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  • 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.
41

Blast-Induced Liquefaction and Downdrag Development on a Micropile Foundation

Lusvardi, Cameron Mark 14 December 2020 (has links)
Frequently, deep foundations extend through potentially liquefiable soils. When liquefaction occurs in cohesionless soils surrounding a deep foundation, the skin-friction in the liquefied layer is compromised. After cyclical forces suspend and pore pressures dissipate, effective stress rebuilds and the liquefied soil consolidates. When the settlement of the soil exceeds the downward movement of the foundation, downdrag develops. To investigate the loss and redevelopment of skin-friction, strain was measured on an instrumented micropile during a blast-induced liquefaction test in Mirabello, Italy. The soil profile where the micropile was installed consisted of clay to a depth of 6m underlain by a medium to dense sand. The 25cm diameter steel reinforced concrete micropile was bored to a depth of 17m. Pore pressure transducers were placed around the pile at various depths to observe excess pore pressure generation and dissipation. Soil strain was monitored with profilometers in a linear arrangement from the center of the 10m diameter ring of buried explosives out to a 12m radius. Immediately following the blast, liquefaction developed between 6m and 12m below ground. The liquefied layer settled 14cm (~2.4% volumetric strain) while the pile toe settled 1.24cm under elastic displacement. The static neutral plane in the pile occurred at a depth of 12m. From 6m to 12m below ground, the incremental skin-friction was 50% compared to pre-liquefaction measurements. The decrease in residual skin-friction is consistent with measurements observed by Dr. Kyle Rollins from previous full-scale tests in Vancouver, BC, Canada, Christchurch, New Zealand, and Turrel, Arkansas.
42

Blast-Induced Liquefaction and Downdrag Development on a Micropile Foundation

Lusvardi, Cameron Mark 14 December 2020 (has links)
Frequently, deep foundations extend through potentially liquefiable soils. When liquefaction occurs in cohesionless soils surrounding a deep foundation, the skin-friction in the liquefied layer is compromised. After cyclical forces suspend and pore pressures dissipate, effective stress rebuilds and the liquefied soil consolidates. When the settlement of the soil exceeds the downward movement of the foundation, downdrag develops. To investigate the loss and redevelopment of skin-friction, strain was measured on an instrumented micropile during a blast-induced liquefaction test in Mirabello, Italy. The soil profile where the micropile was installed consisted of clay to a depth of 6m underlain by a medium to dense sand. The 25cm diameter steel reinforced concrete micropile was bored to a depth of 17m. Pore pressure transducers were placed around the pile at various depths to observe excess pore pressure generation and dissipation. Soil strain was monitored with profilometers in a linear arrangement from the center of the 10m diameter ring of buried explosives out to a 12m radius. Immediately following the blast, liquefaction developed between 6m and 12m below ground. The liquefied layer settled 14cm (~2.4% volumetric strain) while the pile toe settled 1.24cm under elastic displacement. The static neutral plane in the pile occurred at a depth of 12m. From 6m to 12m below ground, the incremental skin-friction was 50% compared to pre-liquefaction measurements. The decrease in residual skin-friction is consistent with measurements observed by Dr. Kyle Rollins from previous full-scale tests in Vancouver, BC, Canada, Christchurch, New Zealand, and Turrel, Arkansas.
43

The Maya Footprint: Soil Resources of Chunchucmil, Yucatan, Mexico

Sweetwood, Ryan V. 19 March 2008 (has links) (PDF)
Agricultural yields in Northwest Yucatán are constrained by climate, thin soils, and low fertility. Despite this, the ancient Maya city of Chunchucmil Yucatán, Mexico, boasted an immense, dense, and wealthy population during the Middle Classic period (ca A.D. 400-700). Soil physical and chemical properties were explored to determine how the ancient Maya of Chunchucmil fed themselves. Soil profiles were collected from various locations within ancient Chunchucmil's suspected sustaining area. The physical and chemical properties, carbon isotopes, black carbon, and coprostanols of soil profiles sampled were compared to ancient rural settlement and remotely sensed images, such as AIRSAR (airborne synthetic aperture radar). Our objectives were to geographically determine the areas of agricultural importance and determine whether evidence of ancient agricultural intensification could be observed in the surrounding soil resources of Chunchucmil. Indigenous Maya of the area identify three major soil classes, boxlu'um, saklu'um, and kancab. The ancient Maya likely preferred kancab because it provided some security with higher soil moisture, greater soil depth, and improved nutrient availability. The land use capability is severely limited in the swamp/estuary and tzekel. The lack of rural settlement within these zones suggests that they were not used for cultivation in ancient times; however, the wood resources likely provided Chunchucmil with vital raw materials. The carbon isotopic signature of ancient C4 crops was not detected suggesting that either maize was not extensively produced or that the mix of native C3 and C4 plants in the savanna hid the signature. There were no soil chemical or biomarker evidences of ancient agricultural intensification, suggesting that ancient agriculture was mainly based on shifting cultivation at Chunchucmil. Concentrations of black carbon, calcium, phosphorus, potassium (Olsen Method), magnesium, and organic carbon within urban and rural settlements were enhanced by incidental human activities. We determined that the land requirement would have been extensive to sustain the population of Chunchucmil during the Middle Classic based on traditional agricultural methods. The ancient Maya of Chunchucmil likely traded marine and estuary products from the Gulf coast and other high value trade items for agricultural products from the nearby Puuc Hills.
44

Solo urbano, solo não urbano e solo rural: classificações do solo pelo critério da funcionalidade

Seifert, Ronaldo Gerd 15 April 2008 (has links)
Made available in DSpace on 2016-04-26T20:27:02Z (GMT). No. of bitstreams: 1 Ronaldo Gerd Seifert.pdf: 498803 bytes, checksum: 839a46e76a239767a6718d78df36959f (MD5) Previous issue date: 2008-04-15 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This work s first objective is to present two proposals of soil classification based on the legal system s property rights. In the first proposal, a differentiation between urban soil and rural soil will be made; in the second, the same will be done between urban soil and non-urban soil. A farther objective is to use this classification, through its uses, to induce the judicial operators to its conclusions related to the application of the law regarding real estate. Doctrine classifies the soil in urban and rural based on many perspectives and ends. Therefore, there are different classifications of the same gender in species with the same nomenclature. Classifications of the soil in urban and rural can be made based on its destiny, based on the localization, and based on fiscal criteria. This work justifies itself by the fact that none of its classifications differentiates the urban and rural soil from the perspective of the rights and duties of the proprietor. None of them has the goal of finding out in which properties it is possible to have urban activities and rural activities. Besides, since not all soil that isn t urban can have a rural use, it is important to classify the soil in urban and non-urban. The delimitation that the city makes of its urban perimeter is not enough to add to the right of property, faculties related to urban activity. The essential element for the alteration of the functionality of the real estate is the urbanization of the area. As for the methodology, the rational deductive method was used, with its normative foundation being the Federal Constitution and general norms. In this way, respecting the constitutional supplemental competencies, the work includes the soil of all national territory. The final result was that two soil classification proposals were presented: urban soil and non-urban soil and; urban soil and rural soil / Este trabalho, como objetivo próximo, visa apresentar duas propostas de classificação do solo, tendo como perspectiva o regime jurídico do direito de propriedade. Na primeira proposta será discriminado o solo urbano do solo rural; na segunda, o solo urbano do solo não urbano. Como objetivo remoto, a classificação, por meio de suas utilidades, visa instrumentalizar o aplicador do Direito às suas conclusões relacionadas ao exercício de direito de propriedade imobiliária. Quanto à justificativa, deve-se destacar que a doutrina classifica o solo em urbano e rural pautada em diversas perspectivas e fins. Há diferentes classificações do mesmo gênero em espécies com a mesma nomenclatura: classificação do solo em urbano e rural pelo critério da destinação fática, pelo critério da localização e pelo critério fiscal. Justifica-se o presente estudo pelo fato de que nenhuma destas classificações discrimina o solo urbano e rural a partir da perspectiva dos poderes e deveres do proprietário do bem. Nenhuma delas atende ao fim de se conhecer em quais imóveis é possível o exercício de atividades urbanas e em quais é possível o exercício de atividades rurais. Ademais, como nem todo solo que não é urbano possui funcionalidade rural, importante também é classificar o solo em urbano e não urbano. Verificou-se que a delimitação pelo município do perímetro urbano não é meio suficiente em si para acrescer ao direito de propriedade faculdades relacionadas à atividade urbana. O elemento essencial para a alteração da funcionalidade do bem é a urbanização da área. Quanto à metodologia, foi utilizado o método racional dedutivo, tendo como fundamento normativo a Constituição Federal e normas gerais. Dessa forma, embora respeitadas as competências suplementares instituídas constitucionalmente, o estudo é atinente aos solos de todo território nacional. Como resultado final, foram apresentadas duas propostas de classificação do solo: solo urbano e não urbano e; solo urbano e rural
45

Enriching flood risk analyses with distributions of soil mechanical parameters through the statistical analysis of classification experiments

Schwiersch, Niklas, Heyer, Torsten, Stamm, Jürgen 04 June 2024 (has links)
The distributions of soil mechanical parameters required for a comprehensive flood risk assessment are often taken from the scarce literature available. This article therefore presents a method to indirectly obtain the distributions from the results of often conducted classification tests. Empirical correlation terms are used for the transformation of the classification data into stability-relevant parameters, in particular the void ratio, the soil unit weight, the friction angle and the saturated permeability. The method is applied exemplarily to a data set collected throughout Germany in the immediate vicinity of water bodies and plausible distributions are obtained for 2/3 of the 13 soil classes considered. For the validation of the results, the extension of (inter)national databases by samples of the considered soil mechanical parameters is recommended due to the current poor validation basis.
46

Green synthesis of geopolymeric materials using Musina Copper Mine Tailings: a case of beneficial management of mine tailings

Matidza, Murendeni 17 September 2019 (has links)
MENVSC / Department of Ecology and Resource Management / Mine tailings (MT) have been a global problem due to the environmental impacts the waste generates such as air, soil and water pollution. The detrimental impacts include a global problem such as acid mine drainage (AMD) which has been difficult to cleanup. Several studies have been conducted to find alternative measures in reducing or mitigating impacts such as AMD and air pollution. Several studies have revealed how alumino-silicate mineral waste can be used as raw material to produce construction materials. This study aimed at evaluating the potential of synthesizing a geopolymer material from Musina copper mine tailings. Tailings were characterized for their physicochemical and mineralogical compositions using standard laboratory techniques in order to evaluate suitability in geopolymerization. First section of the results presented physicochemical and mineralogical characterization of the Musina copper tailings together with the bioavailability of the chemical species. It was observed that the tailings are mainly composed of SiO2 and Al2O3 as the major oxides indicating that they are aluminosilicate material. Mineralogical analysis revealed dominance of quartz, epidote and chlorite as the major minerals. The bioavailability assessment showed that largely Cu and Ca are bioavailable and highly soluble in an aqueous solution while Al, Mg, Ni, Co, Cr and Fe have a high proportion in non-labile phase. Second section presented the preliminary results wherein the potential application of Musina copper tailings in geopolymerization was evaluated. The results showed that Musina copper tailings can be used to synthesize a geopolymer material. However, it was recommended that several parameters influencing geopolymerization need to be evaluated. The third section presented the evaluation of optimum parameters that influence the geopolymerization process, which include type of alkali activators, alkali activator concentration, curing temperature, liquid-solid (L/S) ratio and curing regime. It was observed that a mixture of NaOH:Na2SiO3.5H20 at a ratio of 70:30 yields a better geopolymer material. The concentration of 10 M NaOH:Na2SiO3.5H20 at a ratio of 70:30 was observed to be the best that yielded the UCS that is acceptable according to SANS1215 standards. When evaluating curing regime, it was found that the material cured using greenhouse has lower UCS as compared to the material cured using oven. The v effect of temperature showed that the UCS decreases with increasing curing temperature. An admixture of river sand and cement was introduced which resulted in a high UCS of 21.16 MPa when using an admixture of cement. The mineralogical composition of the geopolymer bricks showed formation of secondary minerals such as phlogopite, fluorapatite, diopside and actinolite. Batch leaching conducted on the geopolymer bricks detected high leaching of Na from the bricks. Based on the findings of the study of the raw MT potential to produce geopolymer bricks, it was concluded that the material can be used to produce bricks that are within the SANS 1215 requirements. The study further recommended that the study a focus on using cylindrical moulds, other alkali activators and a mechanical mixer. It was also recommended that the greenhouse be restructured to contain heat within the greenhouse during the evening so as to allow constant temperature within / NRF
47

Deep anthropogenic topsoils in Scotland : a geoarchaeological and historical investigation into distribution, character and conservation under modern land cover

McKenzie, Joanne T. January 2006 (has links)
Deep anthropogenic topsoils – those augmented through long-term additions of mineral bulk among fertilising agents – retain in both their physical and chemical make-up significant indicators for cultural activity. This project researched the geographical distribution and historical context of deep anthropogenic topsoils in Scotland and the Isles, and used this information to investigate the impact of current land cover upon the cultural information they retain. In so doing, the project investigated the potential for conservation of this significant cultural resource. A review of the historical information available on agricultural and manuring practices for Scotland identified several factors likely to affect deep topsoil distribution and frequency. These were: the availability of bulk manures to Scottish farmers, the significance of the seaweed resource in determining fertiliser strategies in coastal areas, and the influence of urban settlement and associated patterns of domestic and industrial waste disposal on the location of deep topsoils. Evidence for widespread deep topsoil development was limited. The primary data source used – the First Statistical Account of Scotland – was manipulated into a spatial database in ArcView GIS, to which geographical data from the Soil Survey of Scotland and national archaeological survey databases were added. This was used to devise a survey programme aiming both to investigate the potential factors affecting soil development listed above, and to locate deep topsoil sites for analysis. Three sites were identified with deep topsoils under different cover types (woodland, arable and pasture). The urban-influenced context of two of these highlighted the significance of urban settlement to the location of Scottish deep topsoils. Analysis of pH, organic matter, and total phosphorus content showed a correlation between raised organic matter and a corresponding increase in phosphorus content in soils under permanent vegetation. By contrast, soils under arable cultivation showed no such rise. This was attributed to the action of cropping in removing modern organic inputs prior to down-profile cycling. The potential for pasture and woodland cover to affect relict soil signatures was therefore observed. Thin section analysis aimed to both provide micromorphological characterisation of the three deep topsoil sites and investigate the effect of modern land cover on micromorphological indicators. Distinctive differences in micromorphological character were observed between the rural and urban deep topsoils, with the latter showing a strong focus on carbonised fuel residues and industrial wastes. All sites showed a highly individual micromorphological character, reflective of localised fertilising systems. There was no correlation between land cover type and survival of material indictors for anthropogenic activity, with soil cultural indicators surviving well, particularly those characteristic of urban-influenced topsoils. Suggestions for preservation strategies for this potentially rare and highly localised cultural resource included the incorporation of deep anthropogenic topsoil conservation into current government policy relating to care of the rural historic environment, and the improvement of data on the resource through ongoing survey and excavation.

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