Scott D Cylwik - Academia.edu (original) (raw)
Papers by Scott D Cylwik
Four geophysical surveys were conducted at the Nature Conservancy about 20 miles north of Benson,... more Four geophysical surveys were conducted at the Nature Conservancy about 20 miles north of Benson, AZ, in the Upper San Pedro River Basin, in order to better understand the nature of the sub-surface features of the basin. The geophysical methods included TEM (Transient Electromagnetic), seismic, EM34 and magnetic surveys. The TEM, seismic and magnetic surveys were conducted perpendicular to the river basin while the EM34 lines followed the riverbed. The perpendicular surveys were divided into two regions, referred to as the South and North Lines. The TEM, seismic, and magnetic surveys revealed a consolidated bedrock structure at shallow depths (30-40 m) along the South Line. The feature has an east-west extension of approximately 500 meters, and is located just east of the San Pedro River. None of the perpendicular surveys were able to detect bedrock features along the North Line, implying that the depth to bedrock exceeds the maximum depth of this investigation (360 m). Both lines s...
This study combines novel and previously published data to create a new method of estimating anis... more This study combines novel and previously published data to create a new method of estimating anisotropic rock-mass strength in three dimensions that considers both the orientation and the non-persistence of multiple joint sets. Equations are developed to evaluate joint persistence as a function of joint set spacing-to-length ratio, strength reduction as a function of joint persistence, and strength reduction as a function of dip and dip direction difference between a joint set and the shear plane. Vector rotations are used to calculate the dip and dip direction difference between the orientations of joint sets and the assumed shear plane orientation, allowing anisotropic rock-mass shear strength to be estimated for any three-dimensional direction of shear. The result is reduced strength for shear in the directions parallel to jointing and increased strength for shear in directions non-parallel to jointing, with a continuous function of strength in between the two extremes. Input par...
The Evolution of Geotech - 25 Years of Innovation, 2021
Rock slope design requires detailed knowledge of the rock joint fabric, which is the most importa... more Rock slope design requires detailed knowledge of the rock joint fabric, which is the most important parameter in bench-scale analysis. Rock-fabric data for open pit slope design may be difficult to obtain because mine planning often requires design slope angles years in advance of excavation and outcrop exposure. When rockfabric data cannot be obtained from surface mapping, one of the most cost-effective alternatives to obtain these data is oriented-core drilling. Because of various uncertainties in the core orienting process and the scale effect of measuring orientations over the length of a core diameter, oriented-core joint sets typically display greater dispersion than do the same sets from surface mapping. This paper presents a method to quantify some of the errors induced during the core orientation process with a simple measurement taken by the technician at the time of core logging, called the difference angle. The error distribution is quantified from the distribution of th...
Slope Stability 2022, 2022
Profitability and carbon footprint of an open pit mine depend to a large extent on the Overall Sl... more Profitability and carbon footprint of an open pit mine depend to a large extent on the Overall Slope Angle (OSA) of its pitwalls. OptimalSlope, a new software for the design of slopes and pitwalls, determines geotechnically optimal non-linear profiles. Results obtained on four mine case studies in isotropic rock masses show optimal profiles can be up to 8 degrees steeper than their planar counterparts, i.e. fixed slope angle profiles exhibiting the same Factor of Safety. OptimalSlope which has been recently modified to deal with anisotropic rock masses, is here employed to determine optimal profiles for an open pit mine to be excavated in a Cretaceous siltstone featured by 8 different joint sets and one main bedding. The recently introduced Cylwik's method was employed to establish direction dependent c and φ equivalent parameters from information on joint orientation and persistence for the relevant pit cross-sections. OptimalSlope simulations were run for several inclinations of the bedding dip (0, 15, 30, 45, 60, 75, 90) for three pitwall orientations (footwall, hanging wall, sidewall). Measurements of the increase in OSA achieved by adoption of the optimal profiles over their planar counterparts are provided. Stability analyses by Rocscience Slide2 were also performed to independently verify the FoSs of the calculated optimal profiles.
Slope Stability 2022, 2022
Estimations of rock mass strength are required for many types of engineering projects in both min... more Estimations of rock mass strength are required for many types of engineering projects in both mining and civil engineering. This paper reviews the CNI method, an empirical rock mass strength estimation criterion based on quantitative input parameters. The CNI method derives the rock mass strength by scaling down the intact rock strength according to the intensity and strength of discontinuities. Inputs to the method are parameters which can be objectively quantified through laboratory and field measurements; specifically, the intact rock and fracture shear strength and the degree of rock mass fracturing (i.e., RQD and/or fracture frequency). The primary advantage of the criterion is the foundation on direct quantifiable measurements, therefore making it reproducible between practitioners. Since the method combines the intact rock strength with the fracture strength, weighted by the degree of rock mass fracturing, the rock mass strength can never drop below the fracture strength nor exceed the intact strength. The presented strength criterion is compared against published rock mass strength measurements. The strengths of two example rock masses are estimated and directly compared to other established rock mass strength estimation methods. A calculation sheet that implements the methodology is presented and shared for digital download.
Rocscience International Conference: The Evolution of Geotech – 25 Years of Innovation, 2021
The highly variable nature of weak rock in weathered sedimentary deposits poses significant chall... more The highly variable nature of weak rock in weathered sedimentary deposits poses significant challenges to open pit and underground mine design. Traditional probabilistic analysis fails to consider all potential mechanisms of instability that may influence slope stability. An approach with spatially variable strengths allows the natural variability of the shear strength properties within the rock mass to be simulated. This paper examines the congruence of geotechnical block modeling and spatial variability analysis to estimate the probability of failure of a highly variable weathered open pit slope in the Central African Copperbelt. The input parameters for the random spatial field simulations are estimated from variography of composited drill hole data and univariate statistics of a 3D block model of rock-mass shear strength. The Rocscience software Slide2 is used to perform the random field simulations and analysis. It is also demonstrated that the total variance can be reduced by the small-scale variability (nugget effect variance) for spatially averaged shear strengths. Typical rock-mass spatial parameters from other projects are summarized.
55th U.S. Rock Mechanics/Geomechanics Symposium, 2021
This study combines novel and previously published data to create a new method of estimating anis... more This study combines novel and previously published data to create a new method of estimating anisotropic rock-mass strength in three dimensions that considers both the orientation and the non-persistence of multiple joint sets. Equations are developed to evaluate joint persistence as a function of joint set spacing-to-length ratio, strength reduction as a function of joint persistence, and strength reduction as a function of dip and dip direction difference between a joint set and the shear plane. Vector rotations are used to calculate the dip and dip direction difference between the orientations of joint sets and the assumed shear plane orientation, allowing anisotropic rock-mass shear strength to be estimated for any three-dimensional direction of shear. The result is reduced strength for shear in the directions parallel to jointing and increased strength for shear in directions non-parallel to jointing, with a continuous function of strength in between the two extremes. Input parameters for the system are rock discontinuity set statistics, intact rock strength, discontinuity strength, and RQD. A slope instability case history example is back analyzed using the strength estimation procedure. A calculation sheet that implements the methodology is presented and shared for digital download.
Slope Stability 2018, 2018
Rock mass strength is typically estimated from three fundamental components: intact rock strength... more Rock mass strength is typically estimated from three fundamental components: intact rock strength, fracture strength, and intensity of fracturing. The uncertainties regarding the estimation of rock mass shear strength can also be separated into three distinct components: natural variability, statistical uncertainty, and transformation uncertainty. The natural spatial variability of geologic materials typically has the greatest impact on the uncertainty of rock mass design parameters. If the spatial continuity (autocorrelation) of input variables is not considered, a probabilistic slope analysis can result in either over-or underestimation of the probability of failure. It is well established that the stability of a slope is controlled by the total shear resistance along the failure surface, rather than the shear resistance at any one individual location. For probabilistic slope analysis, it is therefore appropriate to determine the variance of the rock mass strength over the entire potential zone of failure. The variance of the shear strength across the failure surface will always be less than the variance of individual small-scale measurements of shear strength at any one location on that surface. The scale of fluctuation of each of the three components of rock mass strength (intact strength, fracture strength, intensity of fracturing) must be considered in order to estimate the variance of rock mass strength over the failure surface area. Intact rock strength and fracture strength typically exhibit a small spatial correlation distance relative to typical open pit slope analysis. Therefore, it is proposed that the natural variability for these parameters can be disregarded and in most cases only the statistical uncertainty of intact and fracture shear strength derived from the total population of representative laboratory tests need to be considered. Conversely, intensity of fracturing, as measured by either RQD or the GSI structure rating, tends to exhibit large spatial correlation distances relative to typical sampling intervals. A variogram model can be used in conjunction with the variance reduction function to characterize the spatial variability of the fracture intensity and to quickly estimate the reduced variance due to spatial averaging for use in probabilistic analysis. Examples are provided to demonstrate the value of these concepts.
Rock slope design requires detailed knowledge of the rock joint fabric, which is the most importa... more Rock slope design requires detailed knowledge of the rock joint fabric, which is the most important parameter in bench-scale analysis. Rock-fabric data for open pit slope design may be difficult to obtain because mine planning often requires design slope angles years in advance of excavation and outcrop exposure. When rock-fabric data cannot be obtained from surface mapping, one of the most cost-effective alternatives to obtain these data is oriented-core drilling. Because of various uncertainties in the core orienting process and the scale effect of measuring orientations over the length of a core diameter, oriented-core joint sets typically display greater dispersion than do the same sets from surface mapping. This paper presents a method to quantify some of the errors induced during the core orientation process with a simple measurement taken by the technician at the time of core logging, called the difference angle. The error distribution is quantified from the distribution of the difference angles and removed from the measured data population. The result is an improved representation of the in situ variation on the joint set. This reduction in data scatter is particularly important when conducting probabilistic bench-scale analysis with a joint set whose dip is near the joint friction angle. An example is given where the design slope interramp angle is increased by two degrees as a result of the reduction in the variance of the oriented-core data utilizing this method.
Four geophysical surveys were conducted at the Nature Conservancy about 20 miles north of Benson,... more Four geophysical surveys were conducted at the Nature Conservancy about 20 miles north of Benson, AZ, in the Upper San Pedro River Basin, in order to better understand the nature of the sub-surface features of the basin. The geophysical methods included TEM (Transient Electromagnetic), seismic, EM34 and magnetic surveys. The TEM, seismic and magnetic surveys were conducted perpendicular to the river basin while the EM34 lines followed the riverbed. The perpendicular surveys were divided into two regions, referred to as the South and North Lines. The TEM, seismic, and magnetic surveys revealed a consolidated bedrock structure at shallow depths (30-40 m) along the South Line. The feature has an east-west extension of approximately 500 meters, and is located just east of the San Pedro River. None of the perpendicular surveys were able to detect bedrock features along the North Line, implying that the depth to bedrock exceeds the maximum depth of this investigation (360 m). Both lines s...
This study combines novel and previously published data to create a new method of estimating anis... more This study combines novel and previously published data to create a new method of estimating anisotropic rock-mass strength in three dimensions that considers both the orientation and the non-persistence of multiple joint sets. Equations are developed to evaluate joint persistence as a function of joint set spacing-to-length ratio, strength reduction as a function of joint persistence, and strength reduction as a function of dip and dip direction difference between a joint set and the shear plane. Vector rotations are used to calculate the dip and dip direction difference between the orientations of joint sets and the assumed shear plane orientation, allowing anisotropic rock-mass shear strength to be estimated for any three-dimensional direction of shear. The result is reduced strength for shear in the directions parallel to jointing and increased strength for shear in directions non-parallel to jointing, with a continuous function of strength in between the two extremes. Input par...
The Evolution of Geotech - 25 Years of Innovation, 2021
Rock slope design requires detailed knowledge of the rock joint fabric, which is the most importa... more Rock slope design requires detailed knowledge of the rock joint fabric, which is the most important parameter in bench-scale analysis. Rock-fabric data for open pit slope design may be difficult to obtain because mine planning often requires design slope angles years in advance of excavation and outcrop exposure. When rockfabric data cannot be obtained from surface mapping, one of the most cost-effective alternatives to obtain these data is oriented-core drilling. Because of various uncertainties in the core orienting process and the scale effect of measuring orientations over the length of a core diameter, oriented-core joint sets typically display greater dispersion than do the same sets from surface mapping. This paper presents a method to quantify some of the errors induced during the core orientation process with a simple measurement taken by the technician at the time of core logging, called the difference angle. The error distribution is quantified from the distribution of th...
Slope Stability 2022, 2022
Profitability and carbon footprint of an open pit mine depend to a large extent on the Overall Sl... more Profitability and carbon footprint of an open pit mine depend to a large extent on the Overall Slope Angle (OSA) of its pitwalls. OptimalSlope, a new software for the design of slopes and pitwalls, determines geotechnically optimal non-linear profiles. Results obtained on four mine case studies in isotropic rock masses show optimal profiles can be up to 8 degrees steeper than their planar counterparts, i.e. fixed slope angle profiles exhibiting the same Factor of Safety. OptimalSlope which has been recently modified to deal with anisotropic rock masses, is here employed to determine optimal profiles for an open pit mine to be excavated in a Cretaceous siltstone featured by 8 different joint sets and one main bedding. The recently introduced Cylwik's method was employed to establish direction dependent c and φ equivalent parameters from information on joint orientation and persistence for the relevant pit cross-sections. OptimalSlope simulations were run for several inclinations of the bedding dip (0, 15, 30, 45, 60, 75, 90) for three pitwall orientations (footwall, hanging wall, sidewall). Measurements of the increase in OSA achieved by adoption of the optimal profiles over their planar counterparts are provided. Stability analyses by Rocscience Slide2 were also performed to independently verify the FoSs of the calculated optimal profiles.
Slope Stability 2022, 2022
Estimations of rock mass strength are required for many types of engineering projects in both min... more Estimations of rock mass strength are required for many types of engineering projects in both mining and civil engineering. This paper reviews the CNI method, an empirical rock mass strength estimation criterion based on quantitative input parameters. The CNI method derives the rock mass strength by scaling down the intact rock strength according to the intensity and strength of discontinuities. Inputs to the method are parameters which can be objectively quantified through laboratory and field measurements; specifically, the intact rock and fracture shear strength and the degree of rock mass fracturing (i.e., RQD and/or fracture frequency). The primary advantage of the criterion is the foundation on direct quantifiable measurements, therefore making it reproducible between practitioners. Since the method combines the intact rock strength with the fracture strength, weighted by the degree of rock mass fracturing, the rock mass strength can never drop below the fracture strength nor exceed the intact strength. The presented strength criterion is compared against published rock mass strength measurements. The strengths of two example rock masses are estimated and directly compared to other established rock mass strength estimation methods. A calculation sheet that implements the methodology is presented and shared for digital download.
Rocscience International Conference: The Evolution of Geotech – 25 Years of Innovation, 2021
The highly variable nature of weak rock in weathered sedimentary deposits poses significant chall... more The highly variable nature of weak rock in weathered sedimentary deposits poses significant challenges to open pit and underground mine design. Traditional probabilistic analysis fails to consider all potential mechanisms of instability that may influence slope stability. An approach with spatially variable strengths allows the natural variability of the shear strength properties within the rock mass to be simulated. This paper examines the congruence of geotechnical block modeling and spatial variability analysis to estimate the probability of failure of a highly variable weathered open pit slope in the Central African Copperbelt. The input parameters for the random spatial field simulations are estimated from variography of composited drill hole data and univariate statistics of a 3D block model of rock-mass shear strength. The Rocscience software Slide2 is used to perform the random field simulations and analysis. It is also demonstrated that the total variance can be reduced by the small-scale variability (nugget effect variance) for spatially averaged shear strengths. Typical rock-mass spatial parameters from other projects are summarized.
55th U.S. Rock Mechanics/Geomechanics Symposium, 2021
This study combines novel and previously published data to create a new method of estimating anis... more This study combines novel and previously published data to create a new method of estimating anisotropic rock-mass strength in three dimensions that considers both the orientation and the non-persistence of multiple joint sets. Equations are developed to evaluate joint persistence as a function of joint set spacing-to-length ratio, strength reduction as a function of joint persistence, and strength reduction as a function of dip and dip direction difference between a joint set and the shear plane. Vector rotations are used to calculate the dip and dip direction difference between the orientations of joint sets and the assumed shear plane orientation, allowing anisotropic rock-mass shear strength to be estimated for any three-dimensional direction of shear. The result is reduced strength for shear in the directions parallel to jointing and increased strength for shear in directions non-parallel to jointing, with a continuous function of strength in between the two extremes. Input parameters for the system are rock discontinuity set statistics, intact rock strength, discontinuity strength, and RQD. A slope instability case history example is back analyzed using the strength estimation procedure. A calculation sheet that implements the methodology is presented and shared for digital download.
Slope Stability 2018, 2018
Rock mass strength is typically estimated from three fundamental components: intact rock strength... more Rock mass strength is typically estimated from three fundamental components: intact rock strength, fracture strength, and intensity of fracturing. The uncertainties regarding the estimation of rock mass shear strength can also be separated into three distinct components: natural variability, statistical uncertainty, and transformation uncertainty. The natural spatial variability of geologic materials typically has the greatest impact on the uncertainty of rock mass design parameters. If the spatial continuity (autocorrelation) of input variables is not considered, a probabilistic slope analysis can result in either over-or underestimation of the probability of failure. It is well established that the stability of a slope is controlled by the total shear resistance along the failure surface, rather than the shear resistance at any one individual location. For probabilistic slope analysis, it is therefore appropriate to determine the variance of the rock mass strength over the entire potential zone of failure. The variance of the shear strength across the failure surface will always be less than the variance of individual small-scale measurements of shear strength at any one location on that surface. The scale of fluctuation of each of the three components of rock mass strength (intact strength, fracture strength, intensity of fracturing) must be considered in order to estimate the variance of rock mass strength over the failure surface area. Intact rock strength and fracture strength typically exhibit a small spatial correlation distance relative to typical open pit slope analysis. Therefore, it is proposed that the natural variability for these parameters can be disregarded and in most cases only the statistical uncertainty of intact and fracture shear strength derived from the total population of representative laboratory tests need to be considered. Conversely, intensity of fracturing, as measured by either RQD or the GSI structure rating, tends to exhibit large spatial correlation distances relative to typical sampling intervals. A variogram model can be used in conjunction with the variance reduction function to characterize the spatial variability of the fracture intensity and to quickly estimate the reduced variance due to spatial averaging for use in probabilistic analysis. Examples are provided to demonstrate the value of these concepts.
Rock slope design requires detailed knowledge of the rock joint fabric, which is the most importa... more Rock slope design requires detailed knowledge of the rock joint fabric, which is the most important parameter in bench-scale analysis. Rock-fabric data for open pit slope design may be difficult to obtain because mine planning often requires design slope angles years in advance of excavation and outcrop exposure. When rock-fabric data cannot be obtained from surface mapping, one of the most cost-effective alternatives to obtain these data is oriented-core drilling. Because of various uncertainties in the core orienting process and the scale effect of measuring orientations over the length of a core diameter, oriented-core joint sets typically display greater dispersion than do the same sets from surface mapping. This paper presents a method to quantify some of the errors induced during the core orientation process with a simple measurement taken by the technician at the time of core logging, called the difference angle. The error distribution is quantified from the distribution of the difference angles and removed from the measured data population. The result is an improved representation of the in situ variation on the joint set. This reduction in data scatter is particularly important when conducting probabilistic bench-scale analysis with a joint set whose dip is near the joint friction angle. An example is given where the design slope interramp angle is increased by two degrees as a result of the reduction in the variance of the oriented-core data utilizing this method.