Trainee Projects
Zachary Wedding
A Laboratory and Numerical Investigation of the Strength of Irregularly Shaped Pillars
Underground mining operations utilize the room-and-pillar mining method that extracts the orebody and creates ‘rooms’ and leaves the remaining in-situ material as ‘pillars’ to support the overburden. Room-and-pillar mines are traditionally designed in square or rectangular-shaped pillars. This work presents laboratory experiments testing the compressive strengths of specimens modeled after square and parallelogram-shaped pillars and numerical models of square and -parallelogram-shaped pillar systems. The uniaxial compressive strength of the specimens’ shape and the observations of the extent of the specimen core post-failure were analyzed. There was insufficient evidence from the laboratory experiments to conclude that there is a difference in strength among the specimen shapes. The inconclusive evidence is a result of the high variance in strength between the specimens and this could be a result of improper preparation. However, there were observations in individual batches that suggested there is a difference in strength. It was concluded from the numerical modeling that the square pillars could bear a higher load than the parallelogram pillars.
Caroline Gerwig
Strain Energy Analysis Related To Strata Failure During Caving Operations
For stiff beams that can form over the gob of longwall panels, the potential seismic magnitude of the energy released upon strata caving is estimated. Analytical calculations are used to verify two-dimensional models of longwall roof beams to determine the strain energy and gravitational energy developed, that will then be released to surrounding mine workings. Models are developed using RS2 to model the stress, strain, and deflection along the bottom of the longwall roof beam to calculate gravitational and strain energies. The total energy is then converted to seismic magnitude. Strain energy was consistently less than gravitational energy, except for beams with heights below 15 m in height. Gravitational energy is shown to be the main driving factor in energy release, except for the beams with low heights. Analyses allow the determination of beam characteristics based on seismic data. The analysis is then refined using swelling factor to compare various beam drop heights. The models show an increase in seismic magnitude for higher drop heights. However, the actual data provided by Buchanan mine displays a decrease in seismic magnitude with increasing drop height, indicating that energy is dissipated into the broken gob material as drop height increases.
Kayla (Mayfield) Henderson
An Approach for Predicting Flow Characteristics at the Continuous Miner Face
As coal and rock are mined, dust is dispersed into the air. This dust, among other contaminants, poses a serious health and safety risk to mineworkers. Very fine dust known as respirable dust can infiltrate the deepest part of the lungs, and long-term exposure to these particles leads to a disease called coal worker’s pneumoconiosis (CWP). Occurrence of this disease declined steadily over the latter half of the 20th century; however, a recent study indicates that CWP has reemerged with an upward trend beginning at the turn of the century. To combat dust exposure, mine operators use a combination of water sprays and dust scrubbers in conjunction with face ventilation. Additionally, the University of Kentucky has developed a device that passively improves air infiltration to the coal face. Researchers use a variety of modeling techniques, including full-scale, reduced-scale, and computer modeling, to understand active-face flow phenomena. A one-twelfth scale model of an active continuous-miner face was constructed to examine airflow patterns under multiple conditions in a controlled environment. Fluid characteristics and boundary conditions have often been assumed in Computational Fluid Dynamics (CFD) models. Using particle-image-velocimetry (PIV), the flow patterns under various conditions can be measured. The results of these scale model experiments can be used to develop scaling laws, which help validate numerical modeling and design of more accurate physical models. This dissertation presents airflow measurements taken within a reduced-scale model at multiple depths of cut by a continuous miner (CM) while utilizing a machine-integrated scrubber (an active device), a passive wing regulator, and a combination of the two. For conditions where the scrubber is on, there are three power settings, 85%, 100%, and 115% of the curtain air quantity. The results of these experiments identify the relationship of the airflow during the cutting phase and help researchers narrow the number of simulations needed as new ventilation controls or schemes are developed. It also provides realistic baseline cases, which can be used for further comparisons.
Caitlin Strong
Application of a Novel Ventilation Simplification Algorithm
Ventilation network analysis is an integral part of maintaining a safe mine environment. Despite its important role, liberties are often taken with the representation of networks in ventilation network analysis software. In order to provide an alternative to heuristic methods used by ventilation engineers, a simplification algorithm has been developed. This algorithm is designed to work as a compliment to ventilation software. Comparisons of original ventilation networks and simplified networks show little to no change in fan operating point. The program utilizing this algorithm provides an alternative to reducing networks with a parallel factor. It can also be used in conjunction with parallel factor to achieve better results. The equivalent networks produced by the algorithm are also reversible. Demonstrations of this feature show its applicability in practical situations.
Nathaniel Schaefer
Predicting Fracture Extension around a Borehole Using the Numerical Displacement Discontinuity Method
The prediction of blast damage radius is integral in the optimization of mining safety and production. The damage radius can be related to blasting variables such as fragmentation size as well as overbreak in hard rock. Since post-blast environments are not conducive to assessing whether the predicted damage radius was correct, this research actively strives to determine the extension of fractures post-blast and compare it to the predicted value. The predictions are based on the use of current fundamental methods in conjunction with a novel methodology proposed in this research. The Displacement Discontinuity Method (DDM) is used, where only the crack (fracture) itself is discretized, saving computational time and increasing solution efficiency. Two small-scale experiments are presented that investigated the damage radius of a borehole loaded with an appropriate explosive and calibrated the explosive use in the large-scale test. One six-foot cube of high-strength concrete was manufactured as an analog for in-situ rock. A small-diameter hole (7/8”) was drilled through the center, loaded, and shot. Instrumentation was utilized to capture the damage radius produced, and this information was used as feedback into the DDM program to model the blast. The DDM model provided accurate results to assess the extension of the cracks for a single-crack condition, while the multiple-fracture two-crack models proved more conservative when assessing the damage radius. The DDM damage envelope developed from randomization of fracture angle using the two-fracture models provides results closer to that of the single-crack model.
Sibley Miller
Concepts for the Development of Shuttle Car Autonomous Docking with Continuous Miner Using 3-D Depth Camera
In recent years, a great deal of work has been conducted in automating mining equipment with the goals of increasing worker health and safety and increasing mine productivity. Automating vehicles such as load-haul-dumps been successful even in underground environments where the use of global positioning systems are unavailable. This thesis addresses automating the operation of a shuttle car, specifically focusing on positioning the shuttle car under the continuous miner coal-discharge conveyor during cutting and loading operations. This task requires recognition of the target and precise control of the tramming operation because a specific orientation and distance from the coal discharge conveyor is needed to avoid coal spillage. The proposed approach uses a stereo depth camera mounted on a small-scale mockup of a shuttle car. Machine learning algorithms are applied to the camera output to identify the continuous miner coal-discharge conveyor and segment the scene into various regions such as roof, ribs, and personnel. This information is used to plan the shuttle car path to the continuous miner coal-discharge conveyor. These methods are currently applied on 1/6th scale continuous miner and shuttle car in an appropriately scaled mock mine.
Austin Gaunce
Predictive Modeling of DC Arc Flash in 125 Volt System
Arc flash is one of the two primary hazards encountered by workers near electrical equipment. Most applications where arc flash may be encountered are alternating current (AC) electrical systems. However, direct current (DC) electrical systems are becoming increasingly prevalent with industries implementing more renewable energy sources and energy storage devices. Little research has been performed with respect to arc flash hazards posed by DC electrical systems, particularly energy storage devices. Furthermore, current standards for performing arc flash calculations do not provide sufficient guidance when working in DC applications. IEEE 1584-2002 does not provide recommendations for DC electrical systems. NFPA 70E provides recommendations based on conservative theoretical models, which may result in excessive personal protective equipment (PPE). Arc flash calculations seek to quantify incident energy, which quantifies the amount of thermal energy that a worker may be exposed to at some working distance. This thesis assesses arc flash hazards within a substation backup battery system. In addition, empirical data collected via a series of tests utilizing retired station batteries is presented. Lastly, a predictive model for determining incident energy is proposed, based on collected data.
John Meuth
Proof of Concept for the Development of a Ground Vibration Sensor System for Future Research in Blasting
Ground vibrations from blasting are one of the leading limitations to mining (underground and surface). There is a need for a low-cost scalable vibration monitoring system to conduct large scale ground vibration projects in the mining industry. Studies conducted on ground vibrations use any number of different sensors to obtain their data, the different sensor capabilities and methods for data processing lead to uncertainties in the research and regulations set for ground vibrations. Commercial Systems do not allow researchers to obtain raw output data, and the data processing procedures are not provided or disclosed for these systems. In order to study ground vibrations and their impact on structures, the University of Kentucky Explosives Research Team is developing a system to obtain raw ground vibration data for their research projects going forward. This study investigates the feasibility of the initial vibration system assembled in conjunction with a significant ground vibrations study happening at a surface coal mine. The assembled system, along with two other systems, were used to study three blast events at structures near the surface coal mine. The two acquired systems were used for data comparison and validation against the assembled system in this document. Additionally, a comparative analysis was performed on the vibration frequency content obtained from the three sensors and a recommendation was made for the continued use of the assembled sensor system in ground vibrations research.
Click to watch: Slow motion video of methane ignition while testing blast suppression methods
Robert B. McCray
Utilization of a Small Unmanned Aircraft System for Direct Sampling of Nitrogen Oxides Produced by Full-Scale Surface Mine Blasting
Emerging health concern for gaseous nitrogen oxides (NOx) emitted during surface mine blasting has prompted mining authorities in the United States to pursue new regulations. NOx is comprised of various binary compounds of nitrogen and oxygen. Nitric oxide (NO) and nitrogen dioxide (NO2) are the most prominent. Modern explosive formulations are not designed to produce NOx during properly-sustained detonations, and researchers have identified several causes through laboratory experiments; however, direct sampling of NOx following full-scale surface mine blasting has not been accomplished. The purpose of this thesis was to demonstrate a safe, innovative method of directly quantifying NOx concentrations in a full-scale surface mining environment. A small unmanned aircraft system was used with a continuous gas monitor to sample concentrated fumes. Three flights were completed – two in the Powder River Basin. Results from a moderate NOx emission showed peak NO and NO2 concentrations of 257 ppm and 67.2 ppm, respectively. The estimated NO2 presence following a severe NOx emission was 137.3 ppm. Dispersion of the gases occurred over short distances, and novel geometric models were developed to describe emission characteristics. Overall, the direct sampling method was successful, and the data collected are new to the body of scientific knowledge.
Elizabeth Maher
Investigation of Elemental Cadmium Sources in Eastern Kentucky
Utilizing data collected by the University of Kentucky Lung Cancer Research Initiative (LCRI), this study investigated potential mining-related sources for the elevated levels of cadmium in Harlan and Letcher counties. Statistical analyses for this study were conducted utilizing SAS. A number of linear regression models and logarithmic models were used to evaluate the significance of the data. The linear regression models consisted of both simple and multivariate types, with the simple models seeking to establish significance between the potential sources and urine cadmium levels and the multivariate models seeking both to identify any statistically significant linear relationships between source types as well as establish a relationship between the potential source and the urine cadmium levels. The analysis began by investigating which ingestion method caused the increased levels of cadmium exposure, including ingestion through water sources and inhalation of dust. The second step was to analyze a number of sources of dust, particularly those related to mining practices in the area. These included the proximity to the Extended Haul Road System, secondary haul roads, rail roads, and processing plants. Of the variables in the analysis, only the proximity to processing plants showed statistical significance.
Joshua Hescock
Calculation of the Edge Effect for High Extraction Coal Panels
The Surface Deformation Prediction System (SDPS) program has been developed as an engineering tool for the prediction of subsidence deformation indices through the implementation of an influence function. SDPS provides reliable predictions of mining induced surface displacements, strains, and tilt for varying surface topography. One of the key aspects in obtaining reliable ground deformation prediction is the determination of the edge effect offset. The value assigned to the edge effect corresponds to a virtual offsetting of boundary lines delineating the extracted panel to allow for roof cantilevering over the mined out area. The objective of this thesis is to describe the methods implemented in updating the edge effect offset algorithm within SDPS. Using known geometric equations, the newly developed algorithm provides a more robust calculation of the offset boundary line of the extracted panel for simplistic and complex mining geometries. Assuming that an extracted panel is represented by a closed polyline, the new edge offset algorithm calculates a polyline offset into the extracted panel by the user defined edge effect offset distance. Surface deformations are then calculated using this adjusted panel geometry. The MATLAB® program was utilized for development and testing of the new edge effect offset feature.
CARERC Mining Health and Safety Core Employment/Internships
Elizabeth (Maher) Gaunce (2018) has recently taken a new position as Health and Safety Coordinator for Aldea’s United States offices.
John Meuth (2020) is currently employed as an Explosives Safety Engineer, A.P.T. Research, Inc.
Caitlin Strong (2021) has accepted a position as General Engineer, Mine Safety and Health Administration in the Directorate of Technical Support, Ventilation Division.
Caroline Gerwig (2022) has accepted a position as General Engineer, Mine Safety and Health Administration in the Directorate of Technical Support, Roof Control Division.
Sky Rose (M.S. candidate) currently has an internship with Nyrstar Middle Tennessee Mines (underground zinc).