Abstract The West Vaughan Sewer System (WVSS) tunnel, at the time of writing, is planned to be co... more Abstract The West Vaughan Sewer System (WVSS) tunnel, at the time of writing, is planned to be constructed in Toronto, Ontario, Canada. A geotechnical program was conducted to characterize the mechanical properties of the anisotropic bedrock, Georgian Bay shale, and was determined to exhibit weak rock strength properties, moderate to fair anisotropy, and extremely low abrasivity. Following characterization, the shale was numerically calibrated using the hybrid finite-discrete element method (FDEM) and used to qualitatively simulate the WVSS tunnel. The major advantage of FDEM is its ability to explicitly simulate fracturing in geomaterials allowing for the excavation damaged zone (EDZ) to be estimated. In addition, anisotropic elastic and fracture models were used to appropriately simulate shale. The objective of the simulations is to explicitly compare the difference between the finite element method (FEM) and FDEM in estimating the deformation and stress in the rock mass and support liner. In FDEM simulations where the virgin stress conditions did not cause the rock to fracture, the FEM and FDEM results are very similar. However, in simulations where the rock is fractured, predominantly consisting of bedding plane slippage due to the orientation of the maximum in-situ stress relative to the strata, several key differences are evident. The liner simulated in FDEM has an asymmetric distribution of stress and strain, liner deformation is approximately 60% greater, stresses can be up to four times larger, and the stresses in the liner are purely compressive.
• Graphical classification based on the UCS:BDS ratio. • Practical tool to estimate the strength ... more • Graphical classification based on the UCS:BDS ratio. • Practical tool to estimate the strength ratio of rock in a variety of engineering construction projects. • Estimating material properties in the pre-feasibility stages of projects. • Database of over 500 pairs of UCS and BDS values.
As a result of ongoing foundation seepage problems, a decision was made to replace the aging Shik... more As a result of ongoing foundation seepage problems, a decision was made to replace the aging Shikwamkwa Dam located near the town of Wawa in Northern Ontario. Construction of the new 35m high zoned embankment dam followed a challenging fast-track design and construction approach with the dam completed in the fall of 2005, five months ahead of schedule (Donnelly et al. 2007). This paper focuses on an evaluation of the hydraulic efficiency of the 21,000-square-metre plastic concrete cut-off wall constructed beneath the new dam. The hydraulic efficiency was analyzed with the aid of two-dimensional finite element seepage analyses based of geotechnical models created based on the results of drilling investigations and laboratory permeability testing. The models were calibrated by adjusting the geometry and hydraulic conductivity of the foundation materials (within the expected range of uncertainty) such that the hydraulic head profiles obtained from the seepage analyses closely matched t...
Rock bolt is a support system extensively utilized in Civil and Mining Engineering applications, ... more Rock bolt is a support system extensively utilized in Civil and Mining Engineering applications, especially for underground excavations projects. The main function of a rock bolt is to stabilize the rock mass around the opening of an excavation by fastening to further stable formations. Previous technical work developed pull-out testing in order to improve understanding regarding the mechanical response within this system. However, due to limitations with conventional laboratory methods of capturing strain, there still exists a lack of understanding in this mechanical response at the micro-scale; more specifically, in the detailed strain profile distribution along fully grouted rock bolts. Aiming to address this knowledge gap, two research programmes were conducted and will be addressed in this paper: numerical modelling of pull-out tests through finite element method (FEM) and hybrid finite-discrete element method (FDEM), and laboratory pull-out tests on concrete samples utilizing a newly developed distributed optical strain sensing technology that provides a spatial resolution of 0.65Â mm in order to capture the strain along the rock bolt. Experimental and modelling results were compared to evaluate the numerical approaches feasibility and their correspondence with the experiments. FDEM modelling demonstrated ability in capturing general mechanical behavior, while the FEM software seems to be a good option to be utilized as a design tool, yet improvements to the interaction model are necessary to achieve a better calibration with experimental results.
Conventionally, the evaluation of fracture surface roughness in brittle geomaterials, such as con... more Conventionally, the evaluation of fracture surface roughness in brittle geomaterials, such as concrete and rock, has been based on the measurement and analysis of two-dimensional profiles rather than three-dimensional (3D) surfaces. The primary reason for doing so was the lack of tools capable of making 3D measurements. However, in recent years, several optical and mechanical measurement tools have become available, which are capable of quickly and accurately producing high resolution point clouds defining 3D surfaces. This paper provides a methodology for evaluating the surface roughness and roughness anisotropy using these 3D surface measurements. The methodology is presented step-by-step to allow others to easily adopt and implement the process to analyze their own surface measurement data. The methodology is demonstrated by digitizing a series of concrete fracture surfaces and comparing the estimated 3D roughness parameters with qualitative observations and estimates of the well-known roughness coefficient, R(s).
The surface roughness of unfilled rock discontinuities has a major influence on the hydromechanic... more The surface roughness of unfilled rock discontinuities has a major influence on the hydromechanical behaviour of discontinuous rock masses. Although it is widely recognized that surface roughness is comprised of large-scale (waviness) and small-scale (unevenness) components, most investigations of surface roughness have been restricted to small fracture surfaces (<1m2). Hence, the large-scale components of roughness are often neglected. Furthermore, these investigations typically define roughness using two-dimensional profiles rather than three-dimensional surfaces, which can lead to biased estimates of roughness. These limitations have led to some contradictory findings regarding roughness scale effects. This thesis aims to resolve some of these issues. The main findings indicate that discontinuity roughness increases as a function of the sampling window size contrary to what is commonly assumed. More importantly, it is shown that the estimated roughness significantly decreases ...
Rock mass discontinuities represent planes of relative weakness and enhanced hydraulic conductivi... more Rock mass discontinuities represent planes of relative weakness and enhanced hydraulic conductivity and, thus, have a substantial influence on the hydro-mechanical behaviour of the overall rock mass. While the shearing of rock mass discontinuities has been extensively studied in the past, there remains uncertainty surrounding the mechanisms by which surface asperities deform and degrade during shear and how this degradation influences the aperture distribution. Although prior studies have attempted to investigate asperity failure mechanisms, they have been hampered by the lack of appropriate visualization and modelling tools. In particular, until recently it was not possible to observe asperity damage without physically separating the joint specimen or explicitly modelling the development of damage during a direct shear test. In the last decade, X-ray Computed Tomography (CT) has emerged as an ideal tool to nondestructively characterize fractures and damage in geomaterials. Over thi...
Numerical simulations are widely adopted in the design of several types of rock structures, inclu... more Numerical simulations are widely adopted in the design of several types of rock structures, including tunnels, caverns, rock cuts, and open pit and underground mines. In recent years, analyses based on the hybrid finite-discrete element method (FDEM) have been shown to provide a realistic representation of rock mass deformation and fracturing processes. To date, the FDEM approach has successfully yielded qualitative and quantitative results for several practical rock engineering applications, yet it has lacked the ability to consider the implementation of rock-reinforcement measures. Since rock reinforcement is often used in civil and mining applications to improve the strength and deformational behaviour of a rock mass, the ability to incorporate such features into FDEM analyses is essential to extend its applicability to a broader range of problems. The work presented in this paper represents an important first step towards developing a simulation tool that can be used for practic...
As a result of ongoing foundation seepage problems, a decision was made to replace the aging Shik... more As a result of ongoing foundation seepage problems, a decision was made to replace the aging Shikwamkwa Dam located near the town of Wawa in Northern Ontario. Construction of the new 35m high zoned embankment dam followed a challenging fast-track design and construction approach with the dam completed in the fall of 2005, five months ahead of schedule (Donnelly et al. 2007). This paper focuses on an evaluation of the hydraulic efficiency of the 21,000-square-metre plastic concrete cut-off wall constructed beneath the new dam. The hydraulic efficiency was analyzed with the aid of two-dimensional finite element seepage analyses based of geotechnical models created based on the results of drilling investigations and laboratory permeability testing. The models were calibrated by adjusting the geometry and hydraulic conductivity of the foundation materials (within the expected range of uncertainty) such that the hydraulic head profiles obtained from the seepage analyses closely matched t...
Abstract The West Vaughan Sewer System (WVSS) tunnel, at the time of writing, is planned to be co... more Abstract The West Vaughan Sewer System (WVSS) tunnel, at the time of writing, is planned to be constructed in Toronto, Ontario, Canada. A geotechnical program was conducted to characterize the mechanical properties of the anisotropic bedrock, Georgian Bay shale, and was determined to exhibit weak rock strength properties, moderate to fair anisotropy, and extremely low abrasivity. Following characterization, the shale was numerically calibrated using the hybrid finite-discrete element method (FDEM) and used to qualitatively simulate the WVSS tunnel. The major advantage of FDEM is its ability to explicitly simulate fracturing in geomaterials allowing for the excavation damaged zone (EDZ) to be estimated. In addition, anisotropic elastic and fracture models were used to appropriately simulate shale. The objective of the simulations is to explicitly compare the difference between the finite element method (FEM) and FDEM in estimating the deformation and stress in the rock mass and support liner. In FDEM simulations where the virgin stress conditions did not cause the rock to fracture, the FEM and FDEM results are very similar. However, in simulations where the rock is fractured, predominantly consisting of bedding plane slippage due to the orientation of the maximum in-situ stress relative to the strata, several key differences are evident. The liner simulated in FDEM has an asymmetric distribution of stress and strain, liner deformation is approximately 60% greater, stresses can be up to four times larger, and the stresses in the liner are purely compressive.
• Graphical classification based on the UCS:BDS ratio. • Practical tool to estimate the strength ... more • Graphical classification based on the UCS:BDS ratio. • Practical tool to estimate the strength ratio of rock in a variety of engineering construction projects. • Estimating material properties in the pre-feasibility stages of projects. • Database of over 500 pairs of UCS and BDS values.
As a result of ongoing foundation seepage problems, a decision was made to replace the aging Shik... more As a result of ongoing foundation seepage problems, a decision was made to replace the aging Shikwamkwa Dam located near the town of Wawa in Northern Ontario. Construction of the new 35m high zoned embankment dam followed a challenging fast-track design and construction approach with the dam completed in the fall of 2005, five months ahead of schedule (Donnelly et al. 2007). This paper focuses on an evaluation of the hydraulic efficiency of the 21,000-square-metre plastic concrete cut-off wall constructed beneath the new dam. The hydraulic efficiency was analyzed with the aid of two-dimensional finite element seepage analyses based of geotechnical models created based on the results of drilling investigations and laboratory permeability testing. The models were calibrated by adjusting the geometry and hydraulic conductivity of the foundation materials (within the expected range of uncertainty) such that the hydraulic head profiles obtained from the seepage analyses closely matched t...
Rock bolt is a support system extensively utilized in Civil and Mining Engineering applications, ... more Rock bolt is a support system extensively utilized in Civil and Mining Engineering applications, especially for underground excavations projects. The main function of a rock bolt is to stabilize the rock mass around the opening of an excavation by fastening to further stable formations. Previous technical work developed pull-out testing in order to improve understanding regarding the mechanical response within this system. However, due to limitations with conventional laboratory methods of capturing strain, there still exists a lack of understanding in this mechanical response at the micro-scale; more specifically, in the detailed strain profile distribution along fully grouted rock bolts. Aiming to address this knowledge gap, two research programmes were conducted and will be addressed in this paper: numerical modelling of pull-out tests through finite element method (FEM) and hybrid finite-discrete element method (FDEM), and laboratory pull-out tests on concrete samples utilizing a newly developed distributed optical strain sensing technology that provides a spatial resolution of 0.65Â mm in order to capture the strain along the rock bolt. Experimental and modelling results were compared to evaluate the numerical approaches feasibility and their correspondence with the experiments. FDEM modelling demonstrated ability in capturing general mechanical behavior, while the FEM software seems to be a good option to be utilized as a design tool, yet improvements to the interaction model are necessary to achieve a better calibration with experimental results.
Conventionally, the evaluation of fracture surface roughness in brittle geomaterials, such as con... more Conventionally, the evaluation of fracture surface roughness in brittle geomaterials, such as concrete and rock, has been based on the measurement and analysis of two-dimensional profiles rather than three-dimensional (3D) surfaces. The primary reason for doing so was the lack of tools capable of making 3D measurements. However, in recent years, several optical and mechanical measurement tools have become available, which are capable of quickly and accurately producing high resolution point clouds defining 3D surfaces. This paper provides a methodology for evaluating the surface roughness and roughness anisotropy using these 3D surface measurements. The methodology is presented step-by-step to allow others to easily adopt and implement the process to analyze their own surface measurement data. The methodology is demonstrated by digitizing a series of concrete fracture surfaces and comparing the estimated 3D roughness parameters with qualitative observations and estimates of the well-known roughness coefficient, R(s).
The surface roughness of unfilled rock discontinuities has a major influence on the hydromechanic... more The surface roughness of unfilled rock discontinuities has a major influence on the hydromechanical behaviour of discontinuous rock masses. Although it is widely recognized that surface roughness is comprised of large-scale (waviness) and small-scale (unevenness) components, most investigations of surface roughness have been restricted to small fracture surfaces (<1m2). Hence, the large-scale components of roughness are often neglected. Furthermore, these investigations typically define roughness using two-dimensional profiles rather than three-dimensional surfaces, which can lead to biased estimates of roughness. These limitations have led to some contradictory findings regarding roughness scale effects. This thesis aims to resolve some of these issues. The main findings indicate that discontinuity roughness increases as a function of the sampling window size contrary to what is commonly assumed. More importantly, it is shown that the estimated roughness significantly decreases ...
Rock mass discontinuities represent planes of relative weakness and enhanced hydraulic conductivi... more Rock mass discontinuities represent planes of relative weakness and enhanced hydraulic conductivity and, thus, have a substantial influence on the hydro-mechanical behaviour of the overall rock mass. While the shearing of rock mass discontinuities has been extensively studied in the past, there remains uncertainty surrounding the mechanisms by which surface asperities deform and degrade during shear and how this degradation influences the aperture distribution. Although prior studies have attempted to investigate asperity failure mechanisms, they have been hampered by the lack of appropriate visualization and modelling tools. In particular, until recently it was not possible to observe asperity damage without physically separating the joint specimen or explicitly modelling the development of damage during a direct shear test. In the last decade, X-ray Computed Tomography (CT) has emerged as an ideal tool to nondestructively characterize fractures and damage in geomaterials. Over thi...
Numerical simulations are widely adopted in the design of several types of rock structures, inclu... more Numerical simulations are widely adopted in the design of several types of rock structures, including tunnels, caverns, rock cuts, and open pit and underground mines. In recent years, analyses based on the hybrid finite-discrete element method (FDEM) have been shown to provide a realistic representation of rock mass deformation and fracturing processes. To date, the FDEM approach has successfully yielded qualitative and quantitative results for several practical rock engineering applications, yet it has lacked the ability to consider the implementation of rock-reinforcement measures. Since rock reinforcement is often used in civil and mining applications to improve the strength and deformational behaviour of a rock mass, the ability to incorporate such features into FDEM analyses is essential to extend its applicability to a broader range of problems. The work presented in this paper represents an important first step towards developing a simulation tool that can be used for practic...
As a result of ongoing foundation seepage problems, a decision was made to replace the aging Shik... more As a result of ongoing foundation seepage problems, a decision was made to replace the aging Shikwamkwa Dam located near the town of Wawa in Northern Ontario. Construction of the new 35m high zoned embankment dam followed a challenging fast-track design and construction approach with the dam completed in the fall of 2005, five months ahead of schedule (Donnelly et al. 2007). This paper focuses on an evaluation of the hydraulic efficiency of the 21,000-square-metre plastic concrete cut-off wall constructed beneath the new dam. The hydraulic efficiency was analyzed with the aid of two-dimensional finite element seepage analyses based of geotechnical models created based on the results of drilling investigations and laboratory permeability testing. The models were calibrated by adjusting the geometry and hydraulic conductivity of the foundation materials (within the expected range of uncertainty) such that the hydraulic head profiles obtained from the seepage analyses closely matched t...
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