Search Documents

By Francis S. Kendorski

INTRODUCTION Caving offers the lowest cost per ton of any large-scale mining method, but its successful application demands an ore body that conforms to several rigid requirements. The deposit must be of wide areal extent, massive and not spotty in ore values, and insensitive to ore dilution. It must also be a rock mass that breaks up readily. There are only three active caving operations in the US-Climax, Henderson, and San Manuel-but caving methods have recently taken on new importance as deeper lower grade mineral occurrences and ore bodies are found. These deposits are too deep for surface min¬ing methods, and too low grade to support any type of underground mining except a bulk method such as caving. Announced discoveries or indications that may be amenable to caving include: Climax's Mt. Emmons molybdenum discovery in Colorado; Molycorp's Goat Hill molybdenum prospect in New Mexico; the Phelps Dodge molybdenum deposit in Beaver County, UT; Arizona copper occurrences such as Asarco's Sacaton, Hanna's Casa Grande, Noranda's Lakeshore, and Ken¬necott's Safford; Anaconda's suspected deep copper de¬posit in Butte, MT; Anaconda's Carr Fork, UT, deposit; and perhaps others. CAVABILITY'S ROLE IN FEASIBILITY STUDIES Caving is a system of underground mining which removes support from underneath an ore body. As a result, the rock mass fractures, fails, and flows vertically downward by gravity to be collected in previously ex¬cavated funnels. Types of ore that have been mined by caving include molybdenum, copper, iron, nickel, as¬bestos, and diamonds (Julin and Tobie, 1973). It is primarily a large-scale method, with production rates of more than 45 300 t/d (50,000 stpd) having been achieved. However, the initial capital investment before return is very high, often in the hundreds of millions of dollars. The cavability of an ore body or mineral occurrence is a critical item in the feasibility study of a proposed mine, not only from the point of overall minability, but from the point of impact on other costs such as blasting, loading, hauling, crushing, and grade recovered. Aside from the often-asked question of, "Will it or will it not cave?" the real questions are, "Can we afford to make it cave, carry the rock away, and extract the mineral?" The last is not a topic of this chapter, but the first two are. The cavability of an ore deposit or mineral occur¬rence is based on many things, but clearly, if a large enough area is undermined, any rock mass will cave. The result could be a violent collapse as occurred at Urad, CO (Kendrick, 1970), or perhaps the rock mass will cave beyond the ore boundary. Another unfavor¬able result could be ore blocks that are too large for the equipment and orepasses to handle without considerable secondary blasting. Weak rock with numerous fractures may produce a very fine ore when it caves, resulting in dilution and ground control problems. DETERMINING STRUCTURAL DOMAINS It has long been recognized that the geologic nature of an ore body is important to cavability (King, 1946). Such items as weak rock material, intensity of fractur¬ing, and severity of faulting all contribute to the success of a caving operation, and information regarding these is required as a minimum for the cavability determination. In practice, the rock mass-defined as the blocks of intact rock together with the intervening fractures, joints, faults, bedding planes, and other discontinuities-that contains the ore body, as well as the surrounding and overlying rock, must be examined in a systematic and detailed fashion. Surficial geology maps must be pre¬pared, exploration holes drilled, and core logged for en¬gineering information. The fracturing of the rock mass must be studied to ascertain the three-dimensional dis¬tribution of fractures and their characteristics, and faults must be located and described. The strength and other mechanical properties of the rock material, the fracture surfaces, and the fault filling materials must be tested and reported for later use by designers and planners. With this basic information and an understanding of the geologic setting, the rock mass can be divided into one or more structural domains which tend to behave similarly in response to engineering activities (Robertson and Piteau, 1970). One must keep in mind that the determination of the structural domains goes beyond the geologic units present. Several lithologic units may be lumped together, while a single lithologic unit can be divided into multiple domains. Major faults often form their own domain, and the direction of engineering ac¬tivity-for example, cave advance to the north rather than the south-may alter rock mass behavior, resulting in different domains. As an example of the detailed rock fracture map¬ping required for such studies, the structural domain determinations at the Climax mine (Kendorski, 1973) are shown in Fig. 1. The circles are Schmidt equal area projections of the three-dimensional attitudes of frac¬tures (Ramsay, 1967) mapped in detail at various rock exposures. The attitude of fractures is important to the cavability determination since it dictates the directional behavior of the rock mass as it fails, and determines the effectiveness of arching, keying, and rock block inter¬locking. Low-angle fractures must be present to allow movement of the rock in the vertical direction during undermining (Mahtab and Dixon, 1976); if low-angle planes of weakness are absent, the rock mass may arch with a keystone effect, rather than moving vertically downward.

Jan 1, 1982

By Charles E. Stack

There are several ways in which to classify refractories. The most suitable one is based on their general composition or raw material content. The categories are: 1. Aluminosilicate brick which include the fire clays and alumina and high alumina raw materials. 2. Basic brick which includes magnesia and chrome ore alone and in various combinations. 3. Silica brick which uses gannister or high purity gravels and sands. 4. Insulating brick are generally of the aluminosilicate type but may be most all refractory raw materials. 5. Special refractories are made from raw materials of zircon, zirconia, ultra high alumina, silicon carbide, fusion cast products, chromic oxide, carbon and graphite. The raw materials that make up these different categories are what we are briefly going to consider. Emphasis is placed more on the most important raw materials.

Jan 1, 1976

By C. S. Simons

The aphorism that provided the title of this paper is probably a couple of hundred years old, but it still expresses a fundamental truth in the metals industry. This truth will be illustrated through a brief review of the major developments in the extractive metallurgy of the oxidized ores of nickel - the "laterite" ores. While the details to be discussed are for the most part specific to nickel, a close parallel with other commodities - particularly in recent years - will be apparent even to those whose interest in nickel itself is slight. Thus it is hoped that this paper will be stimulating, at the least, to anyone who is concerned with the implementation of process improvement, "Invention" in the present context means any change from "conventional" process technology that shows a reasonable chance of reducing costs, increasing revenues, or both, in the production of a commodity. This can be anything from a simple rearrangement of flowsheet steps to a completely different basis for processing. And the result may reduce costs by more efficient use of energy or labor or reagents; may increase revenues by better recovery of the primary product or by introducing the recovery of previously ignored by-products; may insure sales volume (and thereby cash flow) through higher product purity or an improved product form. "Necessity" is the perceived need to attain at least one of these classes of results. This perception of necessity, however, varies widely from management to management and from project to project.

Jan 1, 1983

By William Gleason

"With desert temperatures climbing high at Caterpillar’s Tinaja Hills Demonstration and Learning Center near Tucson, AZ in September, a group of editors were given a reprieve from the sun and stepped inside the new Cat Minestar Command Center. The movie theater-like temperatures inside were a welcome relief, and the computer screens stationed around the room were an indication of not just how much things have evolved in the mining equipment sector, but also a peek into the future of where mining is headed.Equipment manufacturers like Caterpillar have always had to deal with peaks and valleys in demand that come with mining, perhaps never more so than in the last five years. Sudhanshu Singh, global product manager for Caterpillar, said that in one month in 2012, at the height of the mining Super Cycle, Caterpillar produced more than 150 large mining trucks (haul trucks that carry 136 t/150 st or more). By contrast, Caterpillar produced about 80 of those trucks in the full year of 2016. Between 2012 and 2016, Caterpillar saw its profits drop by 40 percent.“This shows how cyclical the industry is, and it is a testament to the strength of Caterpillar to be able to tolerate the wide swings,” said Singh. Demand for commodities is once again on the rise as are commodity prices with many signs pointing toward a recovery for the mining sector, and Caterpillar has positioned itself for the recovery. During its 2017 press event in September, company officials emphasized that Caterpillar has added strength in its technology divisions by forming new partnerships and adjusting its operating plan.“At the heart of our enterprise strategy is the operating & execution (O&E) model, a strategic framework to identify areas of the business that either create or consume the most value,” said Caterpillar chief executive officer, Jim Umpleby. “Using the O&E model as a guide, we gain a deeper understanding of where we have a competitive advantage, which is key to generating high returns.”"

Jan 11, 2017

By BERND SCHÖNHERR, JÖRG DEHNERT, PETER WINDISCH, JENS STOPP

The Quick-Erect Stopping System (QESS) offers a new way of reducing the radon exposure of miners in Germany, especially during remediation work in old mines. The QESS is a lightweight, modular and reusable construction kit of interlocking telescopic aluminum tubes, radon-proof foil and expanding foam. It is designed to seal off radon-rich parts of galleries within minutes. Originally, the QESS was developed to protect miners against radon exposure. Then, the QESS found the attention of several mine rescue teams at a German mining conference. Some mine rescue drills by The Student Mine Rescue of the Technical University Bergakademie Freiberg, Wismut Mine Rescue and Front Range Mine Rescue helped to improve the system and highlighted its potential for mine rescue operations. Now, the QESS is well-suited for small-scale mining. The QESS can be used to both protect miners from radon exposure and to support mine rescue operations. Moreover, the QESS was also successfully used in ventilation experiments.

By P. Kawahata

Newmont?s Twin Creeks Mine, located in northern Nevada, is producing gold ore from surface mining operations. The ore is currently processed at three different on-site facilities depending on ore type and grade. Processing facilities operate under stringent geochemical blending constraints that must be met from mine ore deliveries and off-site sourced ore. To analyze various strategic options, the technical team utilizes the mathematical optimization approach. However, due to the size and complexity of the operation, there are unique challenges in optimizing life-of-mine production scheduling. This paper describes those challenges and methods developed to take advantage of different scheduling software to effectively compensate each other and result in reasonable guidance. This paper also describes how those scheduling results are reflected in detailed mine plan and cost estimate work.

Jun 1, 2013

We have lived through a period of strong metal pricing during the past eight to 10 years. Copper has been hovering in the range of $3-$4/lb during much of the past eight years, averaging close to $3.30/lb. Gold increased steadily from less than $300/oz levels in the early 2000s, reaching almost $1,890/oz in the third quarter of 2011, before tempering back down to the $1,200-1,400/oz range in 2013. Iron ore prices started to rise in 2005 before the staggering increases experienced in 2008- 2010, reaching almost $190/metric ton in early 2011. During the past four years, iron ore prices have ranged from $100-180/t, averaging approximately $140/t. In the aftermath of such a run, it is perhaps too easy to forget where we have come from: The copper price averaged just 77 cents/lb during the six-year period from 1998 to 2003, and averaged just over $1/lb from 1989 to 1997. The gold price averaged $350/oz during the 10-year period from 1994 to 2003. Even more dramatically, iron ore traded in the range of $10-$15/t between 1985 and 2004. So, we have seen sustained, three- to four-fold increases in copper and gold prices, and 8 to 10-fold increases in iron ore prices.

Mar 1, 2014

By James Parkes

"The proposed Baltimore Red Line light rail system includes a 3.4 mile downtown tunnel (DTT) with five underground stations. The design of the underground stations involved overcoming several challenges, including limited right-of-way, high groundwater and uplift pressures, and metamorphic rock within the station depths. An innovative design was developed to maximize the internal station space while minimizing cost. The station designs use slurry walls for temporary and permanent support and groundwater control. Depths within rock are supported with cast-in-place concrete walls, the thickness of which are minimized through the use of permanent rock anchors for support of the rock mass and slurry wall toes. Permanent tiedown anchors are used for uplift resistance, which minimizes the station depths, volume of rock excavation, and the volume of deadweight concrete. Design considerations regarding individual elements and overall integration of the slurry walls, CIP walls, and multiple anchor types are presented.INTRODUCTION The Baltimore Red Line (BRL) project is a proposed light rail transit line for the Maryland Transit Administration (MTA) that runs east to west through Baltimore City and County. The project includes the Downtown Tunnel (DTT) consisting of 3.0 miles of twin running tunnels, two portals, five underground stations, and a pedestrian tunnel, as shown in Figure 1. The tunnels have an outside diameter of 21.8 feet and are designed to be mined using pressurized face tunnel boring machines (TBMs). The stations, portals, and the pedestrian tunnel are designed as cut-and-cover structures using slurry walls (concrete diaphragm walls) for both temporary support of excavation (SOE) and permanent structural walls. The dimensions of the five underground stations are summarized in Table 1. Design challenges included limited right-of-way (ROW), challenging soils conditions, strong metamorphic rock within the station depths, and high groundwater conditions. The final station designs included innovative use of slurry walls, tieback anchors, rock anchors, and tiedown anchors."

Jan 1, 2016

By Alexander N. Winchell

The construction and erection of the Coleraine concentrating plant was commenced in April, 1909, and was completed (with the machinery installed) ready for use in 1910. Attached to the main building is 'a table house large enough to accommodate con¬centrating tables for five units and space for a small machine shop and supply store. For the handling of the' railroad cars in the upper portion of the mill there is provided on the north side of the main structure a trestle approach 650 feet long, and on the south or opposite side a tail track 300 feet long. The latter is so constructed as to permit its being incorporated directly in a possible future extension of the plant. The building, viaduct approach and tail, trestle, as well as the table house, are con¬structed of steel, the total amount used being 6,100 tons. The building is covered by corrugated' steel sheeting over 2 x 6-inch wood sheathing fastened directly to the structural steel. The north end of the trestle approach is connected with the main road-beds forming the track system for delivery of the crude ore to the plant over an embankment of a maximum height of 110 feet containing over 2,000,000 cubic yards of dirt.

Jan 1, 1920

By A. J. Abraham, K. E. Seitz, J. D. Humphrey

Caterpillar has led the way for sound reduction in off highway trucks (OHT) used for mining. In 2000 Caterpillar introduced the 793CXQ sound reduction OHT (Figure 4) to meet local noise level demands in the Hunter Valley near Sydney, Australia. The sound level of the mining equipment in the Hunter Valley is being reduced to pre-serve the quality of life for the residents of the area. To meet the levels established required a major redesign of the 793C, as a result the sound power level was reduced by 9 dB (A), which is a less than 1/8the original sound level.

Jan 1, 2004

By Eugene C. Robertson

The exchange of heat from wall rock to ventilating air was studied in a cross-cut driven through fresh rock on the 4600 level of the Kelley Mine, Six- teen thermocouple probes, 10 inches long, twenty-three probes, 7 feet long, and five probes, 50 feet long, were emplaced in the walls soon after blasting and wall -rock temperatures were monitored intermittently over a two-year period to determine heat loss from the wall rock. Temperatures, humidity, and velocity measurements were made of the air at the same times to determine heat gain. An important but less well-defined variable was the heat transfer by water entering the crosscut from fractures and leaving in the ditch. The balance of heat in and heat out at each probe station is within an acceptable range. Theoretical and empirical models for heat flux into a cylindrical opening fit the data reasonably well, also.

Jan 1, 1970

By H. G. Papacek

The Fabrica Mine of the Brazilian iron ore company Ferteco mines on an extremely inhomogenous ore deposit. A large amount of the crude ore consists of fines minus 100 micron which cannot be sold without further treatment because of its chemical and physical properties. In order to make full use of the mined crude ore an expansion program has been realized which incorporates among others a concentrator to produce classified blast furnace ore , sinter feed and pellet feed. The pellet feed is converted in a 2.5 million tons per year Lurgi Dravo plant into high grade pellets. The paper discusses the selection of the concentration process, the pelletizing process and describes the experiences with the operation plant during the startup and the first years of operation.

Jan 1, 1979

By C. J. Bise

In August, 1977, the Federal Surface Mining Control and Reclamation Act was signed into law [I]. It stated that: "The Congress finds and declares that because of the diversity in terrain ... and other physical conditions in areas subject to min ing operations, the primary governmental res- ponsibility for developing, authorizing, issuing, and enforcing regulations for-surface mining and reclamation operations subject to the Act should rest with the States." Section 516 of Title V (Control of the Environ mental Impacts of Surface Coal Mining) of the Act deals with the surface effects of underground coal mining operations. "Each permit issued under any approved State or Federal program pursuant to this Act and relating to underground coal mining shall re quire tfieoperator to adopt izeasures consist ent with known technology in order to prevent subsidence, causing material damage, to the extent technologically and economically feasible, maximize mine stability, and main tain the value and reasonable foreseeable use of such surface lands, except in those instances vhere the mining technology used requires planned subsidence in a predictable and controlled manner: Provided, that nothing in this subsection shall be construed to prohibit the standard method of room and pillar mining. "

Jan 1, 1980

By David Wilson, T. V. Rao

INTRODUCTION The Alchem trona mine, owned and operated by Allied Chemical Corp., is located approximately 32 km (20 miles) west of the town of Green River, and 8 km (5 miles) north of Interstate 80 in southwest Wyoming. Trona, a naturally occuring sodium sesquicarbonate (NaCO3 • NaHCO3 • 2H2O), is used for the production of sodium carbonate (Na2CO3), commonly known as soda ash. Present annual US consumption of soda ash is approximately 9.07 Mt (10 million st), out of which approximately 7.3 Mt (8 million st) is produced from the Wyoming trona mines. About 44% of soda ash is consumed by the glass industry; 3 % by exports; and the remaining portion by paper, chemical, soap, textile, and nonferrous industries. Allied Chemical operates an underground mine at an average depth of about 488 m (1600 ft). There are three other trona mines in the area operated by FMC Corp., Stauffer Chemical Corp., and Texasgulf Inc. (see Fig. 1). Allied Chemical became interested in southwest Wyoming trona deposits in the early 1940s. Explora¬tion work was begun in 1959 with the acquisition of federal leases. Exploitation of the reserves began in 1968. Two shafts, one 6.1 m (20 ft) and another 3.7 m (12 ft), were completed prior to 1968. The 6.1-m (20-ft) diam service shaft is divided in half by a cur¬tain wall, with one half used for men and material and the other for ventilation as a return air shaft. During the period from 1968 to 1974, the 3.7-m (12-ft) shaft was used as production shaft with two 7.3-t (8-st) skips. Due to the increased demand for soda ash, plant and mine expansions were completed during 1974. Under this expansion, the material handling system capacity was increased by constructing a new 2721-t (3000-st) capacity ore bin, sinking a 6.1-m (20-ft) diam produc¬tion shaft, and installing a friction hoist with two 22.7-t (25-st) skips. The Alchem mine manpower is 484 employees and about 2.3 Mt (2.5 million st) of trona was produced during 1976. Three different mining systems are used at the Alchem mine: conventional, continuous, and longwall. Allied Chemical introduced its first longwall unit in 1973, which was also the first longwall system introduced in the Wyoming trona district. At present, four conventional, seven continuous, and two longwall units are in operation. This equipment is operated in ten production areas. GEOLOGY The bedded trona and trona-halite in the Green River basin of southwestern Wyoming is a major re¬source for the nation. There are 25 beds that exceed 0.9 m (3 ft) in thickness and underlie areas of about 2590 km2 (1000 sq miles). There are other minor beds that range in thickness from 0.3 to 1.2 m (1 to 4 ft). Allied Chemical's Alchem mine is located in bed 17. The trona bed numbering system starts at the lowest elevation and increases upwards. The trona beds are in the Wilkens Peak member of the Green River formation. The Green River formation was deposited in a lake that began in early Eocene as a large body of fresh water, shrank in size and became saline, and then became fresh water again. The sedi¬ment during the saline phase of the lake, which includes the trona beds, is called the Wilkens Peak member. The underlying freshwater lake deposit is called the Tipton member and includes a 25.9-m (85-ft) sand unit which is a high pressure, low permeability aquifer. The over¬lying sediment is called the Laney shale. The Green River formation is underlaid by the Wasatch formation and overlaid by the Bridger formation (see Fig. 2). The structure of the beds in the area of the Allied Chemical mine is mostly postdepositional asymmetrical folds of small amplitude. These folds range in size of 3 to 6.1 m (10 to 20 ft) to as much as 45.7 m (150 ft). The trend of the folds is northwesterly with the north¬east flank of the anticlines having a steep dip and the southwest having gentle dips. Trona bed 17 varies in thickness from 2.4 to 3.4 m (8 to 11 ft) over the 93.2 km2 (36 sq miles) holdings of Allied Chemical and is flat lying except for the rela¬tively minor folding and a negligible regional dip of about 0.017 rad (1°). Trona occurs naturally in several physical forms in the Green River basin, being both massive and crystal¬line. The trona ore in the Alchem mine is a fine-grained massive ore with a compressive strength of approxi-

Jan 1, 1982

By L. R. Todd

Gold Fields' Mesquite mine, located in southeastern California, heap leaches low grade gold ore at an annual rate of 2.7 Mt (3 million st). Ore is crushed in a two stage open circuit and belt agglomerated prior to loading on the leach pads. Since initial heap construction in October of 1985, a number of operating practices have been modified and several agglomeration techniques have been tested in an effort to improve percolation and reduce leaching time. Findings to date are discussed.

Jan 1, 1987

By Jessica M. Wempen, Dallan J. Coons, Bailey S. Simmons, Michael K. McCarter

Gate-road yield pillars are subject to increases in stress as the longwall face advances toward the pillars. Abutment loading conditions are important to gate-road layout and support design in longwall mining systems. Ground support systems are often designed based on mine experience [1,2]. Convergence monitoring is one method of ground support monitoring that can be used to infer increases in pillar stress. Convergence of a yield pillar was measured regularly over the course of six months as the longwall face approached and passed the pillar. Measurements were collected at eight locations surrounding the pillar. The convergence measurements contribute to the knowledge of when yield pillar abutment loading, caused by the encroaching longwall, is first detected. Knowing when abutment loading begins to yield the pillars can help define when standing secondary roof supports are required for head-gate entry access for specific geologic and mining conditions. 

By K. N. Han

The adsorption of gold onto activated carbon in iodide solutions was studied. The adsorption rates were determined as a function of temperature, salt concentration and pH, as well as activated carbon concentration. A kinetic model was developed for the adsorption. The adsorption rate was believed to be controlled by a combined mechanism of film diffusion and pore diffusion with the film diffusion having the most significant effect. Experimental findings were in good agreement with the model developed. The apparent activation energy was found to be 14.9 kJ/mol.

Jan 1, 1995

By Don C. White

Santa Rosa is a mid-Tertiary, volcanic-hosted, gold-silver deposit. Current proven and probable reserves are 8.9 Mt (9.8 million st) grading 1.5 g/t (0.044 oz/ st) gold, minable by open pit and amenable to heap leaching. It is the product of hydrothermal mineralization along an arcuate segment of a caldera collapse ring fault in a probable maar volcanic setting. This segment was later broken by radial faults. Gold at Santa Rosa occurs principally as electrum, finely disseminated through intermediate tuffs, and associated with pyrite. The nearby Alto de la Mina deposit displays stockwork silica-pyrite-gold in a tectonically and hydrothermally shattered andesite flow. Miocene epithermal mineralization was accompanied by central silicification and pyritization and more distal argillization. An andesite flow cap rock at Santa Rosa played a pivotal role as an upward permeability barrier. Highest gold grades and most intense alteration occur closest to the ring faults and immediately beneath the andesite flow. Supergene alteration effects on the gold distribution are minimal.

Jan 1, 1995

By PAITIP THIRAVETYAN, KANJANA KUDPENG

The aim of this study is to compare amino acids and organic acids in the extraction of gold from silicate ore. Amino acids were found to have higher efficiency of gold extraction than organic acids at the same acid concentration, which is likely due to amino acids having both carboxylic and amine groups in their structure, while organic acids only have carboxylic groups. Five amino acids (glycine, aspartic acid, glutamic acid, lysine and tryptophan) and seven organic acids (citric, malic, tataric, fumaric, oxalic, succinic and ascorbic acids) were selected to investigate gold extraction efficiency. Aspartic acid was found to have greater capacity to extract gold than succinic acid. The optimal gold to aspartic acid molar ratio was 1:6, and low concentrations of aspartic acid extracted 35 to 42 percent of gold from silicate ore within 15 days. Further studies are needed to increase gold leaching and reduce incubation time. The results imply that aspartic acid can be used as an alternative reagent to traditional methods for extracting gold from ore. This method is nontoxic to humans, is environmentally friendly and can have real applications.

By ANDREW HOBERT, Maoming Fan

Low-cost and environmentally friendly green froth flotation modifiers of plant origin, such as guar gum, carboxymethyl cellulose (CMC) and starch, have been used in the flotation of some sulfide and nonsulfide minerals. This paper discusses the fundamentals, current applications and potential new applications of guar gum, CMC and starch in minerals flotation. In this study, improved flotation performance was achieved using some green modifiers in flotation columns.