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By W. G. Fischer

Trona ore at the Westvaco mine of FMC Corporation has been obtained by room- and-pillar methods since the mine began operation. The flat-lying, 10-foot bed of trona, Na2CO3 NaHCO3 2H2O, is covered by 1500 feet of weak shale and sandstone. Extraction of pillars on the retreat quite often throws large amounts of weight onto development workings. Weak shales in the roof and floor fail rapidly and the mine ribs slough to such an extent that mining often becomes very difficult. When this occurs efficiency goes down, costs go up, and the risk to men and machinery increases greatly. Difficult mining conditions in the early 60's forced a re-evaluation of all presently known mining techniques in bedded deposits. Many room-and-pillar mining plans' were compared with the system in use at that time, but none of them offered a better solution to the roof control problem. Longwall techniques were seriously considered, but machinery was not available that would cut the hard trona seam and still maintain the productivity obtained from room-and-pillar sections. Roof cones troy in the longwall methods appeared to be more satisfactory than that found in room-and--pillar techniques. It was therefore felt that a new technique using the longwall principle and based on rock mechanics should be tried rather than previously known pillaring methods.

Jan 1, 1966

By John Marsden

Despite the recent pullback in metal and mineral prices, and the associated market adjustments, the mining industry is still facing a serious issue with the declining availability of graduate expertise. This is due to a combination of an aging workforce, retirements and retrenchments, coupled with a lack of suitably qualified graduates entering the workforce. The issue has certainly improved since 2004 when the industry picked up the rates of hiring graduate engineers and mining/mineral school enrollments picked up in response. This hiring effort has helped to cover the ?gap? years from about 1985-2000, when industry demand for graduates was particularly poor. However, the recent market pullback is likely to set back this progress, as recruitment and hiring wavers as a result of cost cutting measures and economic uncertainty. A key issue for the mining industry is how to ensure the survival and growth of relevant ?core? degree programs. Such programs include mining, metallurgical, mineral processing and geological engineering. The mining industry needs a healthy, high-level education program to ensure an adequate supply of appropriately qualified graduates for the mining industry. Two-thirds of the professionals entering the minerals industry who graduated within the past 40 years graduated prior to 1985. Since 1985, we have been living off the legacy of graduation classes from the mid-1970s and early 1980s. It is estimated that we have been producing graduates at approximately 40 to 50 percent of the sustaining rate since about 1985. Further growth in the domestic industry would increase graduate requirements significantly, and the export of U.S.-graduates to other parts of the world (as is currently occurring) also impacts the total graduate requirements.

By David Brown, Adrian St. John, John Comins, Mike King

"INTRODUCTION The Crossrail project provides an East-West link across London enabling an additional 200 million journeys each year linking up major business centres and existing transportation interchanges, while reducing congestion at street level and within the current underground system. The project has built major structures in Sprayed Concrete Linings (SCL), including 5 new stations, 6 crossover caverns and numerous passages, adits and ventilation tunnels. Construction has taken approximately 4 years, and has involved the spraying of over 200,000m3 of concrete. At the start of the project there was a lack of available records from previous projects concerning concrete falls, which hindered risk assessments and the ability to make meaningful comparisons around spraying or material performance. This paper redresses this lack of data by providing information on falls experienced on this project and makes recommendations to assist future projects. Construction Methods Table 1 below summarises the main contracts with elements of permanent SCL. The listed primary lining lengths include pilot tunnels, side drift tunnels and enlargements as separate tunnels.A range of construction sequences were used in order to deal with the design requirements, geometry, and the ground and ground water conditions. The following briefly summarises the build up by layers, with typical design dimensions provided for a platform sized tunnel (approximately 9m internal diameter), excluding tolerance allowances. Some linings were sprayed in more than one layer to allow for inclusion of reinforcement layers or to avoid a too aggressive build-up of thickness: •,Initial shotcrete, or sealing, layer (ISL) of 75mm followed by a Primary Lining (PL) of 300mm. •,Regulating layer of 40mm followed by a Waterproof membrane (Sprayed membrane, 3-6mm). •,Secondary lining (SL) of 250mm with a separate sprayed fire protection layer (FPL) of 50mm."

Jan 1, 2016

By Michael J. Friedel

The permeability and flow capacity in unsaturated media is investigated by the Bureau of Mines for application to in situ copper leach mining at the Cyprus Casa Grande mine site. Moisture retention properties are derived and combined with scanning electron microprobe data to characterize the mineralogy, texture, pore size, distribution, and permeability of the host rock. Finite element modeling is used to derive a saturated permeability, ambient degree of saturation, and assess various injection-recovery schemes. Recommended design modifications for optimization of solution distribution and maximum recovery from the rock matrix requires either (1) the injection pressures on the order of 1500 psi and recovery wells operating in a suction mode, or (2) performing permeability enhancement, through rubblization. By producing a maximum block diameter of 4 m, injection pressures can be reduced to 500 psi with improved recovery and containment of solutions.

Jan 1, 1991

By C. Clark, J. Seymour, D. Benton

"National Institute for Occupational Safety and Health NIOSH is conducting research on jackleg use and related accidents in underground metal mines. This paper provides an analysis and overview of jackleg drill usage, accidents, operational characteristics, and alternatives, based on information from injury reports, legacy research, stakeholder input, and published literature. Jackleg drills are involved in more ground fall accidents in underground metal mines than any other drill. Jackleg-related injuries are most prevalent at the face in the course of installing initial ground support. Alternatives to jacklegs for drilling and bolting under incomplete support in narrow underground openings are not yet available. Small mechanized bolting equipment needs to be developed to address jackleg-related accidents and improve safety at mines where jacklegs are being used. JACKLEG DRILL Description The term “jackleg drill” is a generic name for a class of handheld, rotary, percussion rock drills that are equipped with an attached reaction leg to provide stability and thrust for the drill (Figure 1). All of the drill and leg controls are located near the operator’s handle at the rear of the head portion of the drill. Jacklegs are classified according to the bore size of their pneumatic pistons which normally range from 6.03 to 8.26 cm (2.375 to 3.25 in) [Kurt, 1982; Clark, 2012]. Jacklegs typically weigh 460 N (103 lbs), but their weight can approach 535 N (120 lbs) after they are fitted for operation with drill steel and air and water hoses [McKibbin and Clark, 2001]. In underground mines, jackleg drills are commonly used to drill 3.8-cm (1.5-in) diameter holes 1.83 m (6 ft) deep in rock. Application The jackleg drill is primarily used in underground mines when the size of the ore body, the ground conditions, or the mining method do not permit large openings to be mined using mechanized equipment (e.g., narrow vein mining). Jacklegs are used to drill blast-holes for explosives and also holes for installing ground support. These versatile drills are used in nearly all phases of mining including exploration, development, production, and maintenance [Kurt, 1982; Williams et al., 2007; Chen and McKinnon, 2012]. The jackleg is used to drill holes in rock using drill bits attached to hollow steel bars called drill steels (rotary percussion drilling). After the hole is drilled, the jackleg can be used to install different types of ground support components, depending on the ground conditions and the specific ground support measures that are needed. For example, the jackleg can be used to install expansion-anchor rockbolts or resin-grouted rockbolts using the drill’s rotary-motion feature. On the other hand, the jackleg can also be used to install friction-type Split-Set™ rockbolts using the drill’s percussion (hammer-motion) feature. As shown in Figure 1, various washer-like bearing plates can be installed along with these bolts to provide additional ground support and to help secure surface control products, such as wire mesh and shotcrete that are in turn used to retain small, loose material between the bolts [Clark, 2012]."

Jan 1, 2016

By A. Gungor

Thermal treatment can significantly improve industrial comminution operations by reducing energy requirements and increasing mineral liberation. The assistance of thermal pretreatment prior to grinding by microwave heating is scrutinized in this study. For this purpose three copper ore samples with different chemical composition were used. To see the effect of microwave heating on ore; work index, breakage rate and breakage distribution functions of original and heat treated samples were examined. The results obtained in this study did not show significant improvement in the grindability characteristics of the studied ores with microwave heat treatment. The inadequate amount of microwave transparent matrix was the main reason for the absence of cracks and micro-fractures in the microwave heated copper samples.

Jan 1, 1999

By E. J. Owen, S. Cherotich, V. T. McLemore

Breccia pipes are vertical pipe-like columns of rocks that provide conduits for fluid flow and open spaces for mineral precipitation, hence are focus areas for exploration. In the Gallinas Mountains, Lincoln County, New Mexico, there is recorded production of Cu, Pb, Ag, F, Fe, REE (as bastnäsite), and Au from 1902 to 1980, but no production reported from the breccia pipes. Previous studies described the occurrence of REE in breccia pipes, but their transportation and deposition controls are still unclear. The aim of this research is to characterize the magmatic-hydrothermal breccia pipes in order to understand the geochemical and physical conditions of deposition of REE and gold in the breccia pipes found in the Gallinas Mountains. There are more than 20 exposed breccia pipes that form a NE-trending belt about 3–5 kilometers, mostly gray-brown and consist of angular- to sub-rounded rock fragments, some host high concentrations of REE (80,500 ppm total REE) and Au (175 ppb). Preliminary studies suggest they are magmatic and intruded into the host rock and, subsequently, hydrothermal fluids precipitated F-REE and Au along the edges of some breccia pipes. More studies are underway to test this hypothesis.

Feb 1, 2023

By Tony Dunn

FMC Corp. achieved a significant cost reduction at its Green River, WY soda ash operations using a new proprietary solution-mining and processing technology. In phase one of the program, trona ore is dissolved, recovered and processed with the new technology. It is then fed into an existing refining plant, replacing dry mined and calcined trona ore. Phase two produces a final high-purity product. It also increases capacity by 635 kt/a (700,000 stpy). Both phases were completed under budget and ahead of schedule. This $120-million expansion project uses a new process and a new team to derive soda ash in a more cost-effective and environmentally friendly manner. The team successfully introduced solution-mining technology - with a liquid solution injected into previously mined sections of the mine. This shift in techniques signified a new era for soda ash production. The project is an example of teamwork at its best. For it to be successful, FMC had to work within several different areas inside and outside of the company. Engineers, contractors, mechanical operators and technical people were needed who could blend in with FMC's existing in-house team.

Jan 1, 1999

By R. Srikanth

Dust control in high production longwalls is a major problem requiring, among other things, careful attention to the design of operating practices, and ventilation schemes. Several studies have shown that the shearer is the major source of dust on a longwall face. Support movement has not been regarded as a major source of dust in U.S. longwalls; yet under certain conditions, 31 percent of the shearer operator's dust exposure can be due to support movement. Several methods have been developed for the control of shield-generated dust. Yet the need for better methods is apparent. In this paper, the amount of airborne respirable dust generated per shield move is estimated from specially designed experiments on longwall faces. A total of ten experiments were conducted in five longwall faces in four different mines. Each experiment involved one face visit and lasted three to six hours. The contribution of shield movement to the airborne respirable dust concentration immediately downwind of the shield moved, varied between 0.12 and 1. 75 mg/m3 in the five longwall faces. The mass of airborne respirable dust generated by shield movement was found to vary between 39 and 386 milligrams per shield move. The results from this study reveal that control of dust from longwall shields requires a combination of approaches involving alternative operating practices, reducing shield dust generation rate, increasing face air flow, and decreasing personnel exposure.

Jan 1, 1994

By R. J. Zagrocki

Rekindled public concern about lead toxicity has intensified the awareness of lead-bearing materials in contact with the environment and the human population. Lead's common association with other metals makes the increasingly restrictive lead standards a primary concern for a large number of metal and metal-related industries. In commercial scale demonstration tests with lead-bearing wastes, the HRD Flame Reactor process has a demonstrated ability to separate and recover over 95% of the lead as a recyclable oxide, while rendering the remainder of the material as vitrified, non-leaching, and nonhazardous co-product. Recent Flame Reactor process tests and preliminary cost data for secondary lead soda slag are highlighted.

Jan 1, 1992

By K. T. Valsaraj, L. J. Thibodeaux

Solvent sublation, the separation process for the removal of two hydrophobic compounds (penta- and trichlorophenols) from the aqueous phase, is discussed, as is a steady-state mathematical model for fire process. Solvent Sublation "'as conducted in a continuous countercurrent mode. The underlying mechanisms, theory and experimental details on the effects of process variables on removal efficiency are reported.

Jan 1, 1994

By Bahaa Alyosif, Murat Erdemoğlu, Muhammet Kürşat Aydemir, Turan Uysal

The effect of intensive milling on the conversion of microcline ( KAlSi3O8) to potassium chloride (KCl) occurred during the chlorination roasting process for artificial KCl production was investigated. A feldspar ore with 10.89% K2O grade and containing microcline was dry milled by a planetary ball mill for mechanical activation. Milled ore mixed with calcium chloride was roasted at temperatures between 500 and 1000 °C to get the chlorination roasting process. The product was then leached in water to dissolve KCl occurring during the roasting, which will be precipitated from the pregnant leach solution by evaporation. Results showed that potassium recovery from the unmilled ore increased rapidly up to 800 °C, and dramatically decreased at higher temperatures due to the removal of KCl from the furnace by means of evaporation. A potassium recovery of 31.95% was achieved by the unmilled ore, whereas it was 88.43% when 15 min milled ore was roasted at 750 °C. It was concluded that intensive milling caused mechanical activation of microcline to reduce the roasting temperature of the chlorination roasting process.

May 31, 2023

By M. Stephen Enders

The Little Rocky Mountains host epithermal gold-silver bearing vein and stockwork deposits in a syenite intrusive complex. Pegasus Gold Ltd. is currently mining the oxidized deposits by open-pit methods and recovering gold and silver by heap-leach processes. A geologic program has been designed to effectively determine the basic ore characteristics; 1)mineralization; 2)oxidation; 3)structural setting; 4)lithology; 5)alteration; and ultimately, 6)the leachability of the ore. Geologic mapping, sampling, drilling, assaying, and testing are routinely used in exploration, development, production control, mine planning, and ore reserve estimations. Timely and accurate assay results are essential for the program's success.

Jan 1, 1983

By Edwarde R. May

The Flambeau volcanogenic massive sulfide deposit located in northwestern Wisconsin occurs within the southern lobe of the Canadian Precambrian Shield. The steeply dipping tabular body occurs in a complex pile of cyclic schistose intermediate to felsic fragmental volcanics. No chloritic alteration pipe is recognized but adjacent rocks have undergone magnesia metasomatism and subsequently were metamorphosed to the upper greenschist and lower amphibolite facies. Although modest in size the deposit is of special interest in that it has an extensive and well preserved supergene enrichment blanket. Economic minerals found within a pyritized quartz-sericite schist are chalcocite and bornite overlying primary chalcopyrite.

Jan 1, 1976

By J. Restrepo, N. Ripepi

"The International Organization of Standards defines risk as “the effect of uncertainties on achieving objectives (15).” In mining, many uncertainties can influence the outcome of personal or professional objectives and are often difficult to predict. Risk management, the minimization and control of adverse effects from exposure to identified risks, is a well-established concept that can summarized as “being smart about taking chances” (12). Risk management now consists of management processes unique to numerous organizations across many industries, as varying sectors encounter a variety of needs, including the analysis and mitigation of risks related to physical security, product liability, information security, various forms of insurance, regulatory compliance, and workplace safety (12). The reoccurrence of multiple fatality events in the US mining industry, especially the underground coal sector, suggests an opportunity for improved methods of major safety hazard identification, assessment, and mitigation. A risk management approach would include ready identification and mitigation of these risks, inclusive stakeholder engagement, and rapid integration. While many solutions to reducing the risk of mine disasters have been proposed including stricter regulation and improved technology, a comprehensive risk management approach has yet to be fully integrated in the US mining industry. In December of 2006, R. Larry Grayson of the National Mining Association’s Mine Safety Technology and Training Commission called for “a new paradigm for ensuring safety in underground coal mines, one that focuses on systematic and comprehensive risk management as the foundation from which all life-safety efforts emanate (7).” A risk management approach has already been implemented with success in Australia’s minerals industry as part of a transition during the mid-1990s from a prescriptive based health and safety attitude to a more proactive, duty-of care [risk-based] philosophy (13, 16, 17).FUNDAMENTAL ELEMENTS OF RISK MANAGEMENT TECHNIQUES The fundamental components of a comprehensive risk assessment/management program are well-established within the realm of mining health and safety. Figure 1 depicts the elements of a typical mining hazard management framework. The first step in any safety-based risk management system is to identify and assess hazards by their location, nature, and magnitude within a mine. Next, a decision is made about choosing to eliminate, mitigate, or tolerate each hazard. Ideally, a hazard will be eliminated during the design stages of mining, though dynamic mining conditions often require continuous improvement and reevaluation of existing hazard controls. If elimination is not possible, hazard mitigation actions can consist of methods, rules, equipment, competencies, or other mechanisms. If a hazard is simply tolerated, as many inherent mining hazards must be, then specialized administrative controls must be utilized to minimize losses. During this process, the performance of each action is monitored and modified as needed (13)."

Jan 1, 2015

By S. Iverson

Fall of ground accidents continue to be a source of injury in underground metal mines. MSHA accident statistics indicate that most rock fall accidents occur at a new face where drilling and blasting methods are used. Removing loose rock by scaling is imperative to removing the potential for rock fall injury. Detection of potentially loose rock could improve the scaling process and result in fewer rock falls. Infrared thermal imaging cameras were investigated as far back as 1966 as a tool for loose rock detection. Early on it was clear that sensitivity (e.g. detectable temperature increment) is a key factor in this application. Both pixel resolution and temperature resolution have greatly improved with modern instruments. This paper describes an evaluation of modern infrared thermal imaging camera technology to detect loose rock conditions at six underground metal mines in the western U.S. It was found that thermal images provide a high resolution visual discrimination between loose rock and intact rock. However, detecting loose rock was difficult in cases where the rock and ventilation air were at the same temperature. Loose rock was detected when rock was both warmer and cooler than the ventilation air temperature. Warm rock with cool ventilation air provided the best conditions for detection.

Feb 23, 2014

By R. D. Lopez

The concept of "heat recuperation" for the grate-kiln pelletizing system was first implemented at the Sydvaranger plant in Norway in 1974. Essentially, heat recuperation involves bringing hot air from the second stage of the pellet cooler to the drying zone to increase drying-air temperature to the maximum limit. 'Burner-fuel savings result from a lower kiln secondary-air mass flow at a higher temperature. Because of the fuel benefits achieved at Sydvaranger, heat recuperation has been included innumerous new grate-kiln plants built since then, and some older plants have been retrofitted for heat recuperation. In recent years there has been much confusion about the fuel benefits of heat recuperation. To answer some of the questions, a mathematical model was developed and plant tests were conducted at Minntac Phase 111. Minntac is a magnetite taconite concentrating and pelletizing plant, and Phase III has two indurating lines. This paper presents the results of the studies and plant tests.

Jan 1, 1980

By T. B. Linde

The Morenci In-pit Crusher and Conveyor System has been designed with safe production and cost savings in mind. Large open pit mines around the world have been installing semi-mobile crushers and linking them with a pit conveyor system to lower unit cost. At Morenci two 60/89 in. gyratory crushers are incorporated into the semi-mobile crushing plants. The ore is reduced to -8 in. and transported out of the mine on a 60 in. steel cable belt. This paper includes an overview of the Morenci In-pit Crusher and Conveyor System from the drawing board to open pit installation and finally a discussion on operating and repair considerations.

Jan 1, 1990

By R. E. Hochscheid

Cyclones installed in three closed- circuit grinding systems were changed from conventional, vertical mounting to horizontal mounting with a favorable improvement in classification efficiency. In two of the installations, apex plugging problems were eliminated because horizontal mounting permit- ted the use of much larger apex orifices. Marked reduction in circulating load was accompanied by greatly reduced maintenance requirements for the cyclone and the cyclone feed pump in one of the installations.

Jan 1, 1988

By Jacques LeBel

After a brief definition of asbestos and a review of regulations, the elements of asbestos dust control are outlined for various asbestos manufacturing industries. To prevent the asbestos dust to become airborne, the general procedure is to control the dust at the source by enclosure and exhaustion. The asbestos dust is collected and removed from the air with bag filter collectors of high efficiency (better than 99%) to ensure that the air emitted to the general environment or returned to the workplace are below the existing asbestos emissions regulations. Dust control systems should be regularly inspected and serviced to maintain at all times the efficiency and reliability of the equipment. Other effective procedures for asbestos dust control are also considered.

Jan 1, 1984