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By D. Shaver, M. N. Badonie, J. Newcomer, V. T. McLemore, E. Owen

Rare earth elements and critical minerals have recently become of great economic interest because of their necessity for many new technologies and recent geopolitical unrest affecting the supply and import of resources. The San Juan and Raton basins in northern New Mexico are two structural coal basins that contain elevated concentrations of rare earth elements and critical minerals. These two New Mexican coal basins will be assessed geochemically and petrographically to identify vectors of the rare earth element and critical mineral enrichment. Coalbeds, coal seams, overlying, and underlying rock units will be sampled and characterized to determine any economic viability. Historic data will be compiled into a new and comprehensive coal geochemical database, which will grow with new analyses, and serve as the dataset for this project; this coal resource database will be made available to the public.

Feb 1, 2023

By Lauro Lacerda

Shotcrete is a highly adaptable and widely used underground construction material at infrastructure and mining projects around the world. In fact, many projects could not have been completed without its utilization. As underground projects became larger the use of mechanized wet-mix spraying gradually replaced manual dry-mix shotcrete applications. This paper details some of the reasons for that and provides information on the equipment and operational factors including safety and productivity required to successfully complete underground shotcrete projects.

Jun 13, 2021

By R. L. Hudak, R. F. Randolph, A. S. Azman

The mining workforce experiences high rates of hazardous noise exposure and hearing loss. However, previous studies have identified specific behavioral and attitudinal barriers that keep miners from effectively acting to prevent their own hearing loss. The National Institute of Occupational Safety and Health (NIOSH) has developed several new hearing loss prevention tools and interventions that specifically target these barriers to prevention. The NIOSH Hearing Loss Simulator addresses motivation to take action and knowledge about the consequences of noise exposure. The QuickFit earplug test device and QuickFitWeb online hearing protection tester address barriers to effective earplug and earmuff use by verifying at least 15 decibels of protection. The NIOSH Roll-Pull-Hold technique helps miners obtain better protection through an easy-to-remember set of steps that improves attenuation by nine decibels. The “Inquiring Ears Want to Know” fact sheet helps miners to understand audiograms and to use them to maintain their hearing health. Each of these interventions can be used within the context of a comprehensive hearing loss prevention program.

Jan 1, 2010

By Jean-Michel Rendu

That you are giving the Daniel C. Jackling award to me is a great personal honor. But more significantly, it is a recognition that geostatistics has come of age. And since I am considered by many as belonging to an older generation of geostatisticians, I thought that it would be fitting that I reflect on where geostatistics came from and where it might be going. First, though, let me propose a definition of geostatistics. Etymologically, paraphrasing Webster's definitions of "geo" and "statistics," it is "a branch of mathematics dealing with the collection, analysis, interpretation and presentation of masses of numerical data taken from the earth." This definition is most appropriate in the context of mining geostatistics. It includes both classical and spatial statistics. It emphasizes the earth aspect, or the analysis of geologic features. And it should remind the practitioner that geologic input is a critical part of all geostatistical applications. In the 1910s, statistical methods were already used to analyze geological data. However, the origin of geostatistics, as we know it today, is best set in the late 1940s, when H.S. Sichel recognized the lognormal distribution of sample values in the South African gold mines. In 1951, Daniel Krige observed that "it can be expected that the gold values in a whole mine will be subject to a larger relative variation than those in a portion of the mine." In other words, samples taken close to each other are more likely to have similar values than if taken farther apart. This observation is the foundation on which spatial statistics, which characterizes values defined in a multidimensional space, is built. However, the 1950s were marked by studies based on classical, as opposed to spatial, statistics. It was only in the 1960s that the need was recognized to model the similarity between sample values as a function of the distance between samples and that the semivariogram was defined. A theoretical framework was developed by Matheron that supplied an elegant mathematical explanation to the empirical observations made by Krige. Matheron coined the term "kriging" in recognition of Krige's pioneering work on the geostatistical evaluation of mineral deposits. As soon as this theoretical framework was developed, it was possible to bring geostatistics to the academic world. The "Centre de Geostatistiques" was founded in Fontainebleau. Numerous students were trained there, disciples eager not only to improve the theory and develop more sophisticated mathematical tools, but also to spread the new faith throughout the world. Expansion of geostatistics exploded in the 1970s, arguably the most fertile decade if it is judged by the frequency of theoretical breakthroughs, the number of original publica-

Jan 1, 1995

By Bruce Congleton

One year ago this month, we in Central Florida witnessed the beginning of a most exciting and glamorous attraction. After three years of construction and anticipation, Walt Disney World opened its gates near Orlando and during its first year of operation received a flood of over 10 million visitors---half of all who came to Florida last year! The side effects of this newest addition to Florida have been phenomenal. Traffic on heavy days has been backed up for 30 miles from the amusement park along a major interstate highway. Hotels and motels have been jammed packed for months, and reservations are still difficult to make. Gasoline stations, restaurants and souvenir shops are doing a booming business. Everywhere you look as you ride the highways of Central Florida you see the signs of growth. New hotels spring up almost overnight. Golf courses galore. New housing projects and apartments sprawl where orange groves used to be. New roads criss-cross areas which were once deserted. There seems to be no end to the steady influx of tourists and new residents to the Sunshine State. And it's mainly because that we are the Sunshine State that they come. Air and water pollution is and has been at a minimum in Florida. Pollution and emissions are fighting words among some groups dedicated to preserving the bountiful environment we share in Florida. Little wonder then that some of these people display concern when they learn that just 50 miles from the entrance to the Magic Kingdom of Disney, phosphate draglines strip away thousands of acres of land each year to extract one of our nation's most precious

Jan 1, 1972

By Grant Davis

An International Symposium on the Ecology and Revegetation of Drastically Disturbed Areas was held at the Pennsylvania State University in August 1969. Scientists from 13 foreign countries and 18 states in the United States attended this meeting, which focused on those areas disturbed by mining. The symposium enabled scientists from all over the world to get together for two weeks and discuss informally some of the knotty problems of reclaiming these disturbed areas. Trying to present the results of each of the 64 papers delivered at the symposium might be difficult. So, I will try to bring you up to date on the general status of research on the reclamation of surface-mined areas, particularly in revegetation and hydrology. I will also mention some research that is under way but was not presented at the symposium.

Jan 1, 1970

By A. Chieregati

"A heterogeneity study was conducted at Erdenet Copper Mine in Erdenet, Mongolia, to determine the fundamental sampling error associated with blasthole sampling. Using a custom designed sector sampler, six large blasthole samples were collected to perform the test that was developed by Pierre Gy, to estimate the constitutional heterogeneity factor for several types of ore. The study investigated the entire sampling protocol, from mine site to analytical laboratory, and quantified the contributions to fundamental sampling error (FSE) of the various stages of sampling and sample preparation. The total relative standard deviation (RSD) of sampling error was determined to be ±32% and ±49.4% for copper and molybdenum respectively. A classical statistics analysis conducted on the data confirmed the level of RSD. About 95% of the sampling error was produced from only one step in the sampling protocol: when the 1 kg sample was reduced to 50 g sample for chemical analysis. Therefore, it is recommended that the 1 kg sample be reduced to 50g using a slightly different protocol to minimize the FSE. The 1 kg sample should be first crushed to 0.2cm size. A 250g split should then be taken and fine ground. A 50g split should then be taken from the 250g fine ground split. These two simple steps will reduce the FSE to ±7.9% and ±17% for copper and molybdenum respectively. The modified sampling protocol effectively reduces the probability of misclassification of low grade ore to zero. INTRODUCTION The Erdenet copper-molybdenum open pit mine is located in Erdenet, in Orkhon province, Mongolia. The Erdenetiin-Ovoo copper-molybdenum deposit is between 1.5 and 3 km wide, and about 25 km in length (Erdenet Mining Corporation, 2016). Chalcopyrite, bornite covellite and chalcocite are among the major minerals found in the deposit. The mine processes approximately 26 million tons of ore annually. A study was conducted to evaluate the fundamental error associated with the blasthole cuttings and sampling protocol at the mine. The open pit mine uses 215mm diameter Russian drills to drill 17.5m holes for 15m benches. The total weight of blasthole cuttings for a 215mm diameter hole and 15m bench height is between 1.5 and 2 tonnes. This amount of sample is difficult and time consuming to collect and analyze. Therefore, a sector sampler was designed for the Russian drills to collect large samples that were representative of the blasthole cuttings (Ganguli et al., 2016). In order to eliminate the delimitation and the extraction errors, researchers consider sector samplers to be ideal for sampling blastholes (Pitard, 2008; Chieregati and Pitard, 2009). This method was intentionally more rigorous than the blasthole sampling protocol at the mine to ensure that the blasthole cuttings were properly sampled. This study was part of a broader study that also looked at the relationship between particle size and grade. The samples collected by the custom designed sector sampler were very large (195 kg on average), and therefore, sufficient for both studies. The relationship between particle size and grade has been reported in Ganguli et al. (2016)."

Jan 1, 2017

By Bryan Ulrich

Knight Piésold?s annual roundtable discussion was held at the Red Lion Hotel and Casino in Elko, NV on March 14. This year the title was, ?Roundtable discussion on material co-disposal/ co-placement in the mining industry.? This topic was chosen because of the benefits that the mining industry could realize through the advancement of improved methods of storing tailings and mine waste and from reducing short-and long-term environmental hazards while reducing the footprint of these facilities and making strides toward attaining a walk-away solution. Knight Piésold had a local representative, Bryan Ulrich, as well as representatives from its Denver, CO office, including Tom Kerr, president of Knight Piésold?s U.S. practice, and Jeff Coffin, Ph.D., geotechnical engineer, to help facilitate the discussion. The event played host to about two dozen attendees from several western states. Attendees included personnel from more than 10 mining properties, various corporate offices and academia. The purpose of the roundtable was to exchange ideas and information pertaining to broad topics revolving around the subject of co-disposal/co-placement in the mining industry. Compared with traditional conferences and symposia, the roundtable forum tends to provide a less inhibited format for discussion. In the roundtable format, lively discussions and applicable tangential departures are encouraged. This was the seventh in the series of the Elko Roundtable events. Previous roundtables pertained to: ? Heap leach pad design, construction and operation. ? Design, construction and operation of tailings storage facilities. ? Site-wide water considerations. ? Mine closure and cover design. ? Strides toward sustainability in mining. ? High-density tailings, paste and filtered tailings. Acid rock drainage for engineers and environmental scientists.

Nov 1, 2013

By Neal P. Cochran

The Office of Coal Research Program has been outlined in our Annual Report for a number of years and reported on by various members of the OCR staff as well as by our contractors. The program is national in scope and is intended to develop new and improved uses for our Nation's coal resources and to maintain coal in a favorable economic position, vis-a-vis, the other energy forms. A program has been developed that includes conversion of coal to gas, gasoline and other petroleum-type products, and to electricity. These projects are only one facet of the OCR program albeit an important one. In many of the conversion projects we have underway, original development work has been done with bituminous and sub-bituminous coal. It is the intention of this paper to present a general outline as to how lignite might fit into one or more of these projects as a raw material. Our national lignite reserves are vast in scope and this has been recognized in the OCR program by development of a project specifically for lignite and by including lignite as a test raw material in many other projects. Project Lignite is intended to develop the Cop Acceptor Process for conversion of lignite to a high B.t.u. gas. In this effort we have included the design, construction, and operation of a lignite gasification plant at Rapid City, South Dakota. The work is being conducted by the Consolidation Coal Company and is an outgrowth of their laboratory development of this process. The first portion of our effort included a detailed economic study of a somewhat arbitrary grouping of States designated Market Area A that could be expected to use gas manufactured in a lignite gasification plant. The area included the Dakotas, Minnesota, Nebraska, and Iowa. This geographical area could readily be served if a process could be developed for converting North Dakota's lignite reserves, estimated at 351 billion tons, to high B.t.u. gas. Our study showed that Market Area A had a potential commercial- industrial market of one trillion cubic feet of gas a year. To meet this demand, we believe that part of the load can be obtained from commercial lignite-to-gas plants. At the time of our original study, we concluded that gas could be delivered to the city gate in Market Area A at about 45¢. As a result of price escalation in the interim, our estimate today might be slightly higher, but not significantly so, since some parts of the process appear better today than they did at the time of the original projection.

Jan 1, 1968

By Joern Katzer

It is vitally important to any tunnel project to have an accurate and reliable survey control network inside the tunnel for layouts, as-built surveys, and to provide guidance to the tunnel boring machine (TBM). However, the concepts and methodology to provide such a survey network are sometimes not well understood. For example, the first anticipated survey task that takes place during the bidding process is often ignored, which is to provide a comprehensive survey network preanalysis for the surface network and tunnel traverse based on survey statistics that will be used to make informed decisions on the survey requirements and methodology. Instead, these steps are often only vaguely based on previous results and prior tunneling experience. But each tunnel is different, and a solution that worked for one tunnel project might be unsuitable for another. The purpose of this paper is to provide tunnel project engineers, managers and surveyors with the general concepts for tunnel survey methodologies and examines several statistical tools for a basic horizontal and vertical tunnel survey preanalysis. These survey statistics tools provide useful estimates of the expected lateral and vertical tunnel traverse accuracies, but are not a replacement for a comprehensive tunnel network preanalysis. The proposed formulas do not take centering errors into account, are using average distances for each traverse leg, and assume that the survey data is free of outliers in the measurements. It is very important that the estimated instrument accuracy is based on true values that are reflective of measurement precisions that are actually achievable inside the tunnel to provide accurate results.

Dec 1, 2022

By G. F. Raymond

Discussion by G.F. Raymond Knudsen's study presents two curious conclusions: • The kriging of blasthole assays can systematically overstate mill head grades by as much as 21% as a result of unbiased sample variance. • No estimation method is able to reduce this bias to a small margin. The study is based on a simulation using real data and what are presumed to be actual variogram parameters from a real deposit. Although I have no doubt that the first conclusion (21% overestimation) is correct for the author's simulation, I do not believe this represents a realistic mining situation. Over the past 15 years I have done extensive comparisons between exploration drill-hole assays, blasthole assays and mill head grades on seven major open-pit mines, including some very erratic gold deposits. Commonly, nugget effects on blasthole variograms were 10% - 20% higher than on exploration variograms. And in one extreme case, the difference was 50%. Even in the extreme case, ordinary kriging on blastholes agreed well with the mill head grade over the long term. In Knudsen's simulation, the blasthole nugget effect is assumed to be 200% higher than exploration data's. He supports this by variogram plots from each. My guess is that the apparent, large difference between these variograms results from a failure to account for the proportional effect (blasthole assays are likely from a higher-grade area). A simple check would be a comparison of the variance of exploration samples nearest blastholes. As for a nearly conditionally-unbiased estimator of a large random error, the arithmetic mean of all of the data certainly qualifies, provided there is an even data spacing. As a corollary, so does simple kriging, which would include, in this case, a large weighting to the arithmetic mean. Similarly, using a large number of samples with ordinary kriging or indicator kriging would significantly reduce the bias in the case of a large nugget effect for the variogram.[ ] Reply by H. Peter Knudsen Raymond questions two conclusions in the paper. First, he wonders whether a 21 % overestimation represents a realistic mining situation. I agree that 21 % is high, but overestimation in the range of 10% to 15% is certainly common in my experience. Furthermore, several years ago I consulted on a gold mine that was experiencing a 45% overestimation due, predominantly, to poor blasthole samples: In further questioning of the 21 % value, Raymond wonders whether the nugget effect of the blastholes is really so much larger than the nugget values of the exploration data. It is consistently larger throughout the deposit. In my experience with six Nevada gold mines, the high nugget value is not unusual. In fact, for some reason, nugget values for blasthole samples are typically about 0.0005 (opt squared). I am of the opinion that this high nugget effect observed at many gold mines is predominantly due to the inherent inadequacies of the blasthole sample and subsequent sample preparation. The second conclusion Raymond questions is the inability of the estimators tested to reduce the conditional bias. In fact, the conditional bias is extreme with the polygon estimator and greatly reduced by ordinary kriging. However, it was not eliminated. Raymond suggests using simple kriging, or perhaps a larger number of samples, to reduce the conditional bias. The technique of simple kriging may be less affected by the random errors in the data, but I did not test the technique. Using a larger amount of data presupposes that too few samples were used initially. In ordinary kriging and indicator kriging, the screen effect comes into play and ensures that samples beyond the second screen are given zero weight. Hence, increasing the sample size does not change the estimates nor the conditional bias. The main point of my paper is that the random unbiased errors (a fact of life in blasthole samples) cause a conditional bias in our estimates. The mechanics by which the conditional bias is introduced are nicely explained by Springett. My paper simply shows that the bias is also present when working with linear estimators, such as ordinary kriging, and even with nonlinear estimators, such as indicator kriging.[ ]

Jan 1, 1993

By Vince Saporito

Miners work in dangerous terrain, around the clock, with heavy equipment. Is there room for improvement in safety and standardization in the mining industry? Recent history would suggest there is a need for action. At a 2011 Spring Thaw conference in Denver CO, one speaker commented, ?We are having a number of incidents with workers getting ?pulled? into rollers or ?trapped? at transfer points when trying to manually clean (it) while the conveyor is still in motion.? It?s a troubling thought. These actions are specifically prohibited under U.S. Mine Safety and Health Administration (MSHA) regulation 57.14202. Another official from MSHA earlier this year indicated with today?s technology and policies presently in place, ?we should not be repeating the same incidents and violations year after year as we currently do.? But we are doing exactly that.

Jan 1, 2012

By John Murray, Ryan Smith, Daniel Ebin, Robert Gould, Thomas Hennings

The Atlanta Plane Train Tunnel West Extension was excavated at Hartsfield-Jackson Atlanta International Airport using Sequential Excavation Methods (SEM). At its shallowest point, tunnel cover to bottom of Domestic Terminal footings was limited to 6 feet in soft ground. To mitigate risk of excessive building movement due to tunneling-related activities, the columns near the alignment were directly underpinned. Underpinning was accomplished using a combination of grouted mini-piles, installed under low headroom conditions, that supported steel framing spanning over the tunnel excavations. This paper focuses on design and construction of the underpinning system used to mitigate risk from tunneling.

Jun 13, 2023

By William Gleason

For the first time in many years, the Liebherr Group chose to host its annual conference for the international construction trade press in the United States. The reason for the move is simple ? mining. Like other large corporations, especially those in the construction fields, Liebherr felt the effects of the global economic crisis that began in 2008. The slowdown in the housing market was especially hard on Liebherr?s mobile crane and earth moving divisions. The mining division, however, while affected by crashing commodity prices that led to cancelled orders and the loss of financing for some customers, was not battered as badly as the other divisions. And now, with the price of commodities once again on the rise, it seems that it will be Liebherr?s largest machines that lead the family-owned company to better days. ?We can report that our generally optimistic view during the crisis has proved adequate,? said Joachim Janka, president of Liebherr mining equipment, at the conference in Williamsburg, VA, just down the road from the company?s mining truck division global headquarters in Newport News, VA. ?Since the third quarter of 2009, our mining equipment activities have been recording once more a strong and steady demand. This has already yielded a substantial increase in market shares for our product lines of large mining shovels as well as for mining trucks.?

Jan 1, 2011

By RENE GOMEZ, RAUL CASTRO

Estimation tools and models are now available to estimate fragmentation, but some variables have yet to be studied to understand their effect on the fragmentation process. One such variable whose mechanisms have yet to be studied is the residence time, which in block caving directly depends on the distance that fragments travel from their original position in the broken ore to the drawpoint. In this study, granular material fragmentation was characterized during its flow to understand its characteristics and mechanisms. The results show that the breakage of fragment singularities occurred mainly within medium and smaller sizes, increasing fine material during flow. Thus, the main fragmentation mechanism in experiments was identified as abrasion between rock fragments where fine material continuously increases as distance increases in spite of the high rock strength and the piston flow movement used. The results presented here can be applied to incorporate fragmentation during flow of large travel distance of ore such as in block caving.

By David A. Zegeer

Since 1980, more than 40 miners have lost their lives by being trapped and suffocating in stock-piles, bins, silos, and similar facilities. Mine Safety and Health Administration (MSHA) is concerned about these accidents, most of which could be prevented if management and miners appreciated the hazard. In February 1986, the coal industry had a suffocation accident that drew national attention. A group of engineers were standing on a coal stockpile. It gave way under their feet. Five of the engineers were buried in the coal and suffocated. As with all fatal accidents, MSHA investigated the cause of this tragedy. I also asked my staff to look into the history of similar accidents. I found out it is rare to have multiple fatalities due to suffocation in material. But, over the years, there has been a long series of individual fatalities from this type of accident. Here are some examples. In Oct. 1985, a coal mine employee in Virginia entered a hopper to collect a coal sample. The feeders were started while he was standing in the hopper. He sank into the coal and suffocated. In Sept. 1985, an employee at a Texas sand company climbed onto a surge pile, to check a problem with sand flow. When other employees found him, the sand had swallowed him. Only his face and one hand were showing. Though the victim's face was clear of the sand, he suffocated before rescuers could free him. Many people do not realize you can suffocate in this kind of situation, though your head is free. Every time you exhale, the material has room to shift and press harder against your chest. Then you have less room to inhale. If this goes on long enough, it gets to the point where you cannot inhale at all. That is what happened to the victim in this accident. In May 1985, a plant operator at a Wisconsin sand and gravel operation purposely slid into the drawhole of a surge pile. He tried to break up large rocks that were clogging the drawpoint. Material piled on the side of the surge pile slid down and buried him. The operator was wearing a safety belt and line. But he was covered by 3 to 3.7 m (10 to 12 ft) of material and could not be pulled free. This incident illustrates another point. A safety line can help. But it is not enough. Workers should never put themselves in a position where loose material can fall on them from above. In Jan. 1985, a young Utah coal miner was waiting for a ride home from a co-worker whose job was at the tipple. A jam developed in the coal bin. The men could not clear the jam from the outside. So the young miner jumped into the bin. He started digging with a shovel at the toe of the coal pile. It caved in on him and he suffocated. The young miner had only three months of mining experience. He had not been trained for work around the coal bin. Since 1980, 16 coal miners and 26 nonmetal miners have lost their lives in loose-material suffocation accidents. Suffocation accidents occur in many areas around mines - bins, hoppers, stockpiles, surge piles, and silos, among others. One recent accident occurred at a surface coal mine in Illinois. The victim was walking over an area that had been drilled and blasted the week before. He fell into a void that had been crusted over with earth. He too suffocated. And many materials have been involved in suffocation accidentscoal, crushed stone, sand, salt, different kinds of ore, ammonium nitrate pellets used in blasting, and a powdery byproduct of iron ore milling called calcine. In addition to fatal accidents, there are near misses. We do not know how many. Most of them are not reported. A person who gets trapped in material, but is rescued, is usually unhurt. MSHA sometimes hears about these accidents by chance, or because they are reported in the local media. We do know that near misses are happening far more often

Jan 1, 1987

By A. Mull, J. Weyer, J. Brune

"The “Reiche Zeche” mine in Freiberg, Germany, a 600-year-old lead-zinc-silver mine with extensive open mine workings, experiences severe ventilation losses due to leakage. Much air leaks into abandoned workings, decreasing the airflow available to active working areas. Usually, this leakage occurs in remote areas that lack transportation infrastructure like roadways or rail, making it difficult to haul construction materials to the sites to erect passive ventilation controls such as stoppings, regulators and seals. Transportation distances make it impractical to hand carry traditional construction materials, such as bricks and concrete. Alternative materials, such as brattice, foaming polymers, concrete canvas, and some innovative ventilation control designs have been investigated for this purpose. The suitability of the materials investigated depends on many factors including the pressure it can withstand, the ease of transportation, and workability. Impacts of mine water must be considered, as the Reiche Zeche is below drainage and experiences significant inflow of water. Researchers must consider the effects water inundation as well as how the stopping construction material reacts to being exposed to acidic mine water. INTRODUCTION Problem Statement Mining in the area around Freiberg, Germany began in the 12th century. The mine is used for research, mining engineering education, tourism and air conditioning for a local hospital. The first records of mining in the Reiche Zeche are from around 1384. Due to the strength and competency of the host rock, many of the oldest workings still stand and remain open today, although they may not be accessible. Reiche Zeche also connects to several other, closed mines in the area that are largely unmapped. This allows air to leak into neighboring mines, reducing the air available to ventilate to the working areas of Reiche Zeche. In order to improve ventilation efficiency, it is necessary to control the ventilation and reduce leakage by constructing seals, stoppings and regulators. A challenge with building traditional seals and stoppings in the Reiche Zeche is that the old workings lack transportation pathways or rails. Also, the lack of compressed air, water or electricity makes it difficult to operate power tools and drills. This means that construction materials must be hand carried – some over distances of several kilometers. Figure 1 shows a typical drift in the Reiche Zeche. Researchers investigated using lighter, more easily transportable materials including concrete canvas, expanding polyurethane and polyurea foams, and brattice. The applicability and utility of these materials depends on a variety of factors including the ventilation air pressure, chemical resistance to acidic and mineral-laden mine waters, ease of transport, and ease of construction. Stoppings and seals must be substantially constructed so that they remain tight and do not require maintenance. It is also important to consider the toxicity of the construction materials in case of a mine fire."

Jan 1, 2016

By Michael Michaylov

INTRODUCTUCTICN The coal seams at Bobov dol basin are highly prone to spontaneous combustion in Bulgaria. The risks of endogenous fires (SPONCOM) exist mainly in gob area. During the last 15 years three different technologies for preventing and fighting SPONCOM have been applied in underground mines of this basin: pulp from hard material and water, foam and inerting with nitrogen. On the basis of experimental application of these technologies as well as theoretical and experimental research a new technology - Foam Pulp Technology (FPT) was worked out. It is very effective in difficult to reach places in a gob. BACKGROUND AND THE NEED OF FPT Application of the three methods mentioned above showed advantages as well as some disadvantages, allowing determination of their effective application scope depending on geological and working conditions. Their advantages can be summarized as follows: - Foaming: high viscosity at low density, which allows forming a thick layer; good surfactant wetting properties; excellent effective cooling during evaporation in high temperature zones. - Pulping with mixture of solid particles (e.g., fly ash) and water from surface installation: easy to apply in a mine; low operational and energy costs due to gravity transport from the surface to the gob: good ecological results because the waste material is returned back underground. - Inerting with nitrogen: volumetric action which doesn't restrict the thickness of treated coal pile; easy to apply in a mine; controllable nitrogen delivery depending on fire hazard conditions. Main disadvantages of the same three methods are: - Foaming: rapid disintegration due to intrusion into heterogeneous and porous media and high costs due to the need of frequent large volume foam flows (short foam's life); - Pulping: inapplicable for coal piles with high thickness which is of great importance in the cases of seams with ununiform hypsometry (rapid and frequent changes in a seam configuration) and/or great volumes of coal or ore piles particularly heated to a high temperature; strong dependence on gob floor declination; water draining of the working face area which impedes the movement of supports and chain conveyor's. - Inerting: relatively high costs hardly depending on the rate of face advance (fig.1) in comparison with the other methods; it is difficult to ensure sufficient oxygen at the exit end of the face. This problem is crucial in faces with a high level of methane emissions; accelerating of the oxidation and spontaneous heating of the pile after turning off the nitrogen supply. Inerting should be applied again at higher capacity of nitrogen supply (fig.2) and what is more important, it shouldn't be

Jan 1, 1995

By Felipe Calizaya, Sekhar Bhattacharyya

Noise-induced hearing loss (NIHL) is prevalent in mechanized underground mines. Federal regulations are often not complied with effectively. Miners are also prone to ignoring administrative guidelines and/or personal protective equipment for hearing conservation. As a result, quality of life among experienced miners plummets while occupational risks increase at workplaces. This research focused on auxiliary fans used in underground mines. These fans work at high rotational speed and generate extremely high levels of noise in close proximity to miners. Silencers used are often of little effect due to poor maintenance. A new silencer is tried in the laboratory with the objective of easy maintenance and resulting reduction of noise exposure for miners.

By David Maust, Rob Albinger, Mike Walling, Michael Rispin

The safeguarding of health and life is the number one priority for underground infrastructure projects. While culture and approach are critically important, the industry has also seen the development of innovative tools and technologies that assist in making the underground environment and working places more safe and secure, both on an everyday basis and in the event of an unexpected occurrence.

Dec 1, 2022