Thèse doctorat : Génie civil : Villeurbanne, INSA : 1999. / Titre provenant de l'écran-titre. Bibliogr. p. 292-303.

The study presents a numerical analysis of series of unanticipated events that took place upon the excavation of a landfill in a deep deposit of clayey soil in southwestern Ontario, Canada. During the excavation of a landfill cell to be used for waste disposal, unexpected lateral slope movements were observed followed by gas and water venting in several locations (while the excavation in low permeability clayey till was about 14m above the underlying aquifer). The clayey till is known to be underlain by permeable, natural gas bearing rock, and gas has been diffusing through the clayey deposit over about the last 13,000-15,000 years. Preliminary 2D and 3D elasto-plastic effective stress analyses using conventional soil mechanics –similar to what was used in design- are used to capture the general behaviour of the excavation. However, the analyses revealed the need for model modification to account for other governing factors (gassy soil and hydrofracturing) to be able to explain the mechanism that might have lead to the evolution of gas vents and upward water flow through the thick shale aquitard. The clayey deposit contains silty sand lenses at different elevations. The upward diffusion of methane and chloride from the bedrock aquifer through the clay till is modelled and the potential for chloride migration contributing to the exsolution of methane due to reduction in methane solubility is discussed. Two approaches to modelling the lenses are examined where gas exsolution either occurs prior to or during the excavation. The FE model is modified to account for hydrofacturing and gassy soil behaviour (for sand lenses). 2D and 3D forensic modelling studies are presented examining the potential causes for the unanticipated movements and the gas and water venting observed during the excavation. The model investigates the role of presence of gassy sand lenses and of the presence of a discontinuous weak sandy clayey silt layer between the bedrock and the low permeability till on the hydrofracturing path and gas venting. Finally, a parametric study is conducted to examine the effect of different parameters on the soil behaviour when excavated. Recommendations regarding further excavations within the same soil deposit are presented. / Thesis (Ph.D, Civil Engineering) -- Queen's University, 2012-08-23 16:33:05.062

The most widely accepted approach to long-term storage of nuclear waste is to design and construct a deep geological repository, where the geological environment acts as a natural barrier to radio nuclide migration. Sedimentary rocks, particularly argillaceous formations, are being investigated by many countries because of favorable isolating qualities (laterally continuous and low permeability) and the ability of self-sealing of fractures. Underground construction creates a damage zone around the excavation. The depth away from the excavation surface of the damage zone depends on the rock mass properties, the stress field, and the construction method. This research investigates the fracture development process in sedimentary rocks and evaluates continuum modelling methods to predict the damage zone dimensions. At the laboratory scale, a complete classification system for samples of carbonate and siliciclastic rocks has been developed, with geotechnical considerations, which when applied narrows the variability of the mechanical properties. Using this system, crack initiation (CI) shows the most uniform range in each class, particularly for mud rocks. Tensile strength was found to be higher for the Brazilian method than Direct method of testing. Brazilian reduction to Direct values was found to be rock type dependent. Laboratory testing results are also influenced by the orientation of bedding. Bedding and other structures were also found to influence the excavation behaviour as observed at the Niagara Tunnel Project in a mudstone and in excavations in the Quintner limestone of Switzerland. The conceptual stages of damage development and the potential fracture networks in sedimentary rocks are used to summarize the understanding of excavation damage developed in this thesis. Using a continuum based modelling approach, a set of predictive damage depth curves were developed for the different excavation damage zones. This approach was found to be most sensitive to the tensile strength used as an input. Back analysis of the Niagara Tunnel Project and forward prediction of the excavation damage around a shaft in the Queenston Formation are used to illustrate the importance of this research. The prediction methods were also applied to cut-off design analysis. This research has enhanced the understanding of excavation damage development in sedimentary rocks and provided a methodology to predict the dimensions of the excavation damage zones using a continuum based approach. / Thesis (Ph.D, Geological Sciences & Geological Engineering) -- Queen's University, 2014-01-29 16:08:58.022

The Jot-em-Down Shelter (15McY348) was excavated by U.S. Forest Service archaeologists in 1986. The present study concentrated on the lithic assemblage, with a particular focus on the chipped stone debitage. The Jot-em-Down Shelter lithic assemblage was compared to assemblages recovered from four nearby sites, open sites 15McY570 and 15McY616, and rockshelter sites 15McY403 and 15McY409; and rockshelter sites located in and near the Red River Gorge, Cold Oak Shelter (15LE50) and Rock Bridge Shelter (15WO75). This study determined that Jot-em-Down Shelter was a multicomponent site utilized by mobile groups of people from the Early Archaic through Mississippi periods. Use of the site intensified around the Late Archaic and Early Woodland periods. Prehistoric peoples who occupied the shelter had contact with other groups from the surrounding area, hunted nearby, and processed hides.

NASA‘s planned permanent return to the Moon by the year 2018 will demand advances in many technologies. Just as those pioneers who built a homestead in North America from abroad, it will be necessary to use the resources and materials available on the Moon, commonly referred to as in-situ resource utilization. In this concept study, we propose a role for autonomous, multirobot robotic precursor excavation missions that would prepare a lunar site for the arrival of astronauts, serving to establish methods of collecting oxygen, water and various other critical resources. A novel quantitative approach is presented that combines real-time 3D simulation with the use of Artificial Neural Tissues, a machine learning approach that produces autonomous controllers requiring little human supervision. Advantages of the autonomous multirobot approach to excavation over the traditional manually operated single vehicle ones are analyzed in terms of launch mass, power, efficiency, reliability, and overall mission cost.

NASA‘s planned permanent return to the Moon by the year 2018 will demand advances in many technologies. Just as those pioneers who built a homestead in North America from abroad, it will be necessary to use the resources and materials available on the Moon, commonly referred to as in-situ resource utilization. In this concept study, we propose a role for autonomous, multirobot robotic precursor excavation missions that would prepare a lunar site for the arrival of astronauts, serving to establish methods of collecting oxygen, water and various other critical resources. A novel quantitative approach is presented that combines real-time 3D simulation with the use of Artificial Neural Tissues, a machine learning approach that produces autonomous controllers requiring little human supervision. Advantages of the autonomous multirobot approach to excavation over the traditional manually operated single vehicle ones are analyzed in terms of launch mass, power, efficiency, reliability, and overall mission cost.

Excavation activities like open cutting and tunneling work may cause ground movements. Many of these activities are performed in urban areas where many structures and facilities already exist. These activities are close enough to affect adjacent structures. It is therefore important to understand how the ground movements due to excavations influence nearby structures. The goal of the proposed research is to investigate and develop analytical methods for addressing uncertainty during observation-based, adaptive design of deep excavation and tunneling projects. Computational procedures based on a Bayesian probabilistic framework are developed for comparative analysis between observed and predicted soil and structure response during construction phases. This analysis couples the adaptive design capabilities of the observational method with updated reliability indices, to be used in risk-based design decisions. A probabilistic framework is developed to predict three-dimensional deformation profiles due to supported excavations using a semi-empirical approach. The key advantage of this approach for practicing engineers is that an already common semi-empirical chart can be used together with a few additional simple calculations to better evaluate three-dimensional displacement profiles. A reliability analysis framework is also developed to assess the fragility of excavation-induced infrastructure system damage for multiple serviceability limit states. Finally, a reliability analysis of a shallow circular tunnel driven by a pressurized shield in a frictional and cohesive soil is developed to consider the inherent uncertainty in the input parameters and the proposed model. The ultimate limit state for the face stability is considered in the analysis. The probability of failure that exceeding a specified applied pressure at the tunnel face is estimated. Sensitivity and importance measures are computed to identify the key parameters and random variables in the model.

Thesis (M. Sc.(Mining Engineering))--University of Pretoria, 2002. / Includes bibliographical references (p. 78-81).

Thesis (M. Sc.)--University of Hong Kong, 2006.

Orientador: George de Paula Bernardes / Banca: Eduardo Dell'Avanzi / Banca: Heraldo Luiz Giacheti / Resumo: As construções nos grandes centros urbanos requerem cada vez mais o uso do espaço subterrâneo. Diante dessa necessidade, são necessárias estruturas de contenção eficientes de modo a garantir uma escavação segura e sem comprometimento das estruturas vizinhas. Muitos são os métodos de dimensionamento de estruturas de contenção e os programas disponíveis para este dimensionamento são na maioria deles, comerciais e de interface mais complexa. Este trabalho avalia o potencial do programa Ftool, criado por Luiz Fernando Martha junto ao Tecgraf/PUC-Rio para análise de estruturas, como ferramenta preliminar para o dimensionamento de uma cortina atirantada, mostrando que o programa de computador com apelo em estruturas poderá ser aplicado em geotecnia.O caso principal estudado foi de uma cortina atirantada executada na cidade de Curitiba, estado do Paraná, numa região onde o solo pertence da Formação Guabirotuba. Esta obra contava com instrumentação por inclinômetros posicionada na região mais crítica da estrutura onde foram observadas medidas de deslocamentos horizontais acima dos previstos em projeto.Ao final das simulações chegou-se a uma curva de deslocamentos horizontais a qual foi comparada àquela obtida pela instrumentação (inclinômetro e carga dos tirantes). Para as análises adotou-se o módulo de elasticidade do solo igual a duas vezes e meia o número de golpes do SPT e uma extensão equivalente ao espaçamento entre vigas. Os deslocamentos finais previstos ficaram dentro da... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Building in urban centers increasingly requires the use of underground space. Faced with this, efficient Reinforced Walls are required to ensure safe excavation of neighboring structures. Several design methods for this structures and softwares are available, most of them commercial and with a complex interface. This study evaluates the potential of the software Ftool, created by Tecgraf / PUC-Rio for analysis of structures, as a preliminary tool for anchored wall's design.The principal case studied here, is an anchored wall built in the city of Curitiba, state of Paraná, in a region where the soil belongs to the Guabirotuba Formation. This work counted with instrumentation by inclinometers positioned in the most critical region of the structure where bigger horizontal displacements measurements were observed those the predicted in project.At the end of the simulations a horizontal displacement curve was reached which was compared to that obtained by the instrumentation. The expected final displacements were within the range of measured displacements.A discussion is presented at the end regarding the modeling of the wall by Ftool, with respect to the use of the Winkler's spring element model. / Mestre