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
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:OKQ.1974/5160 |
| Date | 16 September 2009 |
| Creators | Perras, Matthew A. |
| Contributors | Queen's University (Kingston, Ont.). Theses (Queen's University (Kingston, Ont.)) |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English, English |
| Detected Language | English |
| Type | Thesis |
| Format | 16366529 bytes, application/pdf |
| Rights | This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner. |
| Relation | Canadian theses |
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