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By Georges Verly

The estimation of local recoveries is an important issue in a selective mining operation. Two techniques, probability kriging and multigaussian kriging, are applied to estimate local recoveries at Jerritt Canyon. The pros and cons of each method are discussed in light of the results. Both methods provide simple and satisfactory solutions to the problem of estimating local recoveries. Consequently, they can be useful tools to work with in a selective mining operation.

Jan 1, 1984

By Fred Leighton

Miners have long known that rock noise, or the popping and cracking of the rock commonly heard during mining, can indicate instability of the mine structure. For many years, miners have "listened" to the rock talk and many times have interpreted changes in rock noise activity to be a warning of failure and have retreated from the potential failure area. Microseismics, or the study of rock noises, was begun in the early 1940s partly because of this historical fact. Microseismics is based on using geophysical equipment to detect and analyze rock noises on audible and subaudible levels. Thus, these systems are much more sensitive than the human ear and "hear" even more of the rock "talk" than do miners. Research has shown that micro-seismics can be used to precisely locate portions of a working area that are generating rock noise, and that rock noise release rate information from each area can be used to analyze its stability. On the basis of research results, microseismic systems are now commercially available and have been purchased and installed in many mines around the world. Introduction When a rock mass is subjected to changing stress conditions, such as those caused by mining, small-scale adjustments occur within the rock that release seismic energy. When this energy is in the audible range it is called rock noise. Those areas where stress changes occur are also the areas of the structure most likely to fail. Individual rock noises can be detected and analyzed to determine their precise location relative to the mine structure. Over a period of time plots of this data provide a pictorial representation of where stress changes are occurring. This is because rock noise activity tends to concentrate in those structure areas most actively adjusting to the changing stresses. Since these areas are the most likely to fail, they can be pinpointed and mapped relative to the structure. Rock noise rates, or the number of rock noises occurring per unit of time, also tend to vary dramatically before failure. Thus, the ability to locate the source of individual rock noises provides a means of determining where failure may occur, and rate counting within each area offers a means of assessing when failure may occur. This information, properly treated, can be used to avoid, control, or warn of impending failure. Successful applications of this technique have provided recent impetus to the effort of developing microseismics into a practical, reliable, and economically feasible tool. The phenomenon of naturally occurring rock noise was discovered in 1938 by Obert and Duvall (1939) who were measuring seismic velocities in mine pillars. Seismic energy other than what they were generating continually registered on their recording equipment. Further study by these researchers showed that the extraneous seismic energy being recorded was from rock noises that were being generated within the rock in highly stressed areas. Pursuing this interesting phenomena both in the laboratory and in the field, Obert and Duvall documented the dramatic change in rock noise rate before failure (Obert, 1941). They also established the fact that, in many instances, rock burst failures could be predicted by monitoring and listening to the rock noise activity in rock-burst-prone areas (Obert and Duvall, 1945). These early efforts clearly showed that microseismics had great potential as a tool for measuring or estimating mine structure stability. Extended testing, however, showed that sometimes rock bursts occurred with no apparent microseismic warning, and that at other times sharp increases in microseismic data were not accompanied by failure. Also, because precise location of individual rock noises was not possible at that time, one never knew where the failure was going to occur, only that failure near the observation point was likely. Thus, while the technique clearly offered promise, it was not considered practical then. In the mid-1960s, the Bureau of Mines undertook a new research effort to improve the microseismic technique. Major improvements were judged possible mainly because new and vastly improved electronic and system components had become available as an offshoot of space program instrument development. Thus, in 1967, development of a multichannel, broad band, microseismic system began (Blake and Leighton, 1970). Application of this system in rock-burst-prone mines showed it worked well and provided the incentive to develop methods whereby the source location of individual rock noises could be easily and directly calculated (Leighton and Blake, 1970; Leighton and Duvall, 1972; Redfern and Munson, 1982). The improved system and the ability to locate rock noises quickly showed that the microseismic technique offered new and increased poten-

Jan 8, 1983

By Jung-Joo Kim, Jong-Uk Kim, Turab H. Jafri, Han-Kyu Yoo

"INTRODUCTION Steel sets such as H-type and lattice girders are often installed in the tunnels before the hardening of shotcrete to ensure the stability of conventional tunnels in soft ground conditions. In practice, while designing the tunnels with the help of numerical analysis, steel sets are generally considered only as temporary support elements. Only a few studies propose the direct application of composite support in the tunnel design, based on large-scale experiments and numerical analysis. In order to assess the structural performance of the composite support consisting of shotcrete and steel sets, large-scale experiments were performed on two types of arch-shaped specimens by applying the combined effects of axial forces and bending moments. Based on the experimental results, numerical analysis was performed to assess the application of composite support in tunnel design. The crown settlement, axial forces, bending moments, and load distribution in the composite support were analyzed in the light of different structural patterns. LARGE-SCALE EXPERIMENTS USING COMPOSITE SUPPORT Preparation and Procedure of the Experiments The preparation setup as well as the organized procedure of the large-scale experiments using composite support is shown in Figure 1. An appropriate geometry of the specimens was selected by considering the standard cross-section of a two-lane highway tunnel in South Korea. Under the loading conditions meant to develop the axial forces and bending moments simultaneously, arch-shaped specimens were assembled with the ends of the specimens subtending a 60° arc angle at the center of the arc circle as shown in Figure 2. The fabrication of six specimens was completed in two groups based on the dimensions of steel sets, with the first group of three specimens being reinforced by H100 (No.1, No.2, No.3) and the other three by H125 (No.4, No.5, No.6). In order to reduce the voids on the boundary of the shotcrete and steel sets, concrete was casted over the steel sets instead of using shotcrete. The specimens were designed to incorporate the uniaxial compressive strength of 21 MPa. Shear keys and steel plates were installed at the ends of the specimens, so that shear failure could be avoided at the ends and the specimens could also be protected from detachment at the fixation. Translational and rotational movements at the ends of specimens were fixed."

Jan 1, 2016

By J. R. Woolsey, B. G. Noakes

A prototype remote placer drill (RPD) has been designed and successfully tested in the offshore gold district of Nome, AK. The RPD system is unique in its design and in the cooperative support that was provided during its development by industry, academia and government. The RPD was conceived as a low-cost, rapid drill sampling system for the reconnaissance of marine precious metal placer deposits. The drill functions as a counter- f lush system. It incorporates a dual wall casing and a rotating percussion bit driven by way of a drill rod through the central eductor casing by a heavy duty pneumatic rock drill. The cost of drill sampling in the exploration of marine precious metal placers has traditionally been high due to the technical difficulties imposed by the environment and the remoteness of the sampling target. The objective was to reduce capital and operating costs of a drilling program through the development of a portable system incorporating drill compoments having a high power-weight ratio that could be deployed from work vessels of opportunity. A principal design requirement was to operate the system remotely from the sea floor with only flexible connections to the surface. This includes cable for deployment and retrieval and hoses for air supply and sample recovery, thus making the drill system semi-independent of the vessel's sea-induced motion. The prototype RPD underwent full operational test off Nome, AK in late summer 1988. It was deployed from the landing door of a modified LCT vessel, and rigged for a single pass of 5 m (16.5 ft). More than 50 holes were drilled in a wide variety of bottom materials typical of the off shore Nome submerged beach placers. The prototype RPD proved to be an overall success, recovering representative samples throughout the section in all but the heavy boulder ground. Compared with a conventional drill system on board that was assigned to a production drilling system, the RPD was capable of reliably sampling moderate ground less than 6 m (20 ft) in thickness, using a smaller crew and operating in higher sea conditions.

Jan 1, 1991

By K. J. Bruxvoort

Background ground water quality is often used to drive remediation programs at sites with waters affected by mining activities. In the past these levels were sometimes chosen without rigorous statistical and geochemical analysis. A probability distribution approach was used at the Sweetwater Uranium Project to separate a large set of geochemical data into populations that represent contributions from different sources. Natural background populations were identified for major ions, metals, and radionuclides, and were submitted to the Nuclear Regulatory Commission to modify the extent of a Corrective Action Program and to establish control limits for future monitoring.

Jan 1, 1998

By S. Goodfellow, J. C. Ordóñez-Calderón, K. Esmaeili, N. Houshmand

A good understanding of the hardness of ore being handled and processed in a mining operation can significantly improve operational efficiencies by providing valuable data to support decision-making through the mining value chain (drilling, blasting, comminution). This study presents the results from the application of Machine Learning (ML) to predict rock hardness using various geophysical and geochemical features. Core samples from a mine site were logged using a multi-sensor core logging system. Measurements including ultrasonic p-wave and s-wave velocity, elemental concentration via portable XRF, and Leeb Hardness, were measured every 2 cm along the length of the core. The ML model was set up to predict the Leeb Hardness using the elemental concentrations and ultrasonic velocities as predictors. The Leeb Hardness values were grouped into three bins and used as a classification target for the ML models. Various ML models, including linear regression, support vector machines, decision tree, XGBoost, Random Forest, K-Nearest Neighbors, and Naïve Bayes were tested. The model performance demonstrated that the Random Forest and XGBoost models produced the highest accuracy of 74-91%. Random forest and XGBoost were then selected to perform regression models to estimate a Leeb hardness value rather than a hardness class. These models were able to estimate the Leeb hardness value by 4.57-4.87 % error.

Mar 2, 2022

By Lana Alagha, Ashraf Alsafasfeh, Amal Al‑Hanaktah

As freshwater resources are becoming scarce, the use of seawater as replacement of fresh water is appealing in order to make mineral processing operations more sustainable. Since froth stability plays a critical role in determining the performance of flotation operations, there is an urgent need to study the effect of frother dosage and seawater on froth stability. In this study, flotation tests in seawater were conducted to examine the effect of frother’s dosage (MIBC) on the froth stability and flotation performance of low-grade phosphate ore. The stability of the froth layer was assessed by measuring the froth growth velocity and the froth maximum height at equilibrium. Results indicated that the best flotation performance was obtained at 75 g/ton of MIBC where ~ 90% of phosphate minerals were recovered. At this recovery value, the concentrate grade was determined to be ~ 70%. Results from froth stability experiments showed that the stability of the froth layer increased by increasing MIBC dosage. At MIBC dosage of 75g/ton, the calculated values of dynamic froth stability and the froth height were ~ 0.4 cm/sec and 16 cm, respectively.

Jan 17, 2024

By K. S. Venkataraman

The physical properties of clay-water systems depend on the complicated system of forces between the clay particles themselves, and between the clay particles and the ions in the liquid phase. The kind and distribution of ions in, on, and between the clay particles and the size and the shape of the particles are the basic factors determining the macroscopic behavior of clay-water systems. Understanding the system requires a knowledge of the nature of the clay particles, their size, structure, composition, and surface properties, and of the manner in which they interact with ions [and molecules] in the surrounding liquid [or other medium]. The validity of Professor Brindley's words (Brindley, 1958), written three decades ago in the context of making pottery, whitewares, and electrical porcelains, transcends time, and the basic message is perhaps all the more important in the considerably expanded use of ceramics for structural, thermal, tribological, electronic, and other applications. Silicon carbide, silicon nitride, and sialons have been studied in the last two decades for high- temperature structural and tribological applications, particularly for using in internal combustion engines. Titanates, zirconates and niobates of barium, strontium and lead, have high dielectric constants, and are extensively used in the formulations for making capacitors. Hexagonal ferrites (molecular formula MO.6Fe2O3) are in use for making permanent magnets for fabricating miniature motors, and for assembling loud speakers, particle accelerators etc. Cubic ferrites such as magnesium-zinc ferrite and nickel-zinc ferrite are used as transformer cores, and for other high-frequency applications. In this context, Richerson's recent book (Richerson, 1984) on the general scope of traditional and technical ceramics is a good starting point for an overview of contemporary ceramics technology. Glasses are a whole class of amorphous materials used widely as sintering aids, and for making glass-bonded ceramics and glass-ceramic composites. Composites are yet another burgeoning field where two or more particulate components are used for improving the performance of ceramics. For all these applications, the inorganic starting materials are almost always submicron and near-micron powders. Understanding the powders' physicochemical properties, and their surface chemical interactions with the surrounding liquid/gaseous medium is-necessary for making reliable ceramic parts at competitive prices. Even though ceramics science and engineering has attained its separate identity in universities and the industry, ceramists themselves would concede that ceramics science is a cross-disciplinary field, having incorporated and assimilated within itself many principles from several apparently disjointed disciplines. Principles of material science, graduate-level physics and chemistry, polymer science, surface and colloid chemistry, transport phenomena, particle technology, unit operations commonly used in chemical engineering and mineral processing, and statistics and applied mathematics are integral part of any ceramics curriculum in universities. Added to this is the fact that all bench-scale successes in making ceramic parts are to be scaled-up for larger throughput operations. Understanding and applying process engineering principles of comminution, classification, drying, calcination, etc. then becomes essential. CERAMIC FORMING: Despite the diversity of the materials and processes, conceptually, the steps involved in making ceramic parts have remained the same over several decades: The different components for making the pan (usually one or more powders plus other forming and sintering additives) are proportioned and mixed thoroughly, and the well-mixed formulations are consolidated into desirable shapes known as "green bodies." Usually binders such as wax, clay, organic polymers and surfactants, whether dispersed or dissolved in a suitable liquid are used during mixing the batch for giving strength for the green bodies. In the dried green state, the inorganic powders typically occupy only 55 to 60% of the bulk volume of the body, depending on the particle size distributions of the powders and the forming history, with mostly inter- particle voids accounting for the rest of the void volume. SINTERING: The formed bodies are then fired in high- temperatures kilns/furnaces during which the parts are exposed to a predetermined temperature profile, and "soaked" for a certain duration at the final high temperatures, typically between 1200 K and 1900 K, and then cooled to room temperature. The gaseous atmosphere in the furnace is controlled (oxidizing, reducing, or inert) when necessary. During the initial stages of firing, volatile liquids evaporate, and during the intermediate temperatures between 400 and 600 K, the the organic polymeric additives pyrolize and oxidize into water vapor, CO, C02, and other gases. At still high temperature, the glasses, when present, soften, and simultaneously, the ceramic particles rearrange into a network of grains with definite grain boundaries so as to reduce the total interfacial free

Jan 1, 1990

By K. A. Wheeler

To evaluate the effects on groundwater of a proposed in-pit disposal operation at an east Texas lignite mine, the local geologic, hydrogeologic, and geochemical features were thoroughly characterized. Resultant data were used in a flow and transport model (SWIFT) to simulate migration of the ash leachate. Computer simulations indicate that the leachate plume will travel 61-152 meters from the disposal area in 100 years after resaturation of the spoils. A 61-meter buffer zone of mine spoils without ash will surround the disposal area. The proposed landfill operation received regulatory approval and is currently operating as a Class 2 non-hazardous landfill.

Jan 1, 1994

By Allen D. Graham

The coal industry in South Africa is briefly outlined. Test- work carried out on bulk samples of coal in the laboratory and used in the design of the Van Dyks Drift washery are described. Factors affecting the selection of equipment and the designed capacity of the plant are discussed. A description of the crushing plant, washery and load out section is given together with performance data obtained in the final acceptance tests. New features incorporated in the Van Dyks Drift plant and in more recent plants of the Group are outlined.

Jan 1, 1982

By R. E. Ray

As coal reserves at shallow depths continue to be exhausted, a number of U.S. coal mining companies are beginning to develop coal seams previously thought to be coo deep to mine economically. Because of increased cover load, mines operating in deeper seams face unique ground control problems. In addition, the volume of methane gas contained in coal beds increases with depth, and ventilation requirements are much more stringent for deep underground coal mines than for shallower mines. When the longwall mining method is used at great depths, ventilation, ground control, and operational considerations must all be addressed in the design of longwall panels. This paper examines the influence of these factors, particularly ventilation and operational considerations, upon the feasibility of two, three, and four-entry longwall development panels in Jim Walter Resources' four deep mines.

Jan 1, 1986

By Jr. Moulton

Extractions of minerals from Searles Lake brines have taken place since 1873. Early operations were for borax and raw trona found on the surface, expanded after 1914 to include potash, salt cake, and soda ash. A new soda ash plant now in operation will double area production. The evaporite beds were formed by desiccation of Eastern Sierra runoff. The resulting series of brine-bearing salt beds supply the fluids necessary to feed the area chemical plants. Production methods include evaporation and crystallization for potash, borax, and salt cake; carbonation of brine to recover soda ash; and organic extraction of borax.

Jan 1, 1980

By S. Tandanand

The Bureau of Mines, U.S. Department of the Interior, assessed the geological effects on the ratio of maximum subsidence and extraction thickness, hown as the subsidence factor, to develop a simple method for predicting the maximum subsidence. The study is restricted to the Northern Appalachian Coal basin where data were collected from 13 coal mines. A model previously developed to relate the subsidence factor with the lithology and with the width and depth of working panels was used in the assessment. The result shows the possibility of determining maximum subsidence without resorting to a rigorous method.

Jan 1, 1982

By John E. Litz

Coca Mines Inc. is a medium sized company exploring for and developing precious metal properties in the Western United States. They own interests in a number of properties which contain reserves of gold and silver. The Hog Heaven property presently is under development for a combination of open pit and underground mining, followed by recovery of the silver and gold by cyanidation. Property Location The properties included within the Hog Heaven Project are located in Flathead County, northwestern Montana. The property is readily accessible by road from either Polson or Kalispell, Montana, Figure 1. [ ]

Jan 1, 1984

By Ashraf A. M. A. Wali

Many of the economic resources of Egypt have been recognized and exploited for thousands of years (e.g. gold and copper). Most of these minerals, particularly those from hard-rock sited deposits, are found in complex form along with other components while those present in sedimentary sequences are largely in simple compounds or as native elements. Recognition of their characteristic settings (structure, basin development, environment of formation etc.) is the main clue in predicting and locating their presence. The main economic minerals exploited in Egypt today come from sedimentary sequences and include sodium and potassium chlorides, gypsum, sulfur, and sedimentary iron ores. Large amounts of low grade sedimentary phosphates are known but are not of economic value at today's prices. Recent intensive investigation in the north-eastern Sinai (EI Arish) and along the southern coasts of the Gulf of Suez has revealed new and extensive sulfur and chloride deposits, and considerable oil and gas are now being exploited from closely related sediments. Tin is the only mineral that is produced from hard-rock sources, and gold and copper deposits are present but not of high enough grade to be economically viable. However, a significant part of Egypt has not yet been studied in enough detail to close the door on future discoveries. Another point of considerable geological interest is the presence of diverse, modern evaporitic settings, from which we may draw the analogs for many of the older gypsum, anhydrite, chloride and sulfur de-posits. In fact these analogs are so well displayed that both the Sinai and Gulf of Suez-Red Sea evaporites (Middle and Upper Miocene) can be readily compared with these modern deposits.

Jan 1, 1990

By Daryl R. Tweeton

The Bureau of Mines has developed PC-based tomographic computer programs for geophysical applications, and is making them available to potential users as part of a Bureau plan to facilitate the transfer of technology to industry. These programs were initially developed for predicting and monitoring the flow pattern of leach solution during in situ mining. Seismic crosshole tomography has located fractured zones of low seismic velocity and saturated zones of high seismic velocit above the natural water table. The Bureau has applied tomography also to assessing high-wall blast damage, and examining the integrity of mine-related geological structures. The tomographic programs include the straight ray pro ram BOMTOM (Bureau of Mines Tomography? and the program BOMCRATR (Bureau of Mines Curved Ray Tomographic Reconstruction) that can be run with either curved or straight rays. Both programs provide optional mathematical constraints to help counteract the nonuniqueness of reconstructions that occurs with crosshole data. They are available from the Bureau free of charge. With typical data sets, they can be run on a 386 microcomputer with 640 Kb RAM. BOMTOM was described in the Bureau Report of Investigations 9159, so this report emphasizes BOMCRATR. Curved and straight ray reconstructions using seismic field data collected while simulating injection of leach solution were compared. The curved and straight ray tomograms were quite similar even with velocity variations of more than 50 percent.

Jan 1, 1992

By James R. Oehler

Progress, future challenges, and the continual search for more efficient and rapid methods of excavating underground openings and shafts were main themes at the 1983 Rapid Excavation and Tunneling Conference (RETC) held June 12-16 in Chicago, IL. The event, jointly sponsored by the Society of Mining Engineers, the American Society of Civil Engineers, the Canadian Institute of Mining and Metallurgy, and the Engineering Institute of Canada, offered a diverse program for both civil and mining engineering disciplines. Although all papers given at the three-day conference were noteworthy contributions, and each is included in the conference proceedings currently available from SME, there were a few sessions that had particular mining-related interest. Research, Acceptance Needed for Water-Jet Technology Water-jet-assisted rock excavation is seen by some as a technology moving from the prototype phase to a fully developed, accepted system within the next decade. For an industry that is traditionally fairly slow in accepting significant changes, this development appears especially noteworthy. However, speakers at the water-jet technology session generally agreed that many large US manufacturers are not viewing water-jet-assisted equipment as viable replacements for all-mechanical systems. This, they fear, may mean some US manufacturers will lose a significant share of certain equipment markets to foreign competitors who are moving aggressively ahead in this area. Despite the advantages of increased cutting rates, reduced power requirements, less dust, prolonged bit life, and reduced sparking in many cutting situations, water-jet technology applied to mining is apparently having some acceptance problems in the US. R. J. Evans, professor of industrial engineering at the University of Pittsburgh, noted that there are several perceptual barriers to water-jet coal cutting; such as uncertainties concerning the fu¬ture demand for coal and the reliability of equipment, apprehensions that jet-assisted equipment will make the mine operator dependent on specific types of hard-to-obtain equipment, and fears about accessibility of the equipment for repairs. Evans also said numerous parameters need defining before taking advantage of water-jet-assisted cutting systems in under-ground coal mining in the US. For the cutting head, information must be obtained on optimum bit geometry and spacing, and maximum and minimum torque requirements. For a complete US water-jet cutting system, Evans added, research is needed to establish optimum jet pressures, jet powers, number of jets per bit, and location of jets relative to the bit. One research project making progress towards optimizing parameters for a water-jet-assisted drag bit cutting system for coal mining was described by Levant Ozdemir, director of the Earth Me- .

Jan 8, 1983

By John A. Breslin

The U.S. Bureau of Mines develops technology to help ensure that the Nation has an adequate and dependable. supply of minerals at reasonable economic, human, and environmental cost. Our research programs seek improvements for almost every aspect of the mineral production cycle--from evaluating the availability of minerals, removing the ore from the earth, to enhancing the performance of mineral materials. The health and safety of the men and women who work in the Nation's mines and minerals processing plants and the environmental impact of mining and mineral processing are major Bureau research concerns. In recent years, the U.S. mineral industry has found it increasingly difficult to compete for a share of world markets. Many foreign producers benefit from lower production costs and higher grade deposits. Some foreign governments subsidize their mineral industries and impose fewer restrictions with respect to environmental controls and health and safety regulations. If the United States is to compete in world mineral markets, innovative technology must be found to lower the cost of recovering and processing minerals. Mining and mineral processing research by the Bureau identifies ways to help the country maintain a sound, competitive industry and a dependable mineral supply, so vital to economic growth and the national security. This work includes efforts to improve existing techniques and procedures; but more and more of the Bureau's resources are being focused on long-term, high-risk research directed at developing new approaches to mining and mineral activities--approaches like in situ mining. Bureau scientists are studying the mining applications of computer assisted mining and investigating a variety of "high tech" approaches to extractive metallurgy. Such cutting-edge research will be necessary if major advances in health and safety, environmental quality, strategic and critical minerals availability, and overall U.S. competitiveness are to be achieved. It is just such high-risk research that the industry cannot afford to conduct itself, but--in the long run--cannot afford to be without. It is this type of research that will help us arrive at a revolutionary breakthrough rather than small incremental changes in health and safety technology as well as recovery methods. Our mining and mineral processing research is also directed at reducing the Nation's dependence on imports of minerals that have key defense and industrial uses. Some of these strategic and critical minerals are particularly vulnerable to supply disruptions. We are working on technologies that would allow the United States to take advantage of domestic sources of these minerals--sources consisting primarily of deep or low-grade ores, ores with complex mineralogy we do not yet know how to process, and small deposits that are now uneconomical to mine and process. Other research activities focus on ways to reduce the Nation"s consumption of key minerals and increase the recycling of these minerals. The opportunities in this area include coal. The current middle eastern crisis reinforces the need for a stable energy supply--preferably a domestic supply. The extensive reserves of coal in this country are well documented. Perhaps what is not as well recognized is the impact that the price of coal can have on its competitive position both for domestic fuel selection considerations as well as for the ability of this country to compete in the coal export market. Today, the role to the United States is as a reliable, but high-cost exporter of high-quality coal. U.S. export coal competes with supplies from other major suppliers, including Australia, Canada, Poland. If U.S. mining costs were lowered by at least $8 per ton in the year 2000, then coal exports would surge by a projected 46 percent, and U.S steam coal displaces significant quantities of foreign coal imports in Europe. Further cost reductions would make

Jan 1, 1991

By Bernard F. Anderson

INTRODUCTION In this chapter, the term "down-the-hole drill" (DTH drill) is used as a generic name that encompasses the various trade names and other references such as "downhole drill," "in-the-hole drill," etc. This chapter is limited to a description of DTH drills used in stoping large underground ore bodies. DTH drills differ from conventional drills by virtue of the placement of the drill in the drill string. The DTH drill follows immediately behind the bit into the hole, rather than remaining on the feed as with ordinary drifters. Thus, no energy is dissipated through the steel or couplings, and the penetration rate is nearly constant, regardless of the depth of the hole. Since the drill must operate on compressed air and tolerates only small amounts of water, cuttings are flushed either by air with water-mist injection or by standard mine air with a dust collector at the collar. HISTORICAL DEVELOPMENT Mine managers have long known the economies enjoyed by quarry and open-pit operators in producing large quantities of ore. The savings are due primarily to the availability of massive equipment, capable of drilling large blastholes to reduce the amount of drilling, increase the fragmentation, reduce secondary blasting, and im¬prove the flow of the product. In an attempt to reduce underground mining costs, various methods are used for long-hole drilling, includ¬ing standard pneumatic percussion drifters and diamond drills. These systems have their shortcomings; percus¬sion drills are limited to small hole sizes and they ex¬perience excessive deviation and significant loss of energy with increased depth. The diamond drills provide deeper and straighter holes, but only at high cost. Both systems suffer from high noise levels, low penetration rates, and poor explosives distribution, among other problems. When the mining companies approached the drill manufacturers for a compact and portable large-hole jumbo for underground use, they specified not more than 1 % deviation on 60 m (200 ft) of vertical hole and a penetration rate of 15 m/h (50 fph). On Dec. 23, 1960, a test unit was placed in service in Montana and met the performance criteria. Though lacking the so¬phisticated features available today, the economies of surface blasting were brought underground. Unfortunately, the first system did not gain immedi¬ate acceptance in the industry. Among the factors con¬tributing to its demise were resistance to change, the need to alter development methods for the ore bodies, and a lack of flexibility in moving the rig from setup to setup and from level to level. In 1972, the mining industry again challenged the drill manufacturers to provide a workable jumbo that would combine compactness, ease of maintenance, relia¬bility, and efficiency, all on a self-propelled chassis. The manufacturers responded by providing improved jumbos, which have been accepted with enthusiasm throughout the mining industry. Today's DTH jumbos are capable of drilling from 100 to 200 mm (4 to 8 in.) diam holes that can be reamed to even larger diameters. The holes can be drilled to depths of 150 m (500 ft), depending upon ground conditions and the capability of the jumbo to retrieve the steel and drill. Fig. 1 illustrates a typical DTH jumbo. APPLICATIONS The uses to which DTH drill jumbos have been put are quite numerous, with new uses being found regularly. For convenience, these uses may be classified as primary blastholes and nonblasting holes. Primary Blastholes The original purpose for the development of the DTH jumbo was for drilling primary blastholes that could be mined by open-stope methods. Prior to the advent of the DTH jumbo, extensive development was required before production drilling could begin. Sub¬levels were required to allow access for column-and-arm stopers or ring/fan jumbos, to the extent necessary based on the effective penetration of the chosen machine. With the DTH jumbo, the mine engineer is able to reduce preproduction time and development costs. How¬ever, the most significant saving results from an im¬proved cost per ton of broken ore in the production phase. To utilize a DTH system, only a top heading and drawpoints are necessary. The top heading can be the width of the ore body with a 3.7-m (12-ft) back. A drop-raise pattern is drilled and shot to begin the stoping operation, providing a free face for subsequent blasting. A typical layout is illustrated in Fig. 2. The advantages of this system include: 1) Drilling and blasting are independent operations, and blasting can be performed at a rate congruous with the mine's ton-per-day capacity. 2) The development layout is simplified. 3) Good explosive distribution is achieved, provid¬ing more uniform fragmentation. 4) Environmental conditions for operators are im¬proved, including improved safety with all work directed downward (not overhead), lower noise levels, little fog, and a reduced dust count. 5) Improved production per manshift. 6) Simplified and easier operator work cycles. 7) Reduced cost per ton of product. 8) Fewer holes lost due to ground shifts. Nonblasting Holes With the introduction of the compact DTH jumbos, other practical uses became apparent, including the drilling of: 1) Holes for sand fill, from level to level and from level to stope. 2) Drain and dewatering holes. 3) Power and communications cable holes.

Jan 1, 1982

By Fangyu Liu

In the grand tapestry of scientific inquiry, there are individuals whose contributions resonate far beyond the confines of laboratories and lecture halls. It is with profound admiration and respect that we present this special collection of Mining, Metallurgy & Exploration, dedicated to celebrating the remarkable career of Dr. Patrick Taylor. Dr. Taylor, recently retired from the Colorado School of Mines as the Emeritus Ansell Distinguished Professor of Chemical Engineering, possesses over 45 years of expertise in mineral processing and extractive metallurgy. His remarkable journey has seen him traversing the globe, from Canada to Egypt, contributing to pyrometallurgy, hydrometallurgy, and mineral processing. Dr. Taylor’s portfolio encompasses lab work, pilot-plant projects, research, and process development across various metals, with an impressive array of authored papers, presentations, and nine patents to his name. A soughtafter consultant for over 20 companies and an esteemed expert witness, Dr. Taylor also led the Kroll Institute for Extractive Metallurgy at Colorado School of Mines. Under his guidance, more than 100 graduate students and post-docs have undertaken transformative research, while Dr. Taylor’s 45-year tenure as a university lecturer and the creation of 10 industryfocused short courses underscore his dedication to knowledge dissemination. His contributions extend to crafting professional engineering exam questions for a quarter-century and active participation in esteemed organizations like SME, TMS, ASM, and MMSA.

Sep 16, 2023