During soft ground tunnel construction, if the face pressure of a tunnel boring machine is not strictly controlled, excessive ground movements will propagate vertically upwards causing significant damage to adjacent buried infrastructure and surface structures. In order to investigate the face pressure - ground deformation relationship for tunnels in sands, the construction process was modelled using the technique of geotechnical centrifuge modelling and the resulting ground deformations were recorded using digital image correlation. In these tests a unique tunnel face boundary condition was developed which allowed the boundary condition to be initially set as a zero strain condition before it was transformed into a load-controlled boundary to investigate the instability of the face. Tests were preformed at four different burial depths in dry sand, corresponding to cover depths of 0.5, 1, 1.5, and 2 times the tunnel diameter. These results indicate that the face pressure at failure is largely independent of burial depth over the values tested. The ground deformation at the onset of tunnel face instability was found to be very small, and once initiated, the zone of ground deformations was observed to propagate upwards in a narrow chimney in front of the tunnel until it reached the ground surface causing subsidence. Further tests investigated the variation in ground deformations to be expected if a tunnel were to be passing through more complex ground conditions, including unsaturated sand, saturated sand, and the unique case of sand / clay mixed ground conditions. Ground deformations at tunnel face instability were much lower for the case of unsaturated sand, than for either the saturated or dry cases which showed broadly similar responses. In the mixed ground condition of a clay layer over topping a sand layer, the clay layer was found to only influence the tunnel face pressure – deformation response if the bottom of the clay layer was closer than 0.5 diameters above the tunnel crown. / Thesis (Master, Civil Engineering) -- Queen's University, 2007-12-20 15:09:06.156

The Niagara Tunnel Project is a 10.4 km long water diversion tunnel being excavated under the city of Niagara Falls, Ontario by a 14.4 m diameter tunnel boring machine. This tunnel has descended through the entire stratigraphy of the Niagara Escarpment, including dolomites, limestones, sandstones, shales and interbedded zones of these rock types, passed under St. Davids Buried Gorge ascending to surface. Working at the tunnel provided an opportunity to assess and document the horizontally laminated ground behaviour for this large diameter circular tunnel and provided the backdrop for this study. A detailed understanding of the geological history was necessary. Modelling of laminations, ranging between 0.16 to 16 m in thickness, was conducted to determine critical behaviour and cut-offs for failure modes. A critical normalized lamination thickness (thickness/radius) of 0.9 was found to exist, above which the excavation response is similar to the equivalent isotropic model, and below which the laminated behaviour corresponds to a characteristic failure mode controlled by bed deflections and bed parallel shear. Initially, as the normalized lamination thickness is decreased below 0.9, the stresses are channeled through the crown beam which concentrates the yield and increases the crown deflections. This results in crown beam failure. As the lamination thickness decreases, further the stresses are shed to multiple laminations increasing the displacements significantly and changing the shape and extent of the yield zone. From multiple lamination coupling to self-limiting yield the development of chimney style failure is controlled by the degree of tensile yielding. Tensile yielding first begins in the haunch area and progressively extends above the crown, as the lamination thickness decreases, until a self-limiting plastic yield zone shape is reached at normalized lamination thicknesses below 0.026. Incorporation of discrete anisotropy is necessary to accurately model the excavation response in horizontally laminated ground. / Thesis (Master, Geological Sciences & Geological Engineering) -- Queen's University, 2009-09-15 16:34:47.134

Shallow excavations through variable rockmasses in urban centers present significant design challenges, whether considering small diameter tunnels for utilities or large span underground caverns. In designing shallow excavations in urban environs, it is especially critical to minimize the impact of the excavation on surface. In small diameter projects, minimal surface disturbance is often achieved by the employment of TBMs as the excavation method. While reducing the risk of surface subsidence due to displacements in front of the face, TBM progress is sensitive to variable ground conditions and the TBM design must be appropriately matched to the expected geology. Sufficient understanding of the geology and development of geological models are critical in the selection of an appropriate TBM and cutting tools. In this study, recent projects in Calgary, AB are used to highlight the challenges faced with using TBMs through sedimentary rock with distinct, variable units. In larger scale projects, long term excavation stability is critical in the reduction of surface disturbance. Due to the low confining stresses, structural failure is often the primary failure mode in shallow excavations, especially within fractured, heterogeneous rockmasses. In these cases, numerical methods are often used in excavation design. The ability of numerical methods to capture the expected failure modes of shallow excavations through layered rockmasses is explored, with an emphasis placed on the ability of support elements to reduce shear slip for increased stability. Passive bolt models are analysed using both 2D and 3D numerical models to adequately capture the behaviour of a passive support system in shear. The shortcomings of some current support models are discussed, and modifications are suggested. / Thesis (Master, Geological Sciences & Geological Engineering) -- Queen's University, 2012-09-25 20:56:52.083

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Heuristics based upon ray theory are often used to predict the propagation of internal gravity waves in non-uniform media. In particular, they predict that waves reflect from weakly stratified regions where the local buoyancy frequency is less than the wave frequency. However, if the layer of weak stratification is sufficiently thin, waves can partially transmit through it in a process called tunnelling. The first laboratory evidence of internal wave tunnelling through a weakly stratified region is analysed using the synthetic schlieren technique and the Hilbert transform is applied to filter the wavefield into upward- and downward-propagating components. Transmission is calculated as the squared ratio of transmitted and incident wave amplitude and using an appropriate superposition of plane waves to reproduce the structure of the incident wave beam, a corresponding weighted sum of transmissions can be used to predict the beam transmission. These transmission predictions are compared with experimental measurements. / Applied Mathematics

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The Old Yellow Enzyme (OYE) family of enzymes has been shown to reduce industrially important chemicals and has been used to study quantum tunnelling during enzymatic hydrogen transfer. Though extensively studied, only mesophilic homologues have been studied within the enzyme family. This thesis discusses the characterisation of Thermophilic Old Yellow Enzyme (TOYE), from Thermoanaerobacter pseudethanolicus, and provides the first published crystal structure of a thermophilic OYE-family member. In addition to increased thermostability compared to mesophilic homologues, thermophilic enzymes are important for use in industrial as often they are more stable towards organic solvents used in industry than their mesophilic homologues while catalysing the same reactions. This makes thermophiles and hyperthermophiles interesting targets for investigating the importance of enzyme dynamics during catalysis. They have also been used to study the linking of protein motion to quantum tunnelling during hydrogen transfer in other enzyme systems. In the work for this thesis, the basic characteristics of TOYE were examined. Thermal stability up to 70 °C was shown by CD and fluorescence studies and the preference towards reductive coenzyme was analysed by stopped-flow studies. Structural studies were conducted using X-ray crystallography, electron microscopy and sedimentation velocity studies. The crystal structure revealed a tetrameric enzyme with a relatively large active site. Evidence for higher oligomeric states was also obtained. The potential use of TOYE as a biocatalyst was explored by steady-state reaction, biotransformation and organic solvent resistance studies. The temperature dependences of kinetic isotope effects were used to examine the presence of tunnelling and importance active site geometry during catalysis and compared to previously described enzymes. These studies introduce a new and unique OYE-family member, allowing for more in-depth analysis of TOYE.

As the surface areas of cities throughout the world become ever more congested/ and the quality of life deteriorates, those in authority are increasingly turning to the engineering use of created space underground. Transportation systems have been located at least partly underground for generations - particularly in London. Dozens of cities throughout the rest of the world are presently engaged in underground construction, not only for rail transportation schemes, but also for communications purposes, water supply, sewerage, roads, car parks, shopping centres, concert halls, museums and art galleries. Outside the cities underground construction continues to be used for hydro-electric purposes, gas storage, inter-city highways and rail systems, and for nuclear waste storage. This international engineering research study looks at the risks involved in underground construction, and in particular the nature of risks to people directly engaged on this work and to other persons who may be affected by the works and also looks at the nature of risks to the built and natural environment. The study brings together many details of past incidents and disasters that have occurred internationally, and from a broad analysis of the types and causes of failures of one type or another, looks to how such incidents may be prevented in the future. The identification and control of risk in underground engineering projects is seen as the duty and responsibility of all the main parties to the project - the client or promoter of the project, the engineering designers, and those chosen to undertake the construction work. Key components of a broad risk control strategy are described which are applicable regardless of the project's location or what the final purpose of the underground construction work might be. Within this study there are two international Case Studies to illustrate good and poor practice in the identification and control of risk in these types of projects.