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By John R. Marks

Introduction An engineer is a builder and a problem solver. He uses knowledge of the properties of matter and energy to furnish the needs of society. Engineers form the bridge between scientific researchers and the general public, most of whom are technologically illiterate. Mining, metallurgical, and petroleum engineers extract minerals from the ground and process them into usable forms. Then, other engineers further process them into society's needs. Minerals engineers deal with more uncertainty than other engineers. Each ore deposit has its own personality and each ore is metallurgically unique. Minerals engineers, therefore, must be flexible, often applying larger safety factors and contingencies than other engineers, and frequently functioning as a jack of all trades. A minerals engineer can work in coal, oil, oil shale, base metals, ferrous metals, precious metals, industrial minerals, strategic minerals, or in exploration. Other mining jobs include banking and financing, education and research, marketing and sales, and government. As a minerals engineer, you may be among the first to work on the ocean floor or the moon. College Preparation A difference between college and industry is the type of problems to be solved. A typical college problem has an exact answer derived from given information. An industry problem is more apt to have a solution chosen from a number of alternatives. Information required for the solution is not given. It must be measured, calculated, looked-up, estimated, or otherwise derived. Solutions involve trade-offs, economics, and human factors, as well as application of physical laws and theory. When a college problem is answered, you move on to the next one. In industry, however, the headaches may just be starting with the implementation of the solution. Students often complain that they see little use for the theory they are learning. This is valid. A good professor will link theory and practice. Another difference between college and industry is the price of failure. In college, you can make a half-hearted effort in an assignment and take your C or D. On the job, however, poor engineering results in potentially effective projects being rejected and unsound projects being undertaken. Poor performance results in cost overruns, schedule holdups, oversights, disgruntled employees, irate bosses, unsafe structures, and unreliable systems. The costs are time, money, and possibly lives. The student pays the university for his work - not the other way around. So the rewards for good schoolwork often seem nebulous. But education must be viewed as an investment. Working for good grades will help you think better, learn more, receive better job offers, and perform more effectively on the job. There is no substitute for hard work. Avoid taking the easiest electives. If you desire a more liberal education or dislike rigorous physical sciences, mathematics, or engineering courses, change majors. Remember, you are training to be an engineer, not a computer programmer or market analyst. At least one summer of industry employment is necessary for minerals engineering students. The sooner you gain actual experience, the sooner you will know whether to change majors. Most large companies hire students during summer. It is best to send out applications around Christmas break. First and second year students usually work as laborers. Upper-classmen may work as engineering technicians. Students must sometimes choose between returning to a company at a higher position or trying a different company at a lower position, for more varied experience. Both alternatives have advantages. Do your best on these summer jobs. The company is watching. If you do well, the chances are good you will get a job offer when you graduate. Good references are important when you begin job hunting. Interviewing occurs near the end of your school career. The standard procedure is to send your resume with a cover letter to each company you are interested in. The resume for a graduating engineer with little experience need not exceed one page. The cover letter must be written for the individual company.

Jan 2, 1985

By J. K. Grunig

A process consisting of leach, continuous countercurrent decantation, resin-in-column ion exchange, evaporative crystallization of beryllium sulfate, and decomposition of the sulfate was developed for Spor Mountain, Utah, ores. The process is metallurgically sound, has a minimum of process steps, and is applicable to a wide variety of beryllium ores. The most novel aspect of the process is a resin system of ion exchange which is highly selective for beryllium and which rejects substantially all impurities except for minor amounts of aluminum, magnesium, fluorine, and sulfate in addition to beryllium. The oxide from sulfate decomposition meets specifications of potential users.

Jan 1, 1982

By Gordon M. Pugh, David G. Rasmussen

INTRODUCTION Sublevel long-hole stoping is a large tonnage stoping method that may be used when there is a fairly com¬petent straight vein and the walls will stand with little support. It is a method that lends itself to a high degree of mechanization. Two variations of the method are illustrated in Figs. 1 and 2. Fig. 1 illustrates development typical for a 3-m (10-ft) wide vein. Initial development is by a lower haulageway, which may be either track or trackless. A two-compartment raise is driven in the footwall of the vein. At about 12 m (40 ft) above the main head¬ing, a footwall scram is driven and pockets through the vein are cut on 7.6-m (25-ft) centers. Each of the sub¬level blocks selected in this example is 45.7 m (150 ft) long by 12 m (40 ft) high. Stoping starts at the slot raises at stope endlines and retreats to the timbered raise. This retreat sequence starts on the lowest sublevel and the opening cut is blasted into the slot raise. This retreating system is used in order to provide a good safe back over the miners working in any given sublevel. A crawler-mounted down-the-hole or conventional pneumatic drill puts the holes down from one sublevel to the next on any desired drill pattern. Gravity flow brings the broken ore down to the scram level. The illustration shows a large slusher mounted at the timbered raise and slushing from the pockets back to the raise chute. Development of the ore block in Fig. 2 is typical for a 5.5-m (18-ft) wide vein. Initial development is by a trackless heading driven in the footwall of the vein. Pockets are then put into and through the vein on 7.6-m (25-ft) centers. For ease in using trackless rubber tired mucking equipment, these pockets are crosscut to the vein at approximately 1.04 rad (60°) rather than per¬pendicular. A two-compartment timbered raise is driven down from one level to the next. Endline slot raises are again put through from level to level. Each of the sub¬level blocks selected in this example is 40-m (130 ft) long by 33.5 m (110 ft) high. Stoping starts at the slot raises and retreats back to the timbered raise. Long holes are drilled from one sub¬level down to the next by starting between the lowest pair of sublevels and then working up the ore block. Mucking out of the pocket drawpoints is accomplished by rubber-tired load-haul-dump (LHD) units which then dump into a centrally located orepass.

Jan 1, 1982

By Guillermo V. Borquez

The economics of open pit mine design are dictated by three basic elements: cut-off grade, stripping ratio and slope angle. Although these elements are functions of a number of independent parameters, they are interrelated through their influence on the overall economics. The optimum slope angle is the most uncertain element to determine, because rock mass properties are difficult to obtain. However, for preliminary estimation, the slope angle can be determined from the relationship between the probability of failure and the safety factor. The economics of the slope selected will depend on a profit versus risk judgment. In this paper, the author will present an actual case of application of this postulate.

Jan 1, 1977

By John O. Marsden

"This article is an attempt to capture a presentation given at the 2016 SME Mineral & Metallurgical Processing Division (MPD) Luncheon held on Feb. 24, 2016, in Phoenix, AZ. It was presented as a tongue-in-cheek, lighthearted view of several of the issues facing our industry, while identifying some of the challenges and opportunities available to new engineers entering the industry today.Disclaimer• What you are about to read includes personal preferences, biases and occasionally arbitrary opinions.• Some readers may have dissimilar opinions on the contents and/or the rank order of the lists.There are eight top ten lists offered in this article: (1) Industry realities (2) Things a metallurgical or mineral process engineering graduate should do (3) Books every metallurgist should have on their shelf (4) Things I wish I had known (5) Legends of metallurgy (posthumous, with highlights) (6) Things we’ve forgotten (7) Mineral processing innovations of the past 20 years and, finally, (8) The future? For some items, additional context or clarification is provided after the item, while for other items no further explanation is warranted and none is offered. Top 10 industry realities1. Metal price cycles.2. Bigger is better (except when it isn’t).3. Ore grades declining across the board of metals/commodities.4. Ores becoming more complex.5. Three-fold increase in capital costs between 2004 and 2015.6. Three-fold increase in operating costs between 2004 and 2015.7. Less capital availability/challenging financial markets.8. Environmental constraints increasing.9. Socio-political constraints increasing.10. The mine manager is always impossible to work with.As Table 1 shows, there was more than a three-fold increase in gold operating costs between 2004 and 2014. The increases for copper, iron ore and other commodities were similar."

Aug 1, 2016

By R. L. Amelunxen

P. T. Freeport Indonesia (PI) in conjunction with Crescent Technology Inc. has developed a method to predict the metallurgical performance of ores blends based on the behavior of their component ores. The question addressed in this paper is whether ores treated individually could be extrapolated to predict the behavior of a blend of ores. The work further investigates the use of modal analysis to establish individual mineral flotation kinetics in each of the ore zones. This information would lead to the prediction of grade-recovery curves of ores made up of those minerals. Nine samples of ore, representing various zones of FI's Grasberg ore deposit were tested metallurgically and examined microscopically. The same testwork was performed on blends depicting the 1994 mill quarterly feed. Flotation kinetics of the individual ores were then "mathematically" blended and compared to the results obtained from the quarterlies. The calculated kinetics of the actual blends of ore received by the mill were fed to the simulation program and compared to the actual mill performance.

Jan 1, 1995

By Robert E. Moore

Investigators have attempted to develop lime refractories on a scale for broad applications in the metal and ceramic industries for several decades. There was a flurry of activity in the early to mid-fifties but no commercial developments were forthcoming. The literature of that period yields little information on plant trials. A major factor suppressing past interest in lime has to have been the high success with the application of magnesic and dolomitic materials. These materials, usually tar-bonded or impregnated, have become the refractories success story of the past two decades, especially in BOF applications. It is safe to say that their development and application has essentially plateaued, and that work today is focussed on finding cheaper paths to produce MgO-based refractories. For example there are efforts underway to extract MgO from mineral magnesite and to combine natural dolomite with MgO1. Beginning in the late sixties, rather intensive research began on the development of CaO brick, especially in East and West Germany, in Poland, and other communist bloc satellites, 'and also in Italy and Spain. One speculates that the motivation was a regional shortage of good magnesia and dolomitic material. Of course, There has always existed the prospect of cost savings should it be possible to use raw limestone as the starting material. Quite a large literature has appeared treating of these developments which in the early seventies had already reached full plant scale trials and uses. Some of the directions followed in the research have led to novel methods of brick manufacture.

Jan 1, 1985

By R. H. Grau, C. D. Taylor, A. L. Martikainen

Utilization of belt air in underground coal mines has been discussed extensively during the last decade. The Final Report of the Technical Study Panel on the Utilization of Belt Air and the Composition and Fire Retardant Properties of Belt Materials in Underground Coal Mining formed by the Mine Improvement and New Emergency Response (MINER) Act of 2006 recommends research on leakage, use of booster fans, and escapeway safety. This paper discusses the role of ventilation modeling in evaluating primary escapeway pressurization in a three-entry development system to improve emergency escape in a coal mine using belt air. The intake entry of the National Institute for Occupational Safety and Health (NIOSH) Bruceton Experimental Mine was pressurized using a 1.1-m (42-in.) diameter, 37 kW (50 hp) fan. The work details air movement in the simulated three-entry system and the resulting leakage patterns. Three mine ventilation software packages were compared to analyze their performance in predicting the airflows and leakage conditions with different fan settings. NIOSH researchers found that the measurement results correlated well with the results of modeling.

Jan 1, 2010

By Vas P. Srinivasa

This paper examines the role of the heavy media separator in the mineral industry. Procedures used in selecting the separating vessel, developing the process flowsheet, and designing a heavy media circuit are discussed. For comparative purposes, the capital investment and operating costs of different types of operation are included.

Jan 1, 1981

By J. A. M. Cano

A brief introduction is made on the existence of sulphides in the top gas of the Midrex Shaft Furnace, giving consideration to the operation of the furnace and the liberation of sulphur as well as its consequential effects on the reduction process. The text shows a study of sulphur distribution in the pellet, emphasizing the importance of this distribution in relation to the liberation of sulphur during the reduction. A study was made to determine the sulphur compounds that exist in the pellets, showing ways of controlling the sulphur distribution and reducing its liberation?during the reduction.

Jan 1, 1989

By Lihong Zhou, DAVOOD BAHRAMI

A reliable and stable ventilation system is essential to the safe operation of underground mines. The stability of a mine ventilation system becomes extremely critical when responding to a fire incident, as an unstable ventilation system will pose a risk of airflow reversal. The reversed airflow could bring fire contaminants, such as toxic gases and smoke, unexpectedly to working areas. In the past few years, there has been a growing interest in the study of ventilation network stability using the concept of resistance sensitivity, which is described as an indicator of how the airflow in an airway is reacting to a resistance change of other airways. Several methods of calculating the resistance sensitivity in a mine ventilation network have been developed by researchers and scholars around the world. However, those proposed methods rely heavily on a vast number of mine ventilation simulations, which is time-consuming and computer-resource intensive, especially for a large-scale mine ventilation network. In this study, a derivative method calculating the resistance sensitivities with a single mine ventilation simulation is developed and implemented into the MFIRE mine fire simulation software. The results from the derivative method were verified against the results from a traditional method. The derivative method is proved to be reliable and accurate.

Dec 1, 2022

By S. Frimpong, E. Gbadam, W. Nyaaba, G. Somua-Gyimah

Recent studies towards dragline excavation efficiency have focused on incrementally achieving automation of the entire excavation cycle. Initial efforts resulted in the development of an automated dragline swing system, which optimizes the swing phase time. However, the system still requires human operation for collision avoidance. For full dragline autonomy, a machine vision system is needed for collision prevention and big rock handling during the ‘swinging’ and ‘digging’ phases of the excavation operation. Previous attempts in this area focused on collision avoidance vision models which estimated the location of the bucket in space in real-time. However, these previous models use image segmentation methods that are neither scalable nor multi-purpose. In this study, a scalable and multi-purpose vision model has been developed for draglines using Convolutional Neural Networks. This vision system averages 82.6% classification accuracy and 91% detection in collision avoidance. It also achieves an 87.32% detection rate in bucket pose estimation tasks. In addition, it averages 80.9% precision and 91.3% recall performance across terrain recognition and oversized rock detection tasks. With minimal modification, the proposed vision system can be adjusted for other automated excavators. Keywords: Surface mining, dragline bucket, deep learning, machine learning, oversized rock, convolutional neural network, machine vision, object detection, earthmoving equipment. INTRODUCTION Complete excavator automation is widely regarded as the next phase in efforts toward improving earthmoving efficiency. Earthmoving often involves complex, forceful interactions between an excavator and the ground. The nature of these interactions depends largely on the type, properties and physical characteristics of the earth material. This process is further complicated by the random occurrence of tree roots, boulders and other such obstructions. Therefore, the ability of a controller to detect changes in the operating conditions, adjust the digging strategy and respond in real-time is of utmost importance. Early studies into autonomous excavation identified some key performance criteria which included the following [1]: • The autonomous excavator must be able to work in any type of earth material. • Its excavation accuracy must be within 50mm. • It should be able to handle different surface and underground obstacles autonomously. • It should be able to operate at the speed of the average operator in any condition. • Its operation should be capable of safe integration with other site systems.

Jan 1, 2019

By David M. Lapham

In Pennsylvania, 310 sampled sites of clay and shale have been evaluated for: potential use, chiefly as structural clay products, refractories, and lightweight aggregate; lithology; physical properties tests; fired tests, both quick-fire and rotary kiln; major-element chemical analyses, and quantitative five-component X-ray mineralogy for quartz, mica, feldspar, kaolinite, and chlorite-vermiculite-montmoril-lonite. Approximately 80 percent of the samples are of some potential use. Of 220 shale samples, 84 were potential lightweight aggregate sources and 83 potential brick sources. Binary correlations of test data versus potential use indicate that certain empirically determined parameters may be critical. These are: lithology, particularly for medium to super-duty refractories and lightweight aggregate; kaol-finite content for refractories versus low-temperature fired product sources; quartz content illustrating that there is an apparently necessary minimum quantity for brick; quartz content, which is low in high grades of lightweight aggregate; mica content, which is low for refractories and possibly high for lightweight aggregate; total iron, which is low for refractories and shows a 40 percent minimum for lightweight aggregate; carbon dioxide, which is low for refractorfes, beneficial in lightweight aggregate, and probably restrictive for some tiles choroite yermicalite, which is low for refractoies and possibly beneficial in lightweight aggregate. In Pennsylvania, clay and shale materials constitute one of the state's major economic mineral resources. To date, the testing program indicates considerable development potential in brick, tile, and lightweight aggregate industries, and perhaps a future potential for aluminum from shales that exceed 20 percent A12Q3.

Jan 1, 1971

By N. Kuyucak

Uranium ores leached with sulphuric acid typically have poor dewatering properties. Applicability of controlled neutralization where gypsum precipitates as crystalline particles, improving dewatering properties of material was examined. Neutralized material was then dewatered using paste thickener to increase underflow density. The objectives are to maximize water recovery due to water scarcity and to produce suitable cemented paste fill material for optimizing underground ore recovery. Work was performed on acidic slurry samples collected after leaching but before the resin-in-pulp uranium recovery. Controlled neutralization greatly reduced volume of neutralization precipitates giving higher densities and improving the dewatering (filtration) properties. As a result it would be possible to increase the water recycled to the mill. Another benefit is that sulphate in the recycled water was reduced to saturation limit minimizing scaling of process equipment. Additional test work is needed; however, Unconfined Compressive Strength results imply that controlled neutralization increases the strength of paste fill and possibly offers opportunities towards a viable backfill option.

Jan 1, 2010

Australian underground coal mines predominately use the longwall method for coal extraction. In longwall mining at least two parallel roadways known as gateroads are mined to delineate the sides of the longwall block, a longwall installation face is then driven connecting the gateroads to enable the longwall mining equipment to be installed. Roadway development should ideally be ahead of the longwall so that the longwall equipment can be installed into the newly developed panel with minimal delay to coal production. A discrete event model of roadway development can help assess how a particular configuration may perform with high levels of variability and uncertainty in operations. One of the major delays associated with roadway development is caused by the shuttle car due to its cyclic stop-start nature. Shuttle car travelling paths and machine interactions are normally constraint by the mine?s roadway layout and mine safety issues. This paper presents simulations of shuttle car route options which can be considered at the design stage to minimize the cycle time of a shuttle car as part of a general roadway development simulation model developed using 3D Flexsim.

Feb 23, 2014

By S. Tuylu, D. Adiguzel, A. Bascetin, O. Ozdemir, U. Cinar

"In recent years, use of mineral processing tailings as a paste backfill has been significantly increased due to the environmental problems occurred during the disposal of the tailings in mine area. The paste material used to fill the stopes excavated is generally consisted of tailings (solid ratio: 70–85%) and cement (3-7%w/w). Meanwhile, the strength of the paste material is completely related to ratios of these materials. Cemented Paste Backfill (CPB) system is used as support depending on the roof pressure and also as an underground disposal method. Therefore, temporary strength value of the paste material gains a great importance. For example, the paste backfill material must compensate the minimum 4 MPa strength value in order to procure the permanent fortification, and the mixture cost must be minimal as well. For this reason, in this study, the Pb-Zn tailings were used to prepare for the paste backfill material using cement in order to perform the uniaxial compressive strength (UCS) tests. Additionally, a statistical experimental design and linear programming techniques was used to find the optimum mixture in terms of strength and cost. The pulp solid ratios (PSR) of the tailings and cement (by the solid) were varied as 75-85% and 3-8%, respectively. The results of this study; the optimum mixture is ~79.5%PSR and 6.8% cement ratio (by the solid) for 4 MPa UCS (28 day) and 16-17 cm slump value determined by this method with statistically reviewed experimental data. INTRODUCTION Fine-grained tailing waste materials resulting from mining activities are an important environmental problem. In terms of environmental protection, the use of tailings with paste backfill is a very attractive approach and a desirable solution to tailings management. Paste backfill, which is used to fill underground openings, is made by primarly mine tailings mixed with hydraulic binders and water. Its main benefits are not only disposal of mine tailings in underground, but also providing a certain strength to ensure a safe working environment. Therefore, it is necessary to use hydraulic binders due to durability of the system (Benzaazoua et al., 2004). Paste backfill, formed from the mix of dewatered plant tailings (75-85 wt. % solids), water and binder (3-8 wt. %) (Brackebusch, 1994; Landriault et al., 2005).Water is used to determine the chemical reactions between tailing and binder materials for strength as well as increasing pumpability. Portland cement and ash can be used as binder materials (Douglas and Malhotra, 1987). The factors which affect strength and stability of paste backfill separate into two groups called interior and exterior factors. Interior and exterior factors determine the strength, stability and deformation features of backfill in short and long terms and also affect the transportation of backfill to underground (Benzaazoua et al., 2004; Erçikdi et al., 2006; Yilmaz et al., 2010; Nasir and Fall, 2010). Material properties of tailings as well as site operations to fill the underground openings are the most important steps for the design purposes. Grain size distribution, chemical, and physical properties of tailings, and mechanical properties of paste fill material are used to understand the suitability of tailings as paste fill material (Ozturk et al., 2014). In addition, Fig. 1. is also proposed to apply a typical design for the operational stages of paste fill applications on the site."

Jan 1, 2016

By X. Baolin, R. Guru, M. Peiravi, M. K. Mohanty, Z. Qian, R. Ma, Z. Yude, L. A. Ackah

"Acid mine drainage (AMD) is produced when exposed pyrite (FeS2) reacts with air and water to form an acidic solution that usually contain contaminant levels of heavy metal ions. AMD can potentially contaminate surface water and soil if not treated. The primary objective of this study was to investigate the removal of dissolved aluminum, iron and zinc metal ions from natural AMD using water treatment residue (WTR), a low-cost adsorbent. WTR sorbent generated as waste material in drinking water treatment plants (WTP) was characterized and utilized for the sorption of Al, Fe and Zn in AMD collected from an abandoned coal mine site in southern Illinois that generates approximately 20 gallons per minute of AMD. Sorption experiments were performed using batch technique to obtain rate and equilibrium data. The effects of various parameters on sorption capacities of WTR were observed by varying contact time, pH of the AMD and WTR dosage. The adsorption studies showed rapid uptake in general for the first 80 minutes for Fe and Zn but much earlier for Zn. Further increase in contact time did not show significant change in equilibrium concentration indicating the onset of adsorption equilibrium. After the batch treatment of the AMD water with the WTR, the removal of Al, Fe and Zn were 99.8%, 99.85% and 95.5% respectively. The pH of AMD increased from 2.64 to a near neutral point of 6.74 after treatment. The laboratory results show that the low-cost WTR, which is an abundantly available industrial waste, has proven potential to significantly reduce the high metal ions in acid mine drainage. INTRODUCTION Mining activities provide the basic raw materials needed for infrastructure development and economic growth world-wide. However, it is well recognized that mining activities have been the cause of a variety of environmental pollutions, including AMD. Water seeping out of an old abandoned mine is generally characterized by low-pH with heavy loads of dissolved sulfates (SO4) and metal species such as Fe, Al and Zn among other dissolved elements categorized as toxic metals. The Bureau of Land Management’s Abandoned Mine Lands (AML) program reported the existence of about 46,000 abandoned mines in the United States. Several environmental problems have been reported to be associated with these mined out sites such as heavy metal poisoning, loss of vegetation, air pollution etc. (Boulanger & Gorman, 2004)."

Jan 1, 2017

By W. C. Lacy

It is the responsibility of educators to look ahead and prepare young engineers and scientists to cope with industrial and social problems of the future. We are faced with a review of history as well as prophesy of the future. The mining industry exists in a "bubble" with little interaction or communication with the outside. This isolation must be broken down if the industry is to survive in the U.S. and Canada. The ability to communicate with the general public and public officials is essential. Many changes are occurring that will require readjustments in technology and staffing. Aging population will result in raising retirement and increasing available workforce. This may force shorter working weeks to supply additional jobs. Environmental concerns will likely direct more attention not only to these concerns during mining, but to planning for post-mining land usage. Retraining and up-dating educational programs are required to cope with these changes.

Jan 1, 1994

By S. O. Ogden

As most of you have probably surmised from the title of my paper, I am here today to talk with you about the use of diesel engines in the American mining industry and whether or not the free choice to use such equipment will continue to be available to mine operators. Of course, I will present to you my prepared remarks, however, these remarks may be essentially academic in light of a news release, parts of which I would like to read to you. Washington, D. C., The Department of Health, Education, and Welfare today announced proposed new regulations to reduce occupational health risks to workers in the U. S. mining industries by requiring the removal of all diesel powered equipment from American mines by December 31st "While we do not have complete and conclusive information to quantify these health risks we feel it is prudent to undertake this restriction on the use of diesel powered equipment without waiting for the completion of studies that are currently underway to identify and quantify these health risks," said a Department spokesman. HEW has been concerned about the health risks of diesel emissions in the underground coal mines for some time and have investigations underway designed to conclusively demonstrate the nature and magnitude of any health risks. However, HEW has decided to proceed with these regulations without waiting for the final results of these investigations. Further, HEW feels there is sufficient probability that diesel health risks do exist in all mining applications and consequently, the proposed regulations will apply to all surface and underground mining operations. It goes on a little further and indicates that due to the necessity of finalizing these regulations without delay, a period of fifteen days has been provided to receive comments regarding these proposed regulations.

Jan 1, 1978

By J. L. Ellenberger, T. Miller

"A limestone mine in Ohio has had roof instability problems that have led to massive roof falls extending to the surface. This paper describes a collaborative study of these events undertaken by the National Institute for Occupational Safety and Health and the mine owners. The study focuses on the roles that weak, moisture-sensitive floor and weak bands in pillars play in a general instability that led to roof falls at this mine. The NIOSH Stone Mine Pillar Design software (S-Pillar) does not include analysis for weak floor or weak bands and recommends that when such issues arise they should be investigated further using a more advanced analysis. It is important to recognize that without the impact of the floor or weak bands, the calculated inherent stability factor for these pillars is within the recommended design range. Therefore, to further investigate the observed instability occurring on a large scale at the Ohio mine, FLAC3D numerical models were employed to help determine the failure mechanism. Roof-to-floor extensometers were also installed in the areas predicted to have further instability. This case study will provide important information to limestone mine operators regarding the impact of weak floor causing the potential for roof collapse, pillar failure, and subsequent subsidence of the ground surface. This recent case demonstrates that weak floor can be a significant factor in pillar stability and should be assessed during the design stage of the mine.To an area-wide failure (Zipf, 2001). In that case, it appears that the pillars had actually remained intact. However, moisture-related yield of the weak floor caused deformations which passed through pillars and into the roof, triggering roof collapse around the intact pillars (Esterhuizen et al., 2011). This previous case and the case presented in this study, while not identical, both demonstrate that weak floor and/or bands within pillars can be a significant factor leading to instability."

Jan 1, 2015