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By S. Guo

In this paper, a model for the resin anchor bolt system is developed in which the smooth bar is modeled by using one-dimensional truss elements and the resin annulus is modeled by using axisymmetric elements. These two submodels are combined together and then incorporated into the' existing computer code ROOFBOLT. After this development, all of the components in the resin anchor bolt system including smooth bar, bearing plate and resin annulus can be correctly modeled.

Jan 1, 1995

By Stanley C. Suboleski, C. B. Manula

INTRODUCTION In any mining operation all possible steps should be taken to increase efficiency. One area for improvement is mine planning and design, particularly in the area of equipment selection for room-and-pillar systems. Be- cause of the availability of a wide variety of face machines, a fair degree of selectivity can be exercised in the choice of equipment for a particular job. However, this choice must be made on the basis of quantitative facts and forecasts related to the mining application. The purpose of this section is to develop and analyze the details of the mining process. Some specific areas studied include the relationship of system design to productivity, suboptimization as a result of equipment changes, and measurement of system performance. The plan of work leading to a quantitative description of these study areas is based on the growing interest in total system design using simulation as an analytical method (Manula, 1963). CHARACTERISTICS OF PRODUCTION OPERATIONS FROM ROOM-AND-PILLAR SECTIONS For a given mining method, raw production in a given section of a mine is primarily dependent upon the coal seam thickness, roof and floor conditions, methane emission, the mining methods, and the man-machine element. Average section production varies from 300 to 800 st per shift for conventional and continuous mining in high seams and from less than 100 to 300 st per shift in low seams. Since the reject varies from 0 to 40%, these figures must be decreased by the appropriate percentage to reflect the amount of clean coal mined. Personnel requirements per production section per shift for the various methods are listed in Table 1. Table 1. Production Personnel Method No. Method No. Conventional 12-1 5 Longwall 9-14 Continuous 9-1 2 Shortwall 9-12 MINING VARIABLES To evaluate the constraints and interrelationships for various mining methods, it is necessary to categorize the variables which underlie system production potential. Seven critical independent variables which determine production can be identified and categorized (Suboleski, 1978) : Seam Height The five categories are as follows: less than 36 in.;. 36 to 55 in.; 55 to 100 in.; 100 to 180 in.; and greater than 180 in. Floor Quality Floor quality ranges from : Excellent: Smooth, hard, grades less than 1 to 1 % % , and dry. Good: Smooth, soft but dry, with grades less than 3 % . The floor will deteriorate, but cautious operation can prevent it. There may possibly be heaving at some later time. Fair. Soft and damp. There is occasional interference with equipment operation; requires the use of four-wheel drive shuttle cars; ruts with regular use, and may have adverse grades of 5 to 7%. This may be coupled with slippery bottom and/or occasional steep rolls. Poor: Soft and wet. Requires blocking of the bottom to support equipment. There are frequent steep rolls and grades in excess of 7%. Roof Quality Roof quality ranges from : Excellent: Men are able to work under the unsupported top during the initial production cycle if legally permitted. Good: The roof is bolted on a 4 x 4 or 5 x 5 pattern with short bolts (442 in.) or <seam height if the seam >42 in., or requires posting with no bolts on a 4 x 4 or 5 x 5 pattern. There are no falls. Average: The roof is normally bolted on a 4 x 4 or 5 x 5 pattern, but with long bolts (>seam height or >6 ft.). There are infrequent minor falls or there may be an excellent roof which is difficult to drill. Fair: This type often requires spot bolting in addition to the regular pattern or bolting with planks. The roof conditions require shorter than planned cuts, or narrow cuts. Poor: This type requires bolts plus crossbars and posts, or installation of yielding supports or truss-type support. It is almost certain to fall if this is not done. Methane Liberation This ranges from none detected to low (no buildup at the face, even with minimum ventilation requirements) to moderate (the curtains must be extremely tight and tubing close to the face or methane will build up to 1 % during the loading of the car) to high (methane will build up to 170 if the miner is operated at the normal rate, even with proper ventilation). Hardness of Coal Coal hardness falls into the following categories: Soft: Soft coal is easily cut by a continuous miner. A plow could be used by longwall. Average: Coal of average hardness could be easily cut by a miner, and a shearer would be used in the longwall. Moderate: Moderately hard coal causes difficult cut-

Jan 1, 1982

By E. J. Ostrowski

The history of ironmaking dates back to 4000 BC when an open forge was used to produce a sponge iron from a heap of ore and charcoal. Even at this early date, man recognized the need for a fuel and a reducing agent. As time passed, man developed new methods of producing iron; however, these developments were centered on the mechanical aspects, and as a result, a furnace evolved which is now known as a blast furnace. During this period of evolution,&apos; man struggled with the only fuel he knew - charcoal. Some 5600 years passed before any attempt was made to use coal as a fuel for the blast furnace. The use of coal had its beginning in 1619 when Dud Dudley of England first attempted its use in the blast furnace; as a-fuel and as a reducing agent. Coal charged to the top of the blast furnace was not satisfactory. The volatile matter of the coal choked the flues, and also the poor, strength qualities would not support the weight of the ore. Breaking up of the coal compacted the stock column to an impervious mass. One hundred and sixteen. years later in 1735, Abraham Darby of England introduced coke as the fuel and reducing agent in the blast furnace. The acceptance of coke as a fuel for the blast furnace was not spontaneous. As late as 1870, one-half of the pig iron product of the United States was made with anthracite coal, 30 per cent with raw bituminous coal and coke, and 20 per cent with charcoal. However, by 1910, 96.2 per cent of the blast furnace product was made with coke, 2.4 per cent with anthracite and coke admixture, and 1.4 per cent with charcoal. Coke became the standard fuel in the blast furnace. As the art of ironmaking progressed, more pig iron was produced and more coke was consumed. Coke oven capacity was progressively increased. In 1910, there existed approximately 4,000 coke ovens; in 1960 there was approximately 15,000 ovens. This increase in coke oven capacity was necessary to feed the mammoth appetite of modern blast furnaces.

Jan 1, 1962

By Onuralp Yücel, Kağan Benzeşik, Ömür Can Odabaş, Selçuk Kan

Extraction and processing constitute an important area in the metallurgy of molybdenum. Molybdenum trioxide (MoO3) production is one of the most important stages in molybdenum production. In this study, the effects of different furnace types on MoO3 production were investigated by using molybdenum concentrate as a raw material obtained during the enrichment of copper ores. Preliminary experiments have been made using a chamber type furnace, and a transition to a pilot-scale has been carried out with rotary kiln experiments. The effects of a different time and atmospheric conditions on MoO3 roasting kinetics were investigated by experimental studies conducted in the temperature range of 500–650°C. It was determined that the optimum temperature and time for sulfur (S) removal was 625°C and 180 min in the studies carried out in the rotary kiln, and it was determined that 0.61%S content was reached with an average removal efficiency of 98%. The activation energy in these sets was calculated as 89.519 kJ/mol.

May 3, 2021

By C. H. Pitt

A jet slurry apparatus has been constructed to test corrosive/erosive wear properties of grinding ball metal. Plain high carbon steel heat treated to a hardness of about 60 RC was used. Slurries of quartz and chalcopyrite ore concentrate were used as the jetting media. Weight loss due to pure corrosion was determined by the linear polarization technique and weight loss due to pure erosion was determined by jetting while cathodically protecting the sample. By comparing the total weight loss with the sum of the weight losses from pure corrosion and pure errosion it was found that there was a synergistic effect between corrosion and erosive wear. Erosive wear rates are given as a function of pH and mineral type.

Jan 1, 1984

By Norman F. Schulz

Representative sample s of typical manganiferous iron ores from the Cuyuna Range, Minnesota, were reduced to the metallic iron state at temperatures just short of fusion with an excess of coke in the manner prescribed by the R-N Direct Reduction Process. The magnetic separation characteristics of the reduced ores were determined at several grinds by means of the Davis magnetic tube concentrator. The efficiency of metallic iron concentration by magnetic separation was a direct function of the degree of metallization of the ore sample and of the degree of liberation attained in grinding. Some improvement of liberation characteristics was observed if a small amount of sodium chloride was present in the ore during reduction. Despite the extremely fine -grained structure of the crude ores, iron concentrates containing more than 90% Fe at iron unit recoveries of 90% or more were obtained from well-metallized samples of three of the four ores tested. The rejection of manganese to the tailings corresponding to such separations varied from 80 to 95%.

Jan 1, 1967

By Franziska Wolf, Rainer Ellmies, Helmut Mischo

"Mining is an important part of the economy of Namibia. In 2016, 11.1 percent of the GDP was the result of mining activities with 22 active mines (The Chamber of Mines of Namibia, 2016). Only one of them consists of an underground mining operation.The global annual production of fluorspar is approximately 5.4 to 6.3 Mt (6 to 7 million st) (U.S. Geological Survey National Minerals Information Center, 2017). Okorusu has produced on average about 45 kt/a (50,000 stpy) in recent years (U.S. Geological Survey National Minerals Information Center, 2015).The Okorusu Mine is Namibia’s only fluorspar mine. Fluorspar was mined in an openpit mine with four individual pits (A-D) since 1980. In 2014, the mine closed due to the increased stripping ratio and beneficiation problems. The mine assets were bought by Gecko Namibia. Currently, Gecko uses parts of the processing plant for beneficiation of graphite from a neighboring mine. Figure 1 shows a panoramic view with the four pits and the mine village.The intent is to develop a concept for the further underground development of the mine. There are still about 6.3 Mt (7 million st) of measured resources left in the deposit, with an average grade of 27.5 percent CaF2. This study focuses on the underground mine design. The above-ground plant and facilities are considered as remaining unchanged.For solving the task to design the mine, a site visit for data collecting was conducted. Resource estimations were calculated based on existing drill data, and consequently, block models were created. The development of the mine design included the selection of the most suitable mining method, mining technology and mine organization. Moreover, some economic considerations are pointed out, followed by a profitability assessment."

Jan 2, 2018

By Alexander Darío Huamán Ccorahua, Cayo Fernando Soto Buendía, Jhonatan Raphael Rojas Ventura

Lithium is a top-quality mineral in the energy market, with growing demand. It has many applications in medical, nuclear, and energy industries. The purpose of this article is to quantify and analyze the economic potential and projected global demand for lithium annually. It aims to determine Peru’s (specifically Puno) positioning in the global context in 2025 and 2030. The article also seeks to identify the main regulatory, environmental, and social challenges to sustainably exploit lithium in Peru. The study employs applied research (mixed approach), descriptive-correlational scope, and observational, crosssectional design. The methodology demonstrates the use of statistical techniques to model and make predictions about this energy-transition metal. Academic sources were reviewed to enable a comparative approach and projection into the future of lithium for development in the mining industry. In the last 10 years, lithium demand has grown, noting a 600% increase in the economy and projected annual growth of +26%. Exponential growth in resources is projected, where econometric, R-multivariable and R-linear models estimate that Peru could supply 1.5% in 2025 and 3% in 2030 of global lithium. Estimated growth of 5–15% in socio-environmental conflicts is projected with the start of lithium exploitation (Peru – Puno). The global potential of lithium demonstrates exponential growth. Lithium reserves in Puno - Peru would rank 13th between 2025 and 2030. It is necessary to establish a clear regulatory framework to avoid excessive increase in socio-environmental conflicts.

Feb 1, 2024

By O. F. Brown

Excavation and loading are primary operations in the surface mine production chain, constituting a significant component of production costs. This makes excavation and loading important cost centers that need to be improved to lower production costs. Optimizing the design and use of excavators will improve energy efficiency in earthmoving operations, and this requires a thorough understanding of the soil-tool interaction process. Modeling the interaction process accurately is the key to this optimization. Experimental and analytical methods have provided limited information on the behavior of soils during excavation. Finite element (Fe) analysis of soil-cutting blade interaction produces some advantages over experimental and analytical methods. However, the soil constitutive equations used in most of the available Fe analyses fail to adequately model the plastic behavior of the soil. This work uses Fe modeling to study the behavior of formation-cutting blade interactions in dozer excavation. The formation is modeled as a nonlinear elastoplastic material using the modified cam-clay (mCC) model. The model accounts for soil-tool interface friction, and progressive and continuous cutting at the blade tip. The results provide soil forces, a progressive developed failure zone and soil displacement fields. The sensitivity analysis of changes in blade angle on cutting force shows that the cutting force increases with increasing blade angle. The cutting depth of the blade had a similar effect on blade cutting force. Increasing the depth of cut increases the required cutting force. Increasing the coefficient of friction at the soil blade interface increases the blade cutting force. Reducing the coefficient of friction at the soil blade interface from 0.3 to 0.05 reduces the cutting force by 22.3%. The percentage represents the maximum potential savings in blade cutting force. This research initiative advances the frontiers of soil-tool interactions during excavations to expand the limited knowledge in this critical area.

Jan 1, 2012

By Yang Ge, Yuzhu Pan, Mansheng Chu, Jue Tang, Cong Feng, Lihua Gao, Zhenggen Liu

The low-grade nickel laterite ore used in this study was successfully upgraded through selective reduction by industrialized rotary kilns followed by magnetic separation. The results indicated that both iron metallization extent and nickel metallization extent showed obvious linear correlation. In addition, rational roasting temperature and prolonged grinding time could enhance the overall fineness level of reduced laterite nickel ore. The moderate roasting temperature at a range of 1100–1150 °C should be suitable enough to a conversion of total nickel to metallic nickel and partly inhibited the conversion of total iron. Ultimately, the obtained ferronickel alloy with a nickel content of 7.32% and an iron content of 84.15% was prepared successfully from the lowgrade nickel laterite ore containing a nickel content of 1.92%. Nickel and iron recoveries were 96.72 and 89.08% respectively, which achieved the highly efficient recovery and utilization of iron and nickel from low-grade laterite nickel ore

By Jr. McCulloch

Mining operations of Freeport Indonesia (FI) are located approximately 4 degrees -6&apos; south latitude, 137 -7&apos; east longitude in Irian Jaya the eastern most state of Indonesia (Figure I). The mines are located approximately 96 km (60 miles) from coast in the Carstenz Mountain range. The ore bodies are between 2900 and 4000 meters (9500 and 13 000 ft) elevation.

Jan 1, 1989

By S. C. Gambrell

The practice of roof bolting in world-wide mining activities is very well known, having been used extensively for over 50 years. The theory of roof bolting, however, is extremely complicated, and only recently have investigators attempted to explain the theory. Discussions of the mechanics involved usually originate with actual experience gained in the use of roof bolts. The use of roof bolting in mines has grown dramatically during the period after World War II. Other scientific techniques have emerged in mining research in the same period. Included in these techniques is the study of rock mechanics, which has now developed into an impressive research effort. Various means of analysis have been utilized in rock mechanics, most of which reduce rock to an isotropic, homogeneous medium that could be easily analyzed. Because of the inherent nature of rock, direct research methods frequently are not certain to provide satisfactory results, whereas indirect methods must idealize a given set of conditions in order to be useful. One of the indirect research methods is the photoelastic technique, the theory of which is widely known and needs no elaboration. This technique has been used extensively to examine the state of stress around underground openings of various shapes in certain types of strata, and under various configurations (1,2,3,4,5). Much of the theory used now in the design of underground openings is based on photoelastic evaluation. Unless rigorously applied, how- ever, the photoelastic technique is at best a qualitative means of evaluation. It is useful, however, for unusual examples which can be more or less easily analyzed to obtain the overall state of stress which could not be determined by other means. Little work has been done in the photoelastic analysis of rock bolting, mainly because direct research techniques have proven useful.

Jan 1, 1970

By E. C. Robertson

D.G. Wilder I found the suggestion that the amount of displacement of a fault can be numerically related to the thickness of gouge or breccia to be both intuitively satisfying and intriguing. I have long agreed that there is some type of relationship between the amount of gouge and the amount of displacement of faults. I congratulate the author for developing a numerical relationship between them. However, I am concerned that the limits for applying this relationship be fully understood. An underlying assumption in this approach is that there is either a uniform thickness of gouge or breccia along a given fault or the thickness does not vary widely. Since it is not always possible to confirm this, the displacements derived by this method should be viewed with caution unless significant fault extent can be observed. At the Nevada Test Site, in drifts constructed in granite for test emplacement of spent nuclear reactor fuel, we found a fault with 0.3 to 0.4 m (12 to 16 in.) of clay gouge. Within a few meters of this location, the fault had no clay gouge, but rather consisted of a highly fractured zone with significantly altered rock and some slickensides. Based on Fig. 1, the 0.3 to 0.4 m (12 to 16 in.) thickness of gouge would indicate a displacement in excess of 30 m (98 ft). However, no gouge thickness would indicate essentially no displacement. Based on a quartz vein that terminated on the fault, and is not identified nearby, an estimated displacement of more than a few meters was made. This estimate is consistent with that obtained using the regression line proposed in the paper if the 0.3 to 0.4 m (12 to 16 in.) thickness for the gouge is used. However, using the regression curves with zero thickness would not yield results consistent with what was observed in the field. Therefore, it is important to recognize that the suggested procedure would properly yield a range of probable displacements. ? *Work performed under the auspices of the US Department of Energy by the Lawrence Livermore National Laboratory under Contract W-7405-Eng-48. Reply by E.C. Robertson It is certainly true that the t (thickness) of gg-bx (gouge and breccia) on a fault does vary along the fault. My observations have been that near the termination of a fault, the displacement d is small and the t is also small, whereas the maximum d and t will usually be found in the central part of the fault. The information on gg-bx and t of the fault found in granite in the NTS tunnel by Mr. Wilder could be interpreted somewhat differently than he does. He speaks of the fault changing within a few meters from 0.3 to 0.4 m (12 to 16 in.) of clay gg to "a highly fractured zone with significantly altered rock and some slickensides," but no gg. The highly fractured rock may be taken to be bx, rock not so finely ground as gg but still crushed by the fault movement, equivalent to the gg in my usage, and probably occupying about the same t. Mr. Wilder&apos;s estimates for the fault in the NTS tunnel for t of 0.3 to 0.4 m (12 to 16 in.) and for d of a quartz vein, in excess of "a few meters," would place the point on the low side of the central trend line in my Fig. 1, at the lower limit. There is, of course, a problem with determining d using displacement of only one planar surface. It would be greater or lesser depending on the rake of the movement. Finally, estimating the d of a fault from its t should be made with awareness of our present uncertainties, as pointed out by Mr. Wilder. Although the central trend line in my Fig. 1 has a ratio of d/t of 100, I have put the limiting ratios at 10 and 1000. Understanding of the values of the ratio will be improved only with collection of more data, for which the discussion of Mr. Wilder is much appreciated. G.C. Waterman E.C. Robertson&apos;s paper provides significant information to a geologist attempting to deduce fault offset by noting the products of structural dislocation. However, considerable mapping in underground and open-pit mines, and examination of structures produced in different geological settings, have convinced me that gouge and breccia thickness are controlled by geological conditions and fault movement. The following paragraphs suggest geological variables that control them. 1. Depth of Loading A near-surface fault resulting from tensional stress has more breccia/gouge than is produced by a similar stress at considerable depth. A deep-loaded compressional stress may produce a linear zone of schist, or structural dislocation may occur along an earlier formed belt of schist. Such "shear zones" are common in Canadian mines in precambrian rocks. In neither case can offset be directly deduced by an analysis of the minimal gouge/breccia in the shistose rocks. At greater depth, stress may be partially to wholly relieved by flowage. I vividly recall first noting the regional "Midas Thrust" in the Lark mine, Bingham Mining District, UT (where we called the structure the North Fault). My recorded notes, as I remember them, showed a narrow gouge streak separated the `Jordan" and "Commercial" limestone units from impure, muddy limestone beds of uncertain stratigraphic position. The visible structure did not indicate the great importance of this premineral fault

Jan 12, 1984

By P. J. Mackey

A whole new group of non-ferrous pyrometallurgical processes with the ability to utilize tonnage oxygen and capture sulphur dioxide were developed and commercialized over the period 1940s–1980s. Many of these earlier process developments were undertaken with limited knowledge of the process chemistry and influence of key process variables; in many cases, piloting helped provide much new physico-chemical data, but gaps remained. The second generation versions of these technologies of today provide all the primary copper, nickel and lead produced worldwide by pyro-metallurgical smelting. Further, process development has continued and a new generation of copper and lead smelting technologies have also been developed in China since the 1990s. The older reverberatory and blast furnaces have been progressively replaced by the newer technologies—a good example being the introduction in 1992 of the copper IsaSmelt technology at the Mt. Isa smelter in Australia where the former fluid bed roaster and reverberatory furnaces were replaced by a single new smelting unit, together with an acid plant for sulphur dioxide collection. The development of these new technologies was made possible by investment in fundamental and applied research. The lesson for the future is, in order to sustain these improvements, continued investment in research and development capability is required—to do otherwise is to risk obsolescence and lack of competiveness in the world market. Dr. Peter Hayes at The University of Queensland is one of the many researchers and process engineers who have contributed to the fundamental understanding of metallurgical processes over this period of rapid change in technologies. The present paper briefly outlines some of the many contributions Peter Hayes has made to the understanding of kinetics, mechanisms and phase equilibria in metallurgical systems, and metallurgical process development.

By G. H. Friedrich

The distribution of mercury in soils, rocks, and ore was studied in three areas of the Pachuca-Real del Monte District: (1) An area north of the town of Pachuca where ore veins have been found at or near the surface. The mercury content of soil samples taken near the vein zones is far above the background value. The highest value was 1900 ppb (parts per billion) mercury in a soil sample above Veta Vizcaina; the background is about 50 ppb Hg. (2) In the area north of the town of Real del Monte where only a few of the veins are known to crop-out. Regardless of exposure, soils collected over veins show anomalous mercury values ranging from 250 ppb to 1900 ppb. (3) In an area south of the town of Real del Monte. Here, although vein outcrops are lacking, mineralization is known at a depth of about 120 m. All soil samples taken at 50 m. intervals along an east-west traverse contain anomalous amounts of mercury, with peaks corresponding with the known location of the veins.

Jan 1, 1965

By José Mujica, Mónica Campos, María Fe Campos

The extraction and processing of metals and other minerals have played an important role in economic, political and social development worldwide, from the early stages of prehistory to the present day (Gosner, 2020). Mining has been a fundamental part of human civilization, providing the raw materials necessary for technological, infrastructure and industrial advances. As society progresses, the importance of mining continues to grow, supporting the development of everything from the smallest electronic devices to the tallest skyscrapers (Escamilla, 2024). The economy of a nation is connected to its extractive industries (Moreira and McMahon, 2014), which have seen dramatic growth in recent years (Pietrobelli et al., 2018). In a context of increasing demand for natural resources, driven by the development of emerging technologies, the expansion of infrastructure and the foundation of engineering achievements for the coming decades (Minerals Education Coalition, 2024), mining should focus efforts on global development, requiring a comprehensive approach to sustainability that addresses the planet’s needs and protects the well-being, primarily, of the communities and environments where mining operations take place (Figari, 2024). In these areas, diversity and inclusion should be promoted, thus fostering equitable and sustainable development. The sustainable development goals (SDGs), also known as the global goals, could serve as a key framework for fostering a strong social management culture in mining. The SDGs were adopted by the United Nations (UN) in 2015 as a universal call to end poverty, protect the planet, and ensure that all people enjoy peace and prosperity by 2030 (United Nations Development Programme, n.d.). Companies have compelling reasons to align their actions with the SDGs, as their long-term success depends on healthy communities. This is a major challenge that requires collaborative efforts (Singh and Rahman, 2021). As Fraser (2021) mentions, achieving more sustainable outcomes may involve mining companies and communities working together collaboratively. This article proposes an innovative approach: Inclusive mining for sustainable development, which aims not only to maximize economic profitability but also to promote social and environmental well-being by integrating the UN’s SDGs, primar)ily focused on diversity and inclusion. This can be achieved through the implementation of a key value-added initiative for mining companies: the creation and operation of a corporate volunteering program aimed at developing and executing inclusive practices to promote gender equality, the inclusion of local communities and indigenous peoples, and accessibility for people with disabilities. This proposal will educate employees and stakeholders about sustainability and promote concrete actions through corporate volunteering to strengthen the mining company’s commitment to community development, improve social relations and advance toward achieving the UN’s SDGs, establishing the company as a global change agent.

Nov 1, 2025

By N. Del Bel Belluz

Drilling underground in the Grasberg De-watering drifts has routinely hit water aquifers with high flow rates and pressures. Two types of holes are utilized; pilot-holes to probe ahead of the tunnel development to intersect aquifers ahead of the face; and de-watering holes to de-water rock formations that will drain water from the Grasberg pit and allow tunnel development to proceed safely. Recently, rates of 1050 psi static pressure have been recorded with flows from a NQ hole measured at 1350 gpm (US). The water flows can be slightly acidic, necessitating the use of stainless steel collar gear to resist corrosion. These rates were anticipated and contingencies were planned early to deal with these conditions. The collar gear is used to control water flows whereby the water is treated as an important resource. As a result, pm has established procedures to maintain safety of the drill crews, enable coring of the rock and to maintain safety of the miners who are driving the drifts.

Jan 1, 1998

By Carl Erickson, James Hislop

INTRODUCTION As practiced today, longwall mining is a mechanical version of an established mining system. The equipment for longwall mining consists of four basic units: roof supports, face conveyor, winning or mineral-getting ma¬chine, and stage-loader conveyor. The system mines relatively thin slices of mineral across a predetermined face length in a virtually continuous sequence. As the winning machine cuts, the mineral is loaded automatically onto the face conveyor. In turn, the face conveyor is pushed over into the newly cut track by hydraulic rams attached to the conveyor and the roof supports. The roof supports then are lowered individu¬ally from the roof, advanced to the repositioned con¬veyor, and reset to the roof. At the end of the pass, the longwall cutter is pushed over, and a slice is taken in the opposite direction, so the system repeats itself. Fig. I illustrates a typical longwall mining system. The principle behind the longwall mining system is that the roof is supported only immediately adjacent to the worked seam, keeping the blocks of immediate roof clamped securely from the face to the rear of the sup¬ports. At the rear of the supports, the roof is allowed to fall and break up, with the swell of the broken material eventually establishing an equilibrium in the strata be¬hind the mined area. Fig. 2 illustrates the principle of longwall support. There are two distinct types of longwall mining. The longwall retreating system is the most common in the United States, South Africa, and Australia. The longwall advancing system is the most common in the re¬maining industrialized countries such as Britain, Ger¬many, Poland, and the Soviet Union. The longwall retreating system comprises a mining panel, where the roadways that form the head entry (end at which mineral is delivered from the face con¬veyor to a stage-loader conveyor) and the tail entry are predriven before the longwall units starts production. In the longwall advancing system, the longwall unit makes the head and tail entries as the face advances, utilizing various techniques to prevent the entries from being destroyed as they are left in a consolidating gob area. Fig. 3 illustrates the comparative approaches of the longwall retreating and advancing operations. As with most other underground mining systems, there are many variations on these two basic systems, using combinations of the systems that are dictated by

Jan 1, 1982

By Bruce D. Hanson

A computer model capable of simulating the basic production system in a variety of underground mining methods has been developed at the Twin Cities Mining Research Center. This Bureau of Mines paper describes the simulation of the basic production system at the working face, which includes drilling, blasting, mucking, and roof bolting. The model is event-oriented; that is, the status of the system is updated at the occurrence of an event. All event or activity times, including failure and repair of equipment, are treated as stochastic variables. A location dimension, in addition to the time dimension, is used, allowing the simulation of multiple location systems. To aid the user in determining the efficiency of his system, the model provides several reports. An event or activity report gives the frequency of occurrence total active time, and cumulative delay statistics for each event. An equipment report delineates the availability and utilization of all equipment. A production report provides information on various performance measures such as tons produced and holes drilled. The cost report gives the cost of various elements in the system. Operating data from an actual mining situation were used in validating the model. In addition to the description of the model, examples of simulation experiments which were performed on a room-and-pillar mine system are given. Use of the model to determine methods for improving the efficiency of the system is discussed.

Jan 1, 1974

By S. Yerel

In a mineral processing plant, the determination of a preventive maintenance schedule is one of the most important maintenance policies. In this study, to determine the preventive maintenance schedule for the Emet Colemanite Mineral Processing Plant in Turkey, a mean quality control chart was constructed using the historical concentrate B2O3 grade data. The effect of preventive maintenance scheduling on B2O3 grades was monitored using the mean quality control chart. It was determined that recovery increased after each preventive maintenance scheduling. Close examination of the mean quality control charts indicated that there were three periods that showed different grade characteristics. These were identified as the period ?prior to preventive maintenance,? the period ?after preventive maintenance? and the period ?requiring preventive maintenance.? These periods were compared as two independent samples by using the Kolmogorov-Smirnov test. Application of this test for interpretation of the mean quality control chart enabled the authors to analyze the system effectively, and it showed that the preventive maintenance for this plant should be scheduled at four-month intervals.

Jan 1, 2007