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By P. Piga, O. Sammarco

There is a markedly increasing tendency to design deeper and deeper mines, to use larger amounts of explosive per round, to increase the advance rate of the excavations and so the natural ventilation tends to be more intense in the new mines. For this reason, the mines that make use of powerful mechanical ventilation should also take into account such factors as natural ventilation pressures, especially in the case of mines excavated in high-temperature rocks for which natural ventilation is particularly intense. The results of the studies reported here refer to a very hot mine excavated in an area with a high geothermal flow (the Boccheggiano - Campiano mine, southern Tuscany). At various external temperatures, experimental measurements and analyses have been made of the trend of the thermodynamic characteristics of the ventilation air and of the trends of the air/rock heat exchange along the downcast shaft and along the upcast shaft. These data were then used to work out approximate values of the corresponding natural ventilation pressures. After having identified the most conspicuous variations of the thermodynamic parameters of the ventilation air and the factors causing them, an assessment was made of the repercussions they have on the air flow rates and, above all, on the climatic conditions of the underground excavation sites. The natural ventilation pressures were found not to be constant in time; indeed they change continously and it is difficult to predict the changes. Moreover, it was found that their influence on the ventilation of a section of the mine network is greater if the effect of mechanical ventilation on that section is weaker. In the mine section where the measurements were carried out, some portions were found where the ventilation could become insufficient as a result of the effects of natural ventilation pressures. Finally, some guidelines to be followed in designing hot mines have been put forward which ensure efficient ventilation throughout the network at times with the aid of the natural ventilation pressures, which in certain circumstances may reach very high values in mines of this type.

Jan 1, 1987

By H. Colijn

Introduction Bulk commodity prices are ever increasing. This forces buyers and sellers in world markets to look more carefully at methods for obtaining an accurate accounting of commodity transactions in commerce and materials utilization in processes. Weighing and sampling inaccuracies can result in loss of income, product quality, and cost controls. So weighing and sampling accuracies are extremely important. They are the key components of managing the quantity and quality control aspects of bulk materials handling. This article will confine itself to the weighing systems and will deal with various aspects of system design, calibration, and operations. Emphasis will be placed on new developments and requirements in this field. Weighing methods To measure the gravimetric pull on a body being weighed (the load), the gravimetric force must be countered by an opposing force. Measuring this counter-balancing force thus becomes the measurement of weight. The conventional even-arm balance shows the concept of balancing an unknown mass with an equal known counterbalancing mass. But the loads encountered in industry generally range up to many thousands of pounds. So it is obvious that the even-arm approach is not practical. Thus, with the exception of direct load-bearing load cells, most of the weighing equipment uses some form of lever system. This is usually a combination of first- and second-class levers, to gain a mechanical advantage. These levers permit the load force to be counter-balanced and hence measured within a practical range. Lever systems not only perform this force-reducing action, they also serve to focus the load force at a single point, for convenient measurement. They align the force vertically in one direction so that measurement accuracy will not be affected by unrelated side forces. There are five basic methods of gravimetric weight measurements. That is, there are five basic types of opposing forces. • The first is the standard weight counterbalance. It uses a known weight to counterbalance the load directly or through a lever system.

Jan 9, 1988

By Surendra K. Mishra

The increasing volume of wastes being generated by industry is a legacy of the industrial revolution and subsequent industrial growth. Social and regulatory pressures have been mounting on industry to improve its waste management practices. In many industrial sectors, waste disposal has been the only method of waste management. Land farming, underground burial, deep wells and incineration are still practiced. Often, concentration and volume reduction of waste streams are also practiced to reduce the waste management costs. In the recent years, there has been emphasis on waste minimization. Since the 19th century, industry has practiced recycling of usable resources as a way of handling unwanted byproducts. The mining industry has recovered or extracted economic minerals from tailings for decades. For example, during the gold rush period of 1970s, extraction of gold from tailings dams became economically attractive. Similarly, when it was economical, coal and shale fractions have also been recovered from tailings and refuge materials for commercial uses. In the steel industry, with the development of new furnace technology, recycling of flue dust and scrap iron was practiced as early as in the 19th century. Before 1900, there was little incentive for the industry to reduce the waste volumes. Manufacturers, however, did see a rationale for adopting profit-increasing techniques. They made an effort to recover and recycle economic materials from waste sources. One of the pioneering examples of resource recovery is the coke making industry. As the industry was market driven, products recycled from coke batteries included ammonia for use in fertilizers, gas for power generation and heating, and tar for road construction, wood preservation and roofing. Tar had been avery troublesome waste byproduct. But it quickly became a valuable chemical raw material, providing the foundation for Germany's dominance of the world's dye and medicine markets before World War I. Similar trends evolved in the chemical industry. In the context of current environmental regulations and escalating mining and processing costs, recycling of re- [ ] sources is becoming economically more attractive. Solid and liquid wastes generated by industries contain a range of inorganic and organic contaminants. Among these contaminants, metals and hydrocarbons form major groups. Treatment of these wastes is essential to meet regulatory disposal requirements. In the recent years, based on the principles of chemical and mineral process engineering, processes have been developed to treat these industrial wastes. This article reviews some of the processes that have made impacts and have proven to be effective at commercial scales.

Jan 1, 1999

By Claus Becker

At the RETC 1979 in Atlanta/Georgia it was reported about the beginnings of the Hydroshield system and the first site experiences. Since that time over 10 miles of tunnels in various diameters have been built with that system, and the discussion of the two most interesting projects will be the main topics of this paper. AURELIA TUNNEL, ROME In Rome, the railway system is going to be completed and modernized. Therefore, it is necessary to tunnel through the Roman hills. Part of the new railway system is the Aurelia Tunnel, located some 100 feet below the famous Via Aurelia Antigua, close to the Vatican. The double track railway tunnel has an internal diameter of 9.44 m and a length of 2.410 m. It runs through completely differing soil conditions. (Fig. 1) The first 1000 t are situated in watertight clay, the rear part in water bearing loamy, clayey sands with interlayers of loamy clays. The figure shows the soft change-over from clay to sand. The groundwater head is between [ ]

Jan 1, 1983

By James P. Dorian

In 1990, the former Soviet Union ranked first worldwide in the production of asbestos, chromium, iron ore, iron and steel, lime, manganese, mercury, nickel, peat, potash, and titanium. Since the middle of this century, that nation had maintained one of the world's most valuable mineral industries, ranking number two in 1950 and number one in 1990. It is clearly an enormous mining industry, with more than 1300 enterprises and an estimated employment base of 1.2 million persons (Table 1). Despite its size and historical achievements, however, the mining industry of the 1990s in the former Soviet republics is encountering problems in performance, efficiency, transportation and utilization. The industry operates below full capacity and is plagued by outdated technology and equipment, rising production costs, capital shortages and labor strikes, in addition to general economic deterioration and civil unrest. Attempts to boost domestic minerals supply in the republics so far have failed because of economic difficulties. And the republics lack the financing required to initiate new, large-scale development projects.

Jan 1, 1992

By James T. Curry

The steady growth of the Northwest portion of the United States over the past two decades, and the very rapid development of Northern California, Western Nevada, and Oregon in particular, led the Calaveras Cement Company people to Shasta County, California in 1957. The presence of a large deposit of high calcium carbonate limestone had been recognized for many years, but it required the momentum of an expanding economy to make these long known reserves valuable. This, plus the availability of a reliable supply of fuel in the form of natural gas, and the ready means of shipping the product to the consumer both by highway and railroad, seemed to offer the proper combination to launch a successful venture. The Calaveras Cement Company had been manufacturing cement by the wet process since 1925 at their plant at San Andreas, California. Starting with two small kilns, the plant in Calaveras County started an expansion program in 1945 that ultimately resulted in the plant as it exists today, consisting of five kilns with a combined production of 4.5 million barrels annually.

Jan 1, 1967

By J. L. Young

The McLaughlin Mill started operating in January, 1985. For the first eighteen (18) months start-up, initial operation, and circuit debottlenecking have been done. The mill was designed to recover gold from a refractory ore requiring acid autoclaving pretreatment. This paper discusses the problem associated with bringing this complex hydro-metallurgical plant to consistently achieve design tonnages. Also, briefly described are the mill flowsheet, training program, permitting, and process and project development.

Jan 1, 1987

By D. W. Hendrickson

Cliffs views the process as extending from mine planning to cargo loading including auxiliary systems such as material handling and plant utilities. Process automation is recognized as an area that can provide significant improvement opportunities with less capital requirement than major flowsheet modifications. This paper discusses the development and results of a strategy to allow and promote implementation of process automation improvements at individual mines based on their economic priorities taking advantage of common systems and concepts for use at multiple mines where practical. Specific process control upgrade projects a Hibbing Taconite Company and the Empire Mine are reviewed in detail.

Jan 1, 1998

By J. Andres

"Freeport-McMoRan’s Sierrita operations refines molybdenum disulfide in a ferric chloride leach to remove impurities. To understand bottlenecks in the leach process and the true capacity of the leach system, a cross-functional team was established to look at theoretical models, kinetics of the leaching process, equipment limitations and operational strategies. A series of in-plant tests were run which resulted in a road map for improved throughput. INTRODUCTION Molybdenum, a vital component in the steel industry, is often found in nature as molybdenum disulfide (MoS2). Molybdenum disulfide deposits can exist as standalone components in an ore body, or can also be found within copper porphyry nodes. Processing for these copper/molybdenum porphyry ore bodies involves a first stage of flotation to produce a bulk concentrate before separation of the copper and molybdenum concentrates in a second stage of flotation. In this second stage of flotation, a reagent is added to suppress the copper particles, while allowing the molybdenum disulfide particles to remain hydrophobic and continue to float. This separation is very good at keeping the molybdenum out of the copper concentrate; however a portion of the copper continues to float through the circuit. As a result, there is typically some amount of copper in the final molybdenum concentrate. This copper must be removed in order for the molybdenum disulfide product to meet product quality specifications. Once the raw molybdenum disulfide product has been made, a separate process must be applied to remove any copper, lead, or other impurities remaining in the concentrate. This process usually involves the selective leaching of impurities out of the bulk solid. Gupta mentions three specific types of leaching agents, sodium cyanide, ferric chloride, and hydrochloric acid for the removal of sulfide impurities. Sodium cyanide is useful for the removal of copper compounds such as bornite, covellite, and chalcocite.1 Sodium cyanide solution dissolves these copper compounds, and the remaining molybdenum solids are filtered to produce a pure molybdenum concentrate. Ferric chloride works similar to that of sodium cyanide, but is particularly efficient in removing chalcopyrite and galena compounds. These compounds are easily chlorinated at elevated temperatures, producing copper chloride and lead chloride, through the reactions presented below:"

Jan 1, 2015

By Lars A. Stålberg

"This paper will touch several of the topics covered by SDIMI 2005, including,• Sustainability indicators for the minerals industry, • Best practice of sustainable development in the minerals industry, • Social contributions,The complex issues of a company’s "sphere of influence" and "complicity" are important to every discussion of business and Human Rights. The paper will argue that to protect and promote Human Rights needs to be regarded as an integral part of sustainable development policies for the minerals industry. This implies a need for explicit inclusion of Human Rights indicators among the indicators to be applied by the minerals industry."

Jan 1, 2005

Vancouver-based War Eagle Mining Co. is an advanced-stage Canadian junior mining company that is focused on becoming one of the world?s leading germanium producers. War Eagle?s primary focus is on the Tres Marias high-grade germanium mine near Chihuahua, Mexico. The Tres Marias Mine has high-grade zinc mineralization as well. War Eagle acquired the 28-km2 (17.4-sq mile) property in 2001 from Tombstone Exploration and is currently working to put the mine into production. Current exploration is focused on supporting a resource report and prefeasibility study that is expected to be completed in early 2008. War Eagle expects to have completed an estimated 80 underground diamond drill holes, 40 surface diamond drillholes, 31 percussion holes and 1,296 1.5-m (5-ft) channel samples. Eighty-seven additional exploration targets have been identified within the mining concession. Recent drill results have significantly expanded the known mineralized body at the Tres Marias Mine. The exploration and development program is expected to be completed during 2008. War Eagle owns both the drills currently in operation at Tres Marias. An advanced exploration and development program has confirmed historical grades and is producing encouraging new results from diamond and percussion drilling, channel sampling and high-resolution resistivity geophysics. Glenn R. O?Gorman, an independent geologist and consultant to War Eagle, conducted a study on the reporter. He stated that the Tres Marias concession area has the potential to host 5 to 10 Mt (5.5 to 11 million st) of minable ore.

Jan 1, 2008

By A. Goulsbra, S. Gregory, P. Gelfil, V. Martins, R. Dunne

As a general rule for gold treatment the presence of reasonable amounts of 'coarse' free gold will dictate the use of a gravity circuit. The actual particle size of gold that constitutes the por­tion of' coarse' free gold can vary widely. The larger its size the more troublesome it is, mainly because of the tendency for this gold to quickly settle out from slurries in regions of relatively low velocities. There are a multitude of places where 'coarse' gold can find a resting place, namely, in chutes, between and behind lines, in pump hoppers and in pumps themselves. Fortunately, the problems associated with recovering very 'coarse' free gold, say greater than Imm, is rare on most gold mines that have grinding and cyanide leaching circuits. For these operations it is common practice to have a gravity circuit situated within the milling circuit to recover 'coarse' free gold. Should the 'coarse' free gold constitute 15% to 20% of the total gold in a deposit then its recovery by gravity separation is seri­ously considered. As a gold mine 'matures' the availability of soft oxide ore decreases and the likelihood that harder ore having sulphide gold association increases. To maintain gold production rates in this situation either the gold grade of the treated ore must increase or more ore needs to be treated. In the latter case this is achieved by installing more grinding capacity, an expensive option, or coarsing the grind, with the downside of loss in gold recovery. In general the less expensive capital options is fol­lowed. There is, however, some upside to improve recovery when reasonable quantities of sulphide containing gold are pre­sented that can be recovered by flotation or gravity separation. Concentrates produced from these unit operations can be finely ground and reintroduced to the cyanide leach circuit to improve gold recovery. This scenario is a much less costly option than one where all the ore is ground finer. In this paper the experiences of recovering gravity gold from the Telfer Gold Mine, and gold associated pyrite from the New Celebration Mine will be discussed.

Jan 1, 1996

By Pan Eimon

She was young, beautiful, intelligent, virgin. Her name was Barbara and she captured the attention of many men, especially those in dangerous occupations. Her rich and doting father was hopeful of making an advantageous marriage for his daughter. Instead, she defied him, became a Christian, and refused to marry. Traumatized, he killed her and was himself struck dead by lightning. That is not the plot of a new soap opera. It is the melodramatic story of a Turkish teenager who was martyred in the third century but lives still as patron saint of mining. The story begins with a 20th century fact. Santa Barbara is a figment of imagination - perhaps based on an early oriental folk heroine, embroidered by a seventh century storyteller, and reworked by a ninth century Greek martyrologist. The authoritative Lives of the Saints reports: "There is ... Considerable doubt about the existence of a virgin martyr called Barbara and it is quite certain that her legend is spurious. There is no mention of her in the earlier martyrologies, her legend is not older than the seventh century, and her cult did not spread until the ninth." The Catholic Dictionary adds that the Barbara story is probably "a pious legend." Widely revered Santa Barbara was one of the most widely venerated saints of the Middle Ages. She became the patron, not only to miners, but also to artillerymen, engineers, architects, builders, stonemasons, gravediggers, and sailors. Mines, mountains, churches, and places bear her name. Barbara's feast day, Dec. 4, appears on the most ancient holy day calendars. And a Barbara festival is still celebrated throughout central Europe, in Spain, and in mining areas of Latin America on that date. The Pacific coast channel, the city, and the mission of California are named for Santa Barbara. An expedition, sailing that coast under Viscaino in 1602, was saved from shipwreck on Dec. 4 after the sailors prayed for Barbara's intervention. Franciscans gave her name to the modern Franciscan Province of Santa Barbara, which embraces six western states and the Philippine Islands. Barbara is intimately entwined with mining. The origins of both saint and profession are lost in an-

Jan 11, 1985

By A. M. Johnson

Although known primarily for native copper, the Keweenaw Peninsula of northern Michigan also has deposits of copper sulfide (chalcocite) ore. A number of small, but rich, deposits are present at relatively shallow depths near the base of a thick, steeply dipping sequence of volcanic and sedimentary rocks. Because much of the ore is fracture-controlled, the deposits appear to be ideal candidates for in-situ leaching. Fracture mapping from drill core and borehole logs coupled with borehole packer permeability tests are being applied to evaluate the suitability of the ore for in-situ leaching. A leaching scheme utilizing a bacterial-assisted ferric iron lixiviant is being tested at bench scale. A pilot scale test is being designed to evaluate the system in the field.

Jan 1, 1988

By F. W. Brackebusch

In the paper presented by F.W. Brackebusch on the "Basics of paste backfill systems," paste fill was presented as a backfill process that offers many advantages over other alternatives such as hydraulic fill and rock fill. It was observed, however, that the mechanics of paste-fill transportation in pipelines is not fully understood and that the success of its implementation in practice depends on the precise control of the proportions of fines, aggregates and water in the mixture. The author emphasized the necessity for laboratory and full-scale testing to determine the suitability of a material to be used as paste fill. Although experimental testing is definitely an important operation in the design of a reliable paste fill, advances in the understanding of the fundamental laws that govern paste flow in pipelines are equally relevant. Ideally, the results of such efforts would provide predictive models for the rheology of the paste and the corresponding pumping-energy requirements. In an attempt to achieve this objective, an ongoing research program has been active at McGill University's Department of Mining and Metallurgical Engineering. Preliminary results showed that the underlying mechanics of paste-fill flow in pipelines may be described in terms of what is known as "plug flow," as depicted in Fig. 1. Although this flow mechanism has been known qualitatively for many years, few attempts managed to offer a comprehensive model (Gandhi, 1987; Duckworth, 1986). In our model, it is assumed that coarse aggregates present in the mixture form a porous core, which is filled with paste (fines and water) and is surrounded by an annular non-Newtonian (Bingham-plastic) lubrication layer, which enables the mixture to flow with pressure losses that are easily overcome by common positive-displacement pumps. In summary, our model predicts the thickness of the annular lubricating layer, which controls the magnitude of the pressure losses. This is done either by collecting data on the apparent viscosity of the Theologically-active fine fraction and using an analytical equation (Bouzaiene, 1994), or is done by measuring the void content of the coarse aggregates and deducing the thickness as a function of the fine- to coarse (weight or volume) fraction ratio in the mixture for a given pipe diameter and solids concentration. Our model predictions showed good agreement with data from Duckworth et al. (1986), as shown in Fig. 2.? References Bouzaiene, R., 1994, "Hydraulic transportation in mining," Ph.D. dissertation in progress, McGill University, Dept. of Mining and Metallurgical Engineering, Montreal, P0, Canada Duckworth, A., Addie, G.R., and Maffei, J.R.,1986, "Mine waste disposal by pipeline using a fine slurry carrier," Proceedings of the 11th International Conference on Slurry Transportation, Slurry Transport Association, Washington DC. Gandhi, R.L., 1987, "Effect of rheological properties of fines fraction on slurry hydraulics," Proceedings of the 12th International Conference on Slurry Technology, New Orleans, LA.

Jan 1, 1996

By J. A. Bowersmith

The environment in which the surface mining industry operates today is considerably different than that of a few years ago. Increased pressure from the public, government, labor and internal industry factors calling for the fulfillment of rapidly changing expectations is especially intense in the surface coal mining industry. Such things as requirements for increased production, the Mine Health and Safety Act, environmental concerns and land reclamation, shortages of qualified and enthusiastic employees and market cycles coupled with price competition are but some of the specific items that are requiring the surface mining industry to better utilize equipment, materials, and labor resources available, There is one technical tool available which will assist management to increase productivity, improve cost control and assist in planning, organizing and operating surface mines. Industrial Engineering is that tool. Before a discussion of specific applications of Industrial Engineering to surface mining is conducted, it is worthwhile to review a definition of Industrial Engineering and the history of its development. The following definition has been adopted by the American Institute of Industrial Engineers: "Industrial Engineering is concerned with the design, improvement and installation of integrated systems of men, materials and equipment. It draws upon specialized know- ledge and skill in the mathematical, physical and social sciences, together with the principles and methods of engineering analysis and design, to specify, predict and evaluate the results to be obtained from such systems."

Jan 1, 1976

By D. A. Wheeler

Invented by Pierre Boutin in the early 1960s the column was a complete break from the conventional flotation cell. 1. When used as a rougher-scavenger, the column is excellent. 2. When used as a cleaner, the results can be spectacular. The very first column tests were carried out using it as a rougher-scavenger in a reverse float where silica was floated from iron. It produced a concentrate underflow as good or better than that produced from roughing and scavenging stages in cells, The froth tailing overflow was better than that produced by several stages of cell cleaning. Column scaleup progressed rapidly from the two inch diameter unit to a semi automated 12 inch diameter column on material from the Iron Ore Company of Canada. A change in operating philosophy within IOCC brought all flotation development, column or conventional, to a halt. At that time, IOCC had an exclusive right to the use of the column in Canada in the field of iron ore. We moved into the field of sulphides. A Canadian copper producer sent ore for testing and the results led to their purchase of the first commercial size of column - a 36 inch diameter machine. It was a mechanical disaster. It took several years to raise sufficient funds to return to that mill with our basic 18 inch square unit. It was to be tested and modified in order to learn how to properly design a large column. Originally used as a rougher- scavenger, it had to produce tails equal to the final tailings from this well run plant. It did, and did so while producing a rougher-scavenger concentrate almost equal to the plant final concentrate. It was finally used as a cleaner and produced concentrate 5% higher in copper than the plant final concentrate with equal cleaner tails. This phase of the column development was carried out under very difficult circumstances. The mill superintendent had realized that if he took the froth removal system from our original mechanical disaster and applied it to a conditioner while injecting air, he would have a flotation cell. He had personally applied for patents on this Maxwell Cell. Our development work was done in his mill and as our results became better and better, our difficulties became worse and worse. We finally had to terminate this work. The 18 inch column installed at Mines Gaspé 14 years later was identical to the one removed from Opemiska. The 18 inch column was tried on various ores over the following years and always produced excellent results. However, it was not really a production size unit. We had always aimed for the 72 inch column (72" x 72" x 44' 9"). Prior to this huge machine, we needed the intermediate 36 inch column. The failure of the original 36 inch diameter unit at Opemiska had raised the possibility of short circuiting inside the column as the cross section increased. The first 36 inch square unit was tested in parallel with the proven 18 inch column. If the underflow of the 36 incher was not as good as that of the 18 incher, short circuiting was a possibility in the larger unit. It had been designed for insertion of drop in partitions, four feed points had been provided and the 36 inch column would have become a modular unit of four 18 inch columns. Testing showed the underflows of both columns to be identical. There was no short circuiting in the 36 inch column. Once we had the 36 incher, we had no fear of the 72 inch column. It is permanently partitioned into four 36 inch columns but uses only one set of instrumentation. All the component parts of the 72 inch column come from the 36 inch unit. In spite of our results, the mining community did not believe the column could work. Finally, in 1980, Mines Gasp6 ordered an 18 and 36 inch column for their byproduct molybdenum

Jan 1, 1988

By S. Budirsky

J.B. Gwiazda's article deals with an interesting problem that has not been studied thoroughly up to now. Gwiazda has proposed a technical solution that eliminates horizontal load imposed by the supports on the roof. That load is due to a discrepancy between the trajectories of the canopy and the overlying strata. It is true that the improved lemniscate guidance system proposed by Gwiazda could eliminate the horizontal load but, on the other hand, it would represent a higher cost of the supports, and it would complicate the already complicated mechanism of powered supports. That is why we must be convinced that the proposed improvement is actually needed. From that point of view, the following questions should be elucidated. As shown in Fig. 1, the point O travels along the curve a, which produces horizontal load on the roof in the direction of the coal face. As stated by Gwiazda, "such a high load is capable of destroying the roof above the support, causing rock debris to be scattered around the face." The results of our measurements carried out in coal mines of the Czechoslovak part of the Upper Silesian Coal Basin show that the convergence in the modern type of powered supports does not exceed several millimeters (not more than 10) per hour. Similar conclusions were drawn from field measurements performed in the Polish part of the Upper Silesian Coal Basin (see S. Romanowicz and H. Szopka in Proceedings, Scientific and Technical Symposium Simmex '85, Katowice, Poland, pp. 73 -83). The small vertical closure of the supports also induces a small horizontal displacement of the canopy. In addition to this, the transmission of forces between the roof and the canopy is influenced by the layer of debris on it, i.e., the canopy slides without imposing a greater horizontal load on the roof. This was deduced from field measurements of Voest-Alpine F 4/4600 powered supports equipped with rams instead of the common front lemniscate links (denoted as 1 in Fig. 5). In these supports, the pressurizing of the space of piston rod (la in Fig. 5) causes the rams to close, which induces horizontal load on the roof in a direction toward the coal face. After the setting of a support unit, the pressure in the piston rod space was found to drop, frequently to zero, because the small horizontal sliding between the canopy and the debris or inside the debris caused the horizontal reaction from the roof to fall to zero, although the debris were pressurized by vertical setting load. As a consequence, there was no horizontal load imposed by the canopy on the roof. A rise of the horizontal load was recorded only after the passage of the shearer and during lowering of the adjacent units. Thorough information on the results of the afore- mentioned field measurement is given in the paper, "Analysis of the performance of shield powered supports installed in a thick seam," published in Mechanizacja i automatyzacja gornictwa, 1982, No. 12, pp. 38-46. An English translation of the paper is available from the author. We have deduced from our observations that horizontal load imposed by the canopy on the roof in the direction toward the coal face is useful for roof control because it limits the displacement of the immediate roof toward the gob particularly during the rise working. We came to the conclusion that horizontal load on the roof toward the coal face should be induced on purpose. Could Mr. Gwiazda prove with the results of field measurements his contrary opinion? Has the small horizontal displacement of the canopy toward the face actually had an adverse effect on the roof? As shown in Fig. 2, during the setting of a support unit, the canopy imposes a horizontal load on the roof in the direction of the gob. In this case, I share Gwiazda's opinion that the horizontal load could have an adverse effect on the roof. Nevertheless, two important circumstances were neglected - the horizontal compliance of the supports and the interaction of adjacent units. The question of the compliance was analyzed precisely by I. Krumnacker in Gluckauf -Forschungshefle, 1984, NO. 5, pp. 219-223. He found that due to the clearance between the hinge pins and the eyes of the sheild and due to the elasticity of the steel structure,

Jan 1, 1988

By R. L. Wooten

When discussing what Coal Mine Safety in the future will be, it is important to examine three areas which at present provide significant parameters to the industry. These three areas are: 1) Safety improvements in mining equipment; 2) Labor-management relations; and, 3) The politics of coal mine safety. EQUIPMENT Over the past several decades significant safety improvements have been made in the types of equipment now in use in most operations. Many of these improvements have evolved through mandates from either the U. S. Bureau of Nines, MESA, MSHA; and in some instances, the states. Cabs and canopies are examples of federal mandates while the use of ATRS initially was a state mandate.

Jan 1, 1985

By Jürgen F. Brune

The Fourth Industrial Revolution, that of digital technologies and their application, is rapidly impacting the mining industry, as it is manufacturing, transportation, agriculture, trade, and most other industries. Mining is about 40,000 years old and has its origins in Africa. Since its earliest days, it has experienced four distinct “revolutions” that each resulted in significant improvements in production, productivity, and safety and health: The First Revolution in the fifteenth through eighteenth centuries brought technologies that improved miners’ lives and health, including pumps, forced and mechanical ventilation with wind catchers and bellows, the wire rope and black powder, to name a few. Many simple, muscle- or water-driven machines have been pictured and described in great detail by Agricola who wrote De Re Metallica in 1556. Agricola was familiar with, and concerned about, accidents where miners fell off rotten, wooden ladders, acrid smoke, and dust that caused respiratory illnesses and diseases. He also knew the dangers of fatigue and recommended that miners should sing aloud to prevent them from falling asleep.