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By M. J. Sapko

The design requirements for mine ventilation seals have undergone a radical transformation in recent years, and these revisions have greatly increased the cost of the seal designs and their construction. For example, in the past two years, new federal regulations have increased the minimum design requirement to withstand explosion pressures from 138 kPa (20 psig) to 345 kPa (50 psig) or 827 kPa (120 psig), depending on whether the sealed mine volume is monitored continuously or not. Moreover, there is still a possibility that under certain conditions (such as detonations) even higher pressure requirements may be necessary. The ability of a monolithic, stand-alone mine seal to reliably withstand the full range of current and future pressures is becoming increasingly difficult and expensive. In an effort to develop a practical alternative, the West Virginia Office of Miners? Health Safety and Training (WVOMHST) and the National Institute for Occupational Safety and Health (NIOSH) have collaborated in a research effort to develop a practical, economic, and safe mine sealing technique that can enable mines seals to meet the full range of new explosion pressure design requirements. The basic idea is to use a barrier of common mine gob and rubble in combination with a conventional mine seal so that the pressure resulting from a gas explosion is reflected, absorbed, and attenuated, so the pressure on the ventilation seal is reduced. This paper discusses some concepts and preliminary test results for a ?Passive Mine Blast Attenuator? (PMBA) that can provide a useful alternative to increasingly larger and stronger stand-alone mine seals. Numerical models and full-scale experiments conducted at the NIOSH Lake Lynn Laboratory Experimental Mine (LLEM) show that the use of a PMBA can signficantly reduce the blast pressure and impulse on conventional ventilation seals. DISCLAIMER: This information is distributed solely for the purpose of pre-dissemination peer review under applicable information quality guidelines. It has not been formally disseminated by the National Institute for Occupational Safety and Health (NIOSH). It does not represent and should not be construed to represent any agency determination or policy.

Jan 1, 2009

By Joseph Cervik

Common methods of controlling gob gas in U.S. nines are by means of ventilation of gob areas and gas drainage through surf ace boreholes. Costs of drilling surface gob holes increase as deeper coalbeds are mined. Where gob holes cannot be drilled because of topography, ventilation is the only means of control. Even then, sufficient air may not be available to dilute methane in the bleeder entries to acceptable levels. Thus, new methods of gob gas control need to be developed that are independent of surface topography, and of the mine ventilation system, and less costly than present systems. Except for slight variations in procedures and equipment, Great Britain, West Germany, France, Belguim, Poland, and Czechoslovakia use a common methane control method that is different from the system generally used in the United States, This Bureau of Mines paper reviews European mining methods, mining conditions, and methane control technology and discusses their applicability to U.S. mines.

Jan 1, 1979

By James J. Scott

Shale formations are the Nemesis of the Mining Engineer. Shales react to changes in environment in the most unusual and unpredictable manner. Increase in temperature may cause spalling, increase moisture and compression induced fractures may occur, and if a full face is exposed it may deteriorate due to atmospheric exposure. Combine only small amounts of shale in layered fashion with hard brittle competent rock and the whole structure may be fractured and fail due to stresses generated in and around the shale. In this paper the author will discuss failure mechanisms encountered under various field conditions and remedial action which may be employed by the engineer.

Jan 1, 1969

By N. Djordjevic

Introduction The vibration energy that travels beyond the zone of rock breakage is wasted - all it does is cause damage and annoyance. Under favorable geologic conditions, this energy may travel many kilometers before it finally drops bellow the background noise level. This has forced the introduction of more restrictive limits to the allowable vibration levels. To maintain the profitability of a mine or quarry and to comply with environmental protection legislation, blasting needs to be performed in a more predictable way that will ensure that the final results are optimal in both mining and environmental terms. Minimization of ground and induced structural vibration is, therefore, a matter of good blasting practice -not just an attempt to avoid complaints from neighbors. A new approach to blast vibration minimization is presented. The method utilizes the existence of the local minimums in the frequency spectrum of single-hole blast vibration. The results are presented as a delay map showing maximum ground or structural vibration velocity for many combinations of interhole and interrow delays. A blast engineer can use this map to select an optimal combination of delays that will produce a low vibration velocity at a selected location and, at the same time, will be acceptable from the point of view fragmentation or muck pile shape. Response of structures A typical single-story building has two distinctive forms of vibration. The first form is a translatory vibration of the building superstructure (frame), and the second form is a flexural-bending vibration of the structural elements such as walls and floors (Siskind et al., 1980). Walls and floors will have several modes of oscillation. The most important is the fundamental mode of the vibration, as this mode will have the lowest frequency, the largest amplitude and will cause the largest deformations. The vibration of walls and floors is also a source of secondary vibration within a building, due to the movement of loose objects, e.g., furniture and wall fittings (Dowding, 1985). The subjective estimate of the amplitude of a vibration by the occupants of a house will be unrealistically high due to the effect of the secondary vibrations. It is now well recognized that human perception of ground vibration begins at levels that are far below those that will produce minor damage to the most fragile structures. In mining and quarrying operations, complaints regarding vibration levels tend to be determined more by human perception or annoyance rather than by observations of damage. Ground vibrations on the order of 0.08 mm/s (0.0032 ips) (Walter and Walter, 1979; Murray, 1987) can be felt, and they are often subjectively estimated to be about 100 times greater. Amplification of ground vibration in the structure depends on the amount of energy in the ground vibration spectrum that is in the vicinity of the structure's resonant frequencies together with the damping ratio of the structure at these particular frequencies. One way to avoid significant vibration amplification in a structure is to shift the dominant part of the ground vibration away from the resonant frequency range of the structure. The presented method allows for the selection of the optimum blast timing (interhole and interrow delay times) to minimize the resultant ground vibration amplitudes in a given frequency range. It also allows the selection of suboptimal, but still acceptable, blast delay times, which may be preferable from the point of view of overall blast performance. Determining frequency ranges of importance in structures In attempting to avoid amplification of vibrations in the structure, ground vibration amplitude of frequencies close to the resonant frequencies of the building needs to be minimized. The width of the frequency-minimization region is determined by the value of damping in the building. If the damping ratio is low, then the frequency-minimization region around the resonant frequency will be relatively broad. By shifting the dominant part of the ground-vibration energy into the frequency region much higher than the resonant frequency of the building (1.5 to 2 times), it is possible to achieve efficient vibration isolation of the building. In such cases, the structural dynamic amplification of ground vibration will be less than unity. The first step in this minimization process is the determination of the structural resonant frequency. From the frequency spectrum, it is possible to determine the resonant frequency of the structure. Sometimes the

Jan 1, 1998

By Hojong Kim, Isehaq Al-Nafai, Kwadwo Osseo-Asare

The standard Gibbs free energy of formation (ΔGo f, 298) of bastnasite, (Ce, La, Nd, Pr)FCO3, was estimated using four different methods. The obtained average values were − 1589.5 kJ/mol for CeFCO3, − 1599.5 kJ/mol for LaFCO3, − 1589.1 kJ/mol for NdFCO3, and − 1595.4 kJ/mol for PrFCO3. The value for cerium bastnasite, CeFCO3, was used to construct a potential vs. pH (Eh-pH) diagram to investigate the stability relations of cerium bastnasite. The diagram shows that CeFCO3 is stable in neutral to basic conditions (pH ~ 6.5–11).

By M. Kavvadas

Geotechnical design using Factors of Safety recommended by Codes of Practice is based on largely unknown ?margins of safety?, usually without consideration for the importance of the project (i.e., potential consequences of failure) directly or explicitly. On the contrary, probabilistic modelling can be a useful tool in risk management as it provides the means to measure the risk to be managed. This is achieved by calculating the probability of failure associated with a specific design, i.e., by relating the classical factors of safety with the corresponding probability of failure and by using a cost optimization procedure to achieve ?optimal? designs, accounting for the expected costs in case of catastrophic failure. This paper describes the methods used to calculate the probability of failure and its correlation with the classical Factor of Safety using sampling techniques and a simplified method based on the moments of the factor of safety considered as a random variable. These procedures are illustrated in an example which investigates the stability of a slope.

Jan 1, 2005

By T. E. Burns

The process engineer is frequently requested to select equipment to separate brine from solids, In many cases, this is a more difficult task than the selection of most other pieces of process equipment because quite often the operation of the various types of debrining equipment cannot be predicted by calculations, One must rely to a great extent upon experience or empirical test work to predict performance - that is to say one must use a practical rather than a theoretical approach. This is not to say that the solutions to liquid-solids separating problems are wholly an art but rather it is to emphasize that the approach demands a fair knowledge of commercially available liquid-solids separating equipment, some background on the advantages and limitations of each type and in many cases might necessitate a fair amount of test work, or at least, a study of performance of equipment on similar applications.

Jan 1, 1966

A major Brazilian iron ore producer, SA Minerayao da Trindade (Samitri), has recently completed modifications at two operations which involve the use of Derrick high frequency vibrating screens. Details of these modifications are presented, together with a review of product quality improvements.

Jan 1, 1997

By C. Salcedo, J. Vallance, J. Sáez, M. Robles, J. Spangenberg, S. Rosas, L. Fontboté

The Tambomachay ore deposit (13°28'36.78"S, 71°57'35.98"W, about 6 km north of the town of Cuzco, Peru) consists of Cu hosted in arkosic red beds of the Kayra Formation (Lower Eocene). Bornite, chalcopyrite, chalcocite, covelite, digenite, malachite, and chrysocolla occur disseminated in thin layers and in veinlets. The occurrence of the copper ores in a part of the red bed sequence containing green reducing layers, the presence of organic matter in interstices between the hypogene sulfides, and the sulfur composition of the copper sulfides (δ34S values between -16.9 and -12.4‰ vs VCDT) pointing to bacterial sulfate reduction, are strong arguments to propose that mineralization was caused by copper-bearing oxidizing saline basinal fluids that precipitate copper sulfides when they meet reduced sulfur in an organic matter-rich horizon. Faults parallel to the regional Tambomachay Fault could have acted as feeders for oxidizing basinal copper-bearing fluids. Fluid migration was probably driven by tectonically-induced topography gradient. INTRODUCTION A number of red bed Cu occurrences are known in the Cuzco region in the early Eocene – early Oligocene San Jerónimo Group (Gregory, 1916; Carlotto et al., 1996, 2011; Loza et al., 2004). In the past, copper ores were extracted in several small-scale mines in the surroundings of Cuzco, including Tambomachay, Tipón, and Zurite in the Cusco province and Ushpa, Guilda, Giovanna, and Langui in the Sicuani Province. The abandoned Tambomachay Mine (13°28'36.78"S, 71°57'35.98"W), about 6 km to the north of the town of Cuzco (Romero et al., 2015; Salcedo et al., 2017, Fig. 1) was chosen as the main site for the present research aimed to better study the genesis of these copper occurrences. Results deriving from fieldwork, microscopic characterization of ore and host rock, and sulfur isotope determination suggest that the key factor for the genesis of the copper ores is that copper transported by oxidizing basinal fluids is trapped by reduced sulfur of bacteriogenic origin located in a part of the red bed sequence that shows intercalatins of green reduced horizons.

Jan 1, 2019

By A. Vaillant

Classifiers that are used to separate granular materials into a coarse and a fine stream, are considered. Fundamental Equations are presented which apply to all, such Classifiers and all feed size distributions. The practical, real Classifier is compared quantitatively with the perfect. Classifier. A Formula is introduced for the Real Classifier Selectivity, that defines what portion of each particle size is sent to the coarse outlet duct. This selectivity function is characterized by three Parameters, one of which (b) is a numerical measure of the sharpness of classification. A new dimensionless variable (J) appears in Equations and Graphs for recirculating load, product size distribution and specific surface in the classified product. This variable combines the effects of sharpness of separation, Classifier setting and fineness of a Rosin-Rammler Type feed to the Classifier. Classifier efficiency is defined, based on Specific Surface.

Jan 1, 1967

By Kurt Zeidler, Vojtech Gall

London Underground Limited are currently constructing an extension of the Jubilee Line. The approximately 16-km long Jubilee Line Extension Project connects the existing Green Park Underground Station with the Canary Wharf area and Greenwich. Being a part of the project, the London Bridge Station (Contract 104) was built using a combination of the New Austrian Tunneling Method (NATM) with Compensation Grouting. NATM was successfully applied in softground and urban areas under restrictive requirements regarding settlement limitation. Information on the flexibility of the method and the influence of Compensation Grouting on ground and tunnels are given.

Jan 1, 1997

By K. Sharman

Quintette Coal Limited (managed and 50% owned by Denison Mines Limited) operates an open pit coal mine located in northeastern British Columbia, in the foothills of the Rocky Mountains. (See Fig. l). Mining commenced in 1982. The mine currently produces 4.75 million tonnes of medium volatile bituminous coal per year from three pits (Mesa, Wolverine and Shikano), using a truck/ shovel operation. (See Fig. 2). Conveyors and trucks transport run-of-mine coal to the heavy media/froth flotation process plan t, where it is cleaned and loaded into rail cars for delivery to the Ridley Island port at Prince Rupert, British Columbia. All coal is sold to the Japanese steel industry under a long term contract. The coal seams mined at Quintette are contained in the Lower Cretaceous Gates Formation. Mineable seam thicknesses vary from 0.6 m to 10 m. The regional structure of the area is typical of foreland fold and thrust belts, with open to tight folds and imbricate thrust faulting. The range of structural features found in the three pits, and their effect on mining, forms the subject of this paper.

Jan 1, 1991

By E. J. Harvey

The Ozarks has been called "a diamond in the rough". In this region streams have steep gradients, sparkling clear flows of cold water fed by many springs, and a wildness that is almost unique in the central part of the United States today. The Current River and its tributary, Jacks Fork, have been set aside for preservation by the National Park Service as a "Wild River" in the first park of its kind in the country. It is called the Ozark National Scenic Riverway. Similarly, responsibility for the preservation of the Eleven Point River has been assigned to the U. S. Forest Service. Protection of other streams in the Ozarks has been considered by State agencies. The hydrologic system of the Ozarks is a complex network of gaining and losing streams, caves, conduits, and large springs. Increased sewage loads derived from the growing towns and expanding tourist trade are a potential hazard; effluents may flow underground for long distances, polluting springs and wells. To add another dimension to the hydrologic picture a new lead industry is also flourishing in the Ozarks. Although the history of lead mining in the area goes back to 1701 (U. S. G. S., p. 43), the area has not seen a revitalization like the one that has been developing in the last 10 years; and the economic growth promises to continue indefinitely. Although this brings capital expenditures and wages into the area, it also brings potential hydrologic problems. Chemicals, wastes and other substances either stored on the surface or transported across it are subject to accidental spillage. In an area where these substances remain on the surface their effects are subject to surveillance. In the Ozarks, however, this may not be possible.

Jan 1, 1970

By J. Alatalo

Autogenous grinding is a process of reducing the particle size distribution of an extracted ore by using the ore itself as the grinding media. It is a process that is difficult to control and there is a lack of knowledge of the events occurring inside the mill. To find out more about how the mill behaves under different processing conditions, a full factorial test was performed with iron ore in a pilot-scale pebble mill at the LKAB R&D facility in Malmberget. To complement this work, a strain gauge detector was embedded in one of the mill?s rubber lifters, the Metso Minerals continuous charge measurement (CCM) system, and was used to get more information about the charge dynamics. The data from the experiments has been analyzed. For production purposes, an increase in the number of particles smaller than 45 µm can be regarded as a probable increase in the production rate. The analysis shows that there will be an increase in fines at 65% of critical speed, especially when the mill is 45% full. This setting will also increase the power consumption, but improves the grindability of the ore even more. The deflection of the lifters is smaller for lower critical speeds. A higher degree of filling also gives a smaller toe angle and a higher shoulder angle as expected.

Jan 1, 2011

By J. Alatalo

Autogenous grinding is a process of reducing the particle size distribution of an extracted ore by using the ore itself as the grinding media. It is a process that is difficult to control and there is a lack of knowledge of the events occurring inside the mill. To find out more about how the mill behaves under different processing conditions, a full factorial test was performed with iron ore in a pilot-scale pebble mill at the LKAB R&D facility in Malmberget. To complement this work, a strain gauge detector was embedded in one of the mill?s rubber lifters, the Metso Minerals continuous charge measurement (CCM) system, and was used to get more information about the charge dynamics. The data from the experiments has been analyzed. For production purposes, an increase in the number of particles smaller than 45 µm can be regarded as a probable increase in the production rate. The analysis shows that there will be an increase in fines at 65% of critical speed, especially when the mill is 45% full. This setting will also increase the power consumption, but improves the grindability of the ore even more. The deflection of the lifters is smaller for lower critical speeds. A higher degree of filling also gives a smaller toe angle and a higher shoulder angle as expected.

Nov 1, 2011

By M. Baumann

Operating and maintaining the heavy equipment used in open-pit mining operations is an ongoing challenge for mines. Typical operations employ a combination of shovels, wheel loaders, and haul trucks to excavate and transport the material for further processing. As this is the first point of contact for the material after blasting, it is often a bottleneck of all downstream processes, thus, equipment uptime and efficiency is crucial. Automated systems for bucket tooth monitoring, payload measurement, proximity detection, and rock fragmentation analysis will be examined. The impact of these systems on operation safety, efficiency, and reliability, in real-world scenarios will be investigated. The process of managing all the above fleet of equipment in a mine can be streamlined by connecting the equipment monitoring systems to a central server. Using the central server, the distribution of this information can be automated to ensure that the right people see the data in a timely manner, improving both proactive and reactive responses to threats to safety and productivity.

Feb 23, 2014

By W. A. Wilkinson

In creating a surface mine design, a complicated series of events may be required to meet both mining and environmental objectives. Envisioning the mine at every step of the operation can greatly assist the engineer to identify design and operational problems that might otherwise go undetected until the field operations reach the problem. Providing operations a visual progression of the mine ensures that critical designs generated by the engineer are understood and effectively communicated to operations. Providing the plan as electronic data to the surveyors and/or on-board GPS systems can ensure successful implementation of the design. This paper discusses using computer technology to generate a virtual mine plan and strategies to consider when communicating a virtual mine plan through electronic and paper formats.

Jan 1, 2002

By Darrell E. Young

This presentation will define what talc is, how it is mined and processed, and how talc is used in the paper industry. It will also give you some idea about who Luzenac America is and from where it came. Luzenac America was formed in July, 1992 as a result of the acquisition of the talc assets of Cyprus Minerals by RTZ of the United Kingdom. Cyprus Industrial Minerals was then merged with the other RTZ talc interests under the Luzenac name. Luzenac is a town in the Pyrenees of Southern France -and the home of Talc de Luzenac, RTZ's first talc acquisition. The Luzenac Group is the largest talc producer in the world.

Jan 1, 1993

By J. F. T. Agapito

OCI Wyoming mines two flat-lying trona seams that are 3- to 3.5-m- (10- to 11.5-ft-) thick, about10 m (33 ft) apart and 250-m- (820-ft-) deep at its Big Island Mine in Wyoming. Continuous miners and a yielding-pillar system have contributed to improvements in resource recovery and productivity. The use of yield pillars minimizes the stresses transmitted from the upper to the lower seam. However, yielding must not impact the good, long-term stability needed to prevent subsidence for a large portion of the mine beneath the Green River channel.

Jan 1, 2000

By B. DANIEL MARJAVAARA, I. A. SOFIA LARSSON, ANNA-LENA LJUNG

One way to upgrade iron ore is to process it into pellets. The pelletizing process is multifaceted, involving complex fluid dynamics with highly turbulent, high-temperature flow in intricate geometries. This makes it hard to perform measurements during operation, so a useful tool for better process understanding is computational fluid dynamics (CFD), where the challenge is to perform efficient and trustful simulations of complicated problems. A validated simulation model can be valuable for increased process control and development. In this paper, the flow field and coal combustion process in a pilot-scale iron-ore pelletizing kiln is simulated using a CFD model. The objective of this work is to apply a coal combustion model to enable an investigation of thermal effects from the flame on the surrounding flow field.