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By A. V. Kanarskay?

The research is aimed at involving in the processing of poor platinummetal natural and technogenic raw materials. The purpose of the research is the creation of a multifactorial complex of innovations in the system of ore preparation and separation cycles, which ensure a high efficiency of flotation enrichment of hard-to-treat raw materials. In the usual practice of enrichment, minerals of the platinum group (PGM) of less than 10 microns in size are the source of inevitable process losses. For poor raw materials, it is precisely thin PGMs that are characteristic, their proportion sometimes being almost 100%, and their opening leads to the formation of a large amount of slime, which adversely affects the efficiency of flotation. To reduce the yield of slimes and increase the selectivity degree of the opening of the PGM in the ore preparation cycle, a dry grinding scheme and pneumoclassification of the milling material has been developed to obtain fractions of different fineness, density and morphology of the particles. From 2 to 5-fold reduction in the yield of slurries for various ores has been achieved. The separation cycle successfully tested are: flotation of fractions in separate cycles with a differentiated choice of the reagent regime; preliminary selective flocculation of slime fraction material; use of a new generation of bioreagents for flocculation and flotation. A new approach to subsoil research is protected by a patent. The dependence of the efficiency of biocollectors on the composition of biomineral extract from the processed raw materials, which forms the basis of new reagents, is established. The possibility of obtaining the degree of extraction of PGM, native gold and sulphides from finely ground pre-fractionated poor ores with the use of biocollectors of at least 85% is proved. With conventional reagents, the extraction of PGM is 12-23% lower, with the use of traditional ore-preparation apparatuses, the PGM recovery rate was halved. Methods for the long-term storage and preparation in industrial conditions of biocollector reagents that do not require the purification of waste waters from them have been developed. The developed multifactorial system of intensification of flotation enrichment can be introduced to recovery PGM from tailings of enrichment of titanomagnetite, chromite and copper-nickel ores.

Jan 1, 2018

By L. Kuzev

Unknown and unpopular vibrational grinding mills possibilities to horizontal working chambers have been discussed. They can be realized under normal conditions with the typical values of vibrations applied with vibrational grinding which are: vibration frequency from 15 Hz to 50 Hz, vibration amplitude to 6 mm and vibration geometry. These possibilities constantly increase involving new raw materials and processes. Vibration grinding is possible with other technological process accompanied by intensified technological processing, while the process decreases. In many cases these technological decisions are original.

Jan 1, 2014

By Georges Verly

The estimation of local recoveries is an important issue in a selective mining operation. Two techniques, probability kriging and multigaussian kriging, are applied to estimate local recoveries at Jerritt Canyon. The pros and cons of each method are discussed in light of the results. Both methods provide simple and satisfactory solutions to the problem of estimating local recoveries. Consequently, they can be useful tools to work with in a selective mining operation.

Jan 1, 1984

By David Arana

The use of gas-water dispersion of a molten material flow onto a vibrating surface is developed as a process to minimize water pumping requirements, minimize the risks of explosions, and minimize the post solidification dewatering and fines handling equipment requirements. The process uses existing vibration transport technologies and common plant utilities. Plant trials using the smaller footprint and the progressive molten particle cooling time have yielded encouraging results. The results are analyzed and reported.

Jan 1, 2006

By Gunjan R. Bhattarai, K. Bhattarai

Applications of machine learning and robotics in the tunneling industry are still nascent. Research and development are ongoing in TBM guidance; prediction of TBM cutter wear and tunneling induced ground deformations; and robotic arms for segment installation, inspection, cleaning, and maintenance of TBM cutting tools. This paper presents a case study of geological profile reconstruction using multimodal machine learning. The results from this study can aid the development and application of multimodal AI technologies to generate data reports and geological profiles in real time, taking voice recordings, photos, or videos obtained directly from the field as inputs.

Jun 23, 2024

By F Wu, H Wang, W Chen

A pressurisation method with multiparallel fans has been adopted at HongLiuLin Coalmine to control the significant external air leakage through the goaf area of coalface 15207. Potential damaging effects of large external air leakage on a coalmine’s ventilation system are analysed according to the current air leakage status caused by the exploitation of shallow-covered coal seams. The use of pressure balanced ventilation to prevent external air leakage through goaf areas is introduced. The calculation of ventilation network of HongLiuLin Coalmine shows that the air resistance of an external air leakage branch through a goaf area and the air pressure drops from the intake slope to the working face can be adopted to determine the values of pressure to be increased by regulating fans and airflow controlling parameters of regulators. By investigating airflow requirements of the pressure-balanced area as well as the performances of the auxiliary fans currently used in the coalmine, the number of pressurisation fans needed is fixed. The expected result is achieved after the pressurisation method has been carried out, which can be helpful for other coalmines to handle similar problems.CITATION:Wu, F, Chen, W and Wang, H, 2015. Multiparallel fan method to prevent significant external air leakages through a goaf area of a shallow covered coalmine, in Proceedings The Australian Mine Ventilation Conference, pp 267–270 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 31, 2015

By Antonio de Ita, Isaias Hilerio, Miguel Barron

"The influence of an unconventional lance with a central nozzle on the multiphase fluid flow in a steelmaking converter is studied in this work by means of computer simulations. The lance has four peripheral supersonic nozzles and a vertical central nozzle. Besides, the oxygen flow in the central nozzle is considered independent from the main oxygen supply. Transient two-dimensional numerical simulations were carried out considering just molten steel and gaseous oxygen as the existing phases. Numerical results show that bath agitation and droplet generation are enhanced as a result of the central nozzle. However, the performance of this lance strongly depends on the distance of the lance tip to the molten steel surface and the velocity of the oxygen jet.IntroductionCurrently, two thirds of the world crude steel is produced through the steelmaking oxygen converter [1]. Given the unquestionable economic importance of this technology, any improvement or optimization proposal is welcome. In the majority of current oxygen converters a top oxygen supersonic jet is blown onto the molten steel through a water-cooled lance to eliminate by oxidation some impurities such as carbon and phosphorus. Conventional lances have inclined peripheral nozzles whose number depends on the converter capacity. During the process, a large amount of gases evolves, forming metal droplets and a metal-slag-gas emulsion [2]. The droplets and the resultant emulsion increase the reaction interfacial area, promoting in this way carbon removal and dephosphorization of the molten steel bath [3]. However, during the blowing stage, the emulsion rises towards the lance and converter mouth and frequently forms layers which accumulate in the lance, reducing the life of the lance tip [4, 5]. It is possible that some freezing of the molten metal occurs due to the low oxygen injection temperature, however there are no reports on this. Besides, frequently undesirable operating phenomena such as spitting and slopping may arise as a result of inappropriate blowing practices or bad lance design. In the oxygen steelmaking industry, novel lances design are needed in order to enhance the decaburization rate and the slag formation and, at the same time, preventing operating practices that decrease productivity and move away the shop from safety standards."

Jan 1, 2012

By Ioannis Paspaliaris, Dimitrios I. Gerogiorgis, Dimitrios Panias

"Red mud fiberization is a process with remarkable potential, alleviating environmental pressure by transforming an aluminum by-product into mineral wool, thus to various marketable products. A promising mineral wool process is molten slag fiberization via an impinging air jet, which avoids mechanical wear and rotating parts. The molten slag which remains after pig iron casting flows out of a heated ladle orifice at a high temperature (1600 °C) and adjustable flowrate, and forms a free-falling vertical jet which visibly radiates its excessive heat: at a given distance, a high-velocity impinging air jet meets the vertical melt jet perpendicularly (or at an angle), inducing intensive droplet generation, subsequent fiber elongation, collection and processing.This paper focuses on high-fidelity CFD modeling of the molten jet flow under external cooling: the model encompasses all physicochemical phenomena (melt laminar flow, radiative cooling) and considers several temperature-dependent slag transport properties in order to understand which operational degrees of freedom (manipulated variables) are useful to process optimization."

Jan 1, 2012

By I. Stefanou, J. Sulem

"In the last thirty years, the study of earthquake mechanisms has emphasized the major role of rock friction. Earthquakes appear to be the result of a frictional instability and occur by sudden slippage along a pre-existing fault or a plate interface. Multiphysics couplings play a major role in earthquake nucleation and seismic slip. The effect of shear heating and thermal pressurization may be of prime importance in the control of the stability of shear deformation inside the slipping zone. Other mechanisms in relation with thermal decomposition of minerals affect the pore pressure and the temperature evolution of the system, and can play a significant role in the extreme strain localization observed in field. The actual width of the localized zone is a key parameter for understanding fault weakening mechanisms. On the basis of field observations, laboratory experiments and recent advanced modeling, these phenomena are analyzed and discussed in order to bring some new insights in the understanding of earthquakes nucleation.INTRODUCTIONIn the last thirty years, the study of earthquake mechanisms has emphasized the major role of rock friction. Earthquakes appear to be the result of a frictional instability and occur by sudden slippage along a pre-existing fault or a plate interface (Scholz, 1998; Sykes, 1978). The conceptual model of spring slider system is commonly used to represent the interaction between an elastic crustal block and a fault zone. Stick-slip instability is possible if the softening rate of the shear resistance of the fault zone is high enough as compared to the stiffness of the crustal block. Therefore, weakening mechanisms that can explain how the frictional resistance of a fault decreases with slip and/or slip rate is of prime importance to understand how an earthquake nucleates. In recent years, several drilling programs in active faults (e.g. the Nojima fault in Japan, Boullier, 2011; the Aigion Fault in Greece, Cornet et al. 2004, the Chelungpu fault in Taiwan, Ma et al. 2006, and the San Andreas fault in the U.S.A. Ellsworth et al. 2000) as well as high velocity friction experiments (e.g. Tanikawa et al 2012a; Tanikawa et al. 2012b) have highlighted the physico-chemical processes involved in the nucleation of seismic slip (see for the example the review paper of Niemeijer et al. 2012)."

Jan 1, 2015

By S Padekar, C Tapia, D Likhachev, S Harlikar, D Sapkale

In the quest to access valuable critical minerals, humankind is expanding the frontier into extreme environments like space and deep-sea mining. These ambitious enterprises involve considerable costs and lengthy development cycles to ensure the robustness of mining systems in the face of the harshest conditions and unforeseen challenges. Unfortunately, obtaining information from these unexplored territories is complicated. Data is often scarce, incomplete or impossible to obtain until equipment is deployed, leaving engineers facing many uncertainties throughout the design, testing, production and preparation of such missions. Despite these challenges, these extreme environments operate under consistent physical and chemical principles that can be faithfully digitally replicated. However, unexplored areas and dynamic systems like weather and geology continue to carry uncertainties. While eliminating uncertainties remains elusive, Digital Twins offers a means of robust risk management tool. These virtual replicas can excel in simulating extreme conditions and unexpected events, helping optimise and validate mining system designs tailored for such hostile environments. This study takes inspiration from the Mars Science Laboratory (MSL) Curiosity Rover’s wheel damage rate to develop a Multiphysics Modelling and Virtual Motion Simulation (MMVMS) system. Using advanced Generative Design, this MMVMS system refines the MSL’s design, simulates component and system performance, and assesses the risk of premature damage while operating on Mars. Additionally, MMVMS integrates cutting-edge CAD design technologies from aerospace and manufacturing to realistically recreate the Martian environment and a detailed representation of MSL, allowing mobility verification and validation simulation to test different components in terms of materials, design, weight, power and, therefore, cost. The research highlights the precision of MMVMS in replicating extreme conditions, simulating and evaluating internal and external variables influencing the entire system (Rover) in real-time, and predicting movements, failures, and premature damage. This sophisticated Digital Twin technology, showcased in this research, holds promise not only for space missions but also to be adapted for terrestrial and deep-sea mining operations.

Sep 1, 2024

By Daniel Vargas Quispe, Yorhinio León Robles, Marco Jauregui Vargas, Helen Espinoza Bailon, Oshin Quispe Luya

This project describes the methodology applied during the execution of tests to determine the multiple controls that mitigate damage to the final walls of the pit. The different tests were executed on production pattern, which considered: modification of the angle of pre-split drill line, damage evaluation in individual drills with different load designs, varied detonation sequences, capture and analysis of elementary waves. After the evaluation and analysis of the results obtained in the tests, we are in process to standardize various damage controls such as; the combination of pre-split drill line angles at 80° and 90°; charge design in buffer drills that reduce the angle of action of the explosive and a detonation sequence that involves the creation of a relief filter that is made up of the detonation of two rows next to the pre-split drill line, which will have the function of filtering the waves of vibrations produced by the detonation of the production drills and at the same time it modifies the direction of damage towards the blasted material. The analysis of the different controls, as well as their combination, will allow us to improve the compliance results of the formation of benches.

Jan 21, 2025

By Richard Stahura

The longtime rule-of-thumb for conveyors was that only one cleaner was needed to solve carryback problems and help keep belt replacement costs under control. That is now being rethought. Belt-cleaning systems manufacturers, designers, and users are shifting to the view that multiple cleaners, placed at key locations on the conveyor and properly maintained, are necessary to solve today's material build-up (carryback) problems. There are still not many statistics on conveyor belt cleaning. But some recent studies support this belief. One study contends that the plant maintenance engineer's biggest problem is keeping the conveyor system running efficiently. The study also said the conveyor itself is responsible for most plant shutdowns. An unscheduled conveyor shutdown can cost more than $100,000/hr and run into millions in lost production in a given year. Other studies pointed out that belt replacement is the greatest single cost of the conveyor system. These studies allude to an important fact: cleaner belts lead to reliability and longer belt life. They showed that a critical relationship exists between characteristics of material being moved and the design of all major conveyor components. In practically all situations this relationship is keyed to belt cleaners, which have long been considered "add-ons" or "accessories." At the Fifth International Coal Utilization Exhibition and Conference, the Sammis Station-Ohio Edison Co. said it installed four belt cleaners on each problem belt. The company found that under certain conditions, when the coal is wet and sticky, carryback can be so heavy that it will flow over two cleaners. Before installing the cleaners, it was necessary to schedule a cleanup crew of four men each day and rent a large vacuum truck for an eight-hour shift. In addition, the company dredged the harbor three times a year, to remove coal spillage. Once the cleaners became operational, however, cleanup costs were reduced to a few days labor every third month. Renting the vacuum truck crew was also eliminated, and harbor dredging became necessary only once each year. In addition, the Mechanical Handling Engineers' Association (MHEA) in London pointed out that standards for cleaners are sorely lacking in the industry. MHEA called for instituting such standards in the future. They also reaffirm using multiple belt cleaners for increased efficiency. MHEA pointed out that some conveyor belts can be cleaned by one device, provided that it is correctly installed and adequately maintained. But MHEA recommended that a system approach be adopted, since this has proved more effective in practice. There are two main reasons why one belt cleaner fails to solve most carryback problems. First, management often reasons that the design of the current cleaner has probably been around for years, so it "must be good." This logic leads to a continued investment in keeping the current model operating, which includes pouring substantial sums of money in "housekeeping" manpower hours because the cleaner does not clean. Second, most single-belt cleaners are specified too late in the design process (indeed, some after the system is operational). This complicates matters since cleaning efficiency is directly proportional to when they are specified: the later the specification, the less efficiency. Cleaning equipment should be taken into consideration before the conveyor's structure is designed and fabricated. Otherwise the space available to install adequate cleaning equipment at the head pulley may be inadequate. Instead of matching conveyor with proper cleaner (as would occur during the design of the conveyor itself), designing a cleaning system "after-the-fact" becomes a matter of matching cleaner to conveyor. This limits choices in cleaners and, therefore, overall cleaning effectiveness. This is why after-the-fact designs of single belt cleaners are costly and rarely successful. While it is always best to specify belt cleaners during early design stages, the multiple-cleaner systems approach makes the timing of cleaner installation less critical. Because of flexible mounting hardware, a well-designed system can lead to 99% efficiency in cleaning and put an end to carryback even after a system is operational. Multiple-Cleaner Systems Approach In a multiple-cleaner system approach, the first step is to achieve a thorough understanding of the material to be moved under the worst conditions. With such un-

Jan 4, 1984

By Ben Sheneider

AT THE Flin Flon plant of the Hudson Bay Mining and Smelting Co., Limited there are two types of multiple hearth furnaces used in the roasting of sulphides. This pa-per will deal primarily with the wedge-type furnace in the roasting of zinc concentrates. The other furnace, the Nichols-Herroshoff type, is used in the copper smelter and is described in the papers given by (1) J. H. Ambrose in 1935 and (2) R. E. Mast and G. H. Kent in 1954. The design and operation of these roasting furnaces at the present time is essentially the same as given in the write-up in 1954. No at-tempt will be made here to describe these furnaces, except to mention that there are five Nichols-Herreshoff multiple-hearth furnaces, four of which are used to roast a dried mixture of copper concentrate, zinc plant residue, and flux, before this material is fed to the reverberatory furnace.

Jan 1, 1961

By D Guibal, J Vann, M Harley

Many sample value distributions are highly skewed and present variograms with high relative nugget effects and/or short-range structures. In consequence, significant deskewing of the histogram and variance reduction occurs when transforming between sample and block support, where blocks are of significantly larger volume than samples. When making estimates in the mining industry we usually wish to estimate on the basis of block support rather than sample support. The selective mining unit (SMU) refers to the minimum support upon which ore/waste allocation decisions can realistically and practically be made. The SMU is usually significantly smaller than the sampling grid dimensions, in particular at exploration/feasibility stages. In a non-linear estimate, for each large block (by convention called a æpanelÆ) we estimate the proportion of SMU-sized parcels above a cut-off grade threshold. A series of proportions above cut-off defines the SMU distribution. Use of such non-linear estimates reduces distortion of grade-tonnage curves and provides a better basis for mine planning and economic decision-making. At present, Multiple Indicator Kriging (MIK) is the most widely used technique for performing estimation of recoverable resources. MIK is not the only approach available and it has some potentially serious limitations. The MIK technique is described and a number of theoretical and practical implementation issues are examined. In particular: MIKÆs assumptions about spatial distribution of grade; the behaviour of indicator variograms; application of change of support models; order relationship problems; and modelling the tail of the distribution. Some simple tests are described which allow us to determine the suitability of different estimators for a given deposit and criteria to identify a preferred estimator are also examined. Uniform Conditioning (UC), an alternative estimator which may be used instead of MIK, is described.

Jan 1, 2000

By P. V. Golde, R. A. Poole, G. R. Baiden

"The results being presented in this paper are those obtained during 1996 on a drilling automation project at Stobie mine. This project has successfully demonstrated that the remote operation of multiple drills (by a single driller) from surface using Tamrock Data Solo 1000 Sixty drillrigs is technically feasible and can potentially bring significant rewards in terms of productivity and work environment improvements, as well as labour and maintenance savings. BackgroundThe ObjectiveThis paper is an update of a previous report on remote drilling research at Stobie mine. Enabled by the communications system installed at the mine, the ability to remotely control underground equipment from surface has been demonstrated (Poole et al., 1996). This paper discusses the needs and process required to carry this concept to consolidate the operation of multiple machines under a single operator.The TeamThe team assembled to develop and implement the automation and the communi-cations extensions needed to allow the multiple machines’ operation from the surface by one operator included the following:INCO Mines Research supplied the project management and original project initiative. The primary purpose was to prove the advantages of savings associated with the driller not being required to travel to the underground drill location coupled with the savings associated with one-man, multiple-machine techniques.Tamrock EJC supplied the Data Solo 1000 Sixty drills and the Tamrock specific machine-based custom software. The drills were produced in Finland with no provision for remote operation of the drill from other than the umbilical attached local console.Automated Mining Systems supplied the modifications to the drill communications equipment to allow the machine communications to become broadband compatible. As well, Automated Mining Systems also supplied the hardware necessary to be able to remotely control the portable video camera, as well as the data logging equipment.Stobie Mine personnel were made available to test the function and then integrate the concept of remote control drilling into the Stobie operations."

Jan 1, 1997

By Rodolfo V. de la Cruz

The accurate assessment of the in situ deformability of rock masses is very important in the de and construction of underground openings for mining and geotechnical engineering applications. This paper presents a method and device for determining the in situ deformability of rock masses by relating the borehole jack load to the diametral displacements at a number of orientations around the borehole wall. The method called mu1tiple measurement method include the steps in which: a) diametral displacement sensors are installed at different orientations around the borehole to measure the changes in length of various diameters of the borehole; b) a uniaxial load is applied on two opposed octants of the borehole wall, and; c) using elastic theory and assuming a reasonable value for the Poisson's Ratio of the rock mass, the in situ deformability of the surrounding rock materials is determined from the measured diametral displacements and applied unidirectional load. The multiple measurement method has a significant advantage over existing methods since it provides several independent data in a single test from which to calculate the in situ deformability of the rock mass. The multiple data provide a check and counter check on the reliability and accuracy of the various measurements. The multiple data would also provide a means of quantifying the degree of fissuring on the borehole wall. Information on the degree of fissuring is very important in numerical modeling of rock masses.

Jan 1, 1984

By R. K. Mehta

This paper presents the application of a simple genetic algorithm (SGA) to a coal slurry grinding process in order to find the optimum set of conditions under which the desired slurry properties can be attained. The operating parameters of the process were; slurry % solids, dispersant dosage, ball size, and mill speed. The optimization algorithm, which is based upon the mechanics of natural genetics, was used to find near-global optimum points specific to responses measured In terms of fineness, specific energy consumption, viscosity coefficient, and viscosity exponent. In order to minimize the viscosity of the slurry and simultaneously achieve a condition of maximum packing density, optimization was carried out by the penalty method using an overall objective function incorporating several responses. Computer results and analysis demonstrate the ability of the genetic algorithm to perform better than a traditional technique such as response surface methodology (RSM) and to rapidly locate "the global optimum".

Jan 1, 1992

By A. J. H. Newell, K. Doherty

A copper-gold project has required a number of trade-off studies underpinned by test work to settle on pragmatic flowsheets and throughputs to support a pre-feasibility study that provides a compelling financial case. The primary trade-off studies were based on the mine schedule, ore type feed-grade recovery relationships, likely concentrate grades and typical marketing terms as well as the estimated capital and operating costs for a range of throughputs and mining strategies. Secondary trade-off studies were conducted for specific circuits and additional processing options. Although the details of these studies are not presented, the technical options and subsequent flowsheets are discussed. While the flowsheets will be optimised during the feasibility study stage, the basis is now fixed for the four ore types that would be mined from the copper-gold orebody. The ore types, resulting from a strong weathering profile, exhibit a wide range of copper mineralisation and gold associations, as well as gangue types. They display a range of characteristics that necessitated a nuanced approach to flowsheet development. The primary separation techniques that have been employed include gravity, classification, flotation and leaching while a range of comminution methods have been selected to suit the properties of the ore types. While technical issues are important factors in terms of maximising the quality of separations, recoveries and revenues, attention to material handling, equipment characteristics, the mine schedule, and capital and operating costs are equally important considerations for settling upon a suitable and robust flowsheet. Keywords: Flowsheet, testwork, studies, saprolite gold, native copper, chalcocite, chalcopyrite

Jan 1, 2020

By David Newman

Multiple seam underground coal mining is ubiquitous in Appalachia. Many coal properties have from two to ten or more economically mineable coal seams. Because of the ability to penetrate 600-feet to 1,000-feet or deeper into the mountainside leaving panels of web pillars separated by barrier pillars, highwall mining is a hybrid between surface and underground mining. As a result, many of the ground control problems commonly associated with multiple seam underground mining exist with multiple seam highwall mining. These include: i) multiple seam interaction between web and barrier pillars in superjacent mines, ii) subsidence and caving propagating to overlying seams and mines, iii) pooled water and the potential for inundation resulting from a breakthrough between an active highwall mine and abandoned underground mines in the same or superjacent seams, iv) the presence of overlying or underlying mine workings where pillar columnization in the active mine is not possible, and v) the question of whether to mine ?top-down? or ?bottom-up.? Case histories are presented from southeast Ohio where the Middle Kittanning No. 6 and Lower Kittanning No. 5 seams are successfully highwall mined with 20-feet to 40-feet of largely shale interburden. A highwall miner was caught in a highwall collapse in the Middle Kittanning No. 6 seam when it was overmining auger workings in the Lower Kittanning No. 5 seam. Multiple seam interaction caused by the overmining transferred overburden stress onto the Lower Kittanning No. 5 seam. The overburden concentrated through web pillars initiated auger web pillar failure, resulting in roof collapse and subsidence in the Lower Kittanning No. 5 seam that propagated up to the Middle Kittanning No. 6 seam. A second case history involves multiple seam highwall mining in southeast Kentucky. The A3 Rider, A3, B2, and C1 seams are being highwall mined around abandoned underground mines in the A3 and B2 seams and augering in the A3 Rider. Because of spoil storage constraints for the surface contour mines, the highwall miner follows the active pits in each seam so a standard sequence of ?top-down? or ?bottom-up mining does not exist.

Jan 1, 2009

By David Newman

Multiple seam underground coal mining is ubiquitous in Appalachia. Many coal properties have from two to ten or more economically mineable coal seams. Because of the ability to penetrate 600-feet to 1,000-feet or deeper into the mountainside leaving panels of web pillars separated by barrier pillars, highwall mining is a hybrid between surface and underground mining. As a result, many of the ground control problems commonly associated with multiple seam underground mining exist with multiple seam highwall mining. These include: i) superjacent mines, subsidence and caving propagating to overlying seams and ii) mines, pooled water and the potential for inundation resulting from a iii) breakthrough between an active highwall mine and abandoned underground mines in the same or superjacent seams, the presence of overlying or underlying mine workings where iv) pillar columnization in the active mine is not possible, and v) the question of whether to mine ?top-down? or ?bottom-up.? Case histories are presented from southeast Ohio where the Middle Kittanning No. 6 and Lower Kittanning No. 5 seams are successfully highwall mined with 20-feet to 40-feet of largely shale interburden. A highwall miner was caught in a highwall collapse in the Middle Kittanning No. 6 seam when it was overmining auger workings in the Lower Kittanning No. 5 seam. Multiple seam interaction caused by the overmining transferred overburden stress onto the Lower Kittanning No. 5 seam. The overburden concentrated through web pillars initiated auger web pillar failure, resulting in roof collapse and subsidence in the Lower Kittanning No. 5 seam that propagated up to the Middle Kittanning No. 6 seam. A second case history involves multiple seam highwall mining in southeast Kentucky. The A3 Rider, A3, B2, and C1 seams are being highwall mined around abandoned underground mines in the A3 and B2 seams and augering in the A3 Rider. Because of spoil storage constraints for the surface contour mines, the highwall miner follows the active pits in each seam so a standard sequence of ?top-down? or ?bottom-up mining does not exist. The planning and engineering design considerations associated with each case history is presented along with geotechnical information. In the case of the highwall collapse a back analysis is presented of the stability and safety factors for the auger webs, highwall miner web pillars, and barrier pillars.

Jan 1, 2009