A thesis submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, in fulfilrMnt of the requirements for the degreel of Doctor of Philosophy. / This thesis has investigated ways of exerting control over coal breaking during blasting. Its ultimate objective has been to optimise the use of explosive energy in blasting so as to ensure reduced production of coal fines in the comminution process. The investigations reported were conducted on laboratory models at a scale of a controllable energy to enable the development of a theoretical background for the thesis, However, the bulk of the work was undertaken insitu in surface and underground coal operations. The research was conducted in three phases. The first phase dealt with the approach to modelling the primary crushing mechanism which generates the coal fines during the blasting operation. A laboratory apparatus to simulate blast-generated dynamic loading was devised. Dynamic coal crushing test conducted on a set of over 150 samples of coal showed an exponential relationship; between the comminution energy and the subsequent coal damage. A comminution index (Com ) characterising the ability of coal to generate fines was derived. The second phase of the research concerned the field investigations. This had the following double aim: validating the hypothesis of the influence of the dynamic loading of the shock waves and that of the inherent discontinuities imbedded in coal on fines generation; and quantifying the problem of fines in the blasting techniques currently used in the local mining industry. Three sites were used, namely Kleinkopje of AMCOAL, Greenside of Goldfields and ATC, Tavistock of JCI. The investigations undertaken at Kleinkopje (surface mining operation) involved the determination of discontinuities by logging inherent fractures appearing on 75 diamond drilled cores of coal and the monitoring of 76 blasts conducted on the sites sampled for discontinuities. These investigations indicated a good correlation between the fines observed in blasted piles and the fracture frequency of the pre" existing fractures per metre of coal. The work undertaken in underground collieries (Greenside and Tavistock) demonstrated the enormity of the fines' problem in the local mining operations. Approximately a third of the coal broken underground was observed, in 30 blasts sampled and analysed, to fall into the category of fragments of under 6 mm termed 'coal fines', Which generate low income. The third phase of the research dealt with the optimisation of coal breaking during blasting. A series of 100 trial blasts was undertaken with the aim of searching for a blasting technique that enables the generation of fewer coal fines. A number of options were investigated. Trial blasts carried out were evaluated and their results are discussed in this thesis. The results of the fieldwork undertaken confirmed that fines generation is site speolflc, However, the decoupling technique used with high VOD explosive products may be successfully employed to reduced coal fines generation in strong coals (few inherent fractures). / Andrew Chakane 2018

A research report submitted in partial fulfilment of the requirements for the degree of Master of Science in Engineering, to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, 2019 / A dynamic simulation study is a critical deliverable of a mine project feasibility study. Mining houses rely on simulation to confirm that complex, integrated systems can achieve design capacity before investment decisions are made. Dynamic simulations are powerful tools, but only if they are developed using the right methodology, and with information that has been verified. The importance of work in the field of mine dynamic simulation validation was made clear during the early stages of this research report when it was identified that there is limited information available on the subject. Work conducted in the realm of validation can make an invaluable contribution to the success of future projects undertaken around the world. The last few years have been difficult for employees of some mining companies because of looming job cuts due to high production costs, high overheads, and decreasing product demand. For many mining companies, it was a case of survival which gave rise to the development of new strategies and innovative thinking. Coal Mine A Life of Mine (LOM) extension project is a prime example of innovative thinking. In this case, the project was approved for implementation when export coal prices were on the low end of the price cycle. The dynamic simulation of the full materials handling value chain conducted during the project was of utmost importance, and provided assurance to the project review team that annual production targets can be achieved. The simulation development methodology was based on a unique approach that reduced time spent on the simulation through the integration of different, independent models that represented sub-systems in the materials handling value chain. There was, therefore, a strong need to validate the simulation, which could lead to the adoption of this approach on future projects. In this research report, the LOM extension project scope and the mining activities conducted by Coal Mine A are explained, and a brief, but interesting history of Modelling and Simulation (M&S) is provided. The subject of M&S is vast and has evolved into its own separate discipline. M&S is an invaluable tool, and the importance of verification, validation and credibility is elaborated on. The development of the simulation and the inputs and outputs of the simulation are discussed before the validation effort. The work conducted on the validation aimed to confirm the accuracy of the simulation unequivocally. Although the production target was not achieved as predicted by the dynamic simulation during the period of validation, there was an indication that the materials handling value chain could perform as predicted as each of the individual sub-systems had achieved the design capacity. Problem areas were identified which could be attributed to the poor performance, and if these areas are addressed, the system could perform as predicted by the simulation. This confirms that dynamic simulation can add value to predictions about mining system performance such that informed decisions can be made. / TL (2020)

No description available.

In recent times Jamaica has experienced an increase in infrastructure and mineral resource (bauxite) developments. As a result, quarrying activities have also increased to supply the needed construction material. Blasting has been the main technique for loosening insitu rock before transporting to construction site. Consequently there is a growing concern of the effects of blasting activities on the environment. These effects are normally nuisances to the neighbouring residence as they come in the form of: dust, toxic gases, noise, fly rocks and ground vibration. Of the set of nuisances the one that is of most concern is ground vibrations which can cause damage to structures. In most cases worldwide, after blasting activities there are the usual complaints about damage to residence, which is also a focus of the thesis. There have been researches on the subject of ground vibrations to help refute some of these complaints. The works of Lewis Oriard and Charles Dowding are the foundation on which standards and regulations are built as guides to assist blasters in the prevention of creating unnecessary nuisances. Most countries have developed their own regulations with respect to blasting and parameters are set according to the geological conditions. This is of importance as the rock structures determine the transmission of the peak particle velocity. However, most countries in the west adopt standards similar to ones put forward by the United States Bureau of Mines or The Office of Surface Mining. It is my opinion that a whole scale adoption should not take place, as the criteria used may not be suitable for other countries’ geological conditions. For this thesis the aim was to identify a vibration level that will not cause damage to structures close to a quarry. Based on the literature review it was revealed that there are a number of parameters that needed to be considered. These ranges: construction material, age of structures, distance from structures, geology of the location, type and quantities of explosives and the blast design. There was also the review of standards to building threshold with respect to the level of ground vibration. The case study with its main focus on vibration levels at structures in close proximity to the Bengal quarry revealed that a tolerable level can be determined which will not result in any form of damage to the structures. However, having established a PPV limit using the USBM and OSM standards that appears reasonable there is the need for criteria similar to those of the USBM and OSM using blasting and geological conditions in Jamaica. Due to the time constraints (20 wks) it is recommended that future research is carried out in this area especially in relation to assessing the performances of the structures. / <p>Validerat; 20101217 (root)</p>

The complex and non-linear nature of blast fracturing have restricted common blast design mostly to empirical approaches. The code developed for this investigation avoids both empiricism and large memory requirement in order to simulate the pattern of interacting radial fractures from an array of shotholes, at various burdens and spacings, and in simultaneous and delayed modes. The resultant pattern is analyzed and a fragment size distribution calculated. The rules governing the distribution of radial cracks and the way in which they interact are based on model scale experiments conducted by various investigators. Calculated fragment size- distribution agree with data from the field. Powder factor dependence of fragmentation results is also well described by the model. The effect of discontinuities on rock fragmentation by blasting is also incorporated into the model. Discontinuities which are open and filled with air or soil-like material affect destructively the transmission of strain waves and propagation of cracks in the rock mass. These discontinuities can be incorporated into the simulation by inserting cracks to represent them. The cracks representing discontinuities will then terminate the cracks produced by blasting where they intersect. On the other hand, tight joints without filling material or with filling material but with a high bond strength and acoustic impedance close to that of the medium do not affect in a negative way the transmission of shock waves in the rock mass. A mathematical model was developed to treat these discontinuities which was based on principles from Linear Elastic Fracture Mechanics theory and Kuznetsov's equation which relates the mean fragment size obtained to the blast energy, hole size and rock characteristics. / Master of Science

In order to carry out blasting operation with optimal results the influence of rock properties on fragmentation process and the quality of the aggregates should be studied with the proper thoroughness. Recent investigations of granitoid rocks infer that the resistance of rock to abrasion improves with increasing amount of quartz and feldspar. The increasing amount of mica results in the opposite effect. The resistance of granite to the impact effects improves with the increasing amount of mica and decreasing content of feldspar. Another finding states that flakiness positively influenced by the frequency of micro cracks, on the other hand, the increasing micro cracks frequency negatively affects on the rock strength. For practical reasons it can be concluded that safety blasting decreases the propagation of micro cracks, hence improves the quality of the rock material. To obtain desired quality of aggregates the blasting parameters and the types of explosives should be properly considered. This thesis work presents the review of the modern literature concerning the blasting operations and aggregates production. It combines both theoretical and practical parts. It describes the petrographical and mechanical properties of the granitoid rocks, different laboratory tests for mechanical properties and results, types and features of explosives, the parameters that intervene in blast designing and influence of blasting on rock aggregates. The rock mass properties greatly affect the blasting results and the quality of aggregates. However, it’s hard to extend this conclusion on full-scale blasting operations in mines and quarries, because the nature and properties of the rock mass change significantly over the short distances. / <p>Validerat; 20101217 (root)</p>

This thesis recounts the study of contour blasting practices in the Appalachia coal region. Contour blasting practices vary widely and problems are often encountered. Several different sites were visited and contour blasting practices at each were studied. Based on the information gathered, a comprehensive plan was developed for blasting operations to follow and then was tested and compared to an example of blasting practices without use of the plan. The blasting practices were compared by examining monthly production rates as well as a time study to measure the efficiency a contour blast could be loaded and hauled away and a cost per cubic yard of material determined. The plan was found to be successful in keeping safety while increasing profitability. However, the plan will need to be backed and understood by management in order to achieve the same success.

This study was aimed at understanding the environmental performance of two abrasives, coal slag and garnet which are commonly used by shipyards and many other industries in surface preparation of metallic surfaces. Environmental performance evaluated in this study included, (1) productivity (ft2/hr), (2) consumption and or used-abrasive generation rate (ton/2000 ft2; lb/ ft2), (3) particulate emission factors (mg/ft2; mg/lb; lb/lb; lb/kg; lb/ton). In order to achieve the study objectives, an emission test facility was built and necessary equipment and materials were procured. Blasting was performed on rusted steel panels inside the test facility and emissions were measured using EPA Source Test Method to quantify particulate emissions. By measuring the area cleaned, blasting time, and the abrasive consumed, environmental performance of coal slag and garnet was evaluated. Simple mathematical models were developed to predict performance based on feed rate and blast pressure. Garnet was observed to be more productive, less consuming, and more environmentally-friendly compared to coal slag. These study findings will valuable in reducing costs, improving productivity, and protecting the environment.

This thesis presents the results of open stope stability and dilution research which focused on evaluating and quantifying stress, undercutting, blasting and exposure time and their effect on open stope stability and dilution. Open stope mining is the most common method of underground mining in Canada. Unplanned stope dilution is a major cost factor for many mining operations. Significant advances in empirical stability and dilution design methods have improved our ability to predict probable dilution from open stoping operations. However, some of the factors that influence hanging wall dilution are either ignored or assessed in purely subjective terms in existing designs. This thesis attempts to quantify these factors, from a geomechanics perspective, to assist in predicting and minimizing dilution. A comprehensive database was established for this study based on two summers of field work. Site geomechanics rock mass mapping and classification were conducted and case histories were collected from Cavity Monitoring System (CMS) surveyed stopes from Hudson Bay Mining and Smelting Co. Ltd. (HBMS) operations. The stope hanging wall (HW) zone of stress relaxation was quantified based on extensive 2D and 3D numerical modelling. Stress relaxation was linked to the stope geometry and the degree of adjacent mining activity. The influence of undercutting on stope HW stability and dilution was analysed using the case histories collected from HBMS mines. An undercutting factor (UF) was developed to account for the undercutting influence on stope HW dilution. Numerical simulations were conducted to provide a theoretical basis for the undercutting factor. A relationship was observed between the degree of undercutting, expressed by the UF term and the measured dilution. Many factors can significantly and simultaneously affect a blast performance, which may result in blast damage to stope walls. Major blasting factors which influence stope HW stability were identified. The influence of blasting on stope HW stability and dilution was evaluated based on the established database. The HBMS database, Bieniawskis stand-up time graph, as well as Geco mine case histories were used to evaluate the influence of exposure time on stope stability and dilution. Relating increased mining time to increased dilution allows the mining engineer to equate mining delays to dilution costs. Each of the factors assessed in this study was studied independently to assess its influence on stope dilution, based on the HBMS database. The factors influencing dilution often work together, so a multiple parameter regression model was used to analyze the available parameters in the HBMS database. The findings of this research greatly improve an engineers ability to understand and to predict the influence of mining activities and stoping plans on hanging wall dilution.

This thesis presents the results of open stope stability and dilution research which focused on evaluating and quantifying stress, undercutting, blasting and exposure time and their effect on open stope stability and dilution. Open stope mining is the most common method of underground mining in Canada. Unplanned stope dilution is a major cost factor for many mining operations. Significant advances in empirical stability and dilution design methods have improved our ability to predict probable dilution from open stoping operations. However, some of the factors that influence hanging wall dilution are either ignored or assessed in purely subjective terms in existing designs. This thesis attempts to quantify these factors, from a geomechanics perspective, to assist in predicting and minimizing dilution. A comprehensive database was established for this study based on two summers of field work. Site geomechanics rock mass mapping and classification were conducted and case histories were collected from Cavity Monitoring System (CMS) surveyed stopes from Hudson Bay Mining and Smelting Co. Ltd. (HBMS) operations. The stope hanging wall (HW) zone of stress relaxation was quantified based on extensive 2D and 3D numerical modelling. Stress relaxation was linked to the stope geometry and the degree of adjacent mining activity. The influence of undercutting on stope HW stability and dilution was analysed using the case histories collected from HBMS mines. An undercutting factor (UF) was developed to account for the undercutting influence on stope HW dilution. Numerical simulations were conducted to provide a theoretical basis for the undercutting factor. A relationship was observed between the degree of undercutting, expressed by the UF term and the measured dilution. Many factors can significantly and simultaneously affect a blast performance, which may result in blast damage to stope walls. Major blasting factors which influence stope HW stability were identified. The influence of blasting on stope HW stability and dilution was evaluated based on the established database. The HBMS database, Bieniawskis stand-up time graph, as well as Geco mine case histories were used to evaluate the influence of exposure time on stope stability and dilution. Relating increased mining time to increased dilution allows the mining engineer to equate mining delays to dilution costs. Each of the factors assessed in this study was studied independently to assess its influence on stope dilution, based on the HBMS database. The factors influencing dilution often work together, so a multiple parameter regression model was used to analyze the available parameters in the HBMS database. The findings of this research greatly improve an engineers ability to understand and to predict the influence of mining activities and stoping plans on hanging wall dilution.