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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.
1

Energy transfer and grain size effects during the Standard Penetration Test (SPT) and Large Penetration Test (LPT)

Daniel, Christopher Ryan 05 1900 (has links)
The Standard Penetration Test (SPT) is the most widely used in-situ soil test in the world. "Large Penetration Test" (LPT) is a term used to describe any scaled up version of the SPT. Several types of LPT have been developed around the world for the purpose of characterizing gravel deposits, as SPT blow counts are less reliable in gravels than in sands. Both tests suffer from the lack of a reliable means of determining transferred energy. Further, the use of LPT blow counts is generally limited to calculation of equivalent SPT blow counts using correlation factors measured in sands. Variation of LPT blow counts with grain size is assumed to be negligible. This research shows that safety hammer energies can be reliably estimated from measurements of hammer impact velocity for both SPT and LPT. This approach to determining transferred energy is relatively simple, and avoids the primary limitation of existing methods, which is the inability to calibrate the instrumentation. Transferred energies and hammer impact velocities are collected from various sources. These data are used to determine the ratio between the hammer kinetic energy and the transferred energy (energy transfer ratio, ETR), which is found to follow a roughly Normal distribution for the various hammers represented. An assessment of uncertainty is used to demonstrate that an ETR based approach could be superior to existing energy measurement methods. SPT grain size effects have primarily been characterized as the variation of an empirical relative density correlation factor, (CD)SPT, with mean grain size. In this thesis, equivalent (CD)LPT data are back-calculated from measured SPT-LPT correlation factors (CS/L). Results of a numerical study suggest that SPT and LPT grain size effects should be similar and related to the ratio of the sample size to the mean grain size. Based on this observation, trend-lines with the same shape as the (CD)SPT trend-line are established for the back-calculated (CD)LPT data. A method for generating the grain size effect trend-line for LPT is then proposed. These trend lines provide a rational approach to direct interpretation of LPT data, or to improved prediction of equivalent SPT blow counts.
2

Energy transfer and grain size effects during the Standard Penetration Test (SPT) and Large Penetration Test (LPT)

Daniel, Christopher Ryan 05 1900 (has links)
The Standard Penetration Test (SPT) is the most widely used in-situ soil test in the world. "Large Penetration Test" (LPT) is a term used to describe any scaled up version of the SPT. Several types of LPT have been developed around the world for the purpose of characterizing gravel deposits, as SPT blow counts are less reliable in gravels than in sands. Both tests suffer from the lack of a reliable means of determining transferred energy. Further, the use of LPT blow counts is generally limited to calculation of equivalent SPT blow counts using correlation factors measured in sands. Variation of LPT blow counts with grain size is assumed to be negligible. This research shows that safety hammer energies can be reliably estimated from measurements of hammer impact velocity for both SPT and LPT. This approach to determining transferred energy is relatively simple, and avoids the primary limitation of existing methods, which is the inability to calibrate the instrumentation. Transferred energies and hammer impact velocities are collected from various sources. These data are used to determine the ratio between the hammer kinetic energy and the transferred energy (energy transfer ratio, ETR), which is found to follow a roughly Normal distribution for the various hammers represented. An assessment of uncertainty is used to demonstrate that an ETR based approach could be superior to existing energy measurement methods. SPT grain size effects have primarily been characterized as the variation of an empirical relative density correlation factor, (CD)SPT, with mean grain size. In this thesis, equivalent (CD)LPT data are back-calculated from measured SPT-LPT correlation factors (CS/L). Results of a numerical study suggest that SPT and LPT grain size effects should be similar and related to the ratio of the sample size to the mean grain size. Based on this observation, trend-lines with the same shape as the (CD)SPT trend-line are established for the back-calculated (CD)LPT data. A method for generating the grain size effect trend-line for LPT is then proposed. These trend lines provide a rational approach to direct interpretation of LPT data, or to improved prediction of equivalent SPT blow counts.
3

Energy transfer and grain size effects during the Standard Penetration Test (SPT) and Large Penetration Test (LPT)

Daniel, Christopher Ryan 05 1900 (has links)
The Standard Penetration Test (SPT) is the most widely used in-situ soil test in the world. "Large Penetration Test" (LPT) is a term used to describe any scaled up version of the SPT. Several types of LPT have been developed around the world for the purpose of characterizing gravel deposits, as SPT blow counts are less reliable in gravels than in sands. Both tests suffer from the lack of a reliable means of determining transferred energy. Further, the use of LPT blow counts is generally limited to calculation of equivalent SPT blow counts using correlation factors measured in sands. Variation of LPT blow counts with grain size is assumed to be negligible. This research shows that safety hammer energies can be reliably estimated from measurements of hammer impact velocity for both SPT and LPT. This approach to determining transferred energy is relatively simple, and avoids the primary limitation of existing methods, which is the inability to calibrate the instrumentation. Transferred energies and hammer impact velocities are collected from various sources. These data are used to determine the ratio between the hammer kinetic energy and the transferred energy (energy transfer ratio, ETR), which is found to follow a roughly Normal distribution for the various hammers represented. An assessment of uncertainty is used to demonstrate that an ETR based approach could be superior to existing energy measurement methods. SPT grain size effects have primarily been characterized as the variation of an empirical relative density correlation factor, (CD)SPT, with mean grain size. In this thesis, equivalent (CD)LPT data are back-calculated from measured SPT-LPT correlation factors (CS/L). Results of a numerical study suggest that SPT and LPT grain size effects should be similar and related to the ratio of the sample size to the mean grain size. Based on this observation, trend-lines with the same shape as the (CD)SPT trend-line are established for the back-calculated (CD)LPT data. A method for generating the grain size effect trend-line for LPT is then proposed. These trend lines provide a rational approach to direct interpretation of LPT data, or to improved prediction of equivalent SPT blow counts. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate
4

Nova metodologia para interpretação de ensaios de dissipação do piezocone

Pereira, Francisco da Silva January 2017 (has links)
Os ensaios de piezocone são frequentemente utilizados em obras de elevada complexidade e risco geotécnico para a determinação do coeficiente de adensamento de solos argilosos saturados. Contudo, obter o tempo de dissipação de 50% do excesso de poropressão, parâmetro fundamental para estimativa do coeficiente de adensamento, pode demandar demasiado tempo, tornando o ensaio menos atrativo para projetos de engenharia. Ainda, obter a poropressão de equilíbrio pode ser complicada em alguns casos, dificultando a determinação do coeficiente de adensamento através do ensaio de dissipação. Com o motivo de incentivar o uso do ensaio de dissipação para essa finalidade, o presente trabalho tem como objetivo propor uma nova metodologia para a determinação do tempo para dissipação de 50% do excesso de poropressão causado pela cravação do piezocone, fornecendo uma alternativa para a metodologia empregada atualmente, que seja independente da poropressão de equilíbrio e que necessite de menos tempo de ensaio. Para o desenvolvimento da metodologia foi realizada uma campanha de investigação geotécnica no campo experimental de Tubarão-SC. A campanha contou com 10 ensaios de dissipação atingindo valores superiores ou próximos a 70% de dissipação do excesso de poropressão, buscando equalização mais completa da curva de dissipação, a fim de comparar os resultados obtidos através da nova metodologia com os valores obtidos por métodos consagrados na prática de engenharia. Nessa dissertação foram utilizados dois equipamentos, um minipiezocone (MCPTu) de seção de área transversal de 5cm² com medidas de poropressão nas posições u1 e u2 e um piezocone convencional, com seção de área transversal de 10cm² e leitura de poropressão somente na posição u2. Para a validação da metodologia, buscou-se na literatura e junto à Geoforma Engenharia Ltda. (parceira da pesquisa) ensaios de dissipação que tenham atingido elevados graus de dissipação. Valores de coeficiente de adensamento horizontal obtidos pela solução consagrada de Houlsby e Teh (1991) e pela metodologia proposta nesse trabalho foram comparadas e a proposta de metodologia apresentada. / Piezocone tests are frequently employed in high complexity and geotechnical risk construction sites to obtain the coefficient of consolidation of saturated clayey soils. However, the time for 50% dissipation of the excess pore pressure, parameter required for the estimation of the coefficient of consolidation takes too long, rendering the piezocone dissipation test less attractive for engineering projects. Furthermore, in some cases it can be complicated to estimate the equilibrium pore pressure, making difficult to estimate the coefficient of consolidation from the dissipation test. With the goal of encouraging the use of dissipation test for this propose, the present dissertation propose a new methodology for the determination of the time required for 50% dissipation of the excess pore pressure, providing an alternative which is independent of the equilibrium pore pressure and that demands less time in the field. For the development of the methodology proposed by this work, a site investigation campaign was carried out at the Tubarão-SC (Brazil) experimental field. Dissipation tests were performed to degrees of dissipation higher or approximately of 70%, for a more complete equalization of the complete dissipation curve, with the aim of comparing results obtained by the methodology developed in this dissertation and the value obtained from well-established methods. Two equipaments were employed on this dissertation: a mini-piezocone (MCPTu), with a cross area of 5cm² with pore pressure measurement at two locations, u1 and u2 and a standard piezocone, with a cross area of 10cm² and pore pressure measurement at the u2 position. Furthermore, aiming the validation of the proposal methodology, data from dissipation tests available in the literature and provided by Geoforma Engenharia Ltda. (partner on this research) were also used. The coefficient of consolidation was estimated by the well-establish approach and by the methodology proposed on this dissertation, the values were confronted, and recommendations presented.
5

Multi-Scale Behavior at Geomaterial Interfaces

Hebeler, Gregory L. 13 July 2005 (has links)
The design of interface elements in geotechnical engineering traditionally involves empiricism and lacks a solid fundamental underpinning based on the controlling mechanisms. These design shortcomings exist due to deficiencies in the fundamental understanding of geotechnical interface behaviors and the lack of test methods and devices available to directly measure interface properties in situ. The current work strives to improve the state of geotechnical knowledge and design with regard to interface behavior through fundamental laboratory studies and the development and use of a new in situ testing device. The current investigations are focused across a range of scales from micromechanical interactions to full scale field implementation. A series of laboratory investigations at the micromechanical level have been performed, specifically aimed at investigating the mechanisms controlling granular interactions against conventional and textured friction sleeves, and hook and loop type interactions present within textured geomembrane - geotextile systems. Additionally, a new in situ testing device has been designed and developed, the Multi Piezo Friction Attachment (MPFA), to allow for the characterization of geotechnical interface properties in situ within the context of an effective stress framework. The MPFA simultaneously provides four independent measures of interface friction (f
6

Cataloging And Statistical Evaluation Of Common Mistakes In Geotechnical Investigation Reports For Buildings On Shallow Foundations

Ozyurt, Gokhan 01 October 2012 (has links) (PDF)
Information presented in site investigation reports has a strong influence in design, project costs and safety. For this reason, both the quality and the reliability of site investigation reports are important. However in our country, geotechnical engineering is relegated to second place and site investigation studies, especially parcel-basis ground investigation works / do not receive the attention they deserve. In this study, site investigation reports, that are required for the license of design projects, are examined and the missing/incorrect site investigations, laboratory tests, geotechnical evaluations and geotechnical suggestions that occur in the reports are catalogued. Also, frequency of each mistake is statistically examined / for geotechnical engineers, recommendations and solutions are presented to help them avoid frequent problems.
7

Nova metodologia para interpretação de ensaios de dissipação do piezocone

Pereira, Francisco da Silva January 2017 (has links)
Os ensaios de piezocone são frequentemente utilizados em obras de elevada complexidade e risco geotécnico para a determinação do coeficiente de adensamento de solos argilosos saturados. Contudo, obter o tempo de dissipação de 50% do excesso de poropressão, parâmetro fundamental para estimativa do coeficiente de adensamento, pode demandar demasiado tempo, tornando o ensaio menos atrativo para projetos de engenharia. Ainda, obter a poropressão de equilíbrio pode ser complicada em alguns casos, dificultando a determinação do coeficiente de adensamento através do ensaio de dissipação. Com o motivo de incentivar o uso do ensaio de dissipação para essa finalidade, o presente trabalho tem como objetivo propor uma nova metodologia para a determinação do tempo para dissipação de 50% do excesso de poropressão causado pela cravação do piezocone, fornecendo uma alternativa para a metodologia empregada atualmente, que seja independente da poropressão de equilíbrio e que necessite de menos tempo de ensaio. Para o desenvolvimento da metodologia foi realizada uma campanha de investigação geotécnica no campo experimental de Tubarão-SC. A campanha contou com 10 ensaios de dissipação atingindo valores superiores ou próximos a 70% de dissipação do excesso de poropressão, buscando equalização mais completa da curva de dissipação, a fim de comparar os resultados obtidos através da nova metodologia com os valores obtidos por métodos consagrados na prática de engenharia. Nessa dissertação foram utilizados dois equipamentos, um minipiezocone (MCPTu) de seção de área transversal de 5cm² com medidas de poropressão nas posições u1 e u2 e um piezocone convencional, com seção de área transversal de 10cm² e leitura de poropressão somente na posição u2. Para a validação da metodologia, buscou-se na literatura e junto à Geoforma Engenharia Ltda. (parceira da pesquisa) ensaios de dissipação que tenham atingido elevados graus de dissipação. Valores de coeficiente de adensamento horizontal obtidos pela solução consagrada de Houlsby e Teh (1991) e pela metodologia proposta nesse trabalho foram comparadas e a proposta de metodologia apresentada. / Piezocone tests are frequently employed in high complexity and geotechnical risk construction sites to obtain the coefficient of consolidation of saturated clayey soils. However, the time for 50% dissipation of the excess pore pressure, parameter required for the estimation of the coefficient of consolidation takes too long, rendering the piezocone dissipation test less attractive for engineering projects. Furthermore, in some cases it can be complicated to estimate the equilibrium pore pressure, making difficult to estimate the coefficient of consolidation from the dissipation test. With the goal of encouraging the use of dissipation test for this propose, the present dissertation propose a new methodology for the determination of the time required for 50% dissipation of the excess pore pressure, providing an alternative which is independent of the equilibrium pore pressure and that demands less time in the field. For the development of the methodology proposed by this work, a site investigation campaign was carried out at the Tubarão-SC (Brazil) experimental field. Dissipation tests were performed to degrees of dissipation higher or approximately of 70%, for a more complete equalization of the complete dissipation curve, with the aim of comparing results obtained by the methodology developed in this dissertation and the value obtained from well-established methods. Two equipaments were employed on this dissertation: a mini-piezocone (MCPTu), with a cross area of 5cm² with pore pressure measurement at two locations, u1 and u2 and a standard piezocone, with a cross area of 10cm² and pore pressure measurement at the u2 position. Furthermore, aiming the validation of the proposal methodology, data from dissipation tests available in the literature and provided by Geoforma Engenharia Ltda. (partner on this research) were also used. The coefficient of consolidation was estimated by the well-establish approach and by the methodology proposed on this dissertation, the values were confronted, and recommendations presented.
8

Nova metodologia para interpretação de ensaios de dissipação do piezocone

Pereira, Francisco da Silva January 2017 (has links)
Os ensaios de piezocone são frequentemente utilizados em obras de elevada complexidade e risco geotécnico para a determinação do coeficiente de adensamento de solos argilosos saturados. Contudo, obter o tempo de dissipação de 50% do excesso de poropressão, parâmetro fundamental para estimativa do coeficiente de adensamento, pode demandar demasiado tempo, tornando o ensaio menos atrativo para projetos de engenharia. Ainda, obter a poropressão de equilíbrio pode ser complicada em alguns casos, dificultando a determinação do coeficiente de adensamento através do ensaio de dissipação. Com o motivo de incentivar o uso do ensaio de dissipação para essa finalidade, o presente trabalho tem como objetivo propor uma nova metodologia para a determinação do tempo para dissipação de 50% do excesso de poropressão causado pela cravação do piezocone, fornecendo uma alternativa para a metodologia empregada atualmente, que seja independente da poropressão de equilíbrio e que necessite de menos tempo de ensaio. Para o desenvolvimento da metodologia foi realizada uma campanha de investigação geotécnica no campo experimental de Tubarão-SC. A campanha contou com 10 ensaios de dissipação atingindo valores superiores ou próximos a 70% de dissipação do excesso de poropressão, buscando equalização mais completa da curva de dissipação, a fim de comparar os resultados obtidos através da nova metodologia com os valores obtidos por métodos consagrados na prática de engenharia. Nessa dissertação foram utilizados dois equipamentos, um minipiezocone (MCPTu) de seção de área transversal de 5cm² com medidas de poropressão nas posições u1 e u2 e um piezocone convencional, com seção de área transversal de 10cm² e leitura de poropressão somente na posição u2. Para a validação da metodologia, buscou-se na literatura e junto à Geoforma Engenharia Ltda. (parceira da pesquisa) ensaios de dissipação que tenham atingido elevados graus de dissipação. Valores de coeficiente de adensamento horizontal obtidos pela solução consagrada de Houlsby e Teh (1991) e pela metodologia proposta nesse trabalho foram comparadas e a proposta de metodologia apresentada. / Piezocone tests are frequently employed in high complexity and geotechnical risk construction sites to obtain the coefficient of consolidation of saturated clayey soils. However, the time for 50% dissipation of the excess pore pressure, parameter required for the estimation of the coefficient of consolidation takes too long, rendering the piezocone dissipation test less attractive for engineering projects. Furthermore, in some cases it can be complicated to estimate the equilibrium pore pressure, making difficult to estimate the coefficient of consolidation from the dissipation test. With the goal of encouraging the use of dissipation test for this propose, the present dissertation propose a new methodology for the determination of the time required for 50% dissipation of the excess pore pressure, providing an alternative which is independent of the equilibrium pore pressure and that demands less time in the field. For the development of the methodology proposed by this work, a site investigation campaign was carried out at the Tubarão-SC (Brazil) experimental field. Dissipation tests were performed to degrees of dissipation higher or approximately of 70%, for a more complete equalization of the complete dissipation curve, with the aim of comparing results obtained by the methodology developed in this dissertation and the value obtained from well-established methods. Two equipaments were employed on this dissertation: a mini-piezocone (MCPTu), with a cross area of 5cm² with pore pressure measurement at two locations, u1 and u2 and a standard piezocone, with a cross area of 10cm² and pore pressure measurement at the u2 position. Furthermore, aiming the validation of the proposal methodology, data from dissipation tests available in the literature and provided by Geoforma Engenharia Ltda. (partner on this research) were also used. The coefficient of consolidation was estimated by the well-establish approach and by the methodology proposed on this dissertation, the values were confronted, and recommendations presented.
9

Nanolaminate coatings to improve long-term stability of plasmonic structures in physiological environments

Daniel, Monisha Gnanachandra 28 June 2017 (has links)
The unprecedented ability of plasmonic metal nano-structures to concentrate light into deep-subwavelength volumes has propelled their use in a vast array of nanophotonics technologies and research endeavors. They are used in sensing, super-resolution imaging, SPP lithography, SPP assisted absorption, SPP-based antennas, light manipulation, etc. To take full advantage of the attractive capabilities of CMOS compatible low-cost plasmonic structures based on Al and Cu, nanolaminate coatings are investigated to improve their long-term stability in corrosive physiological environments. The structures are fabricated using phase-shifting PDMS masks, e-beam deposition, RIE, Atomic Layer Deposition and Rapid Thermal Annealing. An alternate approach using Nanosphere Lithography (NSL) was also investigated. Films were examined using ellipsometry, atomic force microscopy and transmission measurements. Accelerated in-situ tests of Hafnium Oxide/Aluminum Oxide nanolaminate shells in a mildly pH environment with temperatures akin to physiological environments emulated using PBS show greatly enhanced endurance, with stable structures that last for more than one year. / Master of Science
10

New methods for in situ measurement of mechanical root-reinforcement on slopes

Meijer, Gerrit Johannes January 2016 (has links)
Vegetation can increase the resistance of slopes against landsliding. The mechanical contribution of roots to the shear strength of the soil is however difficult to measure in situ. Existing methodologies are time-consuming and therefore not suitable to quantify spatial variability on the slope. Furthermore, some existing methods, for example large in situ shear box testing, can be difficult to apply on remote sites with difficult access, e.g. steep slopes. Therefore in this thesis novel, simple and portable methods to quantify mechanical root-reinforcement in the field were developed. The ‘blade penetrometer method’, one of these new methods, was based on standard penetrometer testing but used an adapted tip shape to increase sensitivity to roots. Root depths and diameters could be quantified based on characteristics of the depth–resistance trace, both in the laboratory and in the field. Several new analytical interpretive models were developed to predict the force–displacement behaviour of roots loaded under various conditions: one assuming roots broke in tension and another assuming roots broke in pure bending. Both methods did take root–soil interaction into account. Based on these models, some roots were shown to have broken in bending and others in tension, depending on plant species and root diameter. Two new methods were developed to measure the root-reinforced soil strength directly. The ‘pin vane’ was an adaptation of a standard field shear vane, replacing the cruciform blades of the latter by prongs to minimise the effects of soil disturbance and root breakage during installation. This was one of the main problems encountered when using standard vanes in rooted soil. This ‘pin vane’ method was qualitatively shown to be able to measure the reinforcing effects of both fine and thick roots (or root analogues), both in the laboratory and the field. This method will be most useful when the strength of densely rooted surface layers is to be analysed, e.g. for erosion resistance purposes. Another newly developed shear device was the ‘corkscrew’. Rotational installation of the screw ensured minimal soil and root disturbance. During vertical extraction the root-reinforced shear strength was mobilised along the interface of the soil plug caught within the screw. The measured extraction force could be related to the reinforced soil strength. This method underestimated the strength in surface layers (especially at 0–125 mm and less so at 125–250 mm depth) but functioned well in deeper soil layers important for landsliding. Although laboratory results were promising, during in situ testing in deeper layers ( > 125 mm) local variation in soil stress, gravel content and water content, combined with low root volumes, made it difficult to accurately quantify the effect of the roots. Where the effect of roots was pronounced, e.g. in more heavily rooted surface layers (0–125 mm), significant positive trends between the measured soil strength and root strength and quantity were found. Measured reinforcements were small compared with various root-reinforcement model predictions but comparable to direct shear tests on rooted soil reported by others. These new methods, although still in the early stages of development, showed promising results for practical use in field conditions. The equipment was simple to use and portable, enabling measurements on sites with difficult accessibility. However, more work is required to validate the interpretive models developed and to calibrate these methods for a wider range of soil and root conditions.

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