the break-up of Gondwanaland. The model also revealed that these faults segregate the reservoir further creating bigger compartments. The reservoir is highly compartmentalized which will explain the pressure loss within the E-M suite. The production well was drilled within one of these compartments and when the confining pressure was relieved the pressure dropped and the production decrease. As recommendation, additional wells are required to appraise the E-M structure and determine to what extent the granulation seems has affected fluid flow as well as the degree of sedimentation that could impede fluid flow. There are areas still containing untapped resources thus the recommendation for extra wells. / South Africa
20

Srovnání výsledků vsakovaní vody z polních experimentů a numerického modelování / Comparement of results from infiltration tests

Blahut, Dominik January 2017 (has links)
The aim of this thesis is to compare the results of water infiltration from field tests, from laboratories and from numerical modeling at two selected locations. The first objective is the search procedure and the description of both sites and its adjacent areas. Further work continues with infiltration field tests using ring infiltrometer, at first theoretically for each method, and then practically with own personal measurements in the field. Further from the collected soil samples the measurements are performed in the laboratory, first in the permeameter, and followed by the grain size distribution test, from which the hydraulic conductivity is derived by using empirical formulas. At last the numerical modeling is used and all the results are compared. In the final phase of thesis the recommendations are given for infiltration at various locations and comparsion of the infiltration methods.

Page generated in 0.0798 seconds