John M Kemeny
- Department Head, Mining and Geological Engineering
- Professor, Mining and Geological Engineering
No activities entered.
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Directed Research/Mn EMNE 492 (Spring 2018)
DissertationMNE 920 (Spring 2018)
Fractures Rock+Brtl MatMNE 580 (Spring 2018)
Independent StudyMNE 499 (Spring 2018)
Independent StudyMNE 599 (Spring 2018)
Mine EconomicsMNE 560B (Spring 2018)
ResearchMNE 900 (Spring 2018)
ThesisMNE 910 (Spring 2018)
Undgr Constr GeomechanicMNE 447 (Spring 2018)
Undgr Constr GeomechanicMNE 547 (Spring 2018)
DissertationMNE 920 (Fall 2017)
GeomechanicsGEN 427 (Fall 2017)
GeomechanicsMNE 427 (Fall 2017)
GeomechanicsMNE 527 (Fall 2017)
Health+Safety In MiningMNE 526 (Fall 2017)
Health+Safety in MiningMNE 426 (Fall 2017)
Independent StudyMNE 599 (Fall 2017)
Mineral Resourc Engr TpcMNE 296A (Fall 2017)
Ore Deposits & Mine OperationsMNE 560A (Fall 2017)
ResearchMNE 900 (Fall 2017)
ThesisMNE 910 (Fall 2017)
InternshipMNE 593 (Summer I 2017)
ThesisMNE 910 (Summer I 2017)
DissertationMNE 920 (Spring 2017)
Fractures Rock+Brtl MatMNE 580 (Spring 2017)
Independent StudyMNE 399 (Spring 2017)
Independent StudyMNE 699 (Spring 2017)
Master's ReportMNE 909 (Spring 2017)
Mineralgy+Petrolgy/EngrsGEN 210 (Spring 2017)
Mineralgy+Petrolgy/EngrsMNE 210 (Spring 2017)
ResearchMNE 900 (Spring 2017)
Senior CapstoneMNE 498 (Spring 2017)
ThesisMNE 910 (Spring 2017)
Undgr Constr GeomechanicMNE 447 (Spring 2017)
Undgr Constr GeomechanicMNE 547 (Spring 2017)
DissertationMNE 920 (Fall 2016)
Engr Sustainable DevENGR 422 (Fall 2016)
Engr Sustainable DevMNE 422 (Fall 2016)
Engr Sustainable DevMNE 522 (Fall 2016)
GeomechanicsGEN 527 (Fall 2016)
GeomechanicsMNE 427 (Fall 2016)
GeomechanicsMNE 527 (Fall 2016)
Health+Safety In MiningGEN 526 (Fall 2016)
Health+Safety in MiningMNE 426 (Fall 2016)
Independent StudyMNE 599 (Fall 2016)
Intro to Mining EngineeringMNE 205 (Fall 2016)
Mineral Resourc Engr TpcMNE 296A (Fall 2016)
ResearchMNE 900 (Fall 2016)
Senior CapstoneMNE 498 (Fall 2016)
ThesisMNE 910 (Fall 2016)
- Kemeny, J., Ko, T. Y., & Jeon, S. (2014). Fracture characteristics of rocks under shear loading. KSCE Journal of Civil Engineering, 18(3), 760-764.More infoAbstract: Fracture problems in rock structures quite commonly involve shear loadings including in-plane shearing (mode II) or out-of-plane shearing (mode III). Even though a rock mass may be subjected to simple tension or shear loading, due to the complexity of the geometry and the random orientation of cracks in rocks, the crack growth occurs in mode II or mode III manner. In this study, the fracture toughness and strength of Coconino sandstone under in-plane and out-of-plane shear were determined experimentally. A short beam compression test was employed for in-plane shear loading and a circumferentially notched cylindrical specimen was employed for out-of-plane shear loading. In addition, the mode II fracture toughness and strength were determined at different loading rates to examine the effect of loading rate. As a result, the in-plane (mode II) shear strength was approximately 2 times higher than out-of-plane (mode III) shear strength. The mode II fracture toughness was approximately 1.78 times higher than the mode III fracture toughness. As the loading rate increases, the mode II fracture toughness and the shear strength also increase. © 2014 Korean Society of Civil Engineers and Springer-Verlag Berlin Heidelberg.
- Kim, K., Kemeny, J. M., & Nickerson, M. (2013). Effect of Rapid Thermal Cooling on Mechanical Rock Properties. Rock Mechanics and Rock Engineering.
- Ko, T. Y., & Kemeny, J. (2013). Determination of the subcritical crack growth parameters in rocks using the constant stress-rate test. International Journal of Rock Mechanics and Mining Sciences, 59, 166-178.More infoAbstract: Subcritical crack growth plays an important role in evaluating the long-term stability of structures in rocks. The characteristics of subcritical crack growth can be described by a relationship between the stress intensity factor and the crack velocity. This paper presents the results of studies conducted to validate the constant stress-rate test for determining subcritical crack growth parameters in rocks, compared with the conventional testing method, the double torsion test. Various types of specimens including the Brazilian disk, three-point bending, grooved disk, single edge notched bend, and compact tension specimens have been tested on Coconino sandstone under the constant stress-rate scheme and the subcritical crack growth parameters have been determined. The results of the constant stress-rate test are in good agreement with the results of double torsion test. More importantly, the stress-rate tests can determine the parameter A with a much smaller standard deviation than the DT test. Thus the constant stress-rate test seems to be a valid test method for rocks. The results show that the parameter n is almost constant regardless of the test method and specimen geometry, but the parameter A varies with the test method and specimen geometry. © 2012 Elsevier Ltd.
- Lato, M., Kemeny, J., Harrap, R. M., & Bevan, G. (2013). Rock bench: Establishing a common repository and standards for assessing rockmass characteristics using LiDAR and photogrammetry. Computers and Geosciences, 50, 106-114.More infoAbstract: Remote sensing methods are now used to assess rockmass characteristics along transportation corridors, in mines and tunnels, and in other areas where rock falls can affect humans and infrastructure. A variety of sensor methods, primarily LiDAR and photogrammetry, have seen recent use with widespread success and state of practice acceptance. Various commercial and custom tools exist to process the resulting data to extract geometry, surface and location based statistics, and to perform kinematic stability assessments. Although there is a widespread need to assess how different sensors and processing workflows actually perform, these are often compared anecdotally solely with the field practices they replace and using site and sensor data unavailable to other researchers.Two principles must be established to move across-the-board comparisons of remote rockmass characterization forward: (i) establishment of accessible, documented test sites, and (ii) test databases that are accessible to all. We propose the establishment of several key sites for equipment tests, including already-studied areas in Europe and North America, as well as an open approach to adding sites and related data to the collection. Site descriptions must include detailed local geology, photographs, LiDAR and/or photogrammetry datasets, and access notes. Second, we describe and provide a prototype data repository for storing this information, and in particular for providing open access to benchmark data into the future. This initiative will allow for meaningful comparisons of sensors and algorithms, and specifically will support better methodologies for benchmarking rock mass data in the geosciences. Data and metadata will be hosted at the www.rockbench.org domain. © 2012 Elsevier Ltd.
- Annavarapu, S., Kemeny, J., & Dessureault, S. (2012). Joint spacing distributions from oriented core data. International Journal of Rock Mechanics and Mining Sciences, 52, 40-45.More infoAbstract: Oriented core drilling data from the East Ertsberg Skarn System (EESS) area of PT Freeport Indonesia were analyzed to help identify the nature of the joint spacing distributions and their impact on block cave fragment size distributions. The normalized frequencies of overall joint spacing and joint spacing within particular joint sets were examined and were modeled using negative exponential and log-normal models. For the joint sets in each of the four different rock types analyzed, the negative exponential distribution was found to provide a good simulation of the actual joint spacing distribution. The parameters of the log-normal distribution (average and standard deviation of joint spacing) needed to be adjusted to provide a good fit to the observed joint spacing. The adjusted log-normal distributions were found to provide a better fit to the observed joint spacing data than the standard exponential distributions. © 2012 Elsevier Ltd.
- Kim, K., & Kemeny, J. M. (2012). Site Specific Blasting Model For Mine-to-Mill Optimization. SME Transactions.
- Combs, J. H., & Kemeny, J. (2011). Dot study of lidar geotechnical applications in eight states. 45th US Rock Mechanics / Geomechanics Symposium.More infoAbstract: Terrestrial LIDAR is a new technology that produces "point clouds" of reflection points that represent a scanned 3D surface. This data can be processed to determine important geotechnical information, including discontinuity attributes (orientation, roughness, spacing, length, block size, persistence, etc.), detailed 3D surface topography for cross sections and rock fall trajectory studies, and change detection . Eight states are collaborating in a Department of Transportation (DOT) pooled fund study to explore the use of terrestrial LIDAR for collecting and processing point cloud data for geotechnical applications . These states are AZ, CA, CO, NH, NY, PA, TN and TX. The project includes selection of a field site in each state and the scanning of this site, analysis of data from the site, a series of training workshops to review the results and instruct DOT personnel on the use of LIDAR and point cloud processing software, and a final report with detailed results and suggestions for utilizing LIDAR for highway geotechnical applications. This paper will present preliminary results from the eight states that look at a variety of LIDAR applications including slope stability, rock fall simulation, change detection, and rock mass characterization. Based on this study and the final report that will be issued, all states will be able to determine if LIDAR can be an effective alternative to traditional methods of gathering and analyzing geotechnical data. © 2011 ARMA, American Rock Mechanics Association.
- Combs, J. H., Kudenov, M. W., Craven, J., & Kemeny, J. M. (2011). Evaluation of rock faces with hyperspectral imaging. 45th US Rock Mechanics / Geomechanics Symposium.More infoAbstract: Hyperspectral imaging is a technology that uses non-visible portions of the electromagnetic spectrum to identify and categorize different objects. While this technology has been used for decades with satellite imagery it is only recently that ground based applications have been explored for purposes such as mineral identification.  Each mineral has areas on the spectrum where they absorb the most energy, and by filtering the light before it strikes a sensor it is possible to determine what mineral is being observed. Clay minerals have several absorption peaks in the short range infrared spectrum which can be used for identification.  When creating geologic models, the presence of clay minerals can greatly affect the stability of the slope due to reduced friction angle and strength properties. A compact infrared hyperspectral SWIR/MWIR imaging polarimeter (IHIP) was employed in recording the infrared spectrum from 1.4um to 6um and was used to capture several images from a test site on Mount Lemmon, AZ. Mathworks MATLAB was used to view and process the data, including the use of a linear un-mixing algorithm to computer relative abundances of end member spectral data . © 2011 ARMA, American Rock Mechanics Association.
- Kim, K. M., & Kemeny, J. (2011). Site specific blasting model for mine-to-mill optimization. SME Annual Meeting and Exhibit and CMA 113th National Western Mining Conference 2011, 619-623.More infoAbstract: A site-specific blasting model has been developed for the Asarco Mission mine. The main inputs to the model are the in-situ block size (F80), the post-blast fragmentation (P80) and the intact tensile strength (To). The output from the model is the specific blast energy (ESE). Modem techniques are being used to obtain the input parameters for the site-specific blast fragmentation model. In particular, image processing software is used to obtain both the in-situ block size and the post-blast fragmentation, and the Schmidt hammer is used to obtain the tensile strength at numerous locations throughout the rock mass. An initial model was developed using five test shots in one area of the mine that contains Argillite and is relatively homogeneous. This also included calibrating Schmidt hammer readings against actual Brazilian tensile measurements. The model for Argillite will be updated as more tests are conducted, and the model will be extended to the other four primary rock types at the Asarco Mission mine.
- Ko, T. Y., & Kemeny, J. (2011). Subcritical crack growth in rocks under shear loading. Journal of Geophysical Research B: Solid Earth, 116(1).More infoAbstract: In this study, the subcritical crack growth parameters for Coconino sandstone under modes II and III loading were determined experimentally by using the constant stress rate test. We extend the constant stress rate test technique to modes II and III subcritical crack growth in rocks. The experimental results of the modes II and III tests, combined with mode I results published elsewhere, show that the values of the modes I, II, and III subcritical crack growth parameters are very similar to each other regardless of the loading configuration and the specimen geometries. The main reason for this is thought to be that subcritical crack growth is environmentally induced crack growth rather than the mechanical rupture of bonds. The effect of confining stress, specimen size, and water saturation on subcritical crack growth under mode II loading has also been investigated. The parameter n linearly increases with increasing confining stress and the parameter A exponentially decreases with increasing confining stress. Increasing the specimen size results in a linear increase in the subcritical crack growth parameter A. But, the parameter n is independent of the specimen size. The parameter n is almost constant regardless of water saturation, and the parameter A is found to increase slightly when the specimen is fully saturated. These results suggest that the subcritical crack growth parameter n can be considered a material constant for a given rock type. Copyright © 2011 by the American Geophysical Union.
- Kim, K. M., & Kemeny, J. (2009). Effect of thermal shock and rapid unloading on mechanical rock properties. 43rd U.S. Rock Mechanics Symposium and 4th U.S.-Canada Rock Mechanics Symposium.More infoAbstract: Laboratory tests have been conducted to investigate the effects of rapid cooling and rapid unloading on rock damage. Thermal shock experiments were conducted consisting of slow heating up to a temperature of 100°C followed by rapid cooling with a fan. Samples were examined after one cycle (relevant to deep core drilling) and five cycles (relevant to ventilation in deep underground mines). The rock damage due to thermal shock was analyzed using before and after P and S wave velocity, porosity, and tensile strength tests. To analyze the effects of rapid unloading, cores collected from depths of 1000-2000 meters were reloaded back to their in-situ stress levels while simultaneously measuring P and S wave velocity. The results from the thermal shock tests were very interesting and showed that crack growth occurred in some rock types subjected to thermal shock (Granite, Diabase with ore veins, KVS) while crack healing occurred in other rock types (Diabase without ore veins, Quartzite, Skarn). Within a rock type the results were consistently crack growth or crack healing. In an effort to understand this behavior, the thermal stresses induced in the rock samples during the shock tests were analyzed. Our hypothesis is that overall crack healing is expected when the amount of crack healing in the central parts of the rock sample (due to slow heating and rapid cooling) exceed the crack growth that is occurring near the surface of the samples (due to rapid cooling), and vise versa. Copyright 2009 ARMA, American Rock Mechanics Association.
- Ko, T. Y., & Kemeny, J. (2009). Some statistical aspects of constant stress-rate testing for subcritical crack growth. 43rd U.S. Rock Mechanics Symposium and 4th U.S.-Canada Rock Mechanics Symposium.More infoAbstract: In this paper, statistical aspects of the constant stress-rate test were investigated. The effects of the number of specimens on the subcritical crack growth parameters were examined. The grooved disk specimens were used to determine the fracture strength. 7 groups of fictitious data sets with the number of specimens of 5, 7, 10, 20, 40, 80, and 160 at each stress rate were generated by Monte Carlo simulation using the Weibull parameters obtained from the grooved disk tests. Also, the distribution form of the subcritical crack growth parameters and the relation between the parameter A and n was determined. Copyright 2009 ARMA, American Rock Mechanics Association.
- Mansfield, C. H., & Kemeny, J. (2009). The use of terrestrial LIDAR in determining directional joint dilation angle values. 43rd U.S. Rock Mechanics Symposium and 4th U.S.-Canada Rock Mechanics Symposium.More infoAbstract: It is well documented in the field of rock mechanics engineering that joint roughness plays an integral role in the shear strength of discontinuities. The effective friction angle of a discontinuity includes both the saw-cut friction angle, φ, and the inherent natural roughness encountered on fracture faces. This second component is the joint dilation angle, and is the focus of this study. Emphasis is not on a preferred method of characterizing roughness, but rather a new technology as a tool to assist in analyzing joint roughness. Using ground-based laser scanning and point cloud processing software, joint dilation angles can be found by finding the angular difference between poles to a triangulated mesh and the mean pole. Simple vector operations can then project all poles onto a common surface (the fracture surface) and described as rakes on the plane. These two components make up the directional dilation angle, which seems to be a valid took based upon a case study performed at a site near the San Pedro Vista near Tucson. This directional dilation angle value may influence the directional shear strength, for example in a direction parallel to a dip direction of a joint. Future research will also include analyzing the relationship between this directional dilation angle and the overall structure of the rock mass in which it is found. Copyright 2009 ARMA, American Rock Mechanics Association.
- Kim, K. M., & Kemeny, J. (2008). Effect of thermal loading on compressional wave velocity, Mode I fracture toughness and tensile strength. 42nd U.S. Rock Mechanics - 2nd U.S.-Canada Rock Mechanics Symposium.More infoAbstract: Thermal loading can impact the mechanical properties of rock. In deep excavations, for example, ventilation can result in a significant rapid cooling of the rock. In this study sandstone samples were subjected to slow heating followed by rapid cooling, referred to as thermal shock. An initial suite of tests were conducted at temperatures of 100°C, 200°C, and 300°C. In these tests, samples were subjected to a single cycle of heating and cooling and then tested. Measurements included P and S wave velocity, fracture toughness and tensile strength. Even though only small changes were seen at 100°C, further studies were conducted at this temperature because of the practical importance of this temperature range in mining and civil design. Cyclic heating and cooling was conducted at 100°C, with measurements of fracture toughness and tensile strength at 10, 15 and 20 cycles. Even though the overall results from the tree types of measurements (seismic velocity, fracture toughness, and tensile strength) are quite complicated, they can be at least partially explained by considering three types of crack density changes: a small decrease in crack density (crack healing), a small increase in crack density (blunting of macrocracks), and a large increase in crack density (rock damage). © 2008, ARMA, American Rock Mechanics Association.
- Ko, T. Y., & Kemeny, J. (2008). Experimental study of subcritical crack growth under mode I, mode II and mode III loading. 42nd U.S. Rock Mechanics - 2nd U.S.-Canada Rock Mechanics Symposium.More infoAbstract: In this research, the subcritical crack growth parameters for Coconino sandstone under mode I, mode II and mode III loading were determined using a constant stress-rate test. The subcritical crack growth parameter n is approximately determined to be 37, and the parameter n is similar to each other regardless of the loading configuration. The parameter A varies with the loading configuration and the geometry. The mode II shear strength is higher than the mode III shear strength and the ratio of the mode II fracture toughness to the mode I fracture toughness is equal to 1.8. Copyright 2008, ARMA, American Rock Mechanics Association.
- Koo, T. Y., & Kemeny, J. (2008). Size effect on subcritical crack growth in Coconino sandstone. 42nd U.S. Rock Mechanics - 2nd U.S.-Canada Rock Mechanics Symposium.More infoAbstract: The scale effect on subcritical crack growth in rock is important to extrapolate the laboratory test results to the field scale design. A constant stress-rate test has been performed to estimate the mode I and II subcritical crack growth parameters for Coconino sandstone. The experimental results show that the subcritical crack growth parameters of mode I and mode II loading are similar to each other. The subcritical crack growth parameter A values increase with increasing specimen size, whereas the subcritical crack growth parameter n values are independent of specimen size. The subcritical crack growth parameter n was determined to be 35 to 36, and A was determined to be 1.17×10 -2 to 3.02×10-2 m/s. Copyright 2008, ARMA, American Rock Mechanics Association.
- Ko, T. Y., & Kemeny, J. (2007). Effect of confining stress and loading rate on fracture toughness of rocks. Proceedings of the 1st Canada-US Rock Mechanics Symposium - Rock Mechanics Meeting Society's Challenges and Demands, 1, 625-629.More infoAbstract: In this research, the effect of confining stress and loading rate on the fracture toughness has been investigated. The short beam compression test has been used to estimate the fracture toughness for Flagstaff sandstone. A brief theoretical analysis of the effects of confining stress and loading rate the fracture toughness is presented. This analysis considers changes to the critical fracture process zone size due to confining stress and loading rate. It is found that experimental results agree with the fracture mechanics theory. The mode II fracture toughness is found to increase with increasing confining stress and increasing loading rate. © 2007 Taylor & Francis Group.
- Kemeny, J., Apted, M., & Martin, D. (2006). Rockfall at Yucca Mountain due to thermal, seismic and time-dependence. Proceedings of the 11th International High Level Radioactive Waste Management Conference, IHLRWM, 2006, 526-533.More infoAbstract: Over the past 18 months the Electric Power Research Institute (EPRI) has conducted an independent analysis of rockfall in the emplacement drifts in the proposed Yucca Mountain repository. This paper addresses one aspect of this work, the occurrences of rockfall due to thermal loading, seismic loading, and time. The consequences of rockfall on repository performance are addressed in other papers by the EPRI team. Overall, our results are in general agreement with the most recent Drift Degradation AMR .
- Kemeny, J., Norton, B., & Turner, K. (2006). Rock slope stability analysis utilizing ground-based LIDAR and digital image processing. Felsbau, 24(3), 8+10-15.More infoAbstract: This paper describes the use of ground-based LIDAR for rock mass characterization. Ground-based LIDAR (also referred to as laser scanning) consists of a compact instrument that rapidly sends out laser pulses and calculates the three dimensional position of reflected objects. A typical scan takes 10 to 15 minutes and results in a three-dimensional point cloud containing 1 to 1.5 million points. Laser-scanners have a range of up to 800 m and an accuracy of ± 3-10 mm. Along with the laser measurements, high-resolution digital images are also taken which can be geo-registered with the point cloud. Software now exists for automatically processing the point cloud and associated digital images to extract rock discontinuity information. This information includes discontinuity orientation, roughness, size and spacing. The use of LIDAR along with automated point cloud processing address several important problems with traditional field discontinuity characterization, including problems with safety, remote access, cost, time, and accuracy.
- Kessler, J. H., Apted, M. J., Wei, Z., Kemeny, J., King, F., Ross, A. M., Ross, B., & Schwartz, F. W. (2006). Room at the mountain: Estimated maximum amounts of commercial spent nuclear fuel capable of disposal in a Yucca Mountain repository. International Conference on Nuclear Engineering, Proceedings, ICONE, 2006.More infoAbstract: The purpose of this paper is to present an initial analysis of the maximum amount of commercial spent nuclear fuel (CSNF) that could be emplaced into a geological repository at Yucca Mountain. This analysis identifies and uses programmatic, material, and geological constraints and factors that affect this estimation of maximum amount of CSNF for disposal. The conclusion of this initial analysis is that the current legislative limit on Yucca Mountain disposal capacity, 63,000 MTHM of CSNF, is a small fraction of the available physical capacity of the Yucca Mountain system assuming the current high-temperature operating mode (HTOM) design. EPRI is confident that at least four times the legislative limit for CSNF (-260,000 MTHM) can be emplaced in the Yucca Mountain system. It is possible that with additional site characterization, upwards of nine times the legislative limit (-570,000 MTHM) could be emplaced. Copyright © 2006 by ASME.
- Ko, T. Y., Einstein, H. H., & Kemeny, J. (2006). Crack coalescence in brittle material under cyclic loading. Proceedings of the 41st U.S. Rock Mechanics Symposium - ARMA's Golden Rocks 2006 - 50 Years of Rock Mechanics.More infoAbstract: A total of 170 tests (68 tests for monotonic loading, 102 tests for cyclic loading) have been performed to investigate crack initiation, propagation and coalescence. The specimens have two pre-existing flaws which are arranged at different distances and angles. Wing cracks and secondary cracks are observed in both monotonic and cyclic tests. Wing cracks, which are tension cracks, initiate at (or near) the tips of the flaws and propagate parallel to the compressive loading axis. Secondary cracks always appear after wing crack initiation and lead to final failure. Secondary cracks initiate at the tips of the flaws and propagate in the coplanar direction of the flaw or in a horizontal (quasi-coplanar) direction. Six types of coalescence are observed. For coplanar geometry specimens, coalescence occurs due to the internal shear cracks. For non-coplanar geometry specimens, coalescence occurs through combinations of internal shear cracks, internal wing cracks and tension cracks. Contrary to monotonic tests, cyclic tests produce fatigue cracks. Fatigue cracks usually occur when 1) after coalescence, the specimens behave as if they had only one larger crack 2) specimens have been subjected to a particular number of cycles. In these experiments, two different fatigue crack initiation directions are observed: horizontal and coplanar to the flaw. © 2006, ARMA, American Rock Mechanics Association.
- Ko, T. Y., Kemeny, J., & Lee, S. J. (2006). Mode II subcritical crack growth parameters for sandstone. Proceedings of the 41st U.S. Rock Mechanics Symposium - ARMA's Golden Rocks 2006 - 50 Years of Rock Mechanics.More infoAbstract: Subcritical crack growth is important for the long-term behavior of rock and can be used to evaluate the long- term stability of underground and surface structures in rock masses. In this study the mode II subcritical crack growth parameters were determined experimentally using the double notch shear test. A series of tests were performed to determine the appropriate geometry for the double notch shear test. The mode II stress intensity factor was determined using finite element analysis using the displacement extrapolation method. The subcritical crack growth parameters in Flagstaff sandstone were determined to be n =28.27 and A =0.00647 m/s. © 2006, ARMA, American Rock Mechanics Association.
- Lee, J. S., Kemeny, J., & Ko, T. Y. (2006). Modified PTS test and clump modeling on mixed mode crack growth in granite. Proceedings of the 41st U.S. Rock Mechanics Symposium - ARMA's Golden Rocks 2006 - 50 Years of Rock Mechanics.More infoAbstract: This paper describes the development of a new test for measuring the mode II fracture toughness for rock, KIIC. The test is called the Modified Punch Through Shear test (MPTS), which is a modification of the PTS test developed by . Laboratory MPTS tests on Columbia granite were conducted. The lab tests and finite element modeling reveal that a valid shear crack is produced. Tests conducted at different confining stresses show that the shear cracking strength is a function of confining stress. Tests at each confinement were repeated 7 times, and even though the scatter in the results is large, best-fit results for shear cracking strength as a function of confining stress were determined. PFC modeling has also been conducted to simulate in detail the development of tensile and shear cracks in the MPTS test. A clump model rather than the standard Circular Particle Interaction (CPI) model was used to improve the strength envelope. Copyright 2005, ARMA, American Rock Mechanics Association.
- Donovan, J., Handy, J., Kemeny, J., & O'Brien, G. (2005). Automatic acquisition and determination of rock discontinuity properties using three-dimensional laser scanning. Application of Computers and Operations Research in the Mineral Industry - Proc. of the 32nd Int. Symposium on the Application of Computers and Operations Research in the Mineral Industry, APCOM 2005, 113-118.More infoAbstract: Methods of automatically extracting rock discontinuity data from three-dimensional surface models generated using current laser scanning technology are under development. Algorithms for the processing of raw point clouds, created by laser scanning exposed rock surfaces, have been developed. A novel method of triangular mesh generation rapidly creates a three-dimensional model of the scanned surface. The triangular elements of the mesh are grouped together using their normals as a similarity measure, resulting in the identification of larger fracture patches that represent discontinuity surfaces. A field study conducted at a rock cut along the Catalina Highway in Tucson, Arizona suggests that the discontinuity data collected from three-dimensional images, i.e., point clouds, compares favorably to data collected using more traditional manual field mapping methods. Additionally, a much more exhaustive data set is gathered and is done so without bias. Refinement and validation of this process has been initiated through a series of supplementary field studies. Additional algorithms that expand the application of automated rock mass characterization using three-dimensional laser scans are under development. The optimization of algorithms capable of processing three-dimensional data, finding and identifying discontinuities, and determining information such as fracture orientation, length, and spacing, will reduce the time required for data collection, eliminate human bias, make it possible to collect data from inaccessible rock faces, provide rapid data processing, and produce a more comprehensive database of discontinuity information. © 2005 Taylor & Francis Group.
- Hopkins, D., Davis, W. B., Türler, D., & Kemeny, J. (2005). Integrated sensor networks for rock-mass characterization and material handling. Application of Computers and Operations Research in the Mineral Industry - Proc. of the 32nd Int. Symposium on the Application of Computers and Operations Research in the Mineral Industry, APCOM 2005, 535-546.More infoAbstract: Work is underway to develop techniques to integrate, analyze and display data collected during mining that builds upon previous work focused on development of technology to collect data while drilling to improve blasting results and material handling in open-pit mines. This research demonstrated the feasibility of measuring the elemental composition of the rock mass from samples automatically collected during drilling, and drill vibration data measured by a wireless system mounted to the drill stem. The project demonstrated how these data can be used in conjunction with drilling, geological, and post-blast-fragmentation data for blast design, material handling, and potentially, to improve mineral processing. This paper describes how these newly developed rock-mass characterization techniques can be further developed so that they are sufficiently automated to allow the data collected to be easily integrated into a mine-wide information system. Emerging technologies in sensors, networking, communications, and probabilistic network modeling are described that promise to enable process-control applications. © 2005 Taylor & Francis Group.
- Kemeny, J. (2005). Time-dependent drift degradation due to the progressive failure of rock bridges along discontinuities. International Journal of Rock Mechanics and Mining Sciences, 42(1), 35-46.More infoAbstract: An important element of time-dependent drift degradation is the progressive failure of intact segments along discontinuities, referred to as rock bridges. A fracture mechanics model is developed to simulate the time-dependent failure of rock bridges along discontinuities. The time dependence of the rock bridge failure process is modeled utilizing subcritical crack growth. The rock bridges give an effective cohesion to the discontinuities, and this cohesion is time-dependent due to the time-dependent failure of the rock bridges. The resulting first-order differential equation for joint cohesion is implemented into the UDEC distinct element numerical code to model time-dependent drift degradation. The model and its implementation into UDEC are validated using several simple examples, including a direct shear test and a rigid block on a slope. Two time-dependent drift degradation examples are then shown, one with and one without thermal loading. These examples used similar geometry, material parameters and in situ stresses as for the proposed underground drifts for the storage of nuclear waste at Yucca Mountain. Both with and without thermal loading, a large zone develops around the excavation where the joint cohesion and tensile strength drop to zero due to the failure of rock bridges. This in turn results in an excavation that is significantly less stable than if time dependence was not included. The results demonstrate the importance of time-dependence on the stability of underground excavations in hard rock. © 2004 Elsevier Ltd. All rights reserved.
- Kemeny, J., & Donovan, J. (2005). Rock mass characterisation using LIDAR and automated point cloud processing. Ground Engineering, 38(11), 26-29.More infoAbstract: Ground based 3D imaging is a new and emerging technology for rock mass characterisation. This article defines 3D imaging to include ground based LIDAR surveys (also called 3D laser scanning), high resolution digital cameras, and a host of software for data processing, interpretation and visualisation.
- Slob, S., Knapen, B. V., Hack, R., Turner, K., & Kemeny, J. (2005). Method for automated discontinuity analysis of rock slopes with three-dimensional laser scanning. Transportation Research Record, 187-194.More infoAbstract: Three-dimensional (3D) laser scanning data can be used to characterize discontinuous rock masses in an unbiased, rapid, and accurate manner. With 3D laser scanning, it is now possible to measure rock faces whose access is restricted or rock slopes along highways or railway lines where working conditions are hazardous. The proposed method is less expensive than traditional manual survey and analysis methods. Laser scanning is a relatively new surveying technique that yields a so-called point cloud set of data; every single point represents a point in 3D space of the scanned rock surface. Because the density of the point cloud can be high (on the order of 5 mm to 1 cm), it allows for an accurate reconstruction of the original rock surface in the form of a 3D interpolated and meshed surface using different interpolation techniques. Through geometric analysis of this 3D mesh and plotting of the facet orientations in a polar plot, it is possible to observe clusters that represent different rock mass discontinuity sets. With fuzzy k-means clustering algorithms, individual discontinuity sets can be outlined automatically, and the mean orientations of these identified sets can be computed. Assuming a Fisher's distribution, the facet outliers can be removed subsequently. Finally, discontinuity set spacings can be calculated as well.
- BoBo Jr., T. W., Norton, B., Kemeny, J., & Taylor, M. (2004). Split-Online® digital image analysis system to quantify particle size for the industrial mineral industry. 2004 SME Annual Meeting Preprints, 725-732.More infoAbstract: Digital image analysis systems to quantify particle size of crushed materials have successfully been applied in large-scale mining operations throughout the world. Particle size measurement at various crushing and sieving stages, especially in aggregate production, will facilitate the industry's desire and need to achieve higher levels of process control and automation. This paper will 1) summarize applications of digital image analysis in the industrial minerals industries and introduce the Split-Online technology; 2) detail an actual recent test application of digital image analysis that ultimately lead to the installation of an automatic, non-invasive particle size distribution monitoring system; 3) document how this information is being applied: and 4) summarize the new Split-Online Aggregates Module now available.
- Kemeny, J. (2003). The time-dependent reduction of sliding cohesion due to rock bridges along discontinuities: A fracture mechanics approach. Rock Mechanics and Rock Engineering, 36(1), 27-38.More infoAbstract: In this paper, a fracture mechanics model is developed to illustrate the importance of time-dependence for brittle fractured rock. In particular a model is developed for the time-dependent degradation of rock joint cohesion. Degradation of joint cohesion is modeled as the time-dependent breaking of intact patches or rock bridges along the joint surface. A fracture mechanics model is developed utilizing subcritical crack growth, which results in a closed-form solution for joint cohesion as a function of time. As an example, a rock block containing rock bridges subjected to plane sliding is analyzed. The cohesion is found to continually decrease, at first slowly and then more rapidly. At a particular value of time the cohesion reduces to value that results in slope instability. A second example is given where variations in some of the material parameters are assumed. A probabilistic slope analysis is conducted, and the probability of failure as a function of time is predicted. The probability of failure is found to increase with time, from an initial value of 5% to a value at 100 years of over 40%. These examples show the importance of being able to predict the time-dependent behavior of a rock mass containing discontinuities, even for relatively short-term rock structures.
- Kemeny, J. M., Kaunda, R. B., Streeter, D., & BoBo, T. (2003). Effect of blasting on the strength of rock fragments. Proceedings of the Annual Conference on Explosives and Blasting Technique, I, 381-390.More infoAbstract: This paper describes a field/laboratory study that was conducted in cooperation with a mine in Arizona. The primary purpose of the study was to investigate the effect of blasting energy on the crushability and grindability of the post-blast rock fragments. The crushability and grindability of the rock fragments were evaluated through laboratory comminution tests. A secondary purpose of the study was to investigate different laboratory methods for estimating the comminution properties of the rock fragments. In particular, a number of standard rock mechanics tests were conducted and compared with the comminution test results. Finally, the study was used to evaluate new technologies for estimating in-situ rock mass strength and for assessing post-blast fragmentation. To estimate in-situ rock mass strength, the specific energy of drilling (SE) was calculated during blast hole drilling utilizing a continuous drill monitoring system. Post-blast fragmentation was estimated using the Split image processing system. Results from the study support the idea that increases in blast energy can enhance crushing and grinding. Also, several simple rock mechanics tests were found to correlate well with the results from standard comminution tests, which could prove to be useful in practice.
- Kemeny, J., & Post, R. (2003). Estimating three-dimensional rock discontinuity orientation from digital images of fracture traces. Computers and Geosciences, 29(1), 65-77.More infoAbstract: This paper describes a computer approach that has been developed for estimating three-dimensional fracture orientations from two-dimensional fracture trace information gathered from digital images of exposed rockfaces. The approach assumes that the fractures occur in sets, and that each set can be described by a mean orientation and a measure of the scatter about the mean. Mathematical relationships are developed that relate the 3D fracture properties with the trace angles that would be measured on one or more rockfaces. These algorithms are used in conjunction with a genetic algorithm to invert the trace angles to estimate 3D joint orientation. A number of case studies have been conducted indicating a great potential for the technique. © 2002 Elsevier Science Ltd. All rights reserved.
- Latham, J., Kemeny, J., Maerz, N., Noy, M., Schleifer, J., & Tose, S. (2003). A blind comparison between results of four image analysis systems using a photo-library of piles of sieved fragments. Fragblast, 7(2), 105-132.More infoAbstract: Four image analysis systems for measuring rock fragmentation: FragScan, PowerSieve®, Split and WipFrag, have been compared under conditions necessary to provide an objective though limited assessment of their capabilities. The analysis of results is based on a sample of ten photographs taken from a series of photographs of controlled artificial muckpiles. These were created from dumping a blended mixture of sieved samples of limestone aggregate, in order to create a range of near perfect Rosin-Rammler sieve size distributions. Results from the various systems we compared with sieved results using both histogram and cumulative forms, with and without fines corrections in the case of Split and Wipfrag. Statistical indicators are evaluated to examine the match between system prediction values and sieving values. Commentaries on the results by the inventors of each system have been incorporated. All four systems were found to perform both well in some cases and poorly in others. From a detailed examination of the results, some insight into the strengths and weaknesses of the various systems is presented.
- Kemeny, J., Berman, E., Bracke, P., Brent, W., Budhu, M., Coleman, A., Dempsey, R., Frumkin, J., Oxnam, M., Przybylski, L., & Rassmusan, W. (2002). GROW: A digital library for geotechnical, rock, and water aspects of civil engineering. ASEE Annual Conference Proceedings, 5523-5533.More infoAbstract: The Geotechnical Rock and Water (GROW) digital library that focuses on the collections aspect of the digital library is being developed at the University of Arizona. The initial focus of the digital library is on collections in three targeted areas: geotechnical engineering, rock engineering, and water and its use. The library will address specific learning and content needs for a number of different audience groups, including K-12, higher education, professionals and the community at large. The educational value of the submitted material and of the library as a whole will also be assessed through an advisory panel consisting of teachers, students, professionals and other members.
- Kemeny, J., Mofya, E., Kaunda, R., & Lever, P. (2002). Improvements in blast fragmentation models using digital image processing. Fragblast, 6(3-4), 311-320.More infoAbstract: One of the fundamental requirements for being able to optimise blasting is the ability to predict fragmentation. An accurate blast fragmentation model allows a mine to adjust the fragmentation size for different downstream processes (mill processing versus leach, for instance), and to make real time adjustments in blasting parameters to account for changes in rock mass characteristics (hardness, fracture density, fracture orientation, etc). A number of blast fragmentation models have been developed in the past 40 years such as the Kuz-Ram model . Fragmentation models have a limited usefulness at the present time because: 1. The input parameters are not the most useful for the engineer to determine and data for these parameters are not available throughout the rock mass. 2. Even if the input parameters are known, the models still do not consistently predict the correct fragmentation. This is because the models capture some but not all of the important rock and blast phenomena. 3. The models do not allow for 'tuning' at a specific mine site. This paper describes studies that we being conducted to improve blast fragmentation models. The Split image processing software is used for these studies [2, 3].
- Kemeny, J., & Zeitler, B. (2001). An online geomechanics course with a virtual rock lab based on streaming audio and vector graphics. ASEE Annual Conference Proceedings, 1915-1923.More infoAbstract: The development of an online geomechanics with a virtual rock lab, based on streaming audio and vector graphics, is discussed. The course includes in-class lectures that utilize a whiteboard for derivations, problem solving, and drawings. The rock lab provides an hands-on experience, as well as a writing experience in the form of laboratory reports. Several innovative multimedia components have been adapted to meet the challenges in developing such a course.
- Lowery, M. A., Kemeny, J., & Girdner, K. (2001). Advances in blasting practices through the accurate quantification of blast fragmentation. Mining Engineering, 53(10), 55-61.More infoAbstract: A strategy for proactive blast planning to improve the postblast fragmentation size has been implemented at the Phelps Dodge Morenci Mine. This strategy was developed in specific phases that include stabilization of blasting practices, systematic changes in blast design and quantification of the size distribution of blasts. Implementing this new strategy would not be possible without an accurate method for quantifying the postblast fragment size distribution. The Split image-processing system is now being used to assess fragmentation size using muck pile digital imaging taken on a daily basis and an online fragmentation analysis system installed at the primary crushers. Drilling and blasting variables and fragmentation size are entered into a database, spatially evaluated in a geographic information system and subsequently utilized for mine planning purposes. Using this strategy, significant improvements have been made in postblast fragmentation and continued improvements are expected in the next several years.
- Hardy, A. J., Ryan, T. M., & Kemeny, J. M. (1997). Block size distribution of in situ rock masses using digital image processing of drill core. International journal of rock mechanics and mining sciences & geomechanics abstracts, 34(2), 303-307.More infoAbstract: The purpose of an in situ rock fragmentation analysis is to quantify the spatial distribution of the natural fragmentation in addition to developing the complete block size distribution within the rock mass. In situ fragmentation is only concerned with the interaction of the pre-existing fractures within the undisturbed rock mass. Generally the number of fractures increases with the number of joint sets, which in turn directly affect the size and shapes of the rock blocks, and consequently the mechanical behavior of the rock mass. Therefore, the distribution of block sizes can be directly related to the spacing distribution of the joint set. The objective of this Technical Note is to present an empirical approach to the analysis of in situ block size distribution in closely jointed rocks from drill core.
- Hu, K. X., & Kemeny, J. (1994). A fracture mechanics analysis of the effect of backfill on the stability of cut and fill mine workings. International Journal of Rock Mechanics and Mining Sciences and, 31(3), 231-241.
- Kemeny, J. M. (1994). Practical technique for determining the size distribution of blasted benches, waste dumps and heap leach sites. Mining Engineering, 46(11), 1281-1284.More infoAbstract: This paper describes a practical technique to estimate the size distribution of large volumes of rock fragments, including blasted benches, waste dumps and heap leach sites. Images are obtained from a site using a standard video camera and downloaded onto the computer. Image processing algorithms are used to delineate the individual rock fragments in the images, followed by the calculation of the area and shape of each fragment. Statistical calculations are then performed to estimate the complete size distribution of the fragments. The accuracy of the technique has been assessed with a number of field validation studies.
- Du, W., & Kemeny, J. M. (1993). Modeling borehole breakout by mixed mode crack growth, interaction, and coalescence. International Journal of Rock Mechanics and Mining Sciences and, 30(7), 809-812.
- Kemeny, J. M., Devgan, A., Hagaman, R. M., & Xingqiang, W. (1993). Analysis of rock fragmentation using digital image processing. Journal of geotechnical engineering, 119(7), 1144-1160.More infoAbstract: In this paper, a procedure for calculating the size distribution of rock fragments using video images is described. The procedure utilizes a high-resolution video camera for image capturing in the field and a set of computer algorithms for processing the video images. The computer program first delineates the individual rock fragments in the images. This is followed by statistical procedures that take into account fragment overlap and the two-dimensional nature of the images. The computer algorithms can process many images to produce a single size distribution curve, and takes into account sample variability as well as combining images taken at different scales. All the procedures described have been implemented into a single computer program. By comparing the computer procedures with laboratory experiments, the accuracy of the method is demonstrated.
- Smith, M. L., & Kemeny, J. M. (1993). Blast fragmentation model evaluation via image analysis. Emerging Computer Techniques for the Minerals Industry, 229-238.More infoAbstract: In blasting, an optimal muckpile size distribution can be found in terms of mining and milling productivity and cost. Fragmentation control requires a means of modeling and evaluating blast results. A principle problem in the practical application of empirical blast fragmentation modeling is the evaluation of the muckpile's size distribution. Image analysis of video and photographic records of production size blasts at Cyprus's Miami and Thompson Creek mines is being used to provide data for estimating parameters relating fragmentation to blast design, energy factor and rock quality. The application of image analysis to the estimation of particle size distribution is reviewed with regards to the problem of fragmentation modeling.
- Wang, R., & Kemeny, J. M. (1993). Micromechanical modeling of tuffaceous rock for application in nuclear waste storage. International Journal of Rock Mechanics and Mining Sciences and, 30(7), 1351-1357.More infoAbstract: This paper describes the development of micromechanical models for tuffaceous rock. In particular, laboratory tests have been conducted on Topopah Spring tuff from Yucca Mountain, Nevada and Apache Leap tuff from Superior, Arizona. Topopah Spring tuff is the host rock for the proposed underground nuclear waste repository at Yucca Mountain, and Apache Leap tuff is an analog for the host rock. Based on SEM microscopy of the damaged rock specimens, the specific micro-mechanismsfor deformation in tuffs have been determined. Micromechanical models based on fracture mechanics theory are then developed for these specific mechanisms. The micromechanical models are able to predict the nonlinear stress-strain behavior of tuff, including strain-hardening, strain-softening, triaxial strength, and dilatation. © 1993.
- Wang, R., & Kemeny, J. M. (1993). Micromechanics of deformation in Topopah Spring tuff, Yucca Mountain, Nevada. High Level Radioactive Waste Management, 1873-1879.More infoAbstract: Samples of Topopah Spring tuff from Yucca Mountain, Nevada have been tested and analyzed. Laboratory tests conducted include standard uniaxial and triaxial compression tests, and special 'damage' tests in which samples are loaded to some proportion of their strength and analyzed with SEM microscopy. Based on the SEM analysis of the damaged samples, the micromechanics of rock deformation and failure in Topopah Spring tuff is determined. The results indicated that pores are the major initial microstructures in Topopah Spring tuff. Also, several mechanisms have been found for microcracking under compressive stresses, including pore crackling, the linking of pore cracks, and the formation of en echelon arrays of axial cracks. The macroscopic cracks tend to propagate in the locations with the highest pore density. The final failure of Topopah Spring tuff is due to shear localization near the peak stress. The microbuckling of crack-induced columns has been found to be the major mechanism for inducing shear localization. The heating of Topopah Spring specimens up to 200°C results in no significant microcracking.
- Kemeny, J. M., & Hagaman, R. M. (1992). An asperity model to simulate rupture along heterogeneous fault surfaces. Pure and Applied Geophysics PAGEOPH, 138(4), 549-567.More infoAbstract: A model has been developed to simulate the statistical and mechanical nature of rupture on a heterogeneous strike-slip fault. The model is based on the progressive failure of circular asperities of varying sizes and strengths along a fault plane subjected to a constant far-field shear displacement rate. The basis of the model is a deformation and stress intensity factory solution for a single circular asperity under a unidirectional shear stress. The individual asperities are unified through the fault stiffness and the far-field stress and displacement. During fault deformation asperities can fail and reheal, resulting in changes in the local stresses in the asperities, stress drops, and changes in the stiffness of the fault. Depending on how the stress is redistributed following asperity failure and on the strenghts of the neighboring asperities an earthquake event can be the failure of one or more asperities. Following an earthquake event seismic source parameters such as the stress drop, energy change, and moment magnitude are calculated. Results from the model show a very realistic pattern of earthquake rupture, with reasonable source parameters, the proper magnitude-frequency behavior, and the development of characteristic earthquakes. Also the progression of b-values in the model gives some insight into the phenomenon of 'self-organized criticality.' © 1992 Birkhäuser Verlag.
- Kemeny, J. M. (1991). A model for non-linear rock deformation under compression due to sub-critical crack growth. International Journal of Rock Mechanics and Mining Sciences and, 28(6), 459-467.More infoAbstract: Time dependency in rock deformation under compression is modelled by considering an elastic body containing cracks that grow under compressive stresses due to sub-critical crack growth. This is considered the prime mechanism for the time-dependent deformation of brittle rocks at low temperatures. The growth of cracks under compressive stresses is formulated using the "sliding crack" model, which considers extensile crack growth due to stress concentrations around pre-existing flaws. Subcritical crack growt is included into the sliding crack model by utilizing the empirical Charles power law relation between crack velocity and the crack tip stress intensity factor. The model is able to predict the dependence of the stress-strain curve on the applied strain rate, and agrees extremely well with experimental data. Also, the model is able to predict the occurrence of both transient and tertiary creep. The transient creep behavior is derived in closed-form, and is found to give creep that depends on the logarithm of time, which is similar to many empirical formulae for creep in brittle rocks. Tertiary creep in the model is due to crack interaction, and is found to occur at a critical value of crack density. This allows time-to-failure predictions to be made, which could be useful for underground structures required to remain open for long periods of time. © 1991.
- Kemeny, J. M. (1991). Symposium on Damage Mechanics 25-30 November 1990, Dallas, Texas, USA. Geotechnical and Geological Engineering, 9(1), 83-85.
- Long, J. C., Karasaki, K., Davey, A., Peterson, J., Landsfeld, M., Kemeny, J., & Martel, S. (1991). An inverse approach to the construction of fracture hydrology models conditioned by geophysical data. An example from the validation exercises at the Stripa Mine. International Journal of Rock Mechanics and Mining Sciences and, 28(2-3), 121-142.More infoAbstract: One approach for the construction of fracture flow models is to collect statistical data about the geometry and hydraulic apertures of the fractures and use this data to construct statistically identical realizations of the fracture network for fluid flow analysis. We have found that this approach has two major problems. One is that an extremely small percentage of visible fractures may be hydrologically active. The other is that on any scale you are interested in characterizing usually a small number of large features dominate the behaviour ( Transport Processes in Porous Media. Kluwer Academic, The Netherlands, 1989). To overcome these problems we are proposing an approach in which the model is strongly conditioned by geology and geophysics. Tomography is used to identify the large features. The hydraulic behaviour of these features is then obtained using an inverse technique called "simulated annealing." The first application of this approach has been at the Stripa mine in Sweden as part of the Stripa Project. Within this effort, we built a model to predict the inflow to the Simulated Drift Experiment (SDE), i.e. inflow to six parallel, closely-spaced holes, the N- and W-holes. We predict a mean total flow of approx. 3.1 (l/min) into the six holes (two-holes) with a coefficient of variation near unity and a prediction error of about 4.6l/min. The actual measured inflow is close to 2l/min. © 1991.
- Schwartz, F. W., McGuire, R. K., Bullen, D. B., Cook, N., Coppersmith, K. J., Kemeny, J., Long, A., Pearson Jr., F. J., Sheridan, M., & Youngs, R. R. (1991). Demonstration of a decision analysis methodology for assessing the performance of the Yucca Mountain site in southern Nevada. Waste Management, 11(4), 287-306.More infoAbstract: This study develops a methodology for making decisions involving complex earth science systems and demonstrates its feasibility in relation to issues of radioactive waste storage at Yucca Mountain, Nevada. The basic approach involves a team of experts working together to identify and evaluate the key events, processes and parameters that are critical to the decision process. This basic information and calculational models required to represent various phenomena are integrated in a logic tree. The logic tree for the Yucca Mountain analysis is composed of 11 nodes that represent climatic, volcanic and tectonic events, various chemical and mass transport processes, and engineering factors that bear on the performance of the repository. These inputs are integrated into a software package to make calculations of expected releases of radioactivity as a function of time at the accessible environment. The demonstration application identified infiltration, container design and waste leaching rates, and various mass transport parameters as key factors that critically affect releases. At this stage, the most important outcome of the modeling effort is the demonstration that this approach to decision analysis of a radioactive waste repository is feasible with current knowledge and technology. Further, it shows that rational and defensible decisions can be made regarding the acceptability of a site even in the face of recognized uncertainties.
- Kemeny, J. M., & Tang, F. F. (1990). Numerical damage model for rock based on microcrack growth, interaction, and coalescence. American Society of Mechanical Engineers, Applied Mechanics Division, AMD, 109, 103-116.More infoAbstract: Rock deformation and failure in brittle rocks subjected to compressive stresses occurs by the progressive damage of the material, as cracks initiate and grow on the small scale, and coalesce to form large-scale fractures and faults. Micromechanical models based on fracture mechanics theory have been developed by many researchers for the progressive damage due to crack growth, interaction, and coalescence. In this paper it is shown how these micromechanical models can be used to predict nonlinear rock behaviour such as strain hardening and softening, dilatation, σ2 sensitivity, rate dependence, and creep. Also, these micromechanical models have been implemented into a two-dimensional finite element model. In each of the elements, the model considers the growth and interaction of microcracks, and under the appropriate circumstances, the coalescence of microcracks into large-scale splitting or shear fractures. Stress-induced anisotropy due to preferential growth of the microcracks in each of the elements is considered. The damage model has been used to simulate the progressive breakout that occurs around boreholes subjected to compressive stresses. The breakout initiates at the boundary of the hole and progresses inward, finally resulting in a stable breakout shape. The results of this analysis are in agreement with both experimental and numerical results.
- Zheng, Z., Kemeny, J., & Cook, N. G. (1989). Analysis of borehole breakouts. Journal of Geophysical Research, 94(B6), 7171-7182.More infoAbstract: Breakouts are valuable indicators of the direction of the minimum compressive stress orthogonal to the axis of the borehole. Their shapes may provide information about the magnitudes of both the maximum and minimum stresses relative to the strength of the rock. Borehole breakouts also may be impediments to drilling and to in situ measurement techniques, such as hydraulic fracturing. Observations and analyses of borehole breakouts raise three important questions. First, how does the shape of the borehole breakout evolve? Second, why are breakout shapes stable despite the very high compressive stress concentrations that they produce? Third, how is the shape of the breakout related to the magnitudes of the stresses in the rock? The stresses outside the stable breakout are found to be everywhere less than the limiting values of shear strength given by a Mohr-Coulomb criterion. In the regions of great stress concentrations at the ends of a breakout cross section, which have a pointed shape, the state of stress approaches that of equal biaxial compression in plane strain, as it does ahead of a mathematical crack or notch. The fact that the stresses around a breakout are less than the relevant strength establishes both the stability of the final breakout cross section and the appropriateness of an elastic analysis of the stresses. According to this model, the cross-sectional shapes of stable breakouts are not related uniquely to the state of stress and the strength of the rock. -from Authors
- Ewy, R. T., Kemeny, J. M., Zheng, Z., & Cook, N. G. (1987). Generation and analysis of stable excavation shapes under high rock stresses.. Proc. 6th congress International Society for Rock Mechanics, Montreal, 1987. Vol. 2, 875-881.More infoAbstract: Failure criteria based on micromechanical models of splitting failure and shear failure are implemented in boundary element programs to analyze the stability of various two-dimensional excavation shapes under high stress. A technique for modelling the failure processes of progressive spalling, shear, and tensile failure is developed and is used to simulate the formation of stable shapes through progressive failure. The shapes resulting from initially circular openings are strikingly similar to those recognized widely as well-bore breakouts. All the shapes studied lead to the formation of pointed breakout regions, and these final shapes are stable with respect to splitting, shear, and tensile failure. The size of the failed region is smaller for the case of gradually increasing field stress around a pre-existing opening than for an opening made instantaneously in rock with pre-existing stress.-Authors
- Kemeny, J., & Cook, N. G. (1986). Effective moduli, non-linear deformation and strength of a cracked elastic solid. International Journal of Rock Mechanics and Mining Sciences and, 23(2), 107-118.More infoAbstract: Utilizing the principles of Linear Elastic Fracture Mechanics (LEFM), the effective elastic moduli, the stability, and the strength of a solid containing a random distribution of interacting cracks is calculated. In order to account for the effects of interacting cracks, the "external crack" model is introduced, as a high crack density complement to non-interacting crack models. The behaviour of rock may be seen as progressing from the non-interacting crack models to the external crack model as cracks extend, interact, and coalesce. In rock mechanics, it is more common to encounter boundary conditions other than pure load controlled, and therefore we utilize the Griffith locus, which can determine the onset of fracture and the manner in which fractures extend, under any combination of load-controlled and displacement-controlled boundary conditions. Stress intensity factors are also calculated for random distributions of interacting cracks under displacement-controlled boundary conditions. The external crack model is found to exhibit sub-critical strain softening behaviour, and this gives a mechanism, not found in the non-interacting crack models, for the ultimate failure of brittle rock. © 1986.
- Kemeny, J., & Cook, N. G. (1986). FRICTIONAL STABILITY OF HETEROGENEOUS SURFACES IN CONTACT.. Proceedings - Symposium on Rock Mechanics, 40-46.More infoAbstract: Utilizing the principles of elastic-brittle fracture mechanics, stress-displacement relationships are derived for an elastic solid containing a slip plane consisting of various configurations of collinear arrays of cracks. These models take into account the heterogeneous nature of slip planes, and are relevant to the behavior of rock containing faults, joints, bedding planes, and fractures. All models exhibit slip weakening behavior and show regimes of stable (aseismic) and unstable (seismic) deformation. For given configurations of cracks and applied boundary conditions, the results show the energy released through unstable crack growth.
- Kemeny, J., & Cook, N. G. (1985). FORMATION AND STABILITY OF STEEPLY DIPPING JOINT SETS.. Proceedings - Symposium on Rock Mechanics, 1, 471-478.More infoAbstract: In this paper we utilize the principles of linear elastic fracture mechanics (LEFM), and examine the formation and stability of a system of parallel cracks under a combination of bending and hydrostatic compression, as a possible mechanism for the formation of steeply dipping joint sets. In particular, we develop relationships between the length and spacing of joints, in response to changes in tectonic stresses and strains, and changes in rock fracture toughness. Our results indicate closer joint spacing in rocks with a lower fracture toughness, and wider joint spacing in joints formed at deeper depths. Both of these findings are supported by field observations. (Author abstract. )
- Kim, K., & Kemeny, J. M. (2011, Spring). Site Specific Blasting Model For Mine-to-Mill Optimization. In SME (Society for Mining, Metallurgy, and Exploration).
- Kim, K., & Kemeny, J. M. (2011, Spring). Site Specific Blasting Model Using Schmidt Tensile Strength and Image Analysis. In ISEE (International Society of Explosives Engineer).
- Kim, K., & Kemeny, J. M. (2009, Summer). Effects of Thermal Shock and Rapid Unloading on Mechanical Rock Properties. In the 43rd US Rock Mechanics Symposium (ARMA).
- Kim, K., & Kemeny, J. M. (2008, Summer). Effects of Thermal Loading on the Rock Properties. In the 42nd US Rock Mechanics Symposium (ARMA).