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By Samuel S. M. Chan

Rock surrounding mine openings frequently is an impermeable type such as shale or granite. Most rock, however, has joints, bedding planes, cleavage planes, or other potential discontinuities. Permeability to fluids (gas or liquid) may exist via natural joints or fractures in an otherwise impermeable rock. In the mining situation, tectonic and induced tensile and shear stresses may be great enough to cause joints to open or fractures to develop in previously solid rock. The rock, as a result, becomes less self-supporting and may - require artificial support such as rock bolts or timber. Simultaneously, as fractures develop, permeable paths may be created. If fluid can be injected into a previously solid and impermeable rock mass, a logical conclusion is that a fracture (crack) flow path must be transmitting that fluid. The U.S. Bureau of Mines Laramie (Wyo) Energy Research Center has been evaluating results of in-situ oil shale fracturing (hydraulic or explosive) and retorting experiments by. a fluid (air) injection , and borehole air flow profile logging technique since 1956 (1, 14, 15). In the oil shale case, it is imperative to know the location and flow capacity (permeability) of natural fractures, if they exist, and induced fractures that inter-connect vertical wellbores at depths of fifty to several hundred feet. By injecting air into one wellbore in a system of several wells and measuring input volume and pressure while simultaneously measuring the output of other wellbores, the minimum areal extent of interconnecting permeable fractures can be determined. Exact locations (depths) of fractures and individual fracture flow capacities between wellbores can be determined by air flow profile logging (14, 15). Knowledge of fracture locations and permeability is essential to rational experimental in-situ retorting design.

Jan 1, 1973

By P. G. Corser

A gold and silver open-pit mine located in northwestern Chile contracted ACZ in 1991-92 to assess the stability of their spent ore pile and to determine the cause and magnitude of cyanide contamination associated with leaching operations. The mine is a conventional open-pit located at an elevation of approximately 4,800 meters (m.) (15,744 feet). A spent ore pile is located approximately 2,000 m. southwest of the mine and approximately 1,000 m. northeast of the active pad and plant facilities. The pile was constructed on a gentle northwest slope dipping 12 to 13 degrees. The pile is bordered by a small river to the northwest and by a larger river to the northeast. Both rivers eventually flow into Bolivia. Heap leaching and processing commenced at the mine in 1988. Since 1988, nearly 6.0 million tons of ore at an average grade of 1.96 grams/ton (0.07 ounces/ton) of gold and 52 grams/ton (1.83 ounces/ton) of silver have been treated by cyanide heap leach methods with zinc (Merrill Crowe) precipitation. In approximately three years of operation, the mine has yielded more than 225,000 ounces of gold and over 1.5 million ounces of silver. Currently ore is agglomerated and hauled to the leach pad by truck and is top loaded to produce a 5-meter lift height. Four contiguous reusable (on/off) leaching pads were constructed with an asphalt layer above a carefully compacted sub-base of High Density Polyethylene (HDPE) liner and screened fines. Leach solution of pH 10-11 containing 1.2 to 1.5 gram/liter of cyanide is applied to the heap at a rate of 10 liter/hour/square meter for a total active application period of 30 days. Leached (spent) ore is transferred to the spent ore pile located approximately 1,000 meters to the northeast. The pile currently contains approximately 6 million tons of spent ore. The pile liner, which has been constructed over a prepared sub-grade consists of three geosynthetic layers (geotextile/flexible membrane liner/geotextile). Long term objectives include washing the pile to recover an additional 3 to 4 percent gold and silver.

Jan 1, 1993

By Siyu Song, Yanhong Wang, Guohua Gu, Linbo Huang

In this study, the effect of cations, Na+ and Mg2+, in saline water on copper flotation in the presence of calcium bentonite was investigated. It was found that as the concentration of NaCl was increased, the copper recovery initially decreased and then increased to above 99%, while the copper grade initially increased and then decreased. In contrast, as the concentration ofMgCl2 was increased, the copper recovery continuously increased, while the copper grade continuously decreased. The variation of copper recovery and grade was mainly attributed to the synergistic effect of pulp rheology and flotation solution chemistry. The underpinning mechanisms are the compressing electrical double layer and ion-exchange interaction between saline water and bentonite, which occur at the same time. Using salinewater slightly affected the pulp rheologywith a decrease in copper recovery at low NaCl concentration. Increasing the concentration of cations in saline water might even facilitate the flowing out of exchangeable cations, especially divalent cations, from the interlayer space of bentonite to the solution, resulting in the decrease of copper grade at high salt concentration.

Sep 10, 2020

By R. Bishop, J. Baggett, J. Monsalve, J. Hole, N. Ripepi, A. Abassi

This work focuses on the operational and safety issues associated with karst voids in large opening underground mines. Issues include water inrush, structural instability, and engineering uncertainty in these environments. Coupled with the fracturing prevalent in folded sedimentary rocks, karsts are complex and challenging ground control risks. Traditional methods of predicting karst locations, such as probe drilling, are impeded by the inconsistent spatial distribution and variable sizes of the features. Ground penetrating radar (GPR) is a geophysical technique that transmits radio waves into a medium and subsequently detects reflected waves via a receiver. The travel time and energy of received signals are then processed and interpreted. The difference in material properties between limestone and open karsts causes strong reflections. GPR is frequently used as a geophysical surveying technique in several industries, however there is a lack of published research on underground mining GPR applications. The purpose of this work is to prove the viability of GPR in underground stone mines for karst detection, and to discuss the importance of karst detection ahead of mining. INTRODUCTION The Mine Safety and Health Administration (MSHA) currently lists 116 active underground stone mines in the United States, the vast majority of which extract limestone for crushed stone products. These limestone mines have the potential to encounter karst voids at some point in their operation, as most karstic regions of the United States develop in limestone rock masses (Kuniansky, Weary, & Kaufmann, 2016). Karsts, the cavities formed by the dissolution of carbonate rock, have long plagued the mining and tunneling industries, as well as been a hindrance on the Earth’s surface, producing sinkholes and ruining otherwise valuable land for construction and public use. The impact of karsts on the Gavarres tunnel in Spain is well documented by Alija et al; constant instability conditions, material spills into the tunnel, and unexpected cavities seriously delayed the project deadlines and “were not foreseen in the design” (Alija, Torrijo, & Qunita-Ferreira, 2013). At the water supply project in Sohngua River, China, Bin et al detail the presence of both water and sediment filled karsts which are sources of disastrous conditions at this tunnel (Bin, et al., 2017). A hydrological tunnel in Lebanon encountered numerous massive karsts in the tunneling path which required remediation via friction anchors, rockbolts, welded wire fabric, channel steel arch segments, invert steel beams, and shotcrete (Leech, Jaoude, & Ghanem, 2008). From a design standpoint, rock mass classification schemes, such as the RMR from Bieniawski and the Q-system from Barton, are not able to represent the true nature of a karstified carbonate rock mass, and therefore complex case-by-case analyses of underground conditions are necessary (Andriani & Parise, 2017).

Jan 1, 2019

By B. M. Davis

The uncertainty associated with a reserve estimate has generally been expressed as a subjective ranking rather than a quantitative expression of either reliability or uncertainty. These rankings of estimate reliability have taken a very nonquantitative bent as well. For example, the U.S. Securities and Exchange Commission definition of proven reserves is given as: Reserves for which (a) quantity is computed from dimensions revealed in outcrops, trenches, workings, or drill holes, grade and/or quality are computed from the results of detailed sampling and (b) the sites for inspection, sampling and measurement are spaced so closely and the geologic character is so well-defined that size, shape, depth and mineral content of reserves are well-established. (U.S. SEC, Form S-18, Item 17A)

Jan 1, 1992

By R. Hogg

The sedimentation and dewatering characteristics of flocculated slurries are determined by the size and density of the flocs. Studies of the formation and growth of flocs reveal that floc size is limited by breakage of the agglomerates due to shear in the suspension. Floc density measurements indicate that there is an inverse relationship between size and density. This relationship appears to be determined primarily by the nature of the solid particles, especially the size distribution, but it appears that agitation of the suspension can lead to some densification of the flocs, in addition to breakage. It follows that both size and density can be controlled to a significant extent by regulating the physical conditions (agitation, method of flocculant addition etc.) during flocculation. The use of physical floc conditioning to control the sedimentation and dewatering (filtration) behavior of flocculated, fine-particle suspensions is evaluated in terms of its effects on floc size end density.

Jan 1, 1986

By D. K. Steele

The U.S. Bureau of Mines has investigated the recovery of metals from copper industry wastes by sulfuric acid leaching in a semi-continuous, bench-scale system to solubilize arsenic, copper, and molybdenum. Leach residues contained approximately 40 wt pct PbSO4, suitable for processing at a lead smelter. Arsenic and molybdenum removal from leach solution was examined using solvent extraction with tri-n-butyl-phosphate (TBP), and copper was subsequently recovered by cementation. Bleed electrolyte from a copper refinery was determined to be a viable source of acid for the initial leach stage.

Jan 1, 1991

By A. Vien

A major thrust in Industrial automation over the past few years has been the exploration and incorporation of higher level (supervisory and optimizing) control strategies aimed at more fully exploiting the existing control system infrastructure. There is little doubt that this is worthwhile pursuit, however, one must not lose sight of the maintenance and development requirements of the basic control system. Statistics on loop performance indicate that this too is an area of considerable potential. In this paper the authors look at some of the less elegant, but arguably equally important issues in mineral processing plant control. The focus is on controller structures, loop tuning, sampling, filtering, and some of the other principal components of the regulatory control foundations. In many cases significant improvements In control performance can be achieved by getting back to the basics.

Jan 1, 1998

By R. R. Klimpel

The process of flotation is an extremely important solids separation technique employed in a wide variety of industrial process applications. Froth flotation is practiced in the coal industry to recover fines produced during the mining and cleaning of coal. A recent review article by Aplan (1) covers the processing variables encountered in the flotation of coal and the variety of chemicals and operating conditions which affect recovery. Numerous engineering and scientific studies have been performed with the goal of providing semifundamental laws of flotation behavior for improved screening of flotation chemicals, better equipment scale-up factors, etc. Often the results of such work are expressed in the form of mathematical models (e.g. 2, 3, 4, 5, 6) which are potentially useful for evaluating (simulating) on paper such alternatives as possibles process operating or configuration changes, the effects of ore and reagent changes, etc. It appears to be commonly accepted that a complete scientific/engineering characterization of flotation is immensely complicated and not sufficiently developed at the present to accurately predict (or understand) many important industrial facets of flotation. Thus, one is often reduced to detailed experimental characterization in both the laboratory and plant in order to fully evaluate flotation changes or alternatives. It is the purpose of this paper to describe a method of batch laboratory data characterization that is useful in evaluating flotation chemical reagents including froth flotation of coal. The approach consists of running a series of time-recovery curves in a batch float cell followed by the computer curve fitting of this data to a series of mathematical models based on semi-physical reasoning. The unknowns or parameters of these models are then optimally chosen so as to best fit the experimental data. It has been found in both coal and mineral systems that changes in reagent type, concentration, system pH, grind, etc. cause very consistent and logical changes to

Jan 1, 1979

By P. Tsang

To gain insight into the current status of pillar design practice in the underground coal mines of United States, a survey has been undertaken in the late 1993 and early 1994. A total of 552 room-and-pillar mines and 75 longwall mines have been surveyed to collect general, geological and mine plan information. The collected information are critically analyzed with special emphasis on the pillar design criteria adopted in these mines. A safety factor analysis has also been carried out for the pillars in room-and -pillar mines.

Jan 1, 1995

By Frank A. Jerabek

Pneumatic stowing was first introduced in longwall mining in the middle twenties. Since that time it has advanced through many stages of development, particularly abroad, which have greatly improved its efficiency and contributed to its growing use. Pneumatic stowing originated in coal mining but has also been adopted in metal mining. This paper discusses the techniques of pneumatic conveying of. stowing material and equipment and applications of pneumatic stowing.

Jan 1, 1966

Rendering a solid hydrophobic and solid-fluid particle* attachment in flotation are recognized as not necessarily related (1,2). The attachment is governed by forces of attraction and repulsion which need to be considered. The induction time required for attachment after solid and fluid particle are brought into proximity (3-8) illustrates the point. Laskowski(8) showed that a reduced induction time favoured flotation but detected no change in contact angle, a standard indication of solid surface hydrophobicity. Induction .time is observed in fluid-fluid particle coalescence, there being called a rest time (9-11) The induction time phenomenon is related to the presence of a metastable liquid film (disjoining film (2)) of the continuous phase (water in flotation) which must thin and rupture to permit attachment. The lifetime of this film, which is governed by the rate of thinning and the probability of rupture with thicknesss, depends on a complex interaction of forces. Investigating these forces should help clarify the attachment process. Practical benefits would be improved understanding of slimes flotation (12,13) This paper is concerned with the role of the mobile fluid particle-water interface on the film lifetime, in particular, the role of time-dependent or dynamic interfacial properties resulting from deformation of this interface.

Jan 1, 1975

By T. E. Mccandless

Detrital minerals of mantle origin have been found in the Green River Basin of Southwestern Wyoming (Figure 1). Pyrope, pyrope-almandine, and chrome-bearing clinopyroxene and orthopyroxene occur on the antmounds of Pogonomyrmex Occidentalis. These antmounds are a common sight throughout the western U.S., and were used by early paleontologists as fossil mammal collection sites. The mound is composed of two types of material; (1) soil excavated during the digging of the nest below the surface (maximum depth 3 meters) and (2) larger grains collected from the surface and placed on the mound, probably to prevent erosion. The selection of grains to armor the mound seems to be based largely on the mean diameter of the grain, with other factors such as weight, sphericity, roundness and composition in decreasing order of importance (Wheeler and Wheeler, 1963). The minerals of this study happen to fall within that mean diameter range. The garnets are found on the mounds as 3-6 mm diameter subrounded to subangular grains. The pyroxenes are also 3-6 mm in diameter and are most commonly subangular laths. The minerals themselves show evidence of abrasion, such as frosted surfaces and rounded edges. Orange peel texture is present on some of the grains, which suggests that kelyphitic rims were once present, but have been removed. Also, no similar minerals were found in sieved soil auger samples to depths of 2 to 6 meters taken near the antmounds. These observations imply a distal rather than proximal source for the minerals. Lamproitic rocks of upper mantle origin are found bordering the "Green River Basin. The best known are the Leucite Hills, a series of ultrapotassic volcanics found on the north flank of the Rock Springs Uplift (Carmichael, 1967). Minor occurrences of mica peridotite and ultrapotassic volcanics are also found on the western end of the Uinta Mountains in Utah (Best, et al, 1968). None of these rocks are known to contain minerals like those on the antmounds. The garnets are comprised of purple chrome pyrope, red chrome pyrope-almandine, and pink to orange low chrome pyrope/pyrope-almandine. Oxide statistics for these groups are summarized in Table 1. These three groups are distinct when their Cr203 values are plotted against magnesium number (Figure 2). The chrome pyropes are highest in Cr203 (1.28-2.66%) and have high, restricted Mg number values (0.781-0.826). The chrome pyrope almandines have similarly high Cr203 (1.29-2.62%) but a lower Mg number range. The low chrome pyrope/pyrope-almandines have the lowest Cr203 content (0.09-0.73) and the widest Mg number range (0.534-0.836). Using the classification scheme of Dawson and Stephens (1975) the chrome pyropes are most similar to garnets derived from kimberlite and from garnet lherzolite, websterite, and harzburgite xenoliths in kimberlite. The chrome pyrope-almandines and the low chrome pyrope/ pyrope almandines are similar to garnets derived from eclogite nodules (Figure 3).

Jan 1, 1984

By Shingo Morimoto, Toru Sasaki, Masato Shinji

"1. INTRODUCTIONTunnel face stability is one of the most important consideration in New Austrian Tunneling Method. In general, if all of the material properties of ground can be obtained through the field investigations, the tunnel face behavior can be predicted using numerical simulation prior to tunnel construction. However, estimating the safety of a tunnel face is difficult, especially in cases where the ground is very weak such as in an urban area.In this study, numerical analyses of tunnel excavation in very weak ground conditions, such as a low cohesion and low internal friction angle, were carried out. The relationship between the average shear strain distribution on the tunnel face and the overburden was analyzed. This relationship estimates the shear strain of the tunnel face relative to the critical shear strain obtained by the ground properties. The critical shear strain was defined as an allowable value for the maximum shear strain. We proposed the allowable overburden as tunnel face stability index (TFI) that satisfies the critical shear strain criterion of ground. Finally, a design chart of the allowable overburden for various cohesion values and friction angles of ground was created. This chart is useful in the preliminary tunnel design stage to judge the necessity of additional counter measures against normal tunnel support design.2. WEAK GROUND MODELING AND ANALYSIS PROCEDURE2.1 Setting material propertiesWith reference to a past study1), the material properties were adopted on the basis of material properties in the standard worst rock classification case called “DII”2) for standard support pattern of weak ground in Japan. The typical material properties for “DII” are listed in Table 1. In addition, Fig.1 shows the distribution of the representative weak ground according to cohesion and internal friction angle. When the internal friction angle is relatively high and the cohesion is weak, the ground is categorized as sandy ground. Furthermore, when the internal friction angle is low and the cohesion is strong, the ground is categorized as clayey ground."

Jan 1, 2016

By M. S. Celik

Beneficiation of boron minerals by flotation with well defined systems has been very little investigated in the literature. The difficulty arises from the fact that boron minerals cover a spectrum of solubilities. Colemanite, a calcium containing relatively insoluble boron mineral, and borax, a highly soluble boron mineral have been used to exemplify the flotation of boron minerals. The floatability of both minerals using sodium dodecylsulfonate and dodecylamine hydrochloride exhibits considerable differences in their response to flotation. This has been ascribed to variations in the solubilities 0f boron minerals and the presence of the cations in the lattice structure. Flotation tests along with zeta potential measurements are used to elucidate the mechanisms involved in the flotation of boron minerals.

Jan 1, 1992

By Barry D. Simmons

The Millenbach copper-zinc orebody is an ideal Canadian example of a stratabound base metal deposit in volcanic rocks. The mine, operated by Lake Dufault Divison, Falconbridge Copper Ltd. is located five miles north of the city of Noranda in northwestern Quebec. The deposit occurs within an Archean volcanic sequence which forms part of regional acidic volcanic center within the Abitibi greenstone belt. Preproduction ore reserves totalled 2,075,000 tons grading 3.5% copper, 3.6% zinc, 1.1 ounces per ton silver, and 0.02 ounces per ton gold. Stratabound lenses of massive sulphides together with underlying stringer sulphides are closely associated with a dome of quartz-feldspar porphyritic rhyolite approximately 3000 feet below surface. The paper describes the presently known geology of the deposit and includes documentation of sulphide mineralogy and textures as well as sulphide/ host rock relationships. The stratigraphy, petrography and chemistry of the volcanic host rocks are described with emphasis on the alteration intimately associated with the sulphide bodies. Although the volcanic stratigraphy is complex within the mine area, the presence of only low-grade metamorphism and the relative lack of structural deformation allow detailed interpretation of geological history. Presently recognized evidence strongly suggests that the sulphides were deposited at and near sea-floor, by hydrothermal solutions. The dome of porphyritic rhyolite appears to have been the most significant factor controlling sulphide localization.

Jan 1, 1975

By Garry W. Warren

The electrochemical oxidation of chalcopyrite in the absence of-a chemical oxidant was studied in ammonia/ammonium sulfate solutions by anodically polarizing electrodes prepared from massive chalcopyrite. The effects of pH, cupric and ammonia ion concentration were systematically evaluated. Kinetic parameters were obtained from the anodic charge-transfer regions of the anodic polarization curves. Increasing ammonia and hydroxyl ion concentrations increased the rate of oxidation. A mechanism is proposed which explains the first order dependence of (NH3) and (OR) associated with a single electron transfer process. An empirical relationship which accurately describes the dependence of the rest potential (i.e. zero current potential) on solution composition is also given.

Jan 1, 1978

By T. J. Lutz, J. L. Carr, J. A. Yonkey, C. C. Jobes

"Since 1984, the date of the first recorded fatality involving a remote controlled continuous mining machine, 38 miners in the United States have been killed when they were struck by a continuous mining machine. Proximity detection is a valuable tool for preventing fatalities, and the use of these systems is expected to significantly improve safety. Proximity detection provides a means to prevent accidents like these. Researchers at the National Institute for Occupational Safety and Health (NIOSH) conducted a series of underground tests to evaluate the accuracy and repeatability of proximity detection systems under a number of conditions such as varying the orientation and height of the personal wearable device (PWD), moving the PWD close to the trailing cable, and activating the machine’s mining mode. At the 2014 SME Annual Meeting, results from tests on first-generation proximity detection systems were presented. This paper will provide results from the similar tests performed with second-generation systems. The results show that performance has improved. For example, the negative impact of PWD orientation and the trailing cable has been reduced. However, some inconsistencies remain. Notably, performance changes dramatically when mining mode is activated. INTRODUCTION Since 1984 there have been 38 fatalities involving striking and pinning of the operator and other workers by the continuous mining machine (CMM) [1]. In August 2011, the Mine Safety and Health Administration (MSHA) published a proposed regulation that would require proximity detection systems on all continuous mining machines except full-face machines [2]. Proximity detection systems are designed to stop machine motion to protect miners from striking/pinning hazards. Several MSHA-approved proximity detection systems are commercially available. MSHA estimates that of the 38 fatal striking and pinning accidents that have occurred since 1984 involving CMMs, the use of proximity detection could have been a preventative factor in at least 28 cases [1]. Furthermore, MSHA estimates that proximity detection could prevent 20% of all deaths throughout the industry [3]. NIOSH researchers have been involved in the development and testing of proximity detection technology since creating the HASARD system [4] and have recently conducted research intended to develop more advanced proximity detection technology for CMMs [5,6,7,8]. In addition, NIOSH has also conducted research investigating how the signals of a proximity detection system propagate [9,10] and have developed a novel method for determining the location of a personal wearable device (PWD) relative to the magnetic field generators [11,12]."

Jan 1, 2015

A comparison of gold, platinum and sulfide ion selective electrodes was made in this investigation for determination of Eh in solutions containing sulfide ions as a model system. The comparison was made in terms of the accuracy of the measured response, response time, pH dependence, and reproducibility of measurement. In addition, the sensitivity of each electrode towards changes in sulfide ion concentration was measured in terms of the change in measured Eh per decade change in concentration of sulfide ions. On the basis of a detailed investigation of the electrode processes occurring at the surface of gold and platinum electrodes, it was postulated that within the pH range investigated these electrodes respond to changes in the hydrosulfide ion, HS-, concentration in solution. In comparison, the sulfide ion selective electrode is known to respond to changes in the sulfide ion, S-, activity in solution. Although the potentials measured with gold and platinum electrodes were mixed potentials, pretreatment procedures can be used to obtain a signal suitable for process control. For control of sulfide ions in flotation pulps, the use of a gold electrode pretreated at 1.0 V with respect to a standard hydrogen electrode is recommended.

Jan 1, 1990

The Bureau of Mines has studied 260 underground coal mine fires which occurred from 1970 through 1989. Every fire had the capacity to be hazardous to life and property, however upon closer examination some were found to be inherently more dangerous than others. Our research involved reviewing and recording specific information contained in published Mine Safety and Health Administration fire accident reports. The objective was to determine if degrees of hazard relative to fire source or location could be construed from information contained in the reports. We specifically looked at the propensity for fires to cause injuries and fatalities as well as the need to seal the area in order to extinguish the fire. Relative to all underground locations, this review found that fires occurring in main haulage-ways were most likely to cause injuries and fatalities as well as require sealing of at least the immediate area to extinguish.

Jan 1, 1993