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By Eberhard Werner

Existing reports on the effects of mine subsidence on water wells and springs appear to be inconsistent. Some report quick and complete recoveries to pre-mining conditions while others indicate long-term or permanent effects. It is clear that topographic and geological factors as well as precise position with regard to the mine are important in determining probable effects of subsidence on aquifers. Ridgetop aquifers which are well above regional base-level are much more susceptible to disturbance by mining activities than those located topographically lower. Effects seen are attributed largely to increased permeability, both horizontal and vertical. of the aquifer rocks. The deeper aquifers usually show short term losses or water-table declines. but the effects on the ridge-top aquifers persist for longer periods or may be permanent. Subsidence enhances permeability. so that infiltrating water moves much faster to lower levels. causing pond and stream losses and declining levels in wells as well as declining flows of springs of the higher aquifers, while increasing levels and flows of the lower aquifers. Additional effects are shifts of spring locations caused by minor tilts due to differential subsidence and redirection of shallow flows by changes of horizontal fracture permeability. These effects are seen as mining of a panel progresses beneath the site. and are often repeated when adjacent panel mining fronts pass the site. Analysis of water well level and spring flow records indicates that the effects are greatest at the edges of longwall panels in the tensional regime. These effects are amplified for locations close to topographically steep terrain and in close proximity to fracture traces mapped from medium-to small-scale aerial images.

Jan 1, 1986

By M. A. Cornachione

The west central upper Peninsula of Michigan contains a large resource of graphitic slate. The slate has potential industrial use as a substitute for shale currently used in the production of portland cement. Some of the unweathered slate, however, has a high concentration of pyritic sulfur which can create emission problems when processed in a kiln. A low cost method to reduce the sulfur content of the slate through the optimization of pyrite oxidation in a bio-heap leaching operation was investigated.

Jan 1, 1992

By James J. Olson

INTRODUCTION The need for Government-sponsored research and development to increase excavation rates and lower costs for tunneling and mining operations in a variety of rock types has been emphasized in a wide range of publications from advisory panels, symposiums on rapid excavation, and individuals. In response to the predicted demands for mining and construction-oriented underground excavations for the next two decades (1970-1989), a comprehensive 10-year, $200-million research program in rapid excavation was proposed by the National Academy of Sciences in 1968 (1). Although the large program recommended by the Academy has not been funded, substantial Government-sponsored research in rapid excavation has been conducted during the past several years. This paper reviews some of the significant research accomplishments obtained under a three-year, $6.6-million research program in rock mechanics and rapid excavation sponsored by the Defense Department's Advanced Research Projects Agency (ARPA) and managed by the Bureau of Mines. In addition to the rock mechanics research, five major phases of excavation; systems analysis, geologic prediction, rock disintegration, ground support, and materials handling were represented by the projects funded under the ARPA program. The brief outline below recapitulates the major research areas and some of the projects summarized by this paper: Excavation Process Modeling by Computer Geologic Prediction Geologic Reconnaissance for Site Selection Longhole Probe Drilling for Hazard Detection

Jan 1, 1974

By Stephen P. Harrison

The ventilation of coal mines has long been a major challenge for the mining industry. Prior to the 1969 Health and Safety Act, mine ventilation planning was almost entirely handled by individuals in mine operations and engineering who had extensive practical experience. Their background and expertise was sufficient to deal with existing ventilation problems and planning. A recent decline in the number of qualified individuals combined with more stringent state and federal regulations have necessitated a thorough engineering oriented approach to ventilation in mine planning design. To plan for an existing mine, a thorough ventilation survey must be conducted to determine the capabilities of the existing ventilation network. A ventilation survey also provides considerable useful data for long range planning. Essential information such as friction factors, entry resistance, and potential ventilation problem areas is gained from the survey data. With this information a comprehensive computer analysis can be conducted to evaluate alternative mine plans. This evaluation of mine plans is essential to minimize the number of shafts required while still maintaining the quality of mine ventilation. Using an existing mine as an example, this paper outlines a detailed procedure for organizing, con-ducting, and evaluating a ventilation survey. In addition, specific ventilation problem areas are isolated and alternative methods for their solution are considered. Furthermore, a long range mine plan is evaluated and the most feasible variation of the plan is selected.

Jan 1, 1980

By W. M. Ma, Daniel W. H. Su, K. Centofanti, Yi Luo, W. L. Zhong, Syd S. Peng

6.1 INTRODUCTION A surface structure will suffer damage when the additional stresses induced by ground deformations associated with surface subsidence, plus the original stress introduced by construction de¬sign, exceed the strength of the structural elements. In this con¬text, there are two methods available for preventing and control¬ling surface structural damage: one is to strengthen the structure and the other is to design the mining operations such that ground deformations at the structure site can be reduced to an acceptable level. Mining operations include panel layout and mining tech¬niques. These methods are detailed in this chapter. It must be noted that most prevention/control methods men¬tioned in this chapter are used in the countries where the reference papers are cited. In the United States, the coal operators are not required to take those measures mentioned in this chapter. Some of the methods described in this chapter cannot be implemented with¬out changes in the current mining practice as permitted by laws. In addition cost of implementing those methods are not considered here. 6.2 PANEL LAYOUT As shown in Figs. 2.9, 2.10, and 2.11, permanent ground deformations in a subsidence basin mainly concentrate near the edges of the underground opening, and can be divided into four zones. A structure located in different zones will be subjected to different types and magnitudes of ground deformations. In laying out the panels, Table 5.1 and Figs. 2.9, 2.10, and 2.11 could be taken into consideration. Attempts could be made to avoid placing the structure on a location where the ground deformation to which that structure is sensitive is at its maximum. Therefore rational design of the panel is the simplest way to reduce structural defor¬mations. Panel design involves the determination of panel dimension, panel edge location, direction of face advance, and use of yield chain pillars. A. Panel Dimension Since longwalls in the US employ a multiple-entry system, where rows of chain pillars are left unmined, subsidence over those chain pillars is usually smaller. Therefore, whenever possi¬ble, the panel dimension could be designed such that a major structure or structures are over those unmined chain pillars, be¬tween adjacent panels, or some distance beyond both ends of the panels. At the center of the supercritical final subsidence basin, a structure will not be subjected to any final or permanent ground deformations. In order to create such a condition, the panel width must be such that the structure will be located beyond the major influence zone of the final subsidence basin, the minimum dimen¬sion of which must be: [ ] where L is the width or length of the final mined out gob, t is the width or length of the structure to be protected, h is mining depth and [ ] s is the angle of full subsidence. B. Panel Edge Location Wherever there is a permanent panel edge, there are large ground deformations induced on the surface on both sides of the permanent panel edge. Therefore whenever possible the panel di¬mension should be designed such that the permanent panel edges could be located in the areas with the least impacts. In terms of permanent edge location, it is best to eliminate any permanent panel edge under a structure or groups of structures. If this cannot be done, the panel should be lengthened to reduce the number of permanent panel edges, or narrower multiple panels advancing in the same direction in a staggered manner could be employed. If the structures are located in Zones II and III, the longer dimension of the structure must be parallel to the nearest perma¬nent edge (Fig. 6.1). But in Zone IV, the longer dimension should be tangential to the corner of the permanent panel edge. If the structure is inclined to the permanent panel edge, it will be sub¬jected to twisting and shearing. C. Direction of Face Advance The direction of face advance should be parallel to the long axis of the structure. But if the structure is to be located at or close to the center of the final subsidence basin, the direction of face advance should be perpendicular to the long axis of the structure. Careful choice of the direction of multiple face advance is the most effective way to reduce structural deformation and thus dam¬age. This applies the principle of overlapping and cancellations of ground deformations, due to multiple face advance, at the right time and at the right intensity, e.g., opposing tilts, concave and convex curvatures, tensile and compressive strains are induced simultaneously on the structure to be protected by two or more faces. D. Use of Yield Chain Pillars In US longwall panels there are generally two or three rows of stiff chain pillars between the panels. The combined width of the chain pillars ranges from 100 to 350 ft(30 to 107m). depending on mining depth. In general, surface movement above the chain pil¬lars after the panels on both sides have been extracted is much smaller, as compared to that in panel center. Thus in order to create critical or supercritical width of opening and eliminate sur¬face bumps over the chain pillars, yield chain pillars may be em¬ployed (Jarosz and Karmis, 1986). However if yield pillars are to be used, it must be designed such that it yields totally right after the panels on both sides have been extracted. Unfortunately cur¬rent yield pillar design techniques cannot predict when and how much it will yield. In summary, whenever possible attempts could be made to lay out the panel in such a way that surface structures are located above chain pillars between panels or above solid coal beyond both ends of the panels. In those areas the surface structures will most likely be unaffected, or if affected, the damage is so minor that no remedial measures are necessary. 6.3 CONTROLLED MINING TECHNIQUES Several mining techniques are available for reducing the sur¬face ground deformations of specific types. Regardless of tech-

Jan 1, 1992

Mine managers need better information to locate new opportunities and then to assess the effect of their decisions. We are developing the Intelligent Decision Support System (IDSS) and its two major modules, the Pattern Recognition System (PRS) and the Knowledge Representation Subsystem (KRS) to automatically provide the information from monitoring system sensors. This paper focuses on the KRS Algorithms that extract key information from lists of time study type event sequences. Because a static system cannot operate effectively in a dynamic mining environment, we are prototyping an index based technique that allows the system to adapt itself to this dynamic environment.

Jan 1, 1990

By T. L. Heisler

The Cigar Lake project, located in northern Saskatchewan (Figure 1), is one of the world?s largest high grade uranium deposits, with reserves of 150 million kilograms of uranium in a deposit averaging 430 metres below the surface. The Cigar Lake project is being developed by Cigar Lake Mining Corporation (CLMC) which is owned by Cameco Corporation (48.75%), Cogema Canada (36.375%). Idemitsu Uranium Exploration Canada Ltd. (12.875%) and Korea Electric Power (2%). Mining the Cigar Lake orebody is presenting a very real challenge due to the high grade and the ground conditions in and around the orebody. Presently, an underground test of various mining methods is underway.

Jan 1, 1992

By Paul H. Rylund

Substantial priming was a considered necessity for proper initiation of ammonium nitrate-fuel oil mixes as ANFO began to carve its niche in the mining industry in the latter fifties. Heavy priming accompanied the introduction of prills and oil to many blasting operations, large charges of high explosives were commonly used at the bottom, top and frequent intervals through-out the column. As the quality of ammonium nitrate improved and operators became more experienced, primer costs began to diminish. Increased experimentation continued with reduced primer costs a main objective. Cast primers were introduced and became accepted as an excellent companion for ANFO. Although the trend toward larger diameter boreholes became increasingly popular, emphasis on lower and lower priming costs continued. A primer was simply required to produce any type of initiation within the ANFO column to be considered adequate. Suddenly ANFO priming had digressed from excessive to marginal. Early experimental data developed at "test site" and laboratory locations indicated that ANFO had a tendency to react inefficiently in the initiation region of the column unless substantially primed. This was evidenced by the presence of unstable reaction rates detected with newly developed detonation velocity measuring equipment. These 10" order or "transient" velocities were believed to originate because of inadequate primer strength or a primer diameter to column diameter mismatch. How-

Jan 1, 1972

By A. M. McKim

6, 7.3 meter diameter autogenous mills at Wabush Mines are undergoing conversion from a radial configuration of pulp discharger to a curved design. Improved discharging efficiency has effectively lowered the pulp level in the mill. The low level operation enhances the grinding efficiency netting a 12% power reduction. Significant reductions to rate of wear has been a spin off benefit. The design incorporates features for holding the assembly solidly in place thus eliminating bolt hole damage and leakers. Preliminary work in one 11 meter mill at Hibbing Taconite did not indicate that all the same advantages were available in their process.

Jan 1, 1982

By David M. Koogler

If you are contemplating starting a small coal mining operation there is a good possi¬bility that you can not afford it. If you, have already started, you may be on the road to bankruptcy. If you are a small but well established operator you may be trading dollars, or even dissipating your capital, equipment and other assets. A bleak outlook? Yes! Meant to be discouraging? No! Just a reminder that, with todays costs of doing business, high interest rates, rapidly increasing costs and decreasing sales prices, a small businessman/miner had best watch closely or he will be mired in something worse than a soft bottom - namely a cash and credit shortage, and in too many instances In recent times, bankruptcy. We will not dwell on what happens once you are that far gone, though I could cite a good example. But, let us look at what should be done to avoid such a catastrophe.

Jan 1, 1981

By Satya Harpalani

An investigation was carried out to study the microscopic structure of coal in order to understand the phenomenon of methane migration. A Scanning Electron Microscope (SEH) was used to study the surface and pore structure of bituminous coal taken from an underground mine. Micrographs obtained showed the highly porous nature of coal which explains the large quantities of gases that remain within the pores in the compressed and adsorbed forms. These micrographs further showed that most of the pores within the coal matrix are the 'dead-end' type and do not contribute much towards the flow of gas. The most important finding was that solid coal has a network of cracks and fractures indicating that it is these cracks that are primarily responsible for the gas flow, rather than the pores. The size and distribution of the pores within coal influence the capacity of coal to retain methane but movement of the gas molecules is the responsibility of the microfractures. Any mathematical modeling to simulate gas flow through coal must take this into account. For purposes of modeling, the structure of coal can be considered to have dual porosity. First, the gas molecules are released from the pores and there is a gradual migration towards the fractures. Once the gas reaches the fractures, its movement is eased greatly along these fractures.

Jan 1, 1987

The 6th International Mine Ventilation Congress (IMVC) was held May 17-22,1997, in Pittsburgh, PA. This marked the second time that the IMVC was held in the United States. The first congress, organized in 1975 by the Mine Ventilation Society of South Africa, was held in Johannesburg. Since then, the meetings have been held every four or five years, with the 1979 meeting being held in Reno, NV. This was followed by Harrogot, England, in 1984; Brisbane, Australia, in 1988; and Johannesburg, South Africa, again in 1992. The IMVC provides an international forum in the field of mine ventilation for the purpose of sharing technology and experience. The meetings are attended by ventilation engineers, academics, consultants, government employees and vendors interested in mine ventilation. As was evident from this meeting, significant progress has been made in the field of mine ventilation. However, disasters continue to occur around the world and long-term health problems continue to affect workers. So there is a need for further improvements in ventilation technology. The highlight of the conference was the technical sessions in which more than 80 papers were presented by authors from more than 20 countries. In addition to the technical sessions, the conference featured field trips to a number of mine properties throughout the United States. Five short courses were offered on topics ranging from respirable-dust control to mine fires and explosions. The conference also featured a trade show. It exhibited the latest advances in ventilation equipment, computer application software, consulting and engineering services, and health and safety equipment.

Jan 1, 1997

By Fred H. Seymour

In spite of the progress made by geostatistical theory over the years, evaluation of low grade open pit gold deposits continues to be challenging. Many Carlin type deposits are modelled from exploration drilling spaced on 10C foot centers. From these drill holes, 50 by 50 by 20 foot blocks containing about 4000 tons of material are estimated. The block size is a compromise between being large enough for a good geostatistical estimation and being small enough for practical pit limit analysis and mine planning. Most of these gold deposits are highly variable and include ore and waste zones that are too small to be properly defined from exploration drilling information. Because of this, selective mining is controlled by sampling closely spaced blast holes where the density can be as high as 50 blast holes per exploration drill hole intercept. Figure 1 illustrates an example of the ore/waste contact definition before and after blast hole sampling. With exploration information only, a tentative ore/waste contact can be drawn between the exploration blocks.

Jan 1, 1989

By V. G. Hill

The term bauxite was first used by O.P.A.P. Dufrenoy in 1845 for an ore which was discovered by Pierre Berthier in 1821 near the village of Les Beaux de Provence near Arles in southern France. His data suggested that this mineral was an alumina hydrate with two molecules of water. However, it was subsequently shown by thermal analysis that the mineral was a fortuitous mixture of the mono-hydrate and the tri-hydrate. Diaspore had been previously discovered in 1801 and gibbsite in 1822. The term was however retained as a rock name. The name of the village was changed to Les Baux around 1885; Sainte Claire Deville suggested that the mineral name should reflect this, and it was changed to bauxite (Bracewell, 1962, Rkgnier, 1988). Mining of bauxite began around 1860 in the Auriol region in the Bouches du Rhine area in the south of France. This ore was transported toMarseilles by carts and was processed in the Salindres plant, which at that time was the only plant producing alumina using the Deville process and aluminum by the chemical process. During that period white bauxite (low iron content) was particularly sought after for the production of aluminum sulfate, refractory bricks, and quick setting cement. Export of bauxite from France began in 1880 and was initially delivered to Chemische Fabrik, Goldschmischen near Breslau, and to Guilini's Ludwigshafen plant in Germany in 1885. These companies produced alum and aluminum sulfate (RCg- nier, 1988). The next bauxite mining operation was in Antrim County in Northern Ireland in 1873. This was first used for the manufacture of alumina refractory bricks and quick setting cement (Bracewell, 1962). It is important to emphasize that initially almost all of the bauxite which was produced came from France and was mainly used for non-metallurgical purposes. At that time even the production of alumina was mainly for use as a mordant in textile dying. However, with the development of the Hall-Héroult process, the alumina which was available was increasingly used for smelting to aluminum. In spite of this the demand for non-metallurgical bauxite continued to increase and a set of applications were developed. These include refractories, abrasives (including the recently developed proppants), high alumina cements, aluminum chemicals, activated bauxite, and alumina. It became increasingly evident that the high alumina-low alkali raw materials have special advantages. The question however was one of cost benefit. Chin (1989) has pointed out that the non-metallurgical operations have been traditionally grafted on a bauxite/alumina/aluminum industry tree. In this context the non-metallurgical alumina produced was, with few exceptions, regarded as either coproduct or byproduct i.e.: Bauxite Trunk Sector Alumina Trunk Sector Aluminum Trunk Sector

Jan 1, 1994

By J. S. Martin

The redesign and reinforcement of a highwall located adjacent to a $10,000,000 shopping center, destabilized by active subsidence, was conducted after an extensive geotechnical investigation. The highwall was excavated in a hillside where a coal seam had been retreat mined and augered. Engineering geological mapping, determination of the properties and behavior of the intact rock, fractured rock, and urethane grout material, and soil were required to characterize the highwall and conduct a stability analysis. Remedial measures included re-excavating portions of the highwall to reduce the slope angle, and pressure grouting of the immediate roof.

Jan 1, 1988

By Rodrigo Jerez

This paper describes a Mixed Integer Linear Programming model that was developed for planning the coal operations at Mountain Coals, Inc., in Kentucky. The model incorporates the use of stockpiles as practiced and allows the operator to find the least cost combination of raw coal feeds, washing densities and blending to produce the different quality coals as required by the coal contracts.

Jan 1, 1984

The National Institute for Occupational Safety and Health (NIOSH) conducted field tests to evaluate the effectiveness of a wet head continuous mining machine for reducing dust exposure for continuous miner operators. Wet head technology delivers water via sprays to the continuous miner's cutter head as opposed to traditional standard sprays located on the boom and body of the mining machine. The sprays, positioned directly behind each bit on the cutter head, deliver water at the point of attack, serving to cool the bits during mining to reduce the potential for frictional ignitions. The sprays also flood the coal with water to potentially suppress dust generation. Dust surveys were conducted at several mines to evaluate the wet head's effectiveness to control respirable dust exposure at the continuous miner operator location and in the immediate return. Results show that the wet head miner improved air quality at both locations to varying degrees in some cases and not in others when compared to a continuous miner with a standard spray system.

Jan 1, 2010

By S. Alpay

Underground mining method selection (UMMS) is one of the most important decisions that mining engineers have to make. Choosing a suitable underground mining method to extract a mineral deposit is very important in terms of economics, safety and productivity of mining operations. In real life, UMMS is one of the Multiple Attribute Decision Making (MADM) problems and decision makers have always some difficulties in making the right decision in the multiple criteria environment. Analytic Hierarchy Process (AHP) and Fuzzy MADM (FMADM) are the MADM tools and can be used for the selection of the best underground mining method by considering the problem criteria. UMMSMADM is a computer program which is based on AHP and FMADM and it can analyze the UMMS problems and produce the best underground mining method considering different deposit shapes and ore bodies.

Jan 1, 2010

By Harry M. Parker

Exploration for sandstone-type uranium ore bodies which will be exploited using underground mining techniques is usually executed in sequential fashion. Geostatistical methods can be used at the earliest exploration stages to design drilling programs which have a high probability of success in the location and delineation of mineable ore-grade mineralization, should such mineralization exist. In succeeding development stages, geostatistics may be used to outline and define the potential grade of reserves and to apply confidence limits on the grade estimation. Delineation of mineable reserves for mine planning requires extensive development drilling; using such drilling data geostatistical methods may be used to minimize the drilling needed to achieve a desired level of confidence in the calculation of mineable uranium ore grade and tonnage. Because sandstone-type uranium deposits tend to be pod-shaped and are generally aligned along a mineralized trend, this paper proposes a geostatistical method of calculating uranium ore reserves which accounts for this fact and predicts the area within a trend which is underlain by ore. This method uses an indicator value; that is, drill holes which contain mineable ore-grade intercepts are coded as 1, those that do not are coded 0. The indicator may be kriged over the mineralized trend to obtain an estimate of the area underlain by ore. The thickness and grade-thickness may be kriged, and the average ore grade may then be obtained by dividing grade-thickness by thickness, as is conventional for stratabound deposits. The mean grade is then multiplied by the kriged mean thickness to obtain an estimate of the volume, and thence tonnage, of mineable ore within the trend.

Jan 1, 1979

By M. Misra

The dissolution of mercury during gold cyanidation is the cause of many environmental, health and processing problems. A study was undertaken to find a suitable reagent for the removal of mercury bearing complexes from the leach liquor. Removal of mercury from synthetic solutions and process water from a gold mine was investigated using sodium sulfide, sodium and potassium dimethyl dithiocarbamates as precipitating reagents. The results have shown that efficient mercury removal could be achieved by addition of potassium dimethyl dithiocarbamate (KDTC), by formation of stable mercury compounds. The resultant mercury-potassium dimethyl dithiocarbamate precipitates are stable under present plant operating conditions and do not have any deleterious effect on gold adsorption by activated carbon. Furthermore, it is also possible to stabilize the mercury in the heap during cyanidation by adding dimethyl dithiocarbomate.

Jan 1, 1998