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By Ihsan Berk Tulu, Ted Klemetti, Deniz Tuncay

"The Analysis of Retreat Mining Pillar Stability (ARMPS) program was developed by the National Institute for Occupational Safety and Health (NIOSH) to help the U.S. coal mining industry to design safe retreat room and pillar panels. ARMPS calculates the magnitude of the in-situ and mining-induced loads by using geometrical computations and empirical rules. In particular, the program uses the “abutment angle” concept in calculating the magnitude of the abutment load on pillars adjacent to a gob.In this paper, stress measurements from U.S. and Australian mines with different overburden geologies with varying hard rock percentages were back analyzed. The results of the analyses indicated that for depths less than 650 ft, the ARMPS empirical derivation of a 21° abutment angle was supported by the case histories; however, at depths greater than 650 ft, the abutment angle was found to be significantly less than 21°. In this paper, a new equation employing the panel width to overburden depth ratio is constructed for the calculation of accurate abutment angles for deeper mining cases.The new abutment angle equation was tested using both ARMPS2010 and LaModel for the entire case history database of ARMPS2010. The new abutment angle equation to estimate the magnitude of the mining-induced loads used together with the LaModel program was found to give good classification accuracies compared to ARMPS2010 for deep cover cases.INTRODUCTIONIn the early 1990s, the Analysis of Longwall Pillar Stability (ALPS) was introduced by Mark (1990) as a chain pillar design software and was generally accepted and used by the U.S. coal mining industry. Following the success of ALPS, the National Institute for Occupational Safety and Health (NIOSH) developed the Analysis of Retreat Mining Pillar Stability (ARMPS) program for designing retreat mining pillars using a similar approach as ALPS (Mark and Chase, 1997). The Australian mining industry also recognized the success of ALPS, and Colwell, Frith, and Mark (1999) calibrated the program to Australian conditions. The ALPS and ARMPS programs draw their strengths from the large databases that are used to calibrate them (Mark, 2009). However, following the Crandall Canyon Mine collapse in 2007, NIOSH had to reconsider the pillar design criteria used in deep-cover retreat mining (Mark, 2010). The ARMPS overburden load prediction algorithm was improved to more accurately predict the loading of narrow panels with high overburden depths by implementing the pressure arch concept, and this new version is called ARMPS2010."

Jan 1, 2019

By Im C. J.

The addition of coal preparation plants changed the coal industry during the past. Now it is time co once again improve the quality and types of coal products coming from future coal preparation plants to meet the changing needs of our society. Clean Coal Technology, along with federal support provided, is forcing our industry to provide cleaner coal products for industrial applications. Liquid fuels from coal is just one of many new products from a coal preparation plant that has a ready market in the transportation sector. UCC Research Corporation is developing these new liquid coal products and this paper will describe the progress and the new slate of coal products to be provided from future preparation plants.

Jan 1, 1989

By C. Tsamantaki

Water-bentonite suspensions exhibit a yield stress which is defined as the minimum applied stress for flow. Considerable debate exists about the yield stress being a material property, hence different measuring methods should give similar answers, but several investigators have demonstrated that it is an engineering reality. Yield stress is normally estimated indirectly from the rheogram obtained with a viscometer following an extrapolation to zero shear rate (the dynamic yield stress), but the technique may be prone to errors because of slip flow. Direct measurements, not prone to such errors, rely on an independent assessment of the yield stress, normally carried out with the vane method (the static yield stress). In this paper results are presented and compared regarding the yield stress of 14 different water-bentonite suspensions measured using both the direct and the indirect methods. In order to obtain a wide range of yield stress values, two different types and two concentrations of bentonite at various pH were tested. Rheological data were obtained using a rotational speed viscometer and a yield stress vane measuring device. Measured vane yield stress values ranged from 5 Pa to 83 Pa. Rheological data collected with the rotating viscometer were fitted using various conventional techniques (interpolation, linear and non-linear regression analysis) as well as using a golden section yield stress search methodology based on Herschel-Bulkley model, developed in house. The vane instrument measures directly the yield stress of the suspensions and requires no further data handling. A comparison of the measured values of the yield stress with the direct and the indirect method is then made for the water-bentonite samples. Not very large differences are observed among different techniques and the variations are discussed. Similar data from literature are also analyzed and the comparison shows that differences on the various estimation methods are much larger than the differences observed in this study.

Jan 1, 2006

By N. Ohmura, H. Saiki, T. Nagaoka

A microbiological flotation system that facilitates the removal of pyritic sulfurfrom coal is reported. The chemoautotrophic bacterium Thiobacillus ferrooxidans is utilized as a pyrite-selective biological surfactant that augments the flotation-mediated rejection of pyritic sulfur. The bacteria were produced by continuous cultivation in 50-L tanks, where it was possible to produce 3.8 x 1012 cells/day when the dilution rate was optimal and the pH was 1.6, a condition that prevented ferric precipitation. Prior to flotation, the bacteria were mixed with coal, which allowed cells to selectively adhere to the pyrite. The adherence of bacteria made the pyrite surfaces more hydrophilic, which facilitated separation by increasing the tendency of pyrite to sink, while the hydrophobic coal floated. When a synthetic coal/pyrite mixture (10.1 % sulfur) was subjected to microbial flotation, the level of sulfur rejection was stable during the entire period of operation (i.e., one hour). In the absence of bacteria, flotation reduced the sulfur content of a coal/pyrite mixture to within the range of 6.7% to 7.4%, with the combustible recoveries ranging from 93.9% to 99.0%. In the presence of bacteria, the sulfur content of cleaned coal was in the range of 1.3% to 1.4%, with the combustible recoveries ranging from 80.8% to 86.3%. Bacterial activity accounted for 57% of the total sulfur rejected through flotation. The desulfurization capacity of the system was further confirmed by testing it with run-of-mine coal. The pyritic sulfur content was reduced from 2.9% in the feed coal to around 1.2% in the froth product, while 80% of the combustible recovery was retained. Microbial flotation removed 60% of the pyritic sulfur from the feed. These findings demonstrated that micro¬bial flotation could be utilized for the removal of pyritic sulfur from coal in a semicontinuous system.

Jan 1, 2000

By Morgan M. Sears

The LaModel program is widely used to calculate stresses and displacements on thin tabular deposits, particularly when multiple seams or complex mining geometry is encountered. The program itself allows the user to create multiple mining steps to show a progressive sequence of mining. However, LaModel considers each individual step as an independent steady-state condition, and any previous loading conditions of the materials are not tracked. It also does not consider any sort of dynamic stress change during the mining process. In certain circumstances, especially in multiple-seam situations, modeling a scenario of the seam of interest without considering the previous mining sequence in the off seams can potentially lead to inaccurate results. The primary objective of this paper is to present a situation where a potentially dynamic, unstable mining condition was encountered. It was not evident until the previous loading conditions in the off seams and the impact of dynamic stress changes in the active seam were considered. It is important to make the mining community aware of these potential modeling scenarios where the path-dependent nature of the mining sequence is of key importance. This paper presents a case history where room-and-pillar retreat mining was being conducted in a relatively deep cover stress regime where multiple seam interactions were present from both undermining and overmining. Mining in the active seam was being conducted with roomand- pillar mining techniques consisting of a series of parallel production panels being successively developed and retreat mined along a set of Mains. In this situation, the traditional global LaModel analysis without any path-dependent adjustments did not fully identify the area of poor conditions that were encountered. This paper explores the impacts of mining in the active seam on the lower seam which, in turn, has a negative impact on the active seam. This provided a solid foundation for the subsequent analysis of the three seams simultaneously. Based on the calibrated model, it is likely that retreat mining in the active seam resulted in increased stresses in the underlying seam that conceivably resulted in additional convergence and, most likely, additionally convergence of the pillars under the panel being developed. This in turn could have caused active subsid- The LaModel program is extremely useful for analyzing multiple-seam mining scenarios. As multiple-seam situations become even more prevalent, the potential for encountering a path-dependent mining scenario also increases. To successfully model path-dependent mining scenarios, the ground control engineer will be required to make sound judgments on the condition of pillars in sub-adjacent seams. These engineering judgments should be based not only on the current state of stress, but also on any prior or future states of stress. This means considering the stresses from over or undermining as well as stresses applied to the sub-adjacent seams from actively mining the seam of interest.

Jun 25, 2024

By P. Somasundaran

Previous studies on semi-soluble minerals such as calcite (1) and apatite(2) and sparingly soluble minerals such as quartz (3,4) have given evidence for significant changes in their electrokinetic properties as a function of aging time. Such changes are relevant to mineral processing operations where the crushed ore particles might not have yet reached equili¬brium with the water that it is in contact with. In order that these changes be studied under controlled experimental conditions for long periods unattended or with fairly less intermittant attention, a streaming potential apparatus with an automatic streaming system was constructed. Also, a new streaming potential cell was incorporated into the system so that the effect of temperature, a variable coming into increasing usage in mineral processing operations(5), could also be studied. Conventional streaming cells(6) cannot be safely employed to conduct studies as a function of temperature since they have many glass joints that are prone to leakage, parti¬cularly under pressure, in the course of an experiment. This paper describes the new apparatus and some typical results that have been obtained with it far temperature effects.

Jan 1, 1973

The absence of coal face particle management practices heavily penalizes coal transportation from initial loading to final consumption. Penalties include dust problems, significantly reduced mine loading cycle productivity, mine belt spillage, excessively high coal preparation costs and chute and dangerous pulverizer blockages at the final point of utilization. The common environmental and economic enemy is fines. Everyone knows that fines cause safety and environmental dust problems, but few understand that fines also swell broken coal to a point where 5 to 15 percent more time and capacity must be used to deliver the same tonnage. In this paper, methods and rewards for reducing and/or managing fines at the mine face are discussed. Computer-based loading cycle model productivity estimates, viewed from a new perspective, are made on the basis of material volume rather than on the long established and frequently misleading basis of tonnage. After all, it is typically the volume of broken material being transported that defines the capacity of a given transportation system, while the corresponding tonnages are merely a reflection of the specific material densities. Published evidence suggests that the swelling of broken coal can be decreased very significantly using small quantities of certain non-frothing chemicals added to mine face spray water and/or by employing improved mine face breakage practices. In a future paper, the effects on transportation productivity beyond the coal mine will be discussed.

Jan 1, 1994

By J. W. MacDonald

PROPERTY AND PRODUCTION: Around 100 Million Tons of Recoverable Coal are available from the approximate 10,000 acres allocated to the mine. Over 1300 acres of surface land holdings extend well beyond the limits required for plant site, storage tracks, water supply reservoir, settling ponds and waste disposal. COAL: Extensive core drilled testing confirmed the early indicated high quality of the #6 Seam Washability data show less than four percent of the' coal seam required removal to provide a superior product for the available market. PREPARATION PANT DESIGN: The limited needs enabled Preparation Plant Design to meet the requirements without inclusion of novel equipment. The simplified needs afforded ample opportunity for considering increased automation where advantage or economy was antioipated. Plant design included protection of opportunity for pre-drying in advance of air cleaning the fine coal and accommodations for addition of Dense Media separating equipment in event warranted or required by future market changes. Protection is also afforded for addition of Raw Coal Storage accommodations in event warranted. Figure I shows the Preparation Plant Flow Sheet.

Jan 1, 1961

Selective Flocculation process development generally involves single mineral flocculation tests to identify the appropriate polymer and experimental conditions for achieving the desired selectivity. Invariably the selectivity predicted on the basis of such tests is not realized when mixed mineral tests are conducted. A systematic experimental investigation revealed that adsorption of the polymer on various substrates is critical to selecting the suitable flocculent. Simultaneously, a mathematical model was developed to predict the overall process efficiency with a given polymer. In this paper, results of these efforts to scientifically design a suitable selective flocculation process are presented.

Jan 1, 1991

By D. Watson

The Henderson mine has more than 20 years experience and has placed a combined total of more than 400,000 m3 (520,000 cy) of shotcrete and concrete. Over the last 20 years the mine has used a variety of equipment for placing concrete, wet shotcrete and dry shotcrete and is constantly trying to cut costs and increase efficiencies. Henderson has recently received a state of the art wet shotcrete placer, automated its batch plant, fabricated a mobile concrete form jumbo and is soon to receive a new concrete transport truck.

Jan 1, 1992

By J. R. Knudson

A major contribution to the art of blasting was made at the Cleveland- Cliffs Iron Company?s Hawkins Mine in Cashwauk, Minnesota during April of 1956. It was here that the first experiments with fertilizer grade ammonium nitrate were conducted-experiments which led to the development of the ammonium nitrate and fuel oil method of blasting which has been eagerly adopted by open pit and quarry operators throughout the United States. While this new blasting agent was a more or less natural outgrowth of the Akremite Process devised by Maumee Colleries of Terre Haute, Indiana; no one, to our knowledge, had used this particular combination of ingredients prior to this time. Certainly this was a "break-through" as far as the Lake Superior District was concerned. Akremite consists of a mechanical mixture of grained ammonium nitrate and a solid carbonaceous material packed in a plastic bag. At the time of its introduction to the Mesaba Range, Akremite sold for 10.5 cents a pound as compared to the 18 cent powder previously used in both wet and dry large hole blasting. The discovery of this agent was indeed a remarkable achievement, one that afforded a substantial reduction in blasting costs. However, Akremite proved to be only an intermediate step in the evolution of our present low cost explosives. Cleveland-Cliffs utilized prilled ammonium nitrate and fuel oil and then eliminated the mixing and packaging plant entirely by combining the two raw materials in the field at the drill hole collar or in the hole itself. Thus we have approached the ultimate in simplicity, for the blaster and his helper now manufacture their own explosives not only as they are needed but where they are needed, and at a cost of under 4 cents a pound. This two-man crew may charge and explode as much as 8 tons of ammonium nitrate in an eight-hour shift and in so doing break some 65,000 tons of ore.

Jan 1, 1959

By I. A. Molodkina, A. V. Kurkov, V. V. Shatalov

New compound classes previously unknown in flotation practice of non-sulphide ore beneficiation have been developed. The presented study results consider amine salts of alkyl sulphate and alkyl benzene sulphonic acid used as primary collectors, N-methyl amides of alkyl phosphoric acids - as auxiliary modifying collectors and pentaerythritole ethers of tall oil - as flotation accelerators. These reagents synthesized from accessible raw material are almost ready for commercial production. Efficiency of the new reagents for various non-sulphide ores has been demonstrated in a series of flotation tests.

Jan 1, 1995

By Nes?e Çelebi

It has never been easy to finance within mining sector. Leasing may be an alternative source of finance for mining investments. Leasing is acquiring the right of usage for an asset for a definite period of time without having the ownership of it. In this study, a model for analyzing the lease financing opportunities for mining investments under risk and suitable for establishing a satisfactory leasing policy for both lessee and lessor is developed. Using the model, it is possible to obtain an expected equilibrium lease amount acceptable by both lessor and lessee and also the expected range of the equilibrium lease amount as a decision tool. First the existing leasing policies are mentioned, then the developed model is described. A case study is presented to illustrate the use of the model in establishing a leasing policy. In conclusion, the usefulness of the model is discussed.

Jan 1, 1992

By J. C. Yingling, V. Badaker, R. J. Sweigard, P. W. Conrad, J. M. Ringe, D. H. Graves

The University of Kentucky has developed reclamation cells at a surface mine in southeastern Kentucky to evaluate the impact of spoil handling (reclamation methods) and compaction alleviation methods on the physical properties of replaced growing media and on tree survival rate. From 1997 through 2001, penetration depth, penetration resistance, bulk density, and tree survival data have been collected at the reclamation cells and correlated to determine the relationships that exist between the soil physical properties at the site and tree survival. Regression models have been developed for each reclamation method evaluated using the collected data to predict tree survival rates on reclaimed surface mined lands as a function of the soil physical properties of the replaced growing media. Procedures have been developed for handling soil/spoil during reclamation that can minimize compaction in the replaced growing media. Procedures have also been developed for alleviating compaction in growing media on reclaimed and orphaned surface mined sites. These procedures, if implemented, will increase the potential for reforestation success. Finally, procedures have been developed for collecting soil physical property data for use in evaluating the suitability of spoil conditions for reforestation.

Jan 1, 2003

By J. M. Mutmansky, A. Wang

This paper defines the elements of a basic economic model for decision making when considering a methane drainage system for an underground coal mine. A drainage system entails significant capital and operating expense; hence the decision to utilize drainage must be made carefully. The model outlines the basic structure of decision making and considers the costs and benefits when the methane is marketed and when the methane is vented to the atmosphere. The effects on mine safety and the dust levels in the mine are also considered, both in a general format and as economic variables. Sources of information for executing this decision making are provided for an actual mine decision.

Jan 1, 1999

By Dennis L. Boley, Francesco Gallavresi, Donald A. Bruce

The authors describe novel aspects of ground reinforcement and treatment as related to soft ground excavation for tunnels throughout the world. Insitu reinforcement for cut slopes (soil nailing), as underpinning (reticulated micropiles), and as direct tunnel support (infilaggi) is introduced. Ground treatment focuses on new aspects of permeation grouting (by the tube'a manchette system), and on jet grouting-a very powerful and positive new technique. Recent developments in equipment, materials, methods and instrumentation are reviewed, with special reference to major tunnelling projects in Italy and Singapore.

Jan 1, 1987

By S. Bentley

"Everyone has a general idea what mixing means, but describing the mixing process is not so simple. The objective of any mixing process is to distribute and blend the materials with different characteristics, different quantities as evenly as possible resulting in a homogenous mixture. Introducing proportional movement with the optimal intensity into the materials achieves effective homogeneous mixing results. A simple one directional movement with inadequate acceleration of the materials would obviously not achieve the same mixing results. This would be more like stirring than mixing. The amount of relative movement that is introduced is a decisive factor. Circumstances for successful mixing involve distribution of all materials, and achieving the highest probability that all recipe particles located in a specific position at the beginning can be found at any random location in the mixing chamber at the end of the process. This is the only way to ensure that a consistent result is achieved every time mixing is repeated.THREE-PART CYCLE The mixing cycle occurs in three phases; charging the mixer, the mixing process, and discharging. The sequence in which the individual materials to be mixed are filled into the mixer can have a huge impact on the efficiency of the mixing cycle. The mixing cycle overlaps the charging process and the discharge cycle follows the mixing cycle. To achieve optimum results, effective discharging methods should be taken into consideration to avoid risks of segregation. Costs for energy and wear should be as low as possible and finally, it is very important that the mixing cycle takes place as quickly as possible. In concrete or paste backfill production, selecting the best mixing technology is crucial for both the quality of the final product to be blended and the efficiency of the production process. The optimum mixing system is one that rapidly disperses all ingredients evenly throughout the mixing trough and completely surrounds all the course or fine aggregate particles with the slurry cement particles. Specific for paste production it’s the mixers job to also break-down unconditioned tailings to achieve consistent paste viscosity or measured spread. Many paste and concrete formulas also involve small quantities of chemical additives which also must be evenly distributed effectively. The time required per mixing cycle as well as the costs of energy, wear and maintenance will determine the economy of the concrete production."

Jan 1, 2015

By J. S. Jaspal

Mining of thin coal seams is both difficult and uneconomical. As a result, most of thin-seam coal reserves in the U. S. are not being mined. It is estimated that nearly 910 Gt (K. Unrug, 1985) of coal reserves exist in 355 to 710 mm thick seams. The Bureau is attempting to develop new techniques for mining 150 to 1065 mm thick coal seams. This paper summarizes the research work on existing thin-seam mining techniques, testing on small and full scale physical models of the Bureau slot mining concept, and computer modeling of the full-scale process.

Jan 1, 1992

By R. Gerling

A computer program has been developed for finding a near-optimum schedule of the mining sequence for flat lying, tabular orebodies. The deposit is divided in blocks with equal areas and definite grades, thicknesses and ore contents. Mining is done by room and pillar method and trackless haulage to surface. Access from surface is by adits or ramps with additional vent raises. In total eight different general concepts for access and development can be realized. The optimum mining sequence is found by a heuristic method. Criterion is the maximization of the net present value over the lifetime of the mine. Specific stoping costs per t of ore are taken for con¬stant, whereas development and haulage costs for individual blocks and also sequences will be different. Correct ventilation and a technically sensible sequence are guaranteed. Beginning with a single block, neighbouring blocks are tested and an optimum stoping sequence is generated. The net present value of the total mining operation for the planning period is calculated, taking into account ore, which is mined during development. The program can also be used to investigate given mining sequences.

Jan 1, 1986

By D. K. Jorgensen

The Bullfrog and Montgomery-Shoshone deposits, near Beatty, NV, have a combined drill-indicated reserve of 15.8 Mt (17.4 million st) of ore. Average grade is 3.5 g/t (0.103 oz per st) gold and 8.2 g/t (0.24 oz per st) silver. The deposits occur in Miocene volcanic rocks that underwent large-scale movement within a detachment-faulted terrane. The principal host to gold mineralization is a strongly welded rhyolitic tuff that experienced brittle deformation during plate movement. Open space fractures and breccia were filled with quartz, calcite, and adularia accompanied by lesser pyrite, gold, and acanthite. Gold occurs as micrometer-sized particles within and adjacent to the low-angle fault and along associated listric-normal and tear faults. The Bullfrog and Montgomery-Shoshone are volcanic-hosted, detachment fault-related, epithermal quartz calcite stockwork gold deposits. Bullfrog's minable reserve is 13 Mt (14.3 million st) of ore grading 3.8 g/t (0.11 oz per st) of gold. At Montgomery-Shoshone, 2.7 Mt (3 million st) minable tons at 2.5 g/t (0.072 oz per st) are present. Preproduction stripping has begun at the Bullfrog ore body. A 7.7-kt/d (8500-stpd) carbon-in-pulp (CIP) mill is under construction. In 1990, Bond Gold expects to be producing about 6.2 t/a (200,000 oz per year) of gold.

Jan 1, 1990