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By Indranil Roy

Gua supergene enriched iron ore deposit from Jharkhand, India has been geostatistically modeled. Population modeling shows a negatively skewed 3-parameter log-normal fit for Fe and positively skewed 3-parameter log-normal fit for Al2O3 and SO2. Semi-variographic studies for Fe indicate spherical function fit using point kriging cross-validation technique with Co=4.06(%)2, C5.11 (%)2, Co+C=9.1 7(%)2 and 'a'=348m. Kriging with 50mx50mx 10m block size at 740mRL led to a global mean kriged estimate of 61.98% and kriging variance of 4.04(%)2 for Fe with central 90% geostatistical confidence limits at 61.39% and 62.24% for that level. This led to an ore inventory at 740mRL as 7.29 million tonnes of ore.

Jan 1, 2002

By Irwan Halim, Young Jin Park

A new tunnel lining was designed for rehabilitation of the existing unlined Weehawken Tunnel in New Jersey. Structural assessment using beam spring models was performed for the lining design as a drained structure at the invert with a waterproofing umbrella. Empirical Federal Highway Administration (FHWA) guideline was typically adopted for estimating hydrostatic pressure, which recommends full hydrostatic pressure at the crown and ten or twenty-five percent gradual reduction from the initial pressure toward the invert. Finite element seepage analyses were conducted for the actual conditions based on anticipated drainage behind the lining and impact on the structural design. Considerations will be provided on the existing guideline for estimating hydrostatic pressures.

Dec 1, 2022

By Anuradha Khetwal, Tala Tahernia

The estimation of TBM utilization rate can be problematic due to the uncertainty involved in the tunneling system reaction to various geology along the tunnel. Moreover, the impact of operational and management issues on TBM performance is unsettled. This includes the occurrence and duration of downtimes and the uniqueness of projects relative to the geology, machine type, backup system, site setup, crew experience, and operational restrictions imposed on the project by localities. The CSM2020 is a model based on discrete event simulation that predicts machine utilization for single or double shield TBM. This model was developed by the Earth Mechanics Institute (EMI) team, using the database of tunneling activities which was compiled based on field observation and measurements in pertinent projects. In the current study, CSM2020 was modified to simulate the workflow of slurry TBMs. The operating principle of slurry shield TBMs is different than open-mode TBMs. The model was verified by comparing results with a recently completed project in the United States. As a result, the model offers reliable utilization rate estimation in different types of TBM by implementing appropriate workflow.

Dec 1, 2022

By T. S. Golosinski

This paper identifies the components of belt conveyor shifting force as a vertical force. Pv, horizontal force, Ph, and longitudinal force, P1. A method for estimation of these forces is proposed, which relates their value to the properties of the conveyor structure and rails, shifting operation parameters, and other site-specific conditions. The effect of this force on shifter behaviour is analysed and guidelines are developed for selection of a suitable shifter. Also discussed are the requirements of the shifting operation for other equipment.

Jan 1, 1986

By Nikhil Dhawan, Shrey Agrawal

India’s most extensive renewable energy expansion program targets 280 GW of solar energy by 2030. Due to the massive generation of photovoltaic waste (expected 34,600 T by 2030), stringent recycling effort to recover metal resources from endof- life PVs is required for resource recovery, circular economy, and subsequent reduction in the environmental impact. The present study investigates the recycling potential of end-of-life silicon solar modules. The feed characterization reveals that most of the values in PV modules are concentrated in the frame (pure Al), Si wafer (72–84% Si, 9–12% Al, and 0.13–0.71% Ag), and electrical connections (Cu wire coated with Sn). The Si and Ag values in the feed were beneficiated using water fluidization, and concentrate with 90% Si and 2% Ag was attained in the underflow concentrate. Ag values were recovered in the form of AgCl by leaching in nitric acid and precipitation. After the purification step, the residue containing 99% Si can be further utilized to fabricate Si wafer and Al-Si alloy. The preliminary cost estimations suggest that the proposed process is economically viable for the recycling of solar panels with the maximum value generated from the AgCl precipitate followed by Al panels and Si wafers.

Nov 14, 2022

By J. Helton, J. L. Bellanca, M. McNinch, L. R. Swanson

DISCLAIMER The findings and conclusions in this paper are those of the authors and do not necessarily represent the official position of the National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention. Mention of company names or products does not constitute endorsement by NIOSH. ABSTRACT Accident data indicates that mobile haulage poses a significant pinning, crushing, and striking risk. Proximity detection systems (PDSs) have the potential to protect mineworkers from these risks. However, unintended consequences of mobile PDSs can undermine the safety benefit they provide. Soliciting iterative user input can improve the design process. Users help provide a critical understanding of how mobile PDSs may hinder normal operation and endanger mineworkers. Researchers explored users’ perspectives by conducting interviews with mineworkers from seven mines that have installed mobile PDSs on some of their haulage equipment. Mineworkers reported that mobile PDSs affect loading, tramming, section setup, maintenance, and general work on the section. Mineworkers discussed the operational effects and increased burden, exposure, and risk. Mineworkers also suggested that improved task compatibility, training, logistics, and PDS performance might help address some of these identified issues. This paper also gives additional insights into mobile PDS design and implementation. INTRODUCTION Pinning, crushing, and striking accidents are a large problem in underground coal mines, especially for mobile haulage. Between 1984 and 2014 there were 179 non-fatal and 42 fatal pinning, crushing, and striking accidents involving mobile haulage vehicles, including coal hauling machines and scoops [1]. Proximity detection systems (PDSs)—automated systems that decelerate and stop a vehicle in order to prevent a collision—have the potential to protect mineworkers in these situations. In fact, PDSs are now required on all place change continuous mining machines as of March 16, 2018, as a result of the final rule published in January 2015 (30 CFR 75.1732) [2]. To address mobile haulage, later in 2015 the Mine Safety and Health Administration (MSHA) also proposed a new rule that would require PDSs on mobile haulage vehicles [3]. Though there has been no additional actions related to the proposed rule and it is not currently required, mobile PDS can still help to save lives. MSHA estimates that the adoption of mobile PDSs could prevent approximately 70 injuries and 15 fatalities over the next 10 years [4]. As of June 2015, the underground coal industry had already equipped 155 of the 2,116 mobile haulage vehicles in use [1]. In order to capitalize on the projected safety gains afforded by PDSs, it is important that the systems are designed and implemented effectively. Along with others, researchers at the National Institute for Occupational Safety and Health (NIOSH) have been exploring PDSs for more than two decades [5-7]. Throughout this time, NIOSH has also held several stakeholder meetings (2010, 2014, 2016, and 2017) in order to disseminate information and provide an opportunity to discuss on ongoing issues and concerns. Despite some progress, human factors remain a key concern. Previous research examined mineworkers’ attitudes towards PDSs on continuous mining machines [8] as well as how continuous miner operators’ perceptions of risk have changed as a result of PDSs [7]. However, stakeholders have still expressed a need to better understand how mobile PDSs affect the mining process, the mineworker, and whether and how they may present previously unidentified risks.

Jan 1, 2019

When I reached Warren after the "de luxe" South American expedition I had little idea what was in store for me. From the large check Thayer had handed me just before I left New York I was pretty sure the future would be good, and that before long it would involve Anaconda. Evidently, Mr. Thayer had left it to Dr. Ricketts and John Greenway to work out the details The next morning Greenway asked me to come to his office and told me that he and Dr. Ricketts had discussed the question and that Anaconda would make me an offer I could not refuse. They proposed to pay me almost $1000 a month, more than twice my current salary. They had agreed that I should stay with Calumet and Arizona for the rest of the year to help with Bisbee development and anything I could to assist with the New Cornelia plans and construction Of course I could not turn down such a flattering offer, as I had about reached the limit of advancement with a much smaller company in anything save a high executive job, and it would be a long time before I could be ready to change from exploration and geology to operating. Greenway and I agreed that I would stay with him for the remaining eight months of 1916 without any particular title but helping in any way I thought would be most useful. Bisbee and Ajo Study It turned out to be a busy half year, in addition to many good times with my Bisbee friends. The Uplift Club did not meet as regularly as in earlier years, but Mason Ross, Jim Lewis, Bill Gohring, Roy Mitchell, Hubert d'Autremont, Arthur Notman, and I did have many "bull sessions" and poker games. I saw much more of Greenway than before and made many trips with him to Ajo and later to the new

Jan 1, 1976

By J. D. Vincent

The Mission By-Products Plant at the Mission Concentrator of the American Smelting and Refining Company, some 20 miles south of Tucson, Arizona in the Twin Buttes mining area, has been in operation slightly over a year. The plant produces a molybdenite concentrate a copper concentrate and, at times, a zinc concentrate. An intensive test program of over three years was conducted at Mission to make the recovery of molybdenum economic. Briefly it was found necessary to make a scavenger concentrate in the copper mill before it was possible to recover economic quantities of molybdenite. By so doing there were resulting additional recoveries of copper, silver and zinc. This program resulted in the design and construction of the existing plant. A paper by the authors discussing the test work and the design was presented at the, October 1965 meeting of the American Mining Congress in Las Vegas, Nevada, by Mr. Wayne Bossard.

Jan 1, 1966

By M. R. Yalamanchili

Recently, noequilbrium electrokinetic measurements using laser-Doppler electrophoresis were reported by Miller et al. (1992) for alkali halides and the sign of their surface charge thus determined. These results are generally as expected from simplified lattice ion hydration theory with KCI, under normal circumstances, being the most significant exception. In this regard, lattice defects (F centers and oxygen imperfections) have been found to influence the surface charge of KCI and its electrophoretic mobility. In particular, the presence of oxygen defect states in the crystal lattice has been found to be responsible for KCI's unexpected behavior. The concentration of oxygen defect states in KCI, as characterized by UV/Vis absorption, was varied in order to study their influence on the electrokinetic behavior and subsequently on the flotation response of KCl. At low oxygen contents « 60 ppm) KCI is positively charged as expected from lattice ion hydration theory. However, typically, KCI contains substantial oxygen (>300 ppm) sufficient to impart a negative surface charge which accounts for the selective flotation of KCI from NaCl by hetero-coagulation with oppositely charged alkyl amine hydrochloride collector colloids.

Jan 1, 1994

By K. Schonert

Jigging is a separtion process that has already been described by Agricola in 1556. Fine size material is normally treated in a hutch jigging process, in which the heavy particles are penetrating the jigging bed and are recovered in the hutch. In this process, a ragging consisting of the same or higher specific gravity particles is inserted upon the screen. The ragging is used mainly as a valve to maintain a constant upward flow of the water. Since the heavy particles should pass easily into the hutch, the ragging particles are up to ten times larger than the maximum feed size (1). In the fine size range - 1 mm the performance of jigs is mainly insufficient; some of the low density particles percolate the ragging while the hutch water flow prevents the fine heavy particles from entering the bed (2). By giving a thin layer of particles, which posesses a density sensitivity in case of certain adjustment of flow conditions, directly on the screen, the precision of separation can be increased. Stroke length and frequency have to be adjusted to give this filter layer a homogenous porosity between 60 and 70% during the pulsion phase, and the "en masse" lifting of the bed, as it is known in jigging of coarser material, has to be prevented (3). In this case, the jig cycle is only of minor influence.

Jan 1, 1987

By K. Perry, B. Lusk, Q. Huang, R. Honaker

"Rock dust is applied in underground coal mines to prevent the propagation of coal dust explosions. The application is conducted either dry or wet. Both methods have advantages and disadvantages however the formation of caked rock dust particles is cited as a significant concern for wet applications. A study was conducted to evaluate the effect of modifying the rock dust particle surfaces to repel water and each other by the addition of oleic acid (OA) and sodium oleate (NaOL). At a NaOL dosage of 2 lbs/ton, a contact angle of 112o was measured indicating strong surface hydrophobicity and ability to repel water. FTIR studies indicated a chemisorption mechanism which is necessary for long term stability of the surface modification. The dispersion rate of the modified rock dust samples was elevated by the application of both OA and NaOL thereby indicating a significant reduction or elimination of the detrimental effect of caking. Tests in an explosion chamber showed a 79% reduction in the dust explosion potential relative to untreated rock test applied by the wet technique. INTRODUCTION Mine explosions have been a long-time threat to underground coal miners attracting significant attention to the accumulations of combustible dusts and gasses. In the presence of sufficient oxygen and heat, the accumulations of combustible dust and gass can lead to large-scale underground coal mine explosions [Harris et al., 2010]. To alleviate the problem, rock dust such as limestone can serve both as a thermal inhibitor and a heat sink to inert the coal dust explosibility thereby prohibiting the occurrence of dust explosions [Richmond et al., 1975; Amyotte et al., 1995; Dastidar et al., 1997; Man et al., 2009]. The dispersibility of the rock dust is an important characteristic that determines the degree of explosion prevention [Greenwald et al., 1938; Mozumdar et al., 1974; Amyotte et al., 1995]. Unfortunately, the environmental conditions of an underground mine has the potential to cause caking of the rock dust which reduces the dispersive characteristics needed. The dispersive property of rock dust can be enhanced by modification of the particle surface properties by the application of chemical additives [Greenwald et al., 1938; Mozumdar et al., 1974; Spence, 2004; Vogt, 2011; Doidge et al. 2014]. The major mechanism for rock dust caking is the adsorption of water which forms liquid bridges at the particle-particle contact points where saturated solutions of soluble powder ingredients are present. Changes in temperature or relative humidity result in solvent (water) evaporation and the formation of dry bridges [Rumpf, 1958; Specht, 2006]. One method to prevent caking is creating hydrophobic rock dust to repel water from the solid surface thereby preventing the formation of liquid and solid bridges."

Jan 1, 2015

By George H. Davis

The Caribou sulfide deposit near Bathurst, New Brunswick (Figure 1) is illustrative of one variety of strata-bound sulfide deposits. It consists of numerous near-vertical sulfide lenses which are concordant to the foliation and lithologic layering of low-grade metamorphic host rocks. Pyrite is the chief mineral in these lenses, but appreciable quantities of sphalerite, chalcopyrite, and galena are also present. Rocks in the Caribou mine area belong to the Tetagouche Group of Ordovician age. They consist chiefly of (1) quartz-sericite and quartz- sericite- feldspar schists, (2) greenschists, and (3) slate and phyllite. The trends of these steeply dipping rocks define the trace of a tight, steeply plunging fold structure, the Caribou fold (Figure 2). This fold plunges approximately 750 to the north-northwest; its axial plane strikes N.20°E. and dips steeply westward. Sulfide lenses of the Caribou deposit are associated spatially with the Caribou fold. The deposit is located in the fold along the contact between quartz-sericite and quartz-sericite-feldspar schists on the hanging wall and quartz-chlorite-sericite phyllites and graphitic schist on the footwall (Figure 3). Genesis of the Caribou deposit is ambiguous because its strata-bound form suggests syngenetic sulfide deposition, whereas its location within a fold suggests structurally controlled epigenetic mineralization. Acceptability of a particular genetic model rests on establishing the time of mineralization relative to deposition, deformation, and metamorphism of the associated rocks. To establish the timing for Caribou mineralization, the deformational histories of rock and sulfide, respectively, were compared. Epigenetic and syngenetic models can be tested against this interpreted structural history of the Caribou deposit.

Jan 1, 1971

By S. Garcia

The Minera Yanacocha operation presents various operating challenges, due to the complex structure of several heaps interconnected with ponds and gold recovery plants. A comprehensive process model has been developed in order to better understand the effects of certain operating parameters on issues such as water usage and inventory. An integral component of the water/mass balance of the process is a model of each heap that describes the flow and chemical behavior based on the individual characteristics of the heap. A computational fluid dynamic (CFD) software framework is used to model the individual heaps. The structure, calibration and validation of the model are described. Several examples demonstrating application of the process heap model are presented for the La Quinua heap. The effects of loss of solution flow to the heap (i.e., pump failure), increased cyanide levels in applied solutions and higher copper head grades on the process operation and balance are investigated with model simulations and compared to the baseline operating conditions. An example of estimating gold production and inventory based on projected heap loading plans is provided.

Jan 1, 2010

By Hemendra N. Kalia

Several attempts have been made in the past sixty or so years to commerciliaze the vast oil shale deposits of the United States of America. However, the industry has yet to become viable and economic. To date, it has not been possible to produce oil from the oil shales at a competitive price when compared to the oil produced from oilfields by conventional methods. However, the development work has been quite fruitful in furthering the art of thick bed mining and technology of in situ retorting. The in situ method has the potential of recovering oil from thick beds and the resource recovery potential is much greater than that from underground mining and surface retorting. In situ methods require that the shales/ marlstones be fragmented ' in place to induce adequate porosity and permeability to allow in situ' heating of the fragmented shales. This can be accomplished by using explosives. However, it has been found that the existing blasting systems, though very efficient, are somewhat lacking. The explosive become insensitive when shot in multiple vertical decks. They can also become insensitive when spaced horizontally at close proximity to other charges. Also, since the blasting is done in a very limited free face, this limits the delay time that can be allowed between charges. Consequently it is not always possible to predict the performance of the blasting system on a routine basis. Furthermore, since it is not possible to undertake secodary blasting, it is imperative that the blast design function properly. Recent, successful retorting by Occidental Petroleum Company of retorts seven and eight suggests that some of these problems may have been overcome. This paper addresses some aspects of in situ retorting and problems those have impeded the development of a viable oil shale industry in the U.S.A.

Jan 1, 1983

By Sathit Tandanand

Geological differences among various coalfields restrain the applicability of subsidence prediction using existing European methods. To modify these methods for domestic conditions, the Bureau of Mines, U.S. Department of the Interior, developed a method of assessment to evaluate the lithological effects on subsidence in the Northern Appalachian basin by examining data collected from 16 longwall panels in the coalfield. The assessment is partially completed, and the results to date show that the ratio of maximum subsidence to the extraction thickness, known as the subsidence factor, can be expressed in terms of the width-to-depth ratio by a simple exponential equation which has a coefficient tentatively considered as the subsidence index. This index varies with the lithology of a particular site and can be expressed in terms of the percent distribution of weak and strong rocks in the overburden.

Jan 1, 1982

By Gordon M. Bell

Water has received little attention as a variable in flotation, even though it is a known fact that water hardness often has an adverse effect on purity and recovery, particularly on the flotation of non-metallic minerals. Because of this fact, process water used in some flotation plants is treated to reduce hardness to an acceptable level. In the laboratory, distilled water is usually used as the flotation medium in order to standardize conditions, whereas in flotation plants locally available water is used. At Rosiclare Works of Aluminum Company of America, Rosiclare, Illinois, where a vein-type of fluorspar deposit was being processed by flotation to make an acid-grade fluorspar concentrate until February of 1968 when the plant was closed, qualitative correlations had been observed between metallurgy and reagent consumption and the seasons of the year. The observed effects were thought to be due to seasonal variations in the quality of Ohio River water used as the flotation medium. Figure 1 shows the variations in total hardness and chloride contents of Ohio River water at Rosiclare for the period September 1964 through September 1967. During this period, the sulfate content varied from 85 to 245 ppm (as Na2SO4), the calcium from 90 to 160 ppm (as CaCO3) and the magnesium from 50 to 70 ppm (as CaCO3). The data in Figure 1 show that the total hardness and chloride contents are highest in the late summer and fall which are usually periods of low water and lowest in late winter and spring which are usually periods of high water.

Jan 1, 1970

By F. Calizaya

This study summarizes the results of various numerical and laboratory experiments per-formed to study the effect of airflow recirculation on gas concentration. The numerical exercises were carried out on a simulated mine ventilation net-work. The laboratory experiments were conducted at the Mackay School of Mines' airflow monitoring system in Reno, Nevada. In both cases, the airflow was recirculated through the system by means of a main fan and a set of booster fans. The booster fans were positioned to produce two types of recirculation: In line and Cross-cut. For each type, various recirculation conditions were generated by changing the booster fan pressure. During each test, the gas emission rate at the simulated working face was kept constant. The study illustrates the conditions under which controlled airflow recirculation may be used to solve a district ventilation problem.

Jan 1, 1991

By Hamid Maleki

This paper reviews a study conducted for Australian Coal Research Limited (ACARP) to assist Anglo-American operations with better understanding of coal burst mechanics and control based on U.S. practical experience, investigations, and inspections in three major U.S. coalfields over the past 45 years. The study examined both nonviolent and burst-prone case studies to identify contributing risk factors and addressed failure mechanisms for major U.S. coalfields in Utah, Colorado, and Kentucky, which have diverse characteristics. To investigate the mechanics of coal burst, a multipronged approach is used. First, field measurements in three mines from East Mountain, Utah, are complemented with finite-difference stress analyses to address the importance of horizontal stress in coal pillar mechanics of violent failure. Second, the computational procedures for estimating seismicity resulting from slip along geological discontinuities are reviewed, as these measurements point to seismicity being the trigger mechanism for violent failure of marginally stable structures. This joint-slip seismicity mechanism is in agreement with the more recentimproved re-examination of mining-induced seismicity (MIS) data from the Crandall Canyon Mine, Utah by University of Utah (UOU). Third, a hybrid statistical-analytical methodology is applied for identifying significant factors affecting coal burst. It utilizes data from 30 case studies including those from Utah, Colorado, Kentucky, and other eastern U.S. mines. The statistical approach reinforces field measurements and points to strata rigidity, joint spacings, and horizontal stress field as significant factors affecting damage resulting from coal bursts. This provides practical capabilities for identifying operations of higher risk using a rigidity-cavability variable. Overall, the study provides valuable insights into the mechanics and risk factors associated with coal bursts in major U.S. coalfields. By utilizing a multipronged approach that incorporates both field measurements and statistical-analytical calculations, the study offers practical capabilities for identifying operations of higher risk and improving coal burst control.

Jul 1, 2023

By Rees D. Groves

Cement copper is ordinarily converted to marketable metal by processing in a conventional smelter and refinery. Because of rapidly increasing cement copper production and limited excess smelting capacity, other techniques were investigated for preparing marketable copper products. One route was to make copper powder for industrial use. The process scheme employed flotation for rejecting the bulk of the impurities, acid leaching to remove residual iron and aluminum, reduction sintering to eliminate oxygen, and grinding to obtain powder. Another route was to sinter the floated and leached copper into the form of anodes and electrolyze these to yield refined copper cathodes. At a current density of 30 amperes per square foot, power consumption for electrorefining was 185 kwhr per ton of copper. The feasibility of preparing commercial-size anodes by sintering is still to be assessed.

Jan 1, 1970

By Eugene R. Palowitch, Albert W. Deurbrouck, Thomas H. Parrsons

INTRODUCTION Hydraulic concentrators utilize the physical characteristics-size, shape, and specific gravity-of particles suspended in a fluid medium to effect a concentration of desired quality. Fine-coal concentrators include generally those devices which are used to clean roughly 3/4, in. (9.5 mm) top-size coals. While this size designation is somewhat arbitrary, it is consistent with current practice although some fine- coal concentrators can treat coarser coals effectively. A variety of devices have been and are currently being used to wash fine coals and include: dense media cyclones, wet concentrating tables, hydrocyclones, jigs, spirals, launders, and upward-current classifiers. As launders and upward-current classifiers have been replaced by more efficient devices, they no longer warrant consideration as fine-coal washers. And as fine-coal jigs were addressed with the Baum jig under Part 1, Section 2, and heavy media cyclones and hydrocyclones were addressed under Part 2, Section 1, of this Chapter, only the wet concentrating table and the spiral concentrator will be discussed here. WET CONCENTRATING TABLES History The current wet concentrating table evolved from continuous belt concentrators which utilized a flowing film of water to recover heavy metals. In these devices the heavier concentrate moved up the inclined plane of the belt while the lighter impurities were washed away by water flowing down the belt. The natural outgrowth of the continuous belt concentrator was the vanner, a vibrating endless belt which was first developed about 1860 by Hartwig. Later models of the vanner, such as the Frue, incorporated oscillation in a plane transverse to the direction of the water current. Excellent descriptions of these washers are found in The Cleaning of Coal, by Chapman and Mott.80 Further development of tables included the circular stationary table (Linkenbach), the multiple round table (Anaconda-Evans), the bumping table (Campbell), and finally the differential-motion table which is now used extensively for cleaning fine coals.

Jan 1, 1991