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.

Previously, the concept of the tolerant wind tunnel, developed in the Department of Mechanical Engineering, U. B. C., was tested only for stationary models. In the present study, the concept is investigated for unsteady airfoil motion. The new wind tunnel test section, using the opposite effects of solid and open boundaries, is a new approach to reduce wall blockage effects. Consisting of vertical airfoil slats uniformly spaced on both side walls in the test section, it is designed to produce a nearly free-air test environment for the test model, which leads to negligible or small corrections to the experimental results. The performance of this wind tunnel for unsteady model testing is examined experimentally with a two-dimensional NACA 0015 airfoil in a simple plunging sinusoidal motion. The airfoil is mounted vertically in the center plane of the test section between solid ceiling and floor. An oscillating table is designed to give the airfoil an accurate plunging sinusoidal motion. A full range of open area ratio is tested by varying the number of slats mounted inside the side walls. Pressure distribution along the airfoil surface and displacement of the airfoil are measured as functions of time by a data acquisition system designed for this research. Lift and moment are obtained by integration of the pressure distribution at every time increment. Using a numerical model based on the singularity distribution method, the free air case results for a NACA 0015 airfoil in the same unsteady motion are obtained. Comparison with the linear theory results by Sears¹ are discussed. Comparing with the numerical and the linear theory results, the experimental investigation shows that the new test section produces low-correction data. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

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Yes / A Decision Support System (DSS) in tunnelling domain deals with identifying pathologies based on disorders present in various tunnel portions and contextual factors affecting a tunnel. Another key area in diagnosing pathologies is to identify regions of interest (ROI). In practice, tunnel experts intuitively abstract regions of interest by selecting tunnel portions that are susceptible to the same types of pathologies with some distance approximation. This complex diagnosis process is often subjective and poorly scales across cases and transport structures. In this paper, we introduce PADTUN system, a working prototype of a DSS in tunnelling domain using semantic technologies. Ontologies are developed and used to capture tacit knowledge from tunnel experts. Tunnel inspection data are annotated with ontologies to take advantage of inferring capabilities offered by semantic technologies. In addition, an intelligent mechanism is developed to exploit abstraction and inference capabilities to identify ROI. PADTUN is developed in real-world settings offered by the NeTTUN EU Project and is applied in a tunnel diagnosis use case with Société Nationale des Chemins de Fer Français (SNCF), France. We show how the use of semantic technologies allows addressing the complex issues of pathology and ROI inferencing and matching experts’ expectations of decision support.

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As a result of tunnel construction, the ground level surface above will tend to collapse downward as the soil seeks to refill the missing tubular cavity. Many infrastructures that were originally built on that surface may also fall slightly or severely depending on the engineering design and execution of the tunneling project. Engineers then must factor in the development of ground subsidence, examining geotechnical and geological issues to construct a model that would otherwise predict the extent of vertical settlements. Their predictions could help to assess potential damages and make corrective actions. In this thesis submission, analytical methods from the classical elasticity were used to estimate surface displacements for a prospective tunnel. The analytical equation tied in the method of virtual images originating from Sagaseta with the classical Kirsch elastic solutions for stress-displacements of an infinite plate with hole in order to establish a solution of half-space. This approach will be similar to what Verruijt-Booker had developed after Sagaseta but will include higher-order terms to simulate an excavation process in a longitudinal direction below ground and thereby obtain a new subsidence equation including ground parameters associated with tunnel shape changes occurring at its base, springline (sideway point) and crown (top). These parameters were not previously reported by the Verruijt-Booker work or from current technical literature. In addition, the prescribed solution could include any Poisson’ ratios in which only the original Verruijt-Booker could be found correct for only incompressibility conditions (υ = 0.5). The Verruijt-Booker equation considered deep tunnels only. An extra term influencing the subsidence was included in the modified solution which is significant for shallow tunnels. The derived equations were applied to calculate surface deflections using data from a tunnel construction project to test its viability. Comparison analysis was made with the three methods to be described- Peck, Sagaseta, and Verruijt-Booker. In addition, a parametric study was made to examine the amount of subsidence changed when deciding to construct a tunnel from a shallow to deeper zone. Finally, a qualitative study of the derived equation and Verruijt-Booker was conducted to assess potential subsidence behaviour between shallow and deep tunnels.

From the discovery of GMR effect since 1988,spintronic has been extensively developed. Research and application of relative GMR, CMR and TMR topics have progressed rapidly. In the year of 2007, the Nobel prize of physics was awarded to Albert Fert and Peter Grünberg for the great achievement on the research of GMR. The application of development on MRAM is a very hot subject recently and the main operating constructions of MRAM are MTJ. In this thesis, La0.67Ca0.33MnO3¡BLa0.67Sr1.33MnO4 and La0.8Ba0.2MnO3 of CMR materials were growth to multilayer to investigate the properties and characters of the films, in order to built up the MRAM based on CMR MTJ¡¦s.

Current requirements of nonvolatile memory (NVM) are the high density cells, low-power consumption, high-speed operation and good reliability for the scaling down devices. However, all of the charges stored in the floating gate will leak into the substrate if the tunnel oxide has a leakage path in the conventional NVM during endurance test. Therefore, the tunnel oxide thickness is difficult to scale down in terms of charge retention and endurance characteristics. The nonvolatile nanocrystal memories are one of promising candidates to substitute for conventional floating gate memory, because the discrete storage nodes as the charge storage media have been effectively improve data retention under endurance test for the scaling down device. Many methods have been developed recently for the formation of nanocrystal. Generally, most methods need thermal treatment with high temperature and long duration. This procedure will influence thermal budget and throughput in current manufacture technology of semiconductor industry. In this thesis, we used the three kind of high-k dielectric structure as the tunnel oxide (Al2O3, HfO2/Al2O3/HfO2, Al2O3/HfO2/Al2O3) to overcome the limitation of conventional NVMs during the scaling down process. First, we used Al2O3 as tunnel oxide. It observed that device of Al2O3 as tunnel oxide reduce equivalent thickness without lost retention too much. Then, we used HfO2/Al2O3/HfO2 as tunnel oxide. It observed the device of HfO2/Al2O3/HfO2 as tunnel oxide which had bigger window than the device used thermal oxide as tunnel oxide. Moreover it had better retention characteristics than the device used thermal oxide as tunnel oxide with a small charge lose rate. And it reduced equivalent thickness of SiO2.Final, we used Al2O3/HfO2/Al2O3 as tunnel oxide. It observed the device of Al2O3/HfO2/Al2O3 as tunnel oxide which had better retention characteristics than the device used HfO2/Al2O3/HfO2 as tunnel oxide without decrease the electron and hole injection. And we reduce equivalent thickness of SiO2 .

The broad aim of the work presented in this thesis is to investigate the wake of an airfoil under the combined effects of streamwise curvature and pressure gradient. This was accomplished by an experimental investigation using hot-wire anemometry and large eddy simulation (LES). The wake was generated by placing a NACA 0012 airfoil in a uniform stream of air, which is then subjected to an abrupt 90o curvature created by a duct bend. The experimental work was conducted in a subsonic open-return type wind tunnel. The test section measured 457 mm × 457 mm in cross-section and consisted of a 90o bend with radius-to-height ratio of 1.17. The symmetrical airfoil was of chord length (c) 150 mm, and its trailing edge was located one chord length upstream of the bend entry. The effects of airfoil angle of attack and mainstream velocity on the mean velocity and turbulence quantities of the near-wake were examined. In addition, the mean velocity and turbulence intensity profiles of the boundary layer on the upper surface of the airfoil were measured. In the numerical investigation, the three-dimensional, incompressible turbulent flow in the duct was computed using the finite volume method. The effect of modelling parameters, namely, grid resolution and sub-grid scale (SGS) model were studied. Three different sub-grid scale models were employed, namely, the classical Smagorinsky, its dynamic variant (DSMG) and the dynamic kinetic energy transport. The effect of grid resolution was assessed by conducting simulations with the DSMG model on three different grids. The first two grids incorporated the full spanwise extent of the duct (3c), and the third grid comprised a reduced spanwise segment (0.5c) with periodic conditions set in the spanwise direction. A bounded central differencing scheme was employed for the discretization of the convection terms. The temporal discretization was by a second-order implicit method that incorporated a forward difference approximation. The performance of LES in depicting the experimental flow was assessed and compared with the results predicted by the Reynolds Stress Model. The experimental profiles at zero angle of attack revealed the differing effects of curvature on the mean and turbulence quantities in the inner-side and outer-side of the wake. The spanwise distributions of mean velocity and turbulence intensity, in the near-wake, indicated variations with identifiable peaks and troughs which corresponded to the presence of streamwise vortices in the wake. The spanwise variations were larger on the inner side of the wake and significantly reduced on the outer side. The results showed that close to the trailing edge, the dominant effect on the wake was from the airfoil boundary layer, whereas one chord length downstream of the trailing edge, it was the effect of curvature and pressure gradient from the duct which was dominant. The results from the numerical study showed the advantages of LES over Reynolds-averaged Navier-Stokes methods in predicting separation on the convex wall of the bend on relatively coarse grids, but also shortcomings in the prediction of the wake parameters. The dynamic variants of the SGS models were more accurate in predicting the flow in the wake. On a considerably finer grid with near-wall airfoil grid spacings of Δx+ < 80, Δy+ < 0.5, and 20 < Δz+ < 50, LES resulted in much improved comparisons with the experimental data. The improved prediction of the wake parameters was attributed to the improved simulation of the boundary layers on the upper surface of the airfoil. However, the effect of the reduced spanwise extent resulted in a lack of prediction of separation on the convex wall of the duct.