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By Chester A. Rowland

La conminución de Ios minerales es, generalmente, una etapa de preparación de la alimentación para las subsiguientes etapas del proceso. La molienda, fase de conminución de productos finos, requiere una gran inversión de capital y frecuentemente es el área de máxima utilización de potencia y de materiales resistentes al desgaste. La molienda se produce normalmente en tambores rotativos que utilizan un medio de molienda que se pierde en la misma, al elevarse con la rotación del tambor, se rompe el mineral por combinación de los efectos de impacto, atrición y abrasión, hasta producir el producto especificado. El medio de molienda pueda ser: - El propio mineral (molienda autógena - primaria y secundaria). - Medio no metálico, natural o fabricado (pebbles) - Medio metálico (barras o bolas de acero) Este capítulo tratará de molinos de barras y bolas que utilicen medio metálico de molienda.

Jan 1, 1982

By Peter G. Chamberlain

Novel and innovative mining methods are attracting the attention of mining engineers at an unprecedented level. Historically, the US mining industry has responded rather conservatively to new technology. The financial difficulties affecting the domestic mining industry in the early 1980s changed attitudes toward new technology. The market contraction during that period, coupled with an expanding world mine capacity, created a serious oversupply of many raw mineral products. Many mining companies found that retaining a share of world markets while making a profit required drastic cost-cutting measures.

Jan 1, 2008

By D. Leppert

Clinoptilolite zeolite may offer attractive, cost-effective alternatives for remedial cleanup of old minesites, smelters and other sites with heavy metal contamination. Previous research demonstrates the relatively strong affinity of clinoptilolite for numerous metals and clinoptilolite displays a particularly strong affinity for lead (Loizidou and Townsend, 1987), one of the most toxic and problematic heavy metals. Since clinoptilolite can also selectively absorb some radionuclides and organic compounds, it may offer practical solutions to a wide variety of environmental problems.

Jan 1, 1989

By Richard L. Bullock

INTRODUCTION TO COAL MINE PRACTICES To illustrate the trends and the proportions of the various methods used to mine coal underground, Fig. 1 is useful. However, of all the underground coal mining practices in the US, room-and-pillar mining still accounts for 96.5%. This percentage is divided as follows: conventional, machine cut-33.0%; conventional, hand cut -1.7% : and continuous mining-61 .8%. As was stated in Sec. 1, Chap. 7, the term "development" means different things to a coal miner and a metal miner. Though some of the ideas and concepts presented in the first two chapters of this section are valid for all types of mines, they apply particularly to mines using noncoal methods. In coal mines (and many other mines using coal mining systems) development refers to that phase of the mining cycle which advances several entries through the virgin seam, forming pillars by cross- cutting between the parallel entries. Because in the past, coal seams (as well as seams of potash, trona, oil shales, gilsonite, salt, and some uranium) have been much more uniform in their thickness, continuity, and quality, and because they often cover large areas, it has been possible to develop the room-and-pillar mine completely from a preplanned, systematic approach with a minimum of surface drilling information. As the better coal seams of the midwest and east are being depleted (or eliminated because of high sulfur), seams of poor quality and continuity will have to be mined. Also, seams that are not nearly so well known at greater depth will have to be taken as well as some of the steeply pitching and folded seams of the west. The American coal miner is only now feeling the need to do a much more complete job of prospecting the geology of the coal seams than he has ever done before. This is the only way that the risk of unknown rock conditions can be minimized. In many ways, surprises in the rock or coal seams are much more of a disaster to the coal miner developing a room-and- pillar mine than to his metal mining counterpart. Be- cause of the multiple entries, the complex set of the Federal Coal Mine Health and Safety regulations, and the totally dedicated design of coal mining equipment, coal mining systems do not have the flexibility to easily overcome changes in the seams mined or the rocks around them. Thus, if a wide parting of rock shows up unexpectedly in the middle of a coal seam entry being milled away by a continuous miner, it will either have to slowly "chew" through it, convert to a conventional mining system, or stop that particular entry. Likewise, if suddenly the coal disappears completely and in its place are the remains of an old creek bed, the "want" or "wash out" as it's called will usually have to be mined right along with the coal, by the same methods and with the same soft rock equipment, or the entry will have to be abandoned. For reasons such as these, coal seams today should be drilled from the surface just as thoroughly as the ore bodies in metal mines. Having once determined a more precise location of where the coal seams are located and which are suitable for mining, the engineer must still take a systematic approach to planning the mine as completely as possible. The initial series of entries must be planned to be driven either from the side hill portal or from the bottom of the shaft or slope. In either case, they should usually intersect the area close to the midpoint of the mass to be mined.

Jan 1, 1982

By D. Yadon, P. Lee, W. Kelly, C. Stilwell

Rico is a small town in an old zinc mining district in a mountain valley of southeastern Colorado. Mine waste rock and mill “tailings” remained after over 100 years of mining in the area, leaving associated surface water and groundwater impacts. Atlantic Richfield Company is proposing an innovative approach, which uses lime precipitation and wetland ponds (semi-natural system, also called treatment lagoon in a wetland setting) to treat adit water in the Rico area. Besides using a non-conventional treatment approach, a non-conventional (non-Superfund) regulatory/administrative approach is being proposed. This paper will focus on the water treatment issues and solutions, as well as describing the innovative “watershed” regulatory process.

Jan 1, 2004

By R. W. Barbaro

The limitation of sulfur dioxide in power plant emissions dictates that sulfur in coal be reduced to the lowest possible level before combustion so as not to aggravate the emission control problem at the stack. For coal fired power plants, the methods in practice to achieve low sulfur coal include mining areas with relatively low sulfur. reducing sulfur in the mined coal through preparation techniques and blending high and low sulfur coals. A prerequisite to the successful implementation of any of these practices is the knowledge of the spatial distribution and the capability to predict sulfur values in a coal seam.

Jan 1, 1988

By A. Mertzanis

The way and methods used for the surface mining of bauxite until the end of the twentieth century in the area of Ghiona, resulted in a significant burden to the natural environment, especially in the cases where it covered extended parts of forests and forest areas as well as important geomorphological formations. The impacts from the surface mining of bauxite which in fact constitute the object of this study relate mainly to the interruption of the natural continuity of the land relief and the alteration of the natural geomorphological activities and are due to: a) the alternating excavations with fronts of great heights, b) the depositions of large volumes of waste materials which originate from the revealing of the ore and c) the dense road network constructed in order to get access to the mine locations.

Jan 1, 2006

By J. W. T. Ropkins, D. Allenby

The paper describes a technique by which large concrete boxes are unobtrusively inserted beneath existing highway and railway infrastructure to form new subways, culverts and under-bridges, thus avoiding the inconvenience and costs of disruption to traffic associated with traditional cut and cover techniques. A series of project examples, undertaken in the United Kingdom and United States, are used to illustrate the design and construction of the box structures, together with the technology required to control ground disturbance in the tunnel face and around the box, and the jacking systems necessary for box installation.

Jan 1, 2003

By R. L. Loofbourow

R. L. LOOFBOUROW 26.1-WATER FLOW, USE, EFFECTS, CONTROL Sec. 4 discusses ground water as a mineral resource. This section deals wits its control. 26.1.1-IMPORTANCE Flows of water have an important effect on the cost and progress of many deep excavations. The existence of water limits the methods which can be used in some and presents hazards in others. Lowering the water table may reduce the flow of springs and wells, with legal liability. Some mine water is used directly, some must he treated before discharge, and some contains dissolved solids which can be recovered profitably. Loss of life, property and production from flooding is grim, yet scores of mines have worked safely for generations under ground-water reservoirs, lakes and even the sea. The need for better control of mine water is measured by the severity of recent floodings, concern with the quality of the effluent, and direct and indirect costs of working wet ground. There are improvements in freezing in shaft sinking. pumps and their controls, treatment of mine water before it is pumped, bulkhead construction and certain efforts to reduce inflow. 26.1.2-PUMPING COST VS. COST OF WET WORK Direct operating and capital costs of pumping are more evident than indirect items, such as provision of extra standby power and maintenance facilities, The total of all these items is the cost of pumping water from an excavation. This is only a part of the extra cost of working wet as compared to dry ground. Less productive methods, less efficient equipment and more expensive explosives may have to he used in wet work. Wet rock plugs certain equipment. Maintenance is higher and labor less efficient. The cost of any means of keeping work drier should he weighed against the higher cost of working wet. The true difference in the cost of working wet ground, compared with dry, probably is known at only a few places (see checklist of cost items. Sec. 26.4.13). An extreme comparison of mining wet and dry ore is available from Ambrosia Lake, N.M. (Fig. 26-1). Between 1963 and 1967, a wet and a dry mine were worked by the same company under conditions otherwise comparable. Average operating cost at the wet mine, pumping 1,600 to 1,800 gpm. was $16.06 per ton of ore. The comparable figure for the dry mine was $7.50. Principal differences included the fact that the wet mine was worked from drainage levels below the, ore with rail haulage, the dry mine in the ore with off-track equipment loading and hauling to the shaft. In the wet mine, ore packed in chutes, cars and skips and froze in surface bins, stockpiles and trucks. Wet-mine costs included drilling drain holes, building and maintaining ditches and pumping water containing abrasive solids.

Jan 1, 1973

By T. R. von Ow

The method of powering mills such as AG, SAG and Ball has a long and technically interesting history. It can be said that almost every decade in the last half century had its own trend. The trends were dominated by the market demand, the advanced process development and requirement of the mechanical and the electrical technology but mostly by the price of the applied technology. The increasing size of the ring geared mills in the last years requires more awareness on the drive train solution. Special attention must be paid to the mechanics and the requirements of the power grid. Operational challenges such as soft starting and controlled operation as well as the protection of the equipment have gained importance. Frequency converter drive solutions dedicated to single or dual pinion ring-geared mills offer significant advantages over conventional drives due to their application specific features and controls. Solutions with low speed motors as well as high speed motors cover all possible configurations available for ring geared mills.

Jan 1, 2010

By David Court, Rab Brown

The paper discusses the work in progress on the construction of the extension of the High Speed Rail line from the Channel Tunnel into the centre of London UK known as the “Channel Tunnel Rail Link” (CTRL), and particularly on contract 250 which involves the construction of two 5.3Km tunnels 7.15m diameter constructed with two EPB convertible tunnelling machines underneath the densely populated area of East London. In addition the paper will look at an innovative Alliance that has been formed between the Contractors and the Client’s Engineer involved in the construction of the London Tunnel Contracts

Jan 1, 2003

By Timothy Batchler, Khaled Mohamed

Standing supports have been used in coal mines for decades to enhance roof support capability. Occasionally, standing supports are used to resist the lateral movement of spalled ribs. Researchers from the National Institute for Occupational Safety and Health (NIOSH) are conducting a testing program for standing supports to investigate the effect of lateral loading on their vertical loading capacities and the factors affecting their lateral loading capacities. The Mine Roof Simulator (MRS) was used to determine the response of steel props to vertical and horizontal loadings. Finite element models (FEMs) were developed and verified using the tested steel props. Prop models were used to study the effect of a range of roof and floor materials — gray shale, shale and claystone — on the critical buckling loads of the steel props.

Dec 1, 2022

By R. Chandramohan, Landon Jackson, C. Meinke

Understanding constraints within the raw battery material supply chain is essential for making informed decisions that will ensure the battery industry’s future success. The primary limiting factor for long-term mass production of batteries is mineral extraction constraints. These constraints are highlighted in a first fill analysis which showed significant risks if lithium-ion batteries are used to fully support vehicle electrification and intermittent energy storage. Nickel, lithium, cobalt and graphite reserves risk 100 percent depletion with significant consumption of known resources. Furthermore, more than 700 new critical mineral mines will need to be developed to meet the required production rates for decarbonization by 2050. Demand for critical minerals will outpace mine development timelines even as improvements are made to battery energy density and compositions. Governments and the private sector need to align themselves on decarbonization goals to establish cooperative agreements on the critical mineral supply chain by reducing the barriers to entry and increasing exploration efforts. Additional measures must also be taken to reduce the demand for critical minerals. Policy such as incentivizing public transportation and biking infrastructure can be exploited to drastically reduce the mineral demand placed on the mining industry.

Feb 1, 2025

By D. B. Sikka

Porphyry type copper ± molybdenum deposits typically occur in the Phanerozoic rocks and have been well documented. During the past two decades a number of porphyry type Cu ± Mo deposits which range in age from 1055 ± 35 Ma to 2970 Ma have been identified in the Precambrian rocks of Australia, Canada, China, Finland, India, Namibia and Zambia. Kalanjkhand porphyry copper deposit M. P., India which is estimated to contain 789 million tonnes averaging 0. 83 percent Cu (millhead-grade); 0.004 percent Mo; 0.2 gm/t Au; 6 gm/t Ag and a cap of 7.532 million tonnes of oxide are averaging 0.8 percent Cu. The economic potential of the expanded copper mining milling, smelting and refining complex to be built in the future at Kalanjkhand, which is the largest porphyry copper deposit discovered to date in the Precambrian rocks of the world is presented.

Jan 1, 1992

By J. T. Tanner

The research activities of the Minerals Research Laboratory, which is a part of North Carolina State University, is normally confined to solving beneficiation problems, and developing flotation processes for the mining industry. In recent years the laboratory has veered from its main purpose somewhat and has placed some emphasis on the manufacture of products from mineral concentrates. This has been the result of requests for help from industry. One such request came to the MRL from a talc producer in North Carolina who was having a difficult time competing with foreign imports of steel marking crayons. He felt that if a process could be developed whereby a satisfactory crayon could be produced from powdered talc at a low cost that he could compete.

Jan 1, 1986

By SONGHE WANG, YI XUE, PENG HOU, CAIHUI ZHU, XUANYE JIAO, Feng Gao

The abstract discusses the challenges of coalbed methane development in China due to low coal seam permeability. It highlights protective layer mining as a method to reduce in-situ stress and enhance permeability for improved gas drainage and disaster prevention. The study involves experimental and numerical simulations to analyze gas migration and permeability changes during stress release. It includes a stress-strain-seepage coupled test on coal, development of a mathematical model for coal seepage under mining unloading, and a numerical model based on the Wulan coal mine to explore in-situ stress release, permeability evolution, and gas drainage in an unloaded coal seam. The aim is to demonstrate the effectiveness of combining protective layer mining and gas drainage technology for gas outburst risk elimination.

Mar 14, 2022

By Richard L. Bullock, Bruce Kennedy

Vince Lombardi once said, "Practice doesn't make perfect, perfect practice makes perfect." When it comes to building a mine that will operate at the optimum level for the set of geologic conditions from which it was developed, Lombardi's remark might be paraphrased to describe the problem: planning won't guarantee the best possible mine operation unless it is the best possible mine planning. Any sacrifice in the best possible mine planning introduces the risk that the end results may not reach the optimum mine operation desired. This section addresses many of the factors to be considered in the initial phase of mine planning. These factors have the determining influence on the mining method, the size of the operation, the size of the mine openings, the mine productivity, the mine cost, and, eventually, the economic parameters used to determine whether or not the mineral reserve even should be developed. A little-known fact, even within the metal-mining community, is that room-and-pillar mining accounts for most of the underground mining in the united States. According to a 1973 study on noncoal mining (Anon., 1974), more than 76% of the producing mines [of over 1089 t/d (1200 stpd) capacity] produced approximately 70 000 000 t (77,000,000 st) or 60% of the nation's underground tonnage of material by room-and-pillar mining. That same year, 96.8% of the nation's under- ground coal mines produced 262 950 000 t (289,911,000 st) of coal extracted from room-and-pillar mines (Anon., 1976). Thus, nearly 333 000 000 t (367,000,000 st) of the United States' raw material is produced from mines using some form of the room-and-pillar mining system. Because approximately 90% of all mining in the United States is done by some variation of room-and- pillar mining, it is appropriate to give special emphasis to the effects of the various elements of mine planning on room-and-pillar mining. The relationship of these elements to other mining methods will become apparent as the elements are described in later sections herein. TECHNICAL INFORMATION NEEDED FOR PRELIMINARY MINE PLANNING Assuming that the reserve to be mined has been delineated with diamond-drill holes, the items listed in the following paragraphs need to be established with respect to mine planning for the mineralized material. Geologic and Mineralogic Information The geologic and mineralogic information needed includes the following: 1) The size (length, width, and thickness) of the areas to be mined within the overall area to be considered, including multiple areas, zones, or seams. 2) The dip or plunge of each mineralized zone, area, or seam, noting the maximum depth to be mined. 3) The continuity or discontinuity within each of the mineralized zones. 4) Any swelling or narrowing of each mineralized zone. 5) The sharpness between the grades of mineralized zones within the material considered economically minable. 6) The sharpness between the ore and waste cutoff, including whether this cutoff can be determined by observation or must be determined by assay or some special tool; whether this cutoff also serves as a natural parting resulting in little or no dilution, or whether the break between ore and waste must be induced entirely by the mining method; and whether or not the mineralized zone beyond (above or below) the existing cutoff represents submarginal economic value that may be- come economical at a later time. *7) The distribution of various valuable minerals making up each of the minable areas. 8) The distribution of the various deleterious minerals that may be harmful in processing the valuable mineral. 9) Whether or not the identified valuable minerals are interlocked with other fine-grained mineral or waste material. 10) The presence of alteration zones in both the mineralized and the waste zones. Structural Information (Physical and Chemical) The needed structural information includes the following: * 1 ) The depth of cover. 2) A detailed description of the cover including: the type of cover; * the structural features in relation to the mineralized zone; * the structural features in relation to the proposed mine development; and * the presence of and information about water, gas, or oil that may be encountered. 3) The structure of the host rock (back, floor, hanging wall, footwall, etc.), including: * the type of rock; * the approximate strength or range of strengths; * any noted weakening structures; * any noted zones of inherent high stress; noted zones of alteration; the porosity and permeability; * the presence of any swelling- clay or shale interbedding; the rock quality designation (RQD) throughout the various zones in and around all of the mineralized area to be mined out; the temperature of the zones proposed for mining; and the acid generating nature of the host rock. 4) The structure of the mineralized material, including all of the factors in item 3 plus: * the tendency of the mineral to change character after being broken, i.e., oxidizing, degenerating to all fines, recompacting into a solid mass, becoming fluid, etc.; * the siliceous content of the ore; the fibrous content of the ore; and the acid generating nature of the ore. Economic Information The needed economic information includes: *1) The tons of the mineral reserve at various

Jan 1, 1982

By R. J. Watters

Many rock sass classification systems exist' to assist the engineer in assessing the rock support requirements for underground design. Our ongoing research in this area is directed at attempting to utilize the fractal dimension and the acoustic emission' response of the tuffs at Yucca Mountain, Nevada to further aid in rock mass classification. The Topopah Spring' member, the proposed nuclear waste horizon, is characterized by welded and partly welded tuffs, exhibiting a wide range in moduli, strength, porosity and degree of fracturing. Differentiating between the different' types of porosity can be extremely difficult if not impossible. An attempt was made to correlate the acoustic emission response with the porosity of the sample. Events and the peak amplitude may offer a means-to distinguish between, fracture porosity and pore porosity. In addition-, fractal dimension were calculated for several fractures in densely welded tuffs. Two techniques for calculating fractal dimension were-applied' to describe-fracture geometry and roughness. Fractures in-welded-tuff were-found to be relatively smooth.

Jan 1, 1989

By Brian Fulcher, John Eastlund, J. B. Copeland

Following the completion of the 7,600 m primary access tunnel by Kiewit/Parsons Brinckerhoff (K/PB) in April 1997, an exploratory East-West Cross Drift Tunnel was constructed at the Yucca Mountain Project over the proposed future repository block for high level nuclear wastes. The 2,681 m (8,796 LF) East-West Cross Drift Tunnel was excavated through volcanic tuffs having zones of incompetent rock using a re-built Robbins 5.000 m (16’-5”) hardrock TBM with a special arrangement of supporting equipment. Details of the unusual site and contract conditions will be discussed as well as with the unique tunnel equipment specified by the Owner. This portion of the Yucca Mountain project required eight months to complete.

Jan 1, 1999

By T. K. McCranie, A. H. Tousley, A. H. Kackman, L. R. Gregory, A. Jr. McElrath, R. J. Krekel

In Roman and earlier civilizations the term cement was applied only to mixtures of lime, pozzolana, sand, water, etc., used as a mortar to bind larger stones. Today, portland cement, the subject of this section, can be briefly defined as follows: The product obtained by finely grinding clinker produced by calcining to incipient fusion (i.e., sintering) an intimate and properly proportioned mixture of argillaceous and calcareous materials. History The Egyptians were probably the first to join building stones with a mixture of sand and a cementitious material (i.e., having the property of or acting like cement). It is generally accepted that the cement used by the Egyptians on such structures as the Great Pyramid was calcined gypsum, Later the Greeks began to calcine limestone for use as a mortar with sand and water. Still later, broken brick and tile were added to the mortar to make the first concrete. The Greeks and Romans found that some sands produced mortars that were especially resistant to the action of water. Hydraulic (i.e., underwater-hardening) cements formed by combining slaked lime, water, and finely divided siliceous materials (e.g., pozzolana) possess superior strength and are capable of resisting the destructive action of water. They were used on the Pantheon, Colosseum, and other structures, some of which are still standing. In 1756 an English engineer, John Smeaton, found that an argillaceous limestone (i.e., containing an appreciable amount of clay as an impurity) produced a cement with greater resistance to the action of water. Despite Smeaton's findings, the use of the old mixture of lime and pozzolana long retained its popularity. Significant contributions in cement technology from England, Swe¬den, France, and Holland were made in the next 68 years. However, the invention of portland cement is generally credited to Joseph Aspdin, an Englishman, who in 1824 patented "portland cement." The name was selected because, on hardening, it resembled the natural building stone from the Isle of Portland, England. The patent features mixing ground limestone and argillaceous materials in appropriate proportions and calcining (i.e., expelling CO2 by roasting) the mixture. This superseded the existing practice of calcining naturally occurring argillaceous limestone. In about 1845 Isaac Johnson, also English, conducted experiments on proportioning the components and calcining them at higher tem¬peratures. His accomplishments are accepted as the beginning of the present-day portland cement industry. The U.S. cement industry originated with the demand for good hydraulic cement for building structures such as the Erie Canal, which was started in 1817. The first discovery of cement rock (i.e., naturally occurring argillaceous limestone with near-optimum ratios of calcium carbonate, alumina, and silica) near Fayetteville, N.Y., was made by C. White. In 1818, White secured a patent for the manufacture of natural cement from that deposit. Subsequently, several natural cement plants were built in 1830-1840 at Rosendale, N.Y., and in the Lehigh Valley of Pennsylvania. David Saylor, who participated in establishing a natural cement plant at Coplay, Pa., in 1850 discovered that a superior cement could be produced by calcining the rock at higher temperatures than hith¬erto. In 1871, Saylor obtained a patent and commenced the manufac¬ture of portland cement. By 1890, there were 17 portland cement plants in the United States with a combined annual output of 62,300 tons. At the end of 1970, the number of plants producing portland cement in the United States (including Puerto Rico) was 169, down from a maximum of 185 in 1967, with total annual shipments of 73.4 million tons valued at $1,298 million. (Fig. 1). In 1970, annual world production of hydraulic cement (which includes pozzolanic materials, hydraulic limes, natural cement, alumina cement, and portland cement, all of which are in current use in various parts of the world) reached 630 million tons (Table 1). Flowsheets of typical U.S. cement plants are shown in Chapter 13. Chemical Composition and Physical Properties It is generally accepted that portland cement clinker consists of a mixture of compounds or synthetic minerals. The four principal compounds are:

Jan 1, 1985