The box corer is a relatively new tool used in the geotechnical community for collection of soft seabed sediments. Miniature full flow and model pipeline probes were developed as tools to characterize and obtain soil parameters of soft seabed sediments collected in the box core for design of offshore pipelines and analysis of shallow debris flows. Probes specifically developed for this study include the miniature t-bar, ball, motorized vane (MV), and toroid. The t-bar, ball, and MV were developed to measure intact and remolded undrained shear strengths (su and sur). The t-bar and ball can obtain continuous strength profiles and measure sur at discrete depths in the box corer while the MV measures su and sur at discrete depths. The toroid is a form of model pipeline testing which was developed to investigate pipe-soil interaction during axial pipeline movement. Vertical loading and displacement rates can be selected for the toroid to mimic axial pipeline displacement for a variety of pipe weights. A load frame for both miniature penetrometer and toroid testing was developed for testing directly on box core samples offshore. This research presents results from offshore and laboratory testing of the box core and recommended testing procedures for full flow and toroid probes on box core samples.

O descarte do lodo de ETA em corpos de água, como rios, tem sido ainda uma prática comum no Brasil. Alternativas frequentes de destinação têm sido a disposição do lodo em aterros sanitários ou industriais e na rede de esgoto. Porém, os padrões ambientais cada vez mais rígidos têm levado à procura de soluções mais econômicas e benéficas, com o aproveitamento do lodo de ETA como material para diversos usos. Uma das opções promissoras é a utilização do lodo de ETA misturado a solos naturais em obras geotécnicas, como revestimento de fundo e cobertura final de aterros sanitários e industriais, e na construção de aterros em geral. Nessa perspectiva, foram estudadas as propriedades geotécnicas de misturas de um solo laterítico arenoso com um lodo de ETA em três proporções solo:lodo (3:1, 4:1, e 5:1) em massa úmida. Foi realizada a caracterização química e mineralógica do solo e do lodo por meio de ensaios de difração de raios X, fluorescência de raios X, microscopia eletrônica de varredura, determinação de perda ao fogo, pH, capacidade de troca catiônica, soma de bases trocáveis, carbono orgânico, matéria orgânica, entre outros. Foram determinados a curva granulométrica, a massa específica dos grãos e os limites de consistência do solo, do lodo e das misturas. Ensaios de adensamento, permeabilidade e compressão triaxial foram realizados em corpos de prova compactados do solo e das misturas. A caracterização geotécnica das misturas mostrou que a adição de lodo não altera significativamente a granulometria, a massa específica dos grãos e os limites de consistência do solo. Por outro lado, a secagem prévia ao ar das misturas alterou os parâmetros de compactação: a massa específica seca máxima aumentou e o teor de umidade ótimo diminuiu com a redução do teor de umidade inicial no ensaio de compactação. Os índices de compressão das misturas apresentaram-se maiores que o do solo, enquanto as condutividades hidráulicas das misturas foram menores que a do solo. O ângulo de atrito efetivo das misturas apresentou aumento e a coesão efetiva diminuição a medida que a proporção de lodo acrescentado ao solo aumentou. As características e propriedades das misturas apresentaram valores aceitáveis para solos utilizáveis em aterros, o que possibilita o aproveitamento de lodo de ETA em misturas com solo a serem empregadas em obras geotécnicas. / In Brazil, WTS is mostly released in water bodies causing silting and deterioration of water quality, destined to treatment with sewage, or disposed of in sanitary landfills or disposal sites of sewage treatment plants mixed with sewage sludge after a partial dewatering process. An alternative for WTS destination is its application, in natura, treated or mixed with soil, as construction material for covers and bottom liners of sanitary and industrial landfills or in embankments in general. Addition of Water Treatment Sludge (WTS) to soils in earthworks may reduce land disposal of WTS and exploitation of natural soils. In this perspective, geotechnical properties of mixtures of a lateritic sandy soil with WTS in proportions 3:1, 4:1, and 5:1 (by wet weight) were evaluated. WTS and soil were subjected to chemical and mineralogical characterization by X-ray fluorescence and X-ray diffraction tests, and determination of loss on ignition, pH, organic matter content, cation exchange capacity, exchangeable bases, and other chemical parameters. Particle-size distribution curve, specific gravity of solids, and Atterberg limits were obtained for WTS, soil and mixtures. One-dimensional consolidation, permeability and undrained triaxial compression tests were carried out on compacted specimens of the soil and the soil-WTS mixtures. Geotechnical characteristics of the mixtures resulted slightly different from those of the soil, on the other hand, previous air-drying affected the compaction parameters of the mixtures, the maximum dry unit weight increased and the optimum water content decreased for a decrease in the initial water content of the compaction test. Compression index of the mixtures were higher than the soil, whereas hydraulic conductivity decreased with WTS addition for different confining pressures and hydraulic gradients. Effective friction angle of the mixtures increased and effective cohesion decreased when increasing the proportion of WTS added in the mixture. Some of those geotechnical parameter values were acceptable for a compacted soil and indicate high possibility of reuse of this waste in geotechnical works.

Gelfill (GF) is made of tailings, water, binder and chemical additives (Fillset, sodium silicate gel). The components of GF are combined and mixed on the surface and transported (by gravity and/or pumping) to the underground mine workings, where the GF can be used for both underground mine support and tailings storage. Thermal (T), hydraulic (H), and mechanical (M) properties are important performance criteria of GF. The understanding of these engineering properties and their evolution with time are still limited due to the fact that GF is a new cemented backfill material. In this thesis, the evolution of the thermal, hydraulic, mechanical, and microstructural properties of small GF samples are determined. Various binder contents of Portland cement type I (PCI) are used. The GF is cured for 3, 7, 28, 90, and 120 days. It is found that the thermal, hydraulic and mechanical properties are time-dependent or affected by the degree of binder hydration index. Furthermore, a relationship is found between the compressive strength and the saturated hydraulic conductivity of the GF samples. The unsaturated hydraulic properties of GF samples have also been investigated. The outcomes show that unsaturated hydraulic conductivity is influenced by the degree of binder hydration index and binder content, especially at low suction ranges. Simple functions are proposed to predict the evolution of air-entry values (AEVs), residual water content, and fitting parameters from the van Genuchten model with the degree of hydration index (α). Furthermore, two columns are built to simulate the coupled thermo-hydro-mechanical (THM) behaviour of GF under drained and undrained conditions. The obtained results from the GF columns are compared with the small samples. It is observed that the mechanical properties, hydraulic properties (suction and water content), and temperature development are strongly coupled. The magnitude of these THM coupling factors is affected by the size of the GF. The findings also show that the mechanical, hydraulic and thermal properties of the GF columns are different from samples cured in plastic moulds.

Gelfill (GF) is made of tailings, water, binder and chemical additives (Fillset, sodium silicate gel). The components of GF are combined and mixed on the surface and transported (by gravity and/or pumping) to the underground mine workings, where the GF can be used for both underground mine support and tailings storage. Thermal (T), hydraulic (H), and mechanical (M) properties are important performance criteria of GF. The understanding of these engineering properties and their evolution with time are still limited due to the fact that GF is a new cemented backfill material. In this thesis, the evolution of the thermal, hydraulic, mechanical, and microstructural properties of small GF samples are determined. Various binder contents of Portland cement type I (PCI) are used. The GF is cured for 3, 7, 28, 90, and 120 days. It is found that the thermal, hydraulic and mechanical properties are time-dependent or affected by the degree of binder hydration index. Furthermore, a relationship is found between the compressive strength and the saturated hydraulic conductivity of the GF samples. The unsaturated hydraulic properties of GF samples have also been investigated. The outcomes show that unsaturated hydraulic conductivity is influenced by the degree of binder hydration index and binder content, especially at low suction ranges. Simple functions are proposed to predict the evolution of air-entry values (AEVs), residual water content, and fitting parameters from the van Genuchten model with the degree of hydration index (α). Furthermore, two columns are built to simulate the coupled thermo-hydro-mechanical (THM) behaviour of GF under drained and undrained conditions. The obtained results from the GF columns are compared with the small samples. It is observed that the mechanical properties, hydraulic properties (suction and water content), and temperature development are strongly coupled. The magnitude of these THM coupling factors is affected by the size of the GF. The findings also show that the mechanical, hydraulic and thermal properties of the GF columns are different from samples cured in plastic moulds.

Gelfill (GF) is made of tailings, water, binder and chemical additives (Fillset, sodium silicate gel). The components of GF are combined and mixed on the surface and transported (by gravity and/or pumping) to the underground mine workings, where the GF can be used for both underground mine support and tailings storage. Thermal (T), hydraulic (H), and mechanical (M) properties are important performance criteria of GF. The understanding of these engineering properties and their evolution with time are still limited due to the fact that GF is a new cemented backfill material. In this thesis, the evolution of the thermal, hydraulic, mechanical, and microstructural properties of small GF samples are determined. Various binder contents of Portland cement type I (PCI) are used. The GF is cured for 3, 7, 28, 90, and 120 days. It is found that the thermal, hydraulic and mechanical properties are time-dependent or affected by the degree of binder hydration index. Furthermore, a relationship is found between the compressive strength and the saturated hydraulic conductivity of the GF samples. The unsaturated hydraulic properties of GF samples have also been investigated. The outcomes show that unsaturated hydraulic conductivity is influenced by the degree of binder hydration index and binder content, especially at low suction ranges. Simple functions are proposed to predict the evolution of air-entry values (AEVs), residual water content, and fitting parameters from the van Genuchten model with the degree of hydration index (α). Furthermore, two columns are built to simulate the coupled thermo-hydro-mechanical (THM) behaviour of GF under drained and undrained conditions. The obtained results from the GF columns are compared with the small samples. It is observed that the mechanical properties, hydraulic properties (suction and water content), and temperature development are strongly coupled. The magnitude of these THM coupling factors is affected by the size of the GF. The findings also show that the mechanical, hydraulic and thermal properties of the GF columns are different from samples cured in plastic moulds.

[Truncated abstract] This research has studied the penetration and extraction resistance profiles of different types of penetrometers in soft clay. The penetrometers of interest include the cone, T–bar, ball and plate. Effects of the surface roughness and aspect ratio of the T–bar penetrometer on its resistance have also been investigated. Undrained shear strength, Su, profiles derived from the penetration tests are compared with the shear strengths measured from field vane shear tests and laboratory (triaxial and simple shear) tests. Both in situ and centrifuge model penetration tests were undertaken for the research. In addition, ‘undisturbed’? tube samples were retrieved from both the field and the centrifuge strongbox samples (after completion of the centrifuge tests) for laboratory testing. The in situ testing was carried out in Western Australia, at the Burswood site near Perth, with tests including cone, T–bar, ball and plate penetrometer tests, and vane shear tests. Interestingly, the T–bar, ball and plate (‘full-flow’) penetrometers showed a narrow band of resistance profiles both during penetration and extraction, with a range of around 15 % between the highest and lowest profiles and standard deviation of 15 %. However, the cone penetrometer gave similar resistance at shallow depths but increasingly higher penetration resistance at depths greater than 7 m – a phenomenon that is also common in offshore results. During extraction, the cone penetrometer gave a higher resistance profile than the full–flow penetrometers for much of the depth of interest. The Su profile measured directly from the vane shear tests falls within the Su profiles derived from the penetration resistances of the full–flow penetrometers, using a single bearing factor, N = 10.5 (the value originally suggested in the literature for a T–bar penetration test). Again, the cone penetrometer demonstrated diverging results, requiring two separate values for the cone factor, Nkt (10.5 initially increasing to 13 for depths below 10 m) in order to give Su similar to the vane shear tests. This highlights the possible variability of the cone factor with depth. Cyclic penetration and extraction tests were performed at specific depths for each fullflow penetrometer. These tests comprised displacement cycles of ±0.5 m about the relevant depth, recording the penetration and extraction resistances over five full cycles. The results may be used to derive the remoulded strength and sensitivity of the soil. Laboratory tests such as triaxial and simple shear tests were performed on ‘undisturbed’ tube samples retrieved from the same site to evaluate the in situ shear strengths in the laboratory. However, the resulting Su data were rather scattered, much of which may be attributed to variable sample quality due to the presence of frequent shell fragments and occasional silt lenses within the test samples. In general, N factors for the full–low penetrometers, back–calculated using Su values measured from the simple shear tests, fell mainly in a range between 9.7 and 12.8 (between 10.4 and 12.2 for the standard size T–bar (250 mm x 40 mm))

Capacity analysis is a common preliminary step in the design of offshore foundations. Inaccuracies in traditional capacity analysis methods, and the advancement of numerical modelling capabilities, have increasingly led designers to optimise foundations using more complex methods. In this thesis, the ultimate limit state capacity of a range of foundation types is investigated using finite element limit analysis. Novel three-dimensional finite element limit analysis software is benchmarked against analytical solutions and conventional displacement finite element analysis. It is then used to find lower and upper bounds of foundation capacity, with adaptive mesh refinement used to reduce the bound gap over successive iterations of the solution. Rigid foundations subjected to short term loading on clay soil are analysed. The undrained soil is modelled as a rigid--plastic von Mises material, and attention is given to modelling any normal and/or shear stress limits at the foundation/soil interface. Shallow foundations, suction anchor foundations, and hybrid mudmat/pile foundations are considered. Realistic six degree-of-freedom load combinations are applied and results are reported in the form of normalised design charts, and tables, that are suitable for use in preliminary design. Relationships between loading combinations and failure mechanisms are also explored. A number of case studies based on authentic foundation designs are analysed. The results suggest that finite element limit analysis could provide an attractive alternative to displacement finite element analysis for preliminary foundation design calculations.

[pt] O fenômeno de liquefação continua sendo um dos temas mais importantes, complexos e controversos da engenharia geotécnica, sendo a liquefação dinâmica, causada por terremotos, o maior contribuinte de risco sísmico urbano em vários países andinos. O movimento causa incrementos da poropressão que reduz a tensão efetiva e conseqüentemente a resistência ao cisalhamento de solos arenosos. O presente trabalho de pesquisa apresenta e compara algumas das metodologias existentes para a avaliação do fenômeno de liquefação dinâmica, variando desde o método semi-empírico de Seed-Idriss para estimativas do potencial de liquefação até a execução de algumas análises numéricas, no contexto dinâmico, através do programa computacional FLAC 2D v.5. Um estudo de caso, para uma comparação dos diversos procedimentos, consiste na análise dinâmica de uma pilha de lixiviação de minério de cobre, situada em região de atividade sísmica no Peru que, devido a problemas no sistema de drenagem interna, resultou com um alto nível de saturação que poderia colocar sua estabilidade em risco devido à possibilidade de liquefação sob carregamento sísmico. Dos resultados obtidos nessas análises, pode-se afirmar que o método semi-empírico de Seed-Idriss, para determinação do potencial de liquefação, compara-se bastante bem com modelos mais sofisticados baseados em análises dinâmicas empregando tanto o modelo constitutivo de Finn quanto o modelo constitutivo elastoplástico UBCSAND. / [en] The phenomenon of liquefaction is still one of the most important, complex and controversial subjects of the geotechnical engineering, being the dynamic liquefaction, caused by earthquakes, the major contributor to urban seismic risks in several Andesian countries. The shaking increases the pore water pressure which reduces the soil effective stress and, therefore, the shear strength of sandy soils. This dissertation presents and compares some of the proposed methodologies to evaluate the phenomenon of dynamic liquefaction, ranging from the semi-empirical method of Seed-Idriss to estimate the liquefaction potential to the execution of some numerical analyses, within the dynamic context, through the computational program FLAC 2D v.5. The case study, for the comparison among the several procedures, consists of a copper ore heap leach, situated in a high seismic activity zone in Peru, that experimented high levels of saturation, due to problems in the internal drainage system, that could put in risk the stability of the leach pad to the possibility of liquefaction under seismic loading. From the results of such analyses, one can say that the semi-empirical method proposed by Seed- Idriss for the determination of the liquefaction potential compares quite well with outputs from more sophisticated numerical analyses based on dynamic studies that incorporate either the Finn s or the elasto-plastic UBCSAND constitutive models.

O descarte do lodo de ETA em corpos de água, como rios, tem sido ainda uma prática comum no Brasil. Alternativas frequentes de destinação têm sido a disposição do lodo em aterros sanitários ou industriais e na rede de esgoto. Porém, os padrões ambientais cada vez mais rígidos têm levado à procura de soluções mais econômicas e benéficas, com o aproveitamento do lodo de ETA como material para diversos usos. Uma das opções promissoras é a utilização do lodo de ETA misturado a solos naturais em obras geotécnicas, como revestimento de fundo e cobertura final de aterros sanitários e industriais, e na construção de aterros em geral. Nessa perspectiva, foram estudadas as propriedades geotécnicas de misturas de um solo laterítico arenoso com um lodo de ETA em três proporções solo:lodo (3:1, 4:1, e 5:1) em massa úmida. Foi realizada a caracterização química e mineralógica do solo e do lodo por meio de ensaios de difração de raios X, fluorescência de raios X, microscopia eletrônica de varredura, determinação de perda ao fogo, pH, capacidade de troca catiônica, soma de bases trocáveis, carbono orgânico, matéria orgânica, entre outros. Foram determinados a curva granulométrica, a massa específica dos grãos e os limites de consistência do solo, do lodo e das misturas. Ensaios de adensamento, permeabilidade e compressão triaxial foram realizados em corpos de prova compactados do solo e das misturas. A caracterização geotécnica das misturas mostrou que a adição de lodo não altera significativamente a granulometria, a massa específica dos grãos e os limites de consistência do solo. Por outro lado, a secagem prévia ao ar das misturas alterou os parâmetros de compactação: a massa específica seca máxima aumentou e o teor de umidade ótimo diminuiu com a redução do teor de umidade inicial no ensaio de compactação. Os índices de compressão das misturas apresentaram-se maiores que o do solo, enquanto as condutividades hidráulicas das misturas foram menores que a do solo. O ângulo de atrito efetivo das misturas apresentou aumento e a coesão efetiva diminuição a medida que a proporção de lodo acrescentado ao solo aumentou. As características e propriedades das misturas apresentaram valores aceitáveis para solos utilizáveis em aterros, o que possibilita o aproveitamento de lodo de ETA em misturas com solo a serem empregadas em obras geotécnicas. / In Brazil, WTS is mostly released in water bodies causing silting and deterioration of water quality, destined to treatment with sewage, or disposed of in sanitary landfills or disposal sites of sewage treatment plants mixed with sewage sludge after a partial dewatering process. An alternative for WTS destination is its application, in natura, treated or mixed with soil, as construction material for covers and bottom liners of sanitary and industrial landfills or in embankments in general. Addition of Water Treatment Sludge (WTS) to soils in earthworks may reduce land disposal of WTS and exploitation of natural soils. In this perspective, geotechnical properties of mixtures of a lateritic sandy soil with WTS in proportions 3:1, 4:1, and 5:1 (by wet weight) were evaluated. WTS and soil were subjected to chemical and mineralogical characterization by X-ray fluorescence and X-ray diffraction tests, and determination of loss on ignition, pH, organic matter content, cation exchange capacity, exchangeable bases, and other chemical parameters. Particle-size distribution curve, specific gravity of solids, and Atterberg limits were obtained for WTS, soil and mixtures. One-dimensional consolidation, permeability and undrained triaxial compression tests were carried out on compacted specimens of the soil and the soil-WTS mixtures. Geotechnical characteristics of the mixtures resulted slightly different from those of the soil, on the other hand, previous air-drying affected the compaction parameters of the mixtures, the maximum dry unit weight increased and the optimum water content decreased for a decrease in the initial water content of the compaction test. Compression index of the mixtures were higher than the soil, whereas hydraulic conductivity decreased with WTS addition for different confining pressures and hydraulic gradients. Effective friction angle of the mixtures increased and effective cohesion decreased when increasing the proportion of WTS added in the mixture. Some of those geotechnical parameter values were acceptable for a compacted soil and indicate high possibility of reuse of this waste in geotechnical works.

Gelfill (GF) is made of tailings, water, binder and chemical additives (Fillset, sodium silicate gel). The components of GF are combined and mixed on the surface and transported (by gravity and/or pumping) to the underground mine workings, where the GF can be used for both underground mine support and tailings storage. Thermal (T), hydraulic (H), and mechanical (M) properties are important performance criteria of GF. The understanding of these engineering properties and their evolution with time are still limited due to the fact that GF is a new cemented backfill material. In this thesis, the evolution of the thermal, hydraulic, mechanical, and microstructural properties of small GF samples are determined. Various binder contents of Portland cement type I (PCI) are used. The GF is cured for 3, 7, 28, 90, and 120 days. It is found that the thermal, hydraulic and mechanical properties are time-dependent or affected by the degree of binder hydration index. Furthermore, a relationship is found between the compressive strength and the saturated hydraulic conductivity of the GF samples. The unsaturated hydraulic properties of GF samples have also been investigated. The outcomes show that unsaturated hydraulic conductivity is influenced by the degree of binder hydration index and binder content, especially at low suction ranges. Simple functions are proposed to predict the evolution of air-entry values (AEVs), residual water content, and fitting parameters from the van Genuchten model with the degree of hydration index (α). Furthermore, two columns are built to simulate the coupled thermo-hydro-mechanical (THM) behaviour of GF under drained and undrained conditions. The obtained results from the GF columns are compared with the small samples. It is observed that the mechanical properties, hydraulic properties (suction and water content), and temperature development are strongly coupled. The magnitude of these THM coupling factors is affected by the size of the GF. The findings also show that the mechanical, hydraulic and thermal properties of the GF columns are different from samples cured in plastic moulds.