In conventional wind tunnels the solid-wall or open-jet test section imposes on the flow field around the test model new boundary conditions absent in free air. Unless a small model is used, the solid-wall test section generally increases the loadings on the model while the open-jet boundary decreases the loadings compared to the unconfined case. However, the development of a low wall-interference test section and its successful demonstration would allow the testing of relatively large models without the application of often uncertain correction formulae. The Tolerant wind tunnel, which makes use of the opposite effects of solid and open boundaries, is a transversely slatted-wall test section designed to produce at an optimal wall open-area ratio (OAR) low-correction data for a wide variety of model shapes and sizes. Initially intended for low-speed airfoil testing, its use is theoretically and experimentally investigated here in connection with bluff body testing. A simple mathematical model based on two-dimensional potential flow theory and solved with the help of a vortex surface-singularity technique is used to estimate the best wall configuration. The theory predicts an optimum OAR of about 0.45 at which pressure distributions on flat plate and circular cylinder models of blockage ratios up to 33.3 % would differ from the free-air values by not more than 1 %. On the other hand, experiments performed with flat plate, circular cylinder and circular-cylinder-with-splitter-plate models indicate the existence of an optimum configuration around OAR = 0.6. The experiments also show a maximum allowable blockage in the Tolerant wind tunnel to be equivalent to the blockage created by a 33.3 %-blockage-ratio flat plate model. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

The four kilometre twin-bore Du Toitskloof Tunnel is situated in the Klein Drakenstein mountain range, approximately 60 kilometres from Cape Town, near the town of Paarl. The tunnel will form part of the new National road system, upgraded to a freeway standard, linking Johannesburg and Cape Town. The subject of this report is the construction of the Du Toitskloof tunnel, with emphasis on the excavation and construction of the soft ground tunnel, by means of artificial ground freezing for ground support and stabilisation. The soft ground section of the tunnel being situated at the Western portal, and forming approximately 168 metres of the four kilometre main tunnel. The objectives of the report are: 1. to investigate the general history of tunnelling through the ages. 2. to investigate the general aspects and conditions surrounding the Du Toitskloof Tunnel project. 3. to investigate the pertinent geological investigations and conditions which prevail within the tunnel project. 4. to investigate the formation of the main tunnel within the Soft Ground tunnel contract. 5. to investigate the application of the system of artificialground freezing, inserting ground stabilisation, within the decomposed-weathered granite zone of the main soft ground tunnel project. 6. to investigate the methods of testing and monitoring the freezing process being applied to the soft ground for implementing temporary support. 7. to investigate the application of a reinforced Shotcrete lining against the frozen ground of the Du Toitskloof Soft Ground tunnel. 8. to investigate the possible alternatives for the excavation of the Soft Ground section of the Du Toitskloof tunnel.

Records of subglacial drainage features of previous ice sheets, such as tunnel channels (TCs), provide insight into drainage mechanisms of modern ice sheets. More than 60 tunnel channels were identified in the formerly glaciated landscape of Wisconsin, USA, in the footprint of the Green Bay Lobe of the Laurentide Ice Sheet. I used a combination of a reflection-seismic survey and a hydraulic-potential model to reveal the geometry of a TC and attempt to further understand the dynamics of TC formation. The seismic cross section along the Plainfield tunnel channel (PTC), 16 km up-ice from the terminal margin, shows an absence of a channelized feature in the subsurface. Therefore, the Plainfield tunnel channel likely initiates between 7-16 km up-ice from its terminus in a subglacial setting where the water-flow velocity may have increased, as dictated by the regional bed slope. Relatively fast subglacial water flow would have caused erosion at the ice-bed interface, whereas slower velocities produced little to no erosion of the underlying sediments. The hydraulic-potential model suggests a total area of ~107 km2 for potential subglacial lakes up-ice from the PTC, although this estimate is not sufficient to account for the volume of water needed to form the channel. However, when water does pool in subglacial lakes, permafrost in the area helps to seal in large amounts of water at the ice-bed interface. Additionally, an increase in traction at the bed after a single discharge event likely facilitates supraglacial lake formation. The supraglacial water sources subsequently drain into the subglacial system, which can cause successive subglacial drainage events to occur. The results from the seismic cross-section and the hydraulic-potential model, along with inferences from previous studies, indicate that the PTC is likely formed over several drainage events and had a substantial influence from moulin drainage of supraglacial water in addition to the water stored in subglacial lakes. The Laurentide Ice Sheet was able to store large amounts of subglacial water in this region due to the combination of an adverse bed slope, as well as expansive permafrost during the time of TC formation. This likely means that modern ice sheets, such as along the Western edge of the Greenland Ice Sheet or Thwaites Glacier in West Antarctica, could exhibit similar subglacial and supraglacial drainage behavior in areas with adverse bed slopes similar to this portion of the Laurentide Ice Sheet. / Geology

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Carpal tunnel syndrome (CTS) is a common peripheral compression neuropathy which is often idiopathic in etiology. There is evidence that the development of CTS may result from circulatory disturbances. The purpose of this thesis was to improve our understanding of the vascular component to the development and progression of CTS. Ultrasound allowed for non-invasive investigation of median nerve intraneural blood flow and morphology, tissue stiffness, and mechanics of the flexor digitorum superficialis (FDS) tendon and its adjacent subsynovial connective tissue (SSCT). Nerve conduction study (NCS) allowed for investigation of median nerve function. Three studies were completed, two with patients and one involving healthy participants, to investigate the relationship between local blood flow and carpal tunnel tissue function, morphology, and mechanics. Nerve function, intraneural blood flow, individual FDS and SSCT displacements, and measures of shear strain (relative FDS-SSCT displacement and shear strain index (SSI)) were quantified in CTS patients (Chapter 2). These patients were followed-up six months later and the measures were repeated (Chapter 3), allowing me to determine the prognostic value of ultrasound measures. Results from these two studies suggested a high interdependency among intraneural blood flow velocity, nerve function, and FDS-SSCT relative displacement and SSI. Intraneural blood flow velocity, peak FDS-SSCT relative displacement, and SSI were also significant predictors of median nerve function at 6-months follow-up. To directly investigate the effects of circulatory disturbances, temporary partial ischemia of the carpal tunnel was induced in healthy participants through a 30-minute occlusion protocol (Chapter 4). Partial ischemia immediately decreased intraneural blood flow velocity. Nerve dysfunction, and increased SSI and relative displacement were observed soon after. This thesis clearly demonstrates the interrelationship among median nerve vascular dynamics, tendon-SSCT kinematics, and nerve function. Altered nerve blood flow may be a driver in the development of CTS. / Thesis / Doctor of Philosophy (PhD) / Carpal tunnel syndrome (CTS) is due to compression of the median nerve as it passes through the carpal tunnel which is located at the base of the palm. Nerve compression leads to nerve dysfunction, resulting in symptoms of tingling, numbness and weakness of the hand. The purpose of this thesis was to improve our understanding of the effects of altered blood flow on the development of CTS. I conducted three unique studies to investigate the relationship among nerve blood flow, nerve function, and motion of the tendons and connective tissue within the carpal tunnel. The use of ultrasound allowed for real-time, non-invasive investigation of function in these tissues. Results from these three studies clearly demonstrate the interrelationship between nerve function, tendon-connective tissue motion and adequate nerve blood flow. These findings have implications for individuals with cardiovascular conditions and for people working under conditions that may compromise normal blood flow.

Este trabalho apresenta um estudo a respeito do comportamento do solo durante a escavação de um túnel, com foco na metodologia de escavação mecanizada. São abordadas diretrizes para a modelagem numérica de túneis com o emprego de diferentes métodos de cálculo, distintos modelos constitutivos para representação do comportamento do solo e duas maneiras de se representar o revestimento da escavação. Alguns conceitos fundamentais relacionados a escavações de túneis de grande diâmetro em solo com o emprego de máquinas tuneladoras são descritos, como os tipos de máquinas existentes (com ênfase nas máquinas do tipo EPB - Earth Pressure Balance), princípios de funcionamento e modos de operação, além de uma comparação deste método com a metodologia sequêncial tradicional. É realizada uma revisão bibliográfica sobre distintos métodos de cálculo para estimar a estabilidade de uma escavação, a previsão da deformação no maciço e os esforços atuantes no revestimento do túnel. O trabalho também apresenta uma revisão de publicações recentes a respeito da modelagem numérica de túneis escavados mecanicamente, destacando algumas diferenças em relação à metodologia sequencial. Uma das diferenças é com relação à simulação do revestimento do túnel, com a possibilidade de se considerar as propriedades das juntas dos anéis. Outro ponto distinto é o método de cálculo empregado, levando em conta na simulação aspectos específicos da escavação mecanizada, como pressão de frente aplicada, vazio anelar e injeção de grout. É feita uma breve introdução e são apresentados os conceitos básicos de dois modelos constitutivos do solo: o modelo elastoplástico perfeito conhecido como Mohr-Coulomb e o modelo elastoplástico com endurecimento Hardening Soil. Utilizando alguns dos conceitos estudados na revisão bibliográfica, são realizadas análises numéricas bidimensionais retroanalisando um caso real de escavação com tuneladora. Foi utilizado o programa de elementos finitos Plaxis para realizar comparações entre os métodos de cálculo do alívio de tensões e da contração, além da simulação do revestimento com ou sem a consideração das juntas. Por fim é feita uma análise crítica dos resultados obtidos nas diferentes modelagens numéricas. / This research presents a study about the soil behavior during the excavation of a tunnel, focusing on the mechanized excavation methodology. Guidelines for the numerical modeling of tunnels with the use of different calculation methods, distinct constitutive models to characterize the soil behavior and two ways of representing the lining of the excavation are addressed. Relevant aspects regarding excavations of large diameter tunnels in soil with the use of TBM (Tunnel Boring Machine) are presented, like types of machines, with the focus on the Earth Pressure Balance (EPB) machines, fundamental concepts of the methodology and operation modes, besides a comparison of this method with the traditional sequential methodology. A literature review on different methods of calculation to estimate the excavation stability, the prediction of ground deformation and the efforts acting in the tunnel lining is made. The research also presents a review of recent publications regarding numerical modeling of mechanically excavated tunnels, highlighting some differences with the sequential method. One of these differences is related to the simulation of the tunnel lining, with the possibility of considering the properties of the ring joints. Another different point is the calculation method employed, considering in the simulation specific aspects of mechanized excavation, as front pressure applied, ring void and grout injection. A brief introduction is made about constitutive models to represent the soil behavior and the basic concepts of two constitutive soil models are presented: Mohr-Coulomb and Hardening Soil. Using some of the concepts studied in the literature review, it is performed two-dimensional numerical analysis with a back-analysis of a real case, using the finite element model program Plaxis, comparing the calculation methods of stress relieving and contraction, as well as the tunnel lining simulation with or without consideration of the joints. Finally, it is made a critical analysis of the results of the numerical simulations.

Thèse de doctorat : Etudes anglophones : Lyon 2 : 2000. / Titre provenant de l'écran-titre. Bibliogr.. Glossaire. Index.

Η συγκεκριμένη διπλωματική εργασία ως θέμα της πραγματεύεται τις τεχνικογεωλογικές συνθήκες κατά την διάνοιξη του τμήματος από τη Χ.Θ. 85+728,57 έως Χ.Θ. 87+558,70. / This dissertation analyses the technical and geological conditions while opening up Aigion tunnel from 85+728,57km to 87+558,70km national road of Athens to Patras. It is a comparative regard of forecast section with the real conditions of opening up.