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By Edmund W. Murphy

At the first workshop on Surface Subsidence Due to Underground Mining (1 981 ) , Yarbrough delivered a paper (1 ) describing the mine subsidence insurance program in Illinois operated as the Illinois Mine Subsidence Insurance Fund (IMSIF) . In this paper we will present claims data and describe changes that have occurred in the Illinois Insurance Code during the first six years the IMSIF has been in existence. The change in the original Illinois Public Act 80-1 41 3 that most affected the public was an amendment increasing the maximum amount of mine subsidence insurance avail- able on a structure from $50,000 to $100,000. Seventy-two counties in Illinois have been undermined for minerals, primarily bituminous coal. In Franklin County (.in the southern part of the state) 36 percent of the land area has been undermined for coal extraction. In St. Clair and Madison Counties , two counties that include the St. Louis Metropolitan area along the western border of the state, 10 percent and 7 percent of the land surface have been undermined. Most of the undermined area in the two counties is beneath urbanized land. In 34 counties, approximately 1 percent or more of the land surface has been undermined (2). The first shaft mine in Illinois was sunk in the city of Belleville (east of St. Louis) in 1842, and the mines of early vintage have initiated the majority of the mine subsidence claims. Data compiled from the first six years reveals that most Illinois mine subsidence events that affect structures occur over abandoned mines where early methods of high- extraction mining practices were used. Maps of these mines operated in the 1800s reveal irregular development of room and pillar areas and poorly defined production areas (panels). Rooms in the mines varied from 15 to 40 feet in width and the pillars varied in width from 5 to 40 feet. The pillars were often long and narrow. Recovery rates in mines that operated prior to 1900 generally averaged 50 per- cent, and extraction rates as high as 80 percent have been documented (2). Some pillar robbing occurred.

Jan 1, 1986

By Donald L. King, Frank A. Baczek

Sedimentation-based equipment is used in applications where separation of solids from liquid by gravity settling is desired. If a concentrated solids slurry is desired, the equipment is designed to "thicken"; if a clear liquid is desired the equipment is designed to "clarify." Thickeners normally handle higher solids loading rates than clarifiers, which usually process feed slurries containing low concentrations of suspended solids. Thickeners are therefore designed for heavier-duty requirements, and clarifiers have extra features to ensure more complete suspended solids removal. Major components (Figure 1) that are common to all sedimentation-based equipment are: tank, drive-support structure, drive unit and lifting device, rake structure, feed well, and a means of overflow and underflow withdrawal. Specific features are designed interdependently after the overall separation approach is defined conceptually. This conceptual approach is usually based on past experience or evolves from sedimentation studies conducted on samples of the slurry to be handled. Because many variations and combinations of components are possible, the overall conceptual approach has a number of possible designs that will accomplish the desired results. The final choice is based on practicality, potential for minimizing upsets, and cost.

Jan 1, 1986

By Fabrizio Fara

The Ship Canal Water Quality Project (SCWQP) includes a 2.7-mile long, 18'-10" internal diameter tunnel which is located inWest Seattle. Tunneling in urban areas and soft ground conditions (Till and Till-like soils in Seattle) is associated with the risk of settlements, especially in presence of groundwater above the alignment. The Designer foresaw the use of soil improvement (jet grouting) outside of the launch shaft to mitigate the risk of flowing ground and to provide a redundant sealing. The Contractor proposed and ultimately successfully executed a different approach by using a “Steel Bell System” or Pressurized Can as described in this paper.

Jun 13, 2023

By W. Dan Hausel

Archean supracrustal rocks of the South Pass greenstone belt of western Wyoming have been an important source of gold and iron ore. Actual gold production statistics are incom- plete although gold production estimates for the South Pass- Atlantic City district range from a low of 2.0 Mg (70,000 oz) (Koschmann and Bergendal, 1968) to a high of 9.8 Mg (327,000 oz) (Hausel, 1980). From 1962 to 1983 iron ore was also mined from the greenstone belt and production totaled more than 91 Mt (90 million It). The supracrustal rocks of the South Pass greenstone belt occur in a tightly folded synform bounded by Late Archean granite and granodiorite. The youngest of the Archean successions has a reported Rb-Sr isochron age of 2.8 b.y. (Stuckess, et al., 1985). Metamorphism of the supracrustals increases towards the flanks of the belt and is amphibolite-grade enclosing a small island of greenschist facies rocks. The supracrustal sequence consists of metasedimentary and metaigneous rocks that are divisible into four mappable units. The metasediments include metagraywacke, quartzite, pelitic schist, banded iron formation, metaconglomerate, and graphitic schist. Metavolcanics include metabasalt, meta-andesite, and ultramafic schist. These supracrustals have been intruded by mafic sills and dikes and tonalitic stocks and dikes. Two granite plutons and associated pegmatites intrude the supracrustals in the western portion of the belt, and the supracrustals exhibit both fault and intrusive contacts with granitic batholiths along the western and eastern margins. The northeastern flank of the Archean belt is unconformably over- lain by Paleozoic sediments, and the southern portion of the belt is onlaped by Tertiary sediments.

Jan 1, 1990

By Mike Preston

Attrition scrubbers may not be glamorous, but they are an important and sometimes neglected step in mineral processing. Optimal attritioning will significantly improve the results and efficiencies of subsequent processing steps and can lead to reduced costs and improved product yields. Why is attrition scrubbing used? Attrition means to wear away a surface, typically by friction or abrasion. An attrition scrubber does exactly this, using impellers to force particles against each other, causing intense scrubbing, grinding, abrasion and polishing. This process is not a new concept. It has long been used in the glass industry to remove surface contaminants from silica. But it is also widely used in many areas of mineral processing and other applications including soil remediation and plastics recycling. In mineral separation, for example, the scrubbers help improve yield and efficiencies by preparing feed materials for downstream processes such as flotation, magnetic or electrostatic separation. Inefficient scrubbing can lead to coatings remaining on valuable minerals and decreased yields, as the covered minerals cannot be processed efficiently or are mistaken as waste contaminates and removed. In the example of flotation separation, pre-flotation conditioning uses attrition scrubbers to provide better recovery of minerals while using fewer chemicals. If surface contaminants remain on the mineral, yield is reduced, as the unwanted coating acts as a barrier to the reactants, which make it unfloatable and, therefore, unrecoverable.

Oct 1, 2013

By Kot F. v. Unrug

In spite of extensive research and accumulated experience from mining operations, appropriate coal strength values for pillar design remain debatable. Coal strengths determined in the laboratory on standardized samples vary widely among various coal seams with poor repeatability. Penetrometric in situ strength testing obtains multiple measurements at multiple horizons within the coal seam to provide a strength profile. Alliance Coal has used that method in many of its mines for pillar design. Pillars in these mines perform well. This paper presents a series of case studies and discussion of issues related to coal pillar design. The analysis demonstrates that the proposed default in situ strength of 900 psi is appropriate when no other data exist. However, in the case of appropriate strength measurements combined with analysis of pillar structural composition, differing values can be used successfully. In areas where the penetrometric derived in situ strength is greater than the standard 900 psi in situ strength, reserve recovery has been optimized as required by law without compromising safety.

Jan 1, 2009

By William Gleason

At 6,898 ft below surface, the historic No. 9 shaft at Resolution Copper near Superior, AZ is now the second deepest single lift mine shaft in the United States and connects to the deepest single lift mine shaft in the U.S., Resolution Copper’s No. 10 Shaft (6,989 feet). The shafts serve as ventilation and access for future underground development of what could one day become one of the most significant copper mines in the United States. It is from the base of No. 9 and No. 10 shafts that hundreds of employees of Resolution Copper, a joint venture of Rio Tinto and BHP, hope will soon be given the go ahead to begin driving lateral tunnels to reach a copper deposit that is estimated to contain 28 Mt or 40 billion pounds of copper. Copper was recently added to the U.S. Geological Survey’s (UGGS) critical minerals list, in large part because of increasing demand. A study by S&P Global Energy & Market Intelligence “Copper in the age of AI: Challenges of electrification” released on Jan. 8, 2025, “identifies a transformative trajectory for copper demand, projecting a surge from 28 Mt (31 million st) in 2025 to 42 Mt (46.3 million st) by 2040 – a 50 percent increase that underscores the metal's pivotal role in multiple technological and economic domains.” The surge in demand is driven in large part by the global energy transition, electrification of vehicles, growth of artificial intelligence and data centers, and most recently robotics. Meanwhile, geopolitical tensions have increased the focus on the need for the United States to secure more of its own mineral supply chain. S&P Global’s report is one of many warnings that while copper demand has accelerated rapidly, future supply is being held back. Resolution Copper stands out as one example of a known mineral deposit remaining locked in the United States’ complex and lengthy permitting slog.

Feb 1, 2026

By Thomas L. Mell

Continuous processing plants handling liquids have achieved a high degree of centralized automatic control. Many chemical plants are operated from one room, with automatic control of the various process flow rates. These plants know from experience that automatic control can produce higher through-put, better uniformity of product, decreased operating costs and reduction of storage capacity, Plants which process materials in the form of bulk solids have not been able to use control to as great an extent, primarily due to the lack of measuring equipment capable of providing the same types of continuous automatic control available with liquid flow meters. This paper will describe a scale for measuring flows of bulk materials on conveyor belts which is particularly adaptable to remote centralized instrumentation and automatic control, and will also describe some typical control applications. Fig. 1 illustrates the basic method of measurement of this scale. A conveyor belt idler is supported on a rigid carriage which in turn is mounted in two anti- friction bearings on the conveyor stringers. The pivoted carriage is prevented from rotating about the pivot shaft by an electric strain gauge load cell connected between the carriage and a cross support. Increasing load on the conveyor belt increases the moment of the carriage frame about the pivot shaft, and proportionally increases the tension in the load cell. The belt speed is measured by a conventional d. c. tachometer generator driven from a pulley, usually on the return belt. The speed signal from the tachometer generator and the load signal from the load cell are combined to produce a signal proportional to the flow rate of material in tons per hour, or lbs. per foot, or equivalent units, It will be important to remember, in considering various control applications, that the flow rate of material on the belt is composed of these two component signals, namely the weight of material and the speed at which it is moving. The feed rate is then indicated and recorded by a self-balancing potentiometer of the type used for measuring temperature by means of thermocouples. These instruments may also be equipped with integrating mechanisms reading the totalized tonnage over a period of time.

Jan 1, 1958

By Steve Kral

In December 2013, the Colorado Department of Transportation (CDOT) completed the widening of the eastbound tunnel on Interstate 70 (I-70) from two lanes to three. Work on the westbound tunnel began earlier this year and is scheduled for completion in December. The Twin Tunnels project is located in the mountains about 55 km (35 miles) west of Denver. They were bored during the 1960s when I-70 was being built and became the main access to Colorado?s growing number of ski areas and the state?s Western Slope. Throughout the decades following their construction, traffic on I-70 continued to increase and now the tunnels have a major bottleneck. Com-mutes to and from the mountain resorts, particularly on weekends, have become long and slow. Adding a third lane through the tunnels will help alleviate the congestion. (A complete report on the project can be found in T&UC, December 2013, page 61.) Once the eastbound tunnel was completed late last year, CDOT authorized the funding to begin work on the westbound side. That made economic sense, as the equipment used on the eastbound tunnel needed to only be shifted across I-70 to begin work on the westbound side, rather than removing it in December and bringing it back in March when construction began on the westbound tunnel. Work on the westbound tunnel uses essentially the methods that were used on the eastbound tunnel ? removal of the existing concrete lining and using drill-and-blast methods for tunneling widening. The main difference between the two tunnels is that the westbound side requires more blasting on both ends to widen I-70 to three lanes.

By A. Hayatdavoudi, E. Apande

Introduction Troublesome shales have plagued the petroleum industry for more than 50 years. Unstable boreholes have been experienced when drilled into shale formations; sane have been studied almost at the beginning of rotary drilling. A little progress has been made since then, but much is still to be learned. No simple solution exists so far, but good drilling practices combined with good mud practices have been helpful. It is well known that shales in general have a strong affinity for water, and when water is adsorbed, the stability of the shale section of a well is reduced; cohesive strength will be re- bed, properties will be altered and shale will generally expand and/or crumble. The amount of water a shale will adsorb depends on the characteristics of its clay mineral and the ionic concentration of surrounding fluid. Fluid loss and the resulting hydration of an unstable formation can lead to serious downhole problems. The rate of fluid loss depends greatly on the permeability of the deposited cake. In impermeable formations, however, there is no loss of fluid into the formation. As such, shale, because of its very low porosity and almost no permeability, could be termed impermeable. Yet there is strong evidence that shale surfaces are wetted by an invasion of fluid into the formation through microfractures and jointed planes. It is this wetting that causes the shales to swell and slough into the hole, resulting in problems such as increased mud volume and treating costs, bridges and fill-up, stuck pipe, overgauge hole, poor cement jobs and increased cement requirements, and logging and completion difficulties. Drilling operations have been defeated by severe shale problems, resulting in & hole being plugged and abandoned after several weeks of drilling. Shales are we1l known as being difficult and costly to drill. Numerous fishing jobs have plagued drilling operations, and the cost of reaming tight holes ad weighting up the drilling mud to control shale sloughing has been high. The concept of controlling water loss to stop sloughing was introduced in the 1920's. It was known-then that calcium in fresh water re- strains clay £ran excessive swelling (theory of osmosis) . This reinforced the belief that calcium-based muds such as lime, gypsum and calcium chloride should minimize hydration of clays. Lime muds were then introduced for this purpose and others in the 1930-1940 decade1. They were used for shale inhibition but were not effective. In an attempt to improve them, a special calcium-type mud beam popular during the 1950's. Hole enlargement continued and they too were considered ineffective. During & early 1960qs, papers were published claiming that shale swelling could be prevented by using high concentrations of chemical thinner called Chrane Lignosulfonate1. This began the era of highly treated lignosulfote muds. Unfortunately, the hole enlargement problem continued. During & mid-1960’s, oil based muds were used for the purpose of inhibition of shales. Not until 1966 did Mondshine2 suggest that the water phase be saturated with calcium chloride. The cost of using oil based mud was considered by most operators not worth the additional hole stability. The potassium chloride-polymer muds were also used in many fields in the United States and western Canada. The use of these muds has been claimed to prevent clay swelling by inhibition and encapsulation in sane areas of western Canada. They are also expensive and their ueneral application is still experimental. To reduce filtrate loss when sloughing shale becomes a problem during drilling is a reasonable practice. This study will investigate the use of cationic organic additives to mud to form a protective barrier between the shale - which are primarily composed of clays - and water that will keep water from entering the microfractures and will also prevent them from hydrating. In so doing, an understanding of modern clay chemistry and & dispersive properties of cationic additives in water based systems will be our most valuable tools. This study will also present and solve a mathematical model for simulating cation transport phenomena in fractured shales using the Framdlich equilibrium adsorption isotherm. The studies will analyze wellbore failure and stability as affected by cationic organic material.

Jan 1, 1986

Iron ores may be upgraded by flotation of iron oxides or siliceous gangue using either cationic or anionic collectors. The electrostatic mechanism of adsorption can account for the complex chemistry involved. In industrial practice, only cationic silica flotation is used at present in North America. Some of the seemingly paradoxical phenomena of cationic silica flotation behaviors in meeting the demand for low silica concentrates are reviewed.

Jan 1, 1989

By J. C. Ashby

Electric utility response to certain amendments of the Clean Air Act has resulted in a production of several types of alkaline coal combustion byproducts (CCB). Alkaline combustion byproducts are gaining increasing usage for acid mine drainage (AMD) mitigation as research leads to a better understanding of their beneficial applications. Since January 1997, Mettiki Coal has been injecting alkaline flue gas desulfurization material from Virginia Power's Mt. Storm Unit No. 3 wet limestone scrubber into abandoned portions of the active Mettiki Mine.

Jan 1, 1998

By Ulf Georg Gwildis

Overexcavation and ground loss events during pressurized-face TBMadvance in soft ground can result in unplanned deformations above the tunnel and damage to existing infrastructure. Successfully managing the risk of this occurring is crucial for any project in an urban area to proceed. Common risk management approaches include a combination of establishing suitable ranges of TBM operational parameters and using geotechnical instrumentation for deformation monitoring. Another risk management tool is material flow reconciliation, which varies depending on the specified mining method and the equipment choices by the contractor. This paper compares recent and ongoing projects in the Pacific Northwest regarding overexcavation risk management.

Jun 13, 2023

By FHATUWANI SENGANI

The understanding of yielding pillar behavior has been well documented in terms of pillar strength using numerical simulations and empirical formulas, but the understanding of how fracture propagates in a matured yielding pillar is not well established. A new empirical summation chart of fracture distribution along the matured yielding pillar is presented in this paper. The chart was developed using ground penetrating radar (GPR) supported by borescope observations, focusing on monitoring the distribution of extension fracture.

By Wenbing Guo, Gaobo Zhao, Erhu Bai, Brijes Mishra

"Violent damage to overlying strata can occur above the large mined-out space left by high-intensity longwall mining. For the safe mining under the aquifer and surface water body, it is imperative to investigate the criteria of overburden failure degree due to high-intensity mining. In this paper we present the characteristics of high-intensity longwall mining panels and overburden critical failure. Based on the geological and mining conditions of a high-intensity mining panel, 3D numerical models that consider the maximum horizontal principal stress and minimum horizontal stress and their orientations with the panel advance direction were established by using the 3DEC software. Sizes of the panel reaching the critical failure of the overburden under different mining thicknesses (3.5 m, 6.5 m, 9.5 m, 12.5 m, and 15.5 m) were analyzed. Further, criteria of overburden critical failure were proposed for the high-intensity mining. The coefficient of overburden critical failure (Cf) is the ratio of the strike length (Ls) to the mining depth (H). Through curve fitting analysis, a fitting equation between Cf and mining thickness was obtained. The results showed that overburden failure criterion with high-intensity mining panel is 0.38 = Cf = 0.97 with different thicknesses. Field measurements validated the results from the numerical models.INTRODUCTIONHigh-intensity longwall mining refers to a coal mining method with thick coal seam, large panel width, fast face advance rate, and severe damage to the overburden and surface in China (Guo et al., 2018). Violent movement of the roof rock and severe damage to overlying rock strata occur in the large mined-out space left by a high-intensity longwall mining panel, which is a 3D (three-dimensional) structure layout with highly non-uniform stress distribution. Recognition of such fact a will facilitate this overlying rock strata failure problem investigation (Peng et al., 2019).The studies of overlying strata failure due to longwall coal mining have been reported by some scholars with different methods. Kang et al. (2018) studied the sudden massive roof collapse during longwall coal retreat mining by a large-scale two-dimensional physical model and a UDEC numerical model. Ghabraie et al. (2015) researched the mining-related strata movement by applying the three-dimensional laser scanner, optical transducer, and digital image processing techniques to two-dimensional physical models. Wang et al. (2015) analyzed the structural characteristics and fracture failure process of overlying hard and thick main roof by a 3DEC numerical model; this study also investigated the geostress reduction and permeability enhancement redistribution of the adjacent coal measure strata by FLAC3D. Guo et al. (2012) performed a three-dimensional finite element analysis and shared some insights into the dynamic interaction between mining induced strata stress changes, failures, and gas flow patterns. Meng, Shi, and Li (2016) proposed a 3D coupling model between stress and permeability, investigating the dynamics of a stress, permeability coefficient using FLAC3D. Khanal, Guo, and Adhikary (2019) used the 3D numerical modelling approach (COSFOW) to investigate the strata deformation and the change in permeability in the overburden strata due to the underground extraction. However, few studies considered the influence of the horizontal stress on overburden failure in a high-intensity longwall mining panel, and the critical failure criteria of overlying rock strata is unclear."

Jan 1, 2019

By William Gleason

With its 2011 acquisition of rival equipment company Bucyrus International, Caterpillar added underground mining and large shovels to its line of products and further solidified its standing as the leading mining equipment manufacturer in the world with solutions for every aspect of mining. When Caterpillar spent $8.8 billion to acquire Bucyrus, the global mining business was flourishing, as mining companies around the world worked to keep up with demands for nearly every commodity. Flash forward to 2013, and the global mining landscape looks very different. Lower demand for raw material from China and India and falling commodity prices have forced most mining companies to pull back on their production. The reductions from the mining industry have hit equipment makers like Caterpillar and Komatsu hard. In October, Caterpillar reported that its quarterly earnings had fallen 44 percent. The changing conditions have also changed the narrative from Caterpillar and other equipment makers to customers from offering solutions to move the most tons per hour, to now offering solutions for the lowest cost per ton. In September, Caterpillar hosted some of its mining customers and the trade press at its Tinaja Hills Demonstration and Learning Center near Tucson, AZ to talk about its range of products, from its MineStar System designed to help increase efficiency through better equipment management and planning, all the way up to the massive Cat 7495 and 7495HF electric rope shovel lines acquired through the Bucyrus takeover

Dec 1, 2013

By T. J. Jr. DeMull, F. G. Miller, J. P. Matoney

For some time a need had existed in the minerals processing field for a relatively efficient separator that would treat high tonnages of particles in the intermediate size range, i.e., those particles too large for froth flotation and too small for conventional gravity-type separa¬tors. Among those devices developed to meet this need are the centrifu¬gal specific gravity separators. These devices employ centrifugal acceleration to assist gravitational acceleration in separating light¬density minerals from heavy-density minerals. In the category of centrifugal specific gravity separators are the heavy-media centrifugal separator and the water-only cyclone. The two major centrifugal heavy-media separators, i.e., the heavy-media cyclone and the DynaWhirlpool, as well as the water-only cyclone, are discussed in terms of: design features, operating variables, operat¬ing data, and flowsheet design criteria. Examples of plant applications are given in the field of coal processing as well as the processing of other minerals such as iron ores, potash, and tin. Finally, the subject of the staging of centrifugal separators and their use in combination with other separators is discussed. PRINCIPLES For coarse sizes of minerals, efficient specific gravity separations have been possible for many years with open-bath vessels using the natural settling velocity or buoyancy of the particles. These bath ves¬sels process ore by utilizing micron-size solid particles suspended in the slurry fed to the separator. The inclusion of these particles in the slurry increases the effective density of the separating fluid to allow particle separations to be made at densities greater than that of water. However, if vessel size is to remain within economical limits, the particles processed in the bath vessel must have high settling rates in a IG gravitational field. Because of this requirement, heavy¬medium bath vessels are usually restricted to processing +V4-in. sizes. To extend efficient specific gravity separation to smaller sizes, the gravitational acceleration of particles is replaced by centrifugal acceleration. The settling of a small particle in a fluid in a centrifugal force field is similar to that found in a static bath except that the acceleration due to gravity, g, is replaced by a centrifugal acceleration where v, is the tangential velocity at radius r: V=kdm(P-P,), V'. (J) µ In more practical terms where the particles settle in a suspension of finer particles comprising the heavy media and with an effective suspension density p" V = kdm' (P P ) . v'. (2) U r To date the most effective use of this principle has been obtained with devices that rotate a liquid or suspension within a stationary enclosure in order to create centrifugal force. Cyclones are the most common devices used for this purpose, because they generate centrifu¬gal forces far greater than the force of gravity and therefore not only have high capacities but can treat finer sizes than bath-type vessels can. The two main types of cyclones used by industry are the heavy-media cyclone and the water-only cyclone. Also quite widely used is the DynaWhirlpool, which, though based on the same princi¬ple, differs in design from the conventional cyclone. HEAVY-MEDIA CENTRIFUGAL SEPARATORS Like the bath vessels, the heavy-media centrifugal separators em¬ploy media composed of micron-size particles suspended in water. However, the centrifugal force generated in these separators accentu¬ates the difference in settling rate between particles of different density and thus makes possible separations of finer size particles than can be treated in bath vessels. The two most common heavy-media centri¬fugal separators are the heavy-media cyclone and the DynaWhirlpool. Heavy-Media Cyclone Although cyclones were originally developed for use as classifiers or thickeners, it was later found that they could also effectively serve as heavy-media separators.63. 64, Design Features Fig. I I is a schematic of a typical cyclone developed to serve for any one of the following purposes: as a classifier, thickener, or specific gravity separator. The cyclone consists of a cylindrical section joined to a conical section, usually having an included angle of between 14° and 25°. Feed enters the cyclone tangentially through an orifice attached to the cylindrical section. The overflow orifice is located in the base plate of the cylindrical section. The vortex finder, a tube attached to the overflow orifice, extends into the cyclone from the base plate of the cylindrical section. The underflow orifice is located at the apex of the conical section. As some medium together with mineral particles is fed through the feed orifice, a vortex with a hollow air core extending from the overflow to the underflow orifice forms in the cyclone while hollow spray discharges form at each of these orifices. Under the influence of the centrifugal force, high specific-gravity particles move through the medium to the wall of the cyclone and descend in a spiral flow pattern to the underflow orifice. Those particles in the feed stream, lower in specific gravity than the feed medium, follow the major portion of the flow to the center of the core where they are caught in the high-velocity upward central current and are carried out through the overflow orifice. Fig. 12 shows a family of curves that illustrates how materials of varying specific gravity are recovered by a cyclone. Since the specific gravity of the medium is 1.40, the particles of 1.40 sp gr actually act as part of the medium and, regardless of the particle size, split between the underflow and overflow of the cyclone in proportion to the volume split of the medium. Particles higher in specific gravity than 1.40 are recovered in the underflow of the cyclone at increasing rates as the difference in specific gravity increases and the particle size increases. Particles lower than 1.40 in specific gravity are dis¬charged through the overflow orifice at increasing rates as the specific¬gravity difference increases and the particle size increases. However, all the curves originate at the fluid-flow ratio point for the finest particles of any gravity. The fluid-flow ratio is defined as the ratio of the rate of fluid flowing from the underflow to the rate of fluid

Jan 1, 1985

By L. Zhou, D. Bahrami, Y. Xue

Underground mine fires are a threat to the safety and health of mine workers. The timely determination of the location and size of an underground fire is of great importance in developing firefighting strategies and reducing the risk of any injuries. Machine learning was used in this paper to develop a predictive model for fire location and fire size in an underground mine. The ventilation data were obtained by simulating different mine fire scenarios with MFire. The ventilation data of all airways were used as features to predict the fire location. Based on the feature importance, five airways were selected to monitor, and the airflow data of the selected airways were used to predict the fire location and fire size. An accuracy score of 0.920 was obtained for the prediction of fire location. In addition, in-depth analyses were conducted to characterize the wrong predictions with the purpose of improving the performance of the random forest model. The results show that the occurrence of fire at closely connected airways at some locations can generate misleading ventilation data for each other and the model performance can be further improved by grouping them. Fire size is another factor affecting the model performance and the model accuracy increases with increasing fire size. The result from this study can help mine safety personnel make informed decisions during a mine fire emergency.

Mar 2, 2022

By R. Larry Grayson

A survey of 1250 surface and underground coal mines across the United States was made according to a stratified sampling technique based on national coal districts. A total of 171 responses (13.7% response rate) have been returned and summarized, giving a picture of computer usage in the coal industry. Overall, 63.5% of the respondents use computers, but the percent varied from 100% for large mines to only 44.1% for small mines. As expected, a proliferation of microcomputers has pervaded the industry. Importantly, in spite of the high usage of computers in the industry, sophisticated engineering applications have not yet burgeoned.

Jan 1, 1989

By Chris Roos

The mining industry has made strides in planning for operations to be safe for the workforce and public, to protect the natural environment, and to maximize value for shareholders. However, many of the techniques used to accomplish these goals are based on estimated models of mineral content, production efficiency, and economic performance. The industry has begun to recognize the need for understanding the uncertainty in these models, how it affects their decisions, and what the potential impacts are for each project. The challenge has become how technical professionals can effectively communicate the impact of this uncertainty and its importance to both technical and non-technical audiences. This paper presents mining engineers (and other technical professionals) with traditional and modern principles of data visualization and technical communication that can assist with communicating the effects of uncertainty in the mine planning process.

Jun 25, 2023