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By K. Biswas

A finite-element algorithm was developed for an axisymmetric heat-transfer problem involving phase change. The finite-element treatment of the phase-change problem was dealt with by using the enthalpy method. The finite-element algorithm was subsequently applied to model the heat exchange between mine ventilation air and frozen ground in the presence of roof bolts in an underground mine with permafrost. This paper analyzes a single bolt in the problem domain with the convection boundaries at the roof level of the mine airway. A short-term study, comprising the evaluation of roof bolting (friction-anchored type), was conducted, and recommendations were made regarding the applicability of roof bolts as a support system for a given thermal condition.

Jan 1, 1996

By Allen V. Reicks

This paper reviews the impact of the idler set on the performance of belt conveyors. Idler rolls as part of the load support system and their interaction with the conveyor system will be discussed. in particular, the rotating performance of the individual idler roll concentrating on the rotating resistance and life of the bearing and seal design are addressed in detail. A basis for the development of performance specifications for use in conveyor design that takes advantage of the idler manufacturers design and manufacturing expertise is discussed.

Jan 1, 2008

By Carlos A. Jaramillo, Seng Hing Ngu

"The Murum Hydroelectric Project is a 944-MW development consisting of a 145 meter high RCC dam, two 2660 meter long, 9 meter excavated diameter upper pressure tunnels, surge shafts, two 950 meter long 7 even meter OD penstock tunnels and a surface powerhouse. The project is located in the eastern section of the State of Sarawak, Malaysia, about 200 kilometer from Bintulu, in the Rajang Fold-Thrust Belt, an Upper Cretaceous to Upper Eocene fold and thrust belt that extends under most of Sarawak. The Belaga Formation consists of a thick sequence of deep marine sediments currently appearing as steeply dipping strata of thin to thick bedded, fine to medium grained sandstone interbedded with argillaceous rocks, resulting on a “Flysch” type geologic environment. The project pressure tunnels were excavated perpendicularly to these strata resulting on frequent change on rock conditions and behavior, and required rock support. This paper describes the characterization of the rock mass, design of rock support, and incidents during construction. Particularly interesting were convergence issues in Tunnel 1 resulting from Tunnel 2 excavation. INTRODUCTION The Murum Hydroelectric Project is located in the eastern section of the State of Sarawak, Malaysia, about 200 kilometers from Bintulu, and upstream of the Bakun Hydroelectric Project. The project consists of a 145 meter high RCC dam, a 50 meter high intake tower, two nine meter OD and 2660 meter long upper pressure tunnels, two nine meter OD and 175 meter long vertical shafts, two 25 meter diameter and 80 meter deep surge tanks, two seven meter OD and 950 meter long penstock tunnels and four seven meter OD and 50 meter long branch tunnels, two 8 meter diameter to 3.4 meter diameter and 1400 meter long penstocks installed within the shafts, penstock tunnels and branch tunnels ending in a powerhouse with 944 MW installed capacity. LAYOUT OF THE WATERWAY TUNNELS The two waterways tunnels are basically parallel as shown in Figure 1, with each tunnel supplying water to two units in the powerhouse. The tunnels start separated 25 meters center to center, but 250 meter from the intake the separation increases to 35 meters. The tunnels are lined with reinforced concrete until they reach the surge shafts and steel lined from there to the powerhouse. The tunnel profile is shown in Figure 2."

Jan 1, 2016

By E. P. Chen

This investigation involves the development of a two-dimensional continuum model for the description of jointed media. Specific application of the model developed here is for the potential geological disposal of radioactive waste in the layered sequence of fractured volcanic tuffs under Yucca Mountain, Nevada. This is currently being considered by the Nevada Nuclear Waste Storage Investigations Project, administered by the Nevada Operations Office of the U. S. Department of Energy. The work is a direct extension of the previous constitutive model by Thomas (1982) based on the work of Morland (1974). The main feature of Thomas's model includes two parts: a continuum approximation based on average discontinuous displacements across jointing planes within a representative elementary volume, and a material constitutive description based on linear elastic matrix material behavior and nonlinear normal and shear joint behavior between jointing planes. The mathematical descriptions by Morland based on strain partitioning among matrix material and joint sets allow multiple joint sets to be included in the model. However, the initial effort by Thomas to implement Morland's mathematical model included only a single set of joints. To make the material model reflect more realistically the field characteristics, the current work extended Thomas's model to include orthogonal sets of joints. The nonlinear elastic normal joint behavior is retained in the present model. Joint shear response was treated as linear elastic in the shear stress versus shear displacement relationship prior to attaining the stress level governed by the Coulomb friction criterion. Beyond this critical stress value, a horizontal line is assumed in the work of Thomas for the shear stress versus slip displacement relationship such that the shear stress remains constant while the slip displacement increases. Motivated by experimental observation, the current work generalized the shear response to allow a line with finite slope to govern the slip behavior beyond the critical stress level. The inclusion of an orthogonal joint set led to a fourth order algebraic equation for the calculation of stress increments as compared with a second order equation obtained by Thomas. The nonlinear elastic normal joint behavior provides criteria which allow the selection of the root that yields result consistent with the loading condition of the problem. The addition of one more set of joints provides the potential to more completely study the interaction of various parameters representing the characteristics of jointed media behavior. Material responses to various loading conditions based on the present constitutive model have been obtained. These results and their comparisons to single joint set results are presented. Formulation of the Continuum Model The inclusion of an orthogonal joint set led to a fourth order algebraic equation for the calculation of stress increments as compared with a second order equation obtained by Thomas. The nonlinear elastic normal joint behavior provides criteria which allow the selection of the root that yields result consistent with the loading condition of the problem. The addition of one more set of joints provides the potential to more completely study the interaction of various parameters representing the characteristics of jointed media behavior. Material responses to various loading conditions based on the present constitutive model have been obtained. These results and their comparisons to single joint set results are presented. Let us focus our attention on the set with normal n first. Let the jump dilation displacement and jump slip dasplacement associated with the [ ]

Jan 1, 1986

By C. B. Alcock

The control of high temperature processes requires the ability to measure significant variables during operations. With increasing automatic computerized control there is need for sensors which can provide on-line chemical analyses of all phases present in a reactor without the necessity to withdraw samples from the high temperature reaction zone. Probes using electrochemical cells and conductivity measuring devices have provided the answers to some of these problems, notably the measurement of oxygen in liquid metals, and similar potential systems based on the same fundamental principles for the analysis of non-metallic and metallic elements appear feasible. In this discussion, the state-of-the-art in chemical sensors will be discussed in terms of the potential materials of construction, and, in some cases, the limitations of upper temperature at which some promising systems can, at present, be applied. It is concluded that a new phase of basic research could improve the outlook substantially by providing solutions for some problems in chemical sensors which are now well-defined.

Jan 1, 1990

By S. E. Clay, P. R. Taylor

A physical model for the diffusion and flow of gases through porous solids, which accounts for the random nature of individual gas molecules moving through a solid of definite structure, has been formulated. The model was solved using' the Monte-Carlo technique. It was then used to evaluate specific constants related to the dusty gas model and to describe the gas-porous solid diffusion phenomena. Experimental results were used to validate the stochastic model.

Jan 1, 1988

By Frédéric Flament, Daniel Hodouin, Claude Bazin

A control strategy is proposed to meet the following specifications of flotation control: minimize the variations of concentrate and tails grades and recovery while limiting the amplitude of variations of the manipulated variables. The strategy consists of determining future control actions which optimize a performance criterion over a limited time horizon. The desired dynamic behaviour of the controlled flotation plant is specified using reference models. The strategy is tested on a 2-computer plant simulator working in an environment which emulates the industrial conditions.

Jan 1, 1993

By Guillermo Chong Díaz

A brief overview of industrial mineral exploration and exploitation in Chile is given. World class deposits of salt, lithium, nitrate, and iodine are present in northern Chile. The potential for further exploration and exploitation of these deposits, as well as the substantial reserves of other mineral commodities such as gypsum, anhydrite, volcanic rocks, and borates are discussed. In conclusion, industrial minerals mining in Chile has considerable potential, particularly as joint ventures between foreign and domestic companies. This has been demonstrated in the extraction of nitrates, lithium, iodine, and diatomites. However, as outlined in this paper, a number of factors need to be overcome before the true potential of the Chilean industrial minerals industry can be realized.

Jan 1, 2001

By Abb Raymond

Finely processed industrial minerals in "powdered" form have long been utilized by the plastics, paint, rubber, paper, ceramics, and adhesives industries as fillers, extenders, coatings and special additives. These minerals, primarily calcium carbonate, talc, kaolin, titanium dioxide, and the like, have provided economic, uniform and consistent base materials which have, in turn, been used by the referenced industries to manufacture quality products. The focus of this paper will be the development of equipment and systems at ABB Raymond for the dry processing of such non-metallic minerals in order to meet what have become increasingly stringent requirements of the producers of these minerals. Changes in these requirements seem to have been accelerating rapidly during the last ten years, and it is expected this process will continue into the 1990's.

Jan 1, 1990

By J. A. Herbst, Z. Rogovin

In order to develop more accurate procedures for scale-up and design of semi-autogenous grinding mills through detailed mathematical models, a better understanding of the charge motion and rocklball segregation is needed. To achieve this a 0.61 m (2.0 ft) diam by 0.305m (1 .0ft) length plexiglas mill was constructed as a scale model of a commercial SAG mill. Rock motion in the rotating mill was simulated using various sizes of ceramic balls. Quantitative measurements of dynamic angle of repose, water and slurry motion, holdup and size segregation of the charge were taken. In addition, a video presentation (available to the public) was prepared to elucidate charge and water motion at various mill speeds, charge volumes, rocksize distribution, and flow rates.

Jan 1, 1990

By Charles D. Litton

This paper presents a description of the hazards of smoke from fires, the detectability of smoke using smoke sensors, and the operational characteristics of such detectors. It places in perspective the advantage that smoke detectors have over other forms of fire detection and also provides a discussion of smoke as a significant fire hazard.

Jan 1, 1992

By O. A. Velasquez, A. R. Kumar

"Continuous miners are often equipped with a flooded-bed dust scrubber to clean the air from close to an active underground coal mining face. However, its impingement screen is prone to clogging due to an accumulation of dust, thereby lowering the scrubber’s efficiency and potentially exposing the mine workers to higher levels of dust. Fans can compensate for the increased resistance by varying their operating parameters, but the scrubber screen needs significant maintenance which leads to downtime. The authors have proposed a suitably sized Vortecone as an alternative to the conventional flooded-bed dust scrubber system. Water is used as the filter medium, which is replaced and recycled continuously. Preliminary CFD investigations of Vortecone scrubbers have indicated higher cleaning efficacies, especially in the respirable range. This paper presents the results including the flow characteristics and capture efficacies of a full-scale Vortecone. Multi-phase flows, including free-surface modeling and particle tracking methods, have been adopted. ACKNOWLEDGEMENT The authors acknowledge the National Institute for Occupational Safety and Health (NIOSH) for funding this research project. This research is being developed with the support of a NIOSH Grant 200-2014-59922- ‘Coal Mine Dust Mitigation through Novel Scrubber Development and Numerical Modeling’. The views expressed in this paper are those of the authors and do not necessarily reflect those of NIOSH. This project is aimed at designing novel and efficient scrubbing systems for underground mining operations. The authors acknowledge Dr. Thomas Novak of the Department of Mining Engineering, the University of Kentucky for his support and encouragement. The authors also thank Dr. Sunil Vytala, CFD engineer at Cradle CFD for his invaluable inputs to the numerical models.INTRODUCTION Continuous miners are the main production machines deployed in room and pillar mining operations. These miners extract coal by the shearing action of the wethead cutting drums. Strategically placed water sprays on the drum not only cool the bits extending their useful service life, they also suppress the dust at the point of generation itself. A flooded-bed dust-scrubber (Campbell, et al. 1983) is usually integrated onto the continuous miner to arrest dust from close to the active face. These fan-powered scrubbers have an impingement screen flooded with water, which also serves as the filter element. A demister downstream of the screen removes the excess water from the air cleaned. These conventional scrubbers have been found to be very effective in alleviation of respirable dust levels underground (Chao and De-sheng 2000) (Colinet, Reed and Potts 2013). However, the inefficiencies of the flooded-bed dust scrubbers arise out of their internal components. Depending on the mining conditions, the screen may be clogged by the accumulation of the trapped dust particles. The resistance of the scrubber system is increased reducing the airflow. The flooded-bed dust-scrubber system would, therefore, require frequent maintenance of the screen and the demister (Listak 2010). Since any maintenance needs to be carried out under supported roof, this leads to loss of availability of the equipment as well. In addition to this, the continuous miner operators could be exposed to elevated levels of dust when satisfactory airflow at the face is not achieved."

Jan 1, 2018

By David G. Chedgy, Edward A. Zawadzki, Robert D. Stoessner

Extensive research and testing in commercial facilities has clearly demonstrated that heavy medium cyclones are the most effective process for cleaning a 0.6 x 0.15mm (28 x 100 Mesh) coal at low separating gravities, less than 1.35. This paper describes testing performed to deter- mine system characteristics at these lower gravities and the type of circuitry required to maximize performance. The results of these studies include both pilot and commercial scale tests of cleaning 0.6 x 015mm (28 x100M) coal.

Jan 1, 1988

By Pradip

The development of highly selective mineral processing reagents, which are not merely metal-ion specific, but specific to the particular mineral surface structure, is essential for the exploitation of relatively more difficult-to-process ore deposits, in particular for the separation amongst minerals having the same constituent ion. Both the choice of the functional group as well as the molecular architecture of the reagent determine its selectivity. Several examples are presented in this paper to illustrate the concepts of structure specificity and molecular recognition at mineral surfaces - the concepts crucial to the advancement of the emerging science of reagents design. Recent advances made in the understanding of molecular interactions involved in the synthesis of biomineralized materials are discussed so as to delineate the utility of this approach in the design of selective reagents for mineral separation.

Jan 1, 1994

By George McArthur

GEOLOGY One of the largest copper resources in North America occurs in the Bingham mining district, located 40 km (25 miles) southwest of Salt Lake City, UT. Anaconda's present contribution to the development of this resource is the Carr Fork mine. (Fig. 1, Bingham district plan map.) The Carr Fork story began about 300 million years ago when a thick sequence of sedimentary quartzite and limestone was deposited in the Oquirrh Basin. Subsequent earth stresses formed a series of west-northwest-trending overturned anticlines and synclines that were later offset by northwest-striking thrust faults and northeast-trending normal faults. (Fig. 2, Bingham district cross section.) About 38 million years ago the Bingham stock was intruded into some of the folds, resulting in the formation of porphyry ore in the intrusive, and fissure, replacement, and skarn ore deposits in the sediments. The Carr Fork skarns were formed preferentially in two limestone units, called the Yampa and Highland Boy, which average about 46 m (150 ft) in thickness, separated by about 76 m (250 ft) of quartzite. Copper mineralization consists almost entirely of chalcopyrite associated with pyrite and molybdenite in a gangue of garnet, diopside, magnetite, quartz, and carbonate. Molybdenum, gold, and silver are economic byproducts. (Figs. 3 and 4, indicated ore in plan and section.) EXPLORATION HISTORY The West Mountain mining district, of which Carr Fork is a part, was organized in 1863, after leaf-silver ore was discovered in the Carr Fork of Bingham Canyon. However, it was not until 1873, when the Bingham and Camp Floyd railroad to the town of Bingham was completed, that the mining camp flourished. Many small mining companies in the district were reduced, often through consolidation. By 1937 only the National Tunnel and Mines Co. was active in the Carr Fork area. In 1948 it declared bankruptcy, and was later purchased by The Anaconda Co. Anaconda conducted geologic investigations in the Bingham district until 1968, when a concerted diamond drilling program was initiated to fully evaluate the geologic potential of the Carr Fork area. The exploration program commenced with one diamond drill, but was enlarged to three drills following discovery of the first major ore intercept. Near completion of the exploration effort, large oil well rotary drills were used to drill to depths of 762 to 914 m (2500 to 3000 ft), after which the holes were completed by standard diamond drilling techniques. All holes were collared vertically, but considerable deviation occurred because of structure and rock conditions. Wedging and directional drilling were used to keep the holes on target and to provide multiple ore intercepts in the deeper holes. Geophysical surveys, in-

Jan 1, 1982

By Pieter Hoekstra, Jim Hild, Mark Blohm

In the Basin and Range Province of Nevada, geophysics is used to assist exploration for bulk minable gold deposits, particularly over pediments. It is employed for mapping thickness of alluvium and Tertiary valley fill, for mapping covered structures, and for identifying alteration zones. In addition to potential field and seismic methods, three different electrical and electromagnetic methods are frequently used, resistivity-induced polarization, controlled source audiomagnetotellurics, and time domain EM. A review and comparison of the principles of these methods, illustrated by case histories, is the topic of this paper.

Jan 1, 1989

By Masaji Kato, Yuusaku Tominaga

To maintain good condition of ventilation for both safety and economy, many regulators are installed in a network. In case the open state of a regulator is different from the set point, identification of a broken regulator and a countermeasure to recover airflow distribution in a network must be initiated as soon as possible. An experienced mining engineer can sense a deviation from ordinary airflow quantity. In this paper, a new system to monitor all the regulators in a network is introduced. The basic concept of the system is utilization of both human sensing of airflow rate and computer simulation to understand the macroscopic characteristics of a ventilation network. A fuzzy pattern distinction method is used to process human determination of airflow rate that may be ambiguous. The applicability of the system is demonstrated using the ventilation network of the Horonai coal mine, Japan. In particular, it is shown that the system can identify the regulator to be repaired from information supplied by workers relating to air- flow in a few sensor branches.

Jan 1, 1997

By A. W. Scaroni, C. Y. Tsai

The effect of particle size and composition on the pyrolysis and combustion of a pulverized bituminous coal in an entrained-flow reactor has been investigated. Predicted time-temperature histories of the coal particles and experimental weight loss data indicate a strong coupling of heat and mass transfer to the pyrolysis and combustion rates. A higher combustion rate following ignition was observed as particle size was increased to 112 µm (about 140 mesh). This is related to a higher particle temperature after ignition for the larger particles. Although the heating rate before ignition decreases with increasing particle size, higher slip velocities and surrounding gas temperatures for the larger particles promote early ignition. The presence of liptinite in the coal increases the weight loss rate before and immediately after ignition. Similar behavior was observed for pyrolysis. Fractions of an HVA bituminous coal that were rich in mineral matter or semi-fusinite were found to have a higher heterogeneous char combustion rate than vitrinite-rich samples.

Jan 1, 1987

By Lawrence A. Ph. D. Hansen, J. David Deatherage

Laboratory testing programs were conducted to investigate the performance under compression loading of several types of geomembranes and geotextiles proposed for use in heap and dump leach projects. Synthetic liners of several thicknesses were sandwiched between representative subgrade soils and cover materials, thus modeling in the laboratory the actual installation conditions expected. Performance was evaluated by visual inspection and vacuum testing. Several testing procedures and equipment were used to investigate the effect of these testing parameters on the predicted performance.

Jan 1, 1987

By M. G. Ayat

Engineers in the field of coal preparation are continually striving to increase the efficiency of various circuits used in preparation plants. Undoubtedly, one of the important factors concerning the processing efficiency of a coal preparation plant is improved analyses and control of the processing equipment. The necessary link between the performance criteria of a circuit may be provided through on-line determination of various parameters. Currently, there are a certain number of on-line instruments developed for measurement of ash content of coal (Watt and Sowerby, 1983; Kawatra, 1976; Fauth et al., 1984; Lyman and Chester, 1980), moisture content (Hall et al., 1969), and sulfur content (Stewart et al., 1974). In the case of coal separatory units, these parameters are often directly related to the quality of the product. In other words, the extent of misplacement of refuse in the product, or vice versa, would indicate the performance characteristics of any particular coal washing equipment. Partition curves are therefore established to predict the performance of coal cleaning operations. Conventional sampling and testing is currently the major tool with which partition curves are produced and the performance efficiency of the operation is assessed. While conventional analysis techniques are accurate, they are slow and time-consuming.

Jan 1, 1987