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By S. A. McGhee

Introduction ASARCO's Ray Operations include an open-pit copper mine in the Mineral Creek Mining District of Pinel County. The district is located in east central Arizona, 132 km (82 miles) southeast of Phoenix, AZ, and 126 km (78 miles) north of Tucson, AZ. The mine lies 8 km (5 miles) north of the Gila River in Mineral Creek Valley, between the Tortilla Mountains to the west and the Dripping Springs Range to the east. The rich copper deposits of the Mineral Creek mining district were first noted by a US Army Officer in 1847. The Ray Copper Company was the first major operation in the area. The company was named after the Ray mining claim, which was one of the earliest recorded claims. After decades of sporadic and unsuccessful mining ventures, the Ray Consolidated Mining Company was formed in 1910. The company introduced one of the first successful block caving operations in the world. In 1933, the Kennecott Copper Corporation acquired the Ray Consolidated Mining Company and continued operation of the mine under the same name until 1943, when the property was renamed the Ray Mines Division of Kennecott. Underground mining continued until 1955, when the mine was converted to an open pit operation. In November 1986, ASARCO Inc. purchased the Ray Mines Division and related facilities from Kennecott. The purchase also included the Hayden concentrator and the Ray Smelter, located approximately 32 km (20 miles) from the Ray Mine. This paper summarizes the 54,400 tpd (60,000 stpd) in-pit crusher and overland-conveying system and the 24,200 tpd (30.000 stpd) copper SAG concentrator and tailings disposal system constructed at ASARCO's Ray Complex - Ray Operations. General description of facilities The Ray concentrator includes a sulfide SAG concentrator, a "relocatable" in-pit primary-crushing plant and overland-conveyor system, a concentrator tailings-disposal system and plant ancillary facilities, The major elements of the project include: • A relocatable Fuller-Traylor in-pit 1524-mm (60-in) x 2261-mm (89-in) primary gyratory crusher at the 442 m (1450 ft) mine elevation. The crushing plant has a nominal capacity of 54,400 tpd (60,000 stpd) of sulfide ore. • A 1524-mm (60-in) wide x 1253-m (4110-ft) long overland belt conveyor, which runs from the in-pit crushing facility to a transfer station serving both the Ray Concentrator and the existing Hayden concentrator railroad load-out facility. • A 1524-mm (60-in) wide x 152-m (500-ft) long stackerbelt conveyor, which delivers a nominal 27,200 tpd (30,000 stpd) of ore from the transfer station to a 23,600 t (26,000 st) live-capacity coarse-ore stockpile serving the Ray Concentrator. • A nominal 27,200-tpd (30,000-stpd) concentrator, including semiautogenous grinding, flotation, copper concentrate filtration and associated plant ancillary facilities. • A tailings disposal system. Flotation tailings are pumped from the Ray Concentrator to a 122-m (400-ft) diam. thickener, located 4.8 km (3 miles) southeast of the Ray Concentrator site. The thickener overflow is pumped to two 76.2-m (250-ft.) diam. concrete process-water reservoirs. The thickener underflow, at 45% solids, is pumped to a new tailings disposal site located at Elder Gulch. • An HDPE-lined temporary-containment area to collect material from Ray Concentrator plant upsets and local storm-water run-off from a 100-year, 24-hour rain event. •A reclaim-water system from the Elder Gulch tailing pond area to the Ray Concentrator. • A 610-mm (24-in.) diam. x 31.9-km (19.2 mile) long fresh-water pipeline from the Hayden fresh-water-well field system to the Ray Concentrator. The overall process design criteria for the new Ray Concentrator is based on a nominal throughput of 27,200 tpd (30,000 stpd) of ore at 90% plant availability. However, based on the maximum performance capacity of the installed grinding equipment, it may be possible to achieve a sustained operating level in excess of 36,300 tpd (40,000 stpd) when processing soft ores. The balance of this paper will cover the major process systems including:

Jan 1, 1995

By B. Anamaeric

Economic, environmental and operational disadvantages of the traditional blast furnace process has led to the development of direct smelting reduction processes, including those that utilize self reducing/ fluxing dried greenballs as iron oxide feed materials. This is mainly due to improved carbothermic reduction, carburization and reaction kinetics. In this paper, the morphological changes of the greenballs as they transform to pig iron nuggets are examined over time at a constant temperature of 1,400° C. The products produced after each treatment were characterized using optical microscopy, scanning electron microscopy/energy dispersive spectroscopy and point counting/image analysis. The changes in the percent metallized area, wustite dendrite and slag matrix content of the structures were calculated. It was determined that the transformations were initially controlled by dissolving and containment of iron oxides in the molten slag and their consequent reduction to iron, followed by coalescence of the metallized areas. The final transformations were controlled by the carburization of the metallized areas.

By L. Zhou, L. Yuan, D. Bahrami

Underground mine fires remain a concern for mine operators, posing a health and safety risk to mineworkers. In the last decade, the number of mine fires has decreased significantly; however, dealing with an unknown fire in underground mines can be a challenging task, which could lead to a hazardous condition for miners during an evacuation and rescue operation. A timely detection of a mine fire and monitoring its characteristics, namely size and location, are of great importance in reducing the risk of mine fire injuries. A new improved fire location algorithm has been developed and integrated into an Atmospheric Monitoring System (AMS) program by researchers from the National Institute for Occupational Safety and Health (NIOSH). This paper describes the new fire location model and presents the results of verification fire tests conducted at the Safety Research Coal Mine (SRCM) facility of the Pittsburgh Mining Research Division (PMRD) using the collected AMS data. NIOSH is endeavoring to develop workplace solutions to improve detection of and reduce the risk of hazardous conditions in mines. The results demonstrate successful application of the improved fire location model and provide a useful tool for solving the problem of unknown fire location and reducing the risk of hazardous conditions.

Sep 29, 2020

By Louis M. Schlesinger

KMG Minerals, Inc., a mica-feldspar-quartz producer in Kings Mountain, N.C., uses about 50% of its plant's -200 mesh slimes to manufacture brick. However, the company is unable to market the remaining 50% of this fine mineral mixture. The NCSU Minerals Research Laboratory operated a pilot plant to process these slimes to produce an additional product. The process, consisting of blunging and hydraulic sizing, was designed to separate a kaolin-enriched -270 mesh product from the bulk of the coarser +270 mesh "grit" minerals. Size analysis showed that this product was 80% finer than 20 microns and 50% finer than 6 microns (in equivalent spherical diameter). An evaluation indicated that it is a hydrous aluminum silicate that might be suitable in the filler and extender markets for traffic paint, some types of plastics, joint cements, and dusting compounds. Because of its high viscosity, it will be difficult to use more than a small percentage in cast ceramic bodies. However, it might be possible to use up to 10% in extruded ceramic bodies (i.e., electrical porcelain). The 15.2 cm (6 in,) diameter Linatex Hydrosizer was tested using a range of teeter water flowrates, so that the net rise velocity was varied from 0.10 cm/s to 0.40 cm/s. The solid feed rate to the sizer was maintained at approximately 1.1 t/hr/m2 (0.12 ton/hr/ft2). Tests were run using both "shallow" (i.e., 6 in.) and "deep" (i.e., 15 in. teetered beds. The best overall result was obtained when the sizer was operated with the "deep" teeter bed and a net rise velocity of 0.10 cm/s. About 97% of the +270 mesh material was rejected and approximately 79% of the -270 mesh material was recovered in a 14% solids slurry.

Jan 1, 1994

By F. Rudloff, C. Karageorgos, J. Moyo, I. Boadi, M. Struble, B. Lumsden

Over it’s more than 100-year history, the Kennecott operation has often been at the forefront of innovation; driven by the demands of the lower grade ore-body and the higher costs of operating in the US where wages are generally higher and regulation more restrictive. One way of reducing operating costs in c/lb is to increase the lbs produced at minimal cost. Despite the relatively coarse grind at Kennecott - about 30% >150μm, approximately 20% of the Cu lost to tail is liberated chalcopyrite in the <20μm fraction, and about 30%-40% in the <37μm fraction. In 2020 Kennecott undertook a detailed plant scale test of the magnetic aggregation technology to increase copper recovery by reducing fine copper losses. A paired statistical plant test of magnetic conditioning on one rougher line showed a 1.12% increase in Cu recovery to 97% statistical confidence. The next challenge, unforeseen at the start of the project, was the fabrication and transportation to site of the equipment for the three remaining rougher rows, during the severe supply-chain constraints of the Covid pandemic in 2021. This resulted in delays and unforeseen costs as world-wide transportation became chaotic, particularly transportation via west coast USA. Nevertheless, the project was completed and commissioned, with only minor delays and cost increases, due to a flexible approach to overcoming the hurdles encountered.

Feb 1, 2023

By Paul W. Johnson

Chemical mining is the in situ extraction of metals from ores located within the confines of a mine (broken or fractured ore, stope fill, caved material, ores in permeable zones) or in dumps, prepared ore heaps, slag heaps, and tailing ponds on the surface. These materials represent an enormous, untapped, potential source of all types of metals. The field of chemical mining, now in its infancy, encompasses the preparation of ore for subsequent in-place leaching, the flow of solutions and ionic species through rock masses and within rock pores, the leaching of minerals with inexpensive and regenerable lixiviants under prevailing conditions of the in-place environment, the generation and regeneration of such solutions, and the recovery of metals or metal compounds from the metal-bearing liquors. It is not inconceivable that eventually our ore reserves will consist largely of low-grade, refractory, and inaccessible new deposits and low-grade zones near previously worked deposits, caved and gob-filled stopes, waste dumps, tailing ponds, and slag-heaps. Chemical mining promises economic recovery from these types of deposits. Before it can come of age, however, a much better understanding is needed concerning its chemical and physical aspects.

Jan 1, 1967

By Xuezhong Wang, Hao Guo, Tao Tu, Qingsheng Liu

The scheelite concentrate was leached with a mixture of sulfuric and oxalic acids. Chemical compositions, mineral phases, and morphology were characterized by XRF, XRD, and SEM–EDS. Based on the results of the single-factor experiments, the response surface methodology (RSM) was chosen to optimize the leaching parameters: temperature, time, and concentrations of sulfuric and oxalic acids. The RSM results indicate that the optimum values for those parameters are as follows: temperature 72 ℃, sulfuric acid concentration 1.48 mol/L, oxalic acid concentration 0.96 mol/L, and reaction time 2 h. Under the optimal leaching conditions, the model predicts a maximum leaching yield of 99.5%, compared to the value of 99.1% obtained experimentally, that is, a discrepancy of only 0.04%. This good correlation shows that the quadratic polynomial equation obtained by the RSM optimization is reliable. The importance on leaching parameters of scheelite is, in decreasing order, temperature, time, sulfuric acid concentration, and oxalic acid concentration.

Oct 11, 2021

By B. Eiter, M. Barham, T. Bauerle

Fatigue-related risk is a persistent safety concern for the mining industry. However, fatigue and sleepiness are often treated interchangeably, which can lead to confusion and potentially less effective reduction of safety risk. To provide clarity, we present an overview of similarities and differences between work-related fatigue risk and sleepiness including definitions, theories, measurements, and mitigation strategies. As a supplement, a summative visual model which highlights these similarities and differences is presented. Expanding industry knowledge in this area will assist safety professionals in crafting more targeted risk management practices appropriate for work-related fatigue risk, sleepiness, or both.

Feb 1, 2023

By Lee W. Abramson, Kenneth P. Akins

The authors have accumulated published data on residual soil and rock tunnels in the United States and have compared it to transit tunneling experience in Atlanta, Georgia, and tunnels in other soil and rock conditions. Two 6.1 meter (20 foot) diameter shield driven, compressed air tunnels were constructed for the Metropolitan Atlanta Rapid Transit Authority (MARTA) connecting the Five Points Station (central hub) with the Peachtree Center Station (first station on the north line). Because of the historic multi-story structures above the tunnels and the variety of subsurface conditions, a comprehensive ground monitoring and observation program was conducted. Conclusions are drawn regarding residual soil and rock ground response due to tunneling. Comparisons are made to ground response due to tunneling in other soil and rock conditions.

Jan 1, 1983

By S. Shankar

Available literature on the effect of re-entrainment on overall airborne dust concentration in mine airways or the fundamental mechanisms of coal dust re-entrainment in mine atmosphere is scant. Therefore, as part of the Respirable Dust Center&apos;s ongoing research, a three part study was envisaged: study of the re-entrainment phenomena of anthracite and bituminous coal dust particles in a wind tunnel under the influence of varying air velocities; study of the same in the Lake Lynn Laboratory Mine of the USBM with both airflow and walking by personnel causing re-entrainment; and mathematical modeling and computer simulation of the re-entrainment phenomenon. In this paper, results from the re-entrainment studies in the wind tunnel and the Lake Lynn Laboratory Mine are presented. Further, the results from the wind tunnel studies are compared with the results from in-mine studies conducted at the Lake Lynn Laboratory Mine of the USBM. Comparing the results from the two studies it was observed that increasing air velocity increased the rate of re-entrainment, but increased time of exposure decreased the airborne dust concentration. Compared to same size particles, a mixture of sizes created more airborne dust concentration when re-entrained. It was also observed that contribution of airborne dust concentration due to airflow was negligible compared to the contribution due to walking.

Jan 1, 1995

By Michael F. Roach, Joseph K. Cavey, Gary E. Taylor

A rigorous horizontal drilling and chemical grouting program was specified beneath the Hollywood Freeway (U.S. Route 101) section of Los Angeles Metrorail Contract C-311.Twin 6.67-m (22-ft.) diameter starter tunnels were to be conventionally mined through amixed alluvial and bedrock face consisting of silty sand, gravel, and weathered sandstone and siltstone of the Topanga Group. The contact between the alluvium and bedrock dipped toward the Crossover Excavation where the horizontal drilling and grouting operations were performed. The intent of this grouting program was to stabilize the mixed face to minimize ground loss and surface settlement, and to reduce groundwater inflow into the tunnel headings. Given the highly variable mixed face conditions, horizontal drilling up to 86 m (284 ft.) resulted in upward trending trajectories which likely followed the bedrock contact. Chemical grouting was performed in a primary, secondary and tertiary, three dimensional sequence. Evaluation of the primary and secondary grouting parameters indicated where tertiary grouting was required. Grouting pressures induced a small rock failure at the tunnel heading as well as increased stresses on the tiebacks of the excavation.

Jan 1, 1997

By Shawn P. Coughlin, Michael A. Schimmenti, Juan Leonardo Tello del Pino

"PROJECT OVERVIEWThe Sistema de Potabilización Área Norte project (Northern Area Purification System) was a major expansion of the potable water system in Buenos Aires Province, Argentina. The aim of the project was to transport and purify raw water from the Paraná River to provide potable water for five communities in the northern part of the province, benefitting up to two million inhabitants. The project was constructed by a joint venture of four South American contractors (“the JV”), and consisted of the following key components:• Treatment Plant: A 16 hectare area was cleared for the construction of a treatment plant to purify 900,000 m3/day of raw water from the Paraná River and distribute it to the surrounding communities.• Bored Tunnel: Nearly 15 km of 3.6 m inner diameter tunnel, ranging from 18 to 22 m below grade, was bored with two EPB tunnel boring machines to draw the raw water from the river. The TBMs started from a central launch shaft and proceeded in opposite directions: Cristina advanced northbound to the Paraná River Intake System, and Liliana advanced southbound to the new treatment plant.• Access & Ventilation Shafts: Five access shafts and eight ventilation shafts were installed along the length of the tunnel. The access shafts were designed to provide entry points for inspection and maintenance of the final tunnel. The five shafts consisted of: one central launch shaft in the middle of the tunnel alignment, one retrieval shaft at each end of the tunnel (Intake and Treatment Plant, respectively), and two intermediate shafts. The intermediate shafts were installed before the TBM passed, with a final liner to be installed afterwards. Access Shaft 3, the intermediate shaft located between the launch shaft and the treatment plant, experienced persistent leaks during initial excavation attempts."

Jan 1, 2016

By Raj K. Singhal

Canada produces close to 42 million tonnes of coal per annum of which some 38 million tonnes is produced by surface mining methods. The two Western Canadian provinces, Alberta and British Columbia, produce 31 million tonnes of coal by surface mining. These two provinces provide the bulk of the metallurgical coal for export. The geological conditions in the Western provinces particularly in the mountain region are complex. The coals are friable and the seams are steeply inclined, sheared, intensely folded and faulted. There may be as many as 15 to 20 coal seams present with true thickness ranging from 2.5 m to over 8 m. This paper reviews the surface mining methods used to extract such seams. The difficulties associated with steep seam and multiple seam mining of friable coal resulting in lower coal recovery, high dilution and the problem of cleaning fine coal in the wash plant have been highlighted.

Jan 1, 1984

By V. J. Hucka

A 0.5 m (20 in) diameter high pressure natural gas pipeline crosses over a coal mine located in Central Utah. Ground movement induced by the mining operation could possibly place excessive strain on the pipeline causing it to rupture. The mining operation extracts coal from two seams using the room and pillar method. The seams are situated one on top of the other and both lie directly under the pipeline. At present, only the upper seam is being mined beneath the pipeline. However, in the future, the mining operation of the lower seam will also affect the pipeline. As would be expected, mining of both coal seams causes surface subsidence. This is especially true when the pillars are extracted during retreat.

Jan 1, 1983

By C. L. Coldren

Recently there has been much discussion of the use of pipelines for the long-distance transportation of solids. Many have come to recognize the economies inherent in pipeline transportation. The widespread movement of oil and gas at astonishingly low costs - a gallon of oil moves from Montana to New York for less than that for the delivery of a postcard - has spurred others to sturdy this mode of transportation. Most interested people are aware of the inherent advantages of pipelines - continuity and reliability of operations - low manpower requirements per ton mile - moderate capital costs per ton mile - low maintenance costs per ton mile - low operating costs per ton mile.

Jan 1, 1963

By M. S. Prasad

In earlier work it has been shown that paper filler clay products can be obtained from primary kaolin deposits of Minnesota. The objective of the current work was to reduce silica and iron contaminants and to maximize kaolin recovery to higher value products suitable for paper coating. This results in achieving a finer and cleaner product conforming to paper coating specifications. Cationic flotation and high gradient magnetic separation were used to remove free silica and iron, respectively, while attrition grinding and ultrasonics have been examined for particle size reduction. The results of this work are presented and discussed particularly with respect to application-oriented product properties. Budgetary estimates are presented for a 200,000 ton/year processing plant based on the process flowsheet developed and optimized by the study.

Jan 1, 1991

By Horry Parker Jr, Jason Gillespie, Justin Kolster, Stephen O’Connell

Construction of the 5,932-ft Reedy River Basin Sewer Tunnel in Greenville, SC was marked by a critical transition from drill-and-blast mining in mixed-face conditions to TBM excavation with limited rock coverage. In this paper, we discuss the geological, geotechnical, and risk management considerations for transitioning to TBM operations in variably weathered gneissic bedrock. After construction of an unexpected 230-ft starter tunnel due to differing site conditions, the 11-ft diameter TBM was successfully launched in December 2019 without significant ground support issues. This project highlights the effectiveness of extensive rock probing to fully characterize bedrock topography prior to the TBM launch.

Jun 13, 2021

By J. A. Lepinski

The FASTMETSM Process is a coal-based process for converting iron oxide fines into metallic iron. The end product, direct reduced iron (DRI) is used as a low residual charge material in electric arc furnace steelmaking. This paper describes the FASTMET Process and its potential application in the United States. Operating results from a 175 kg/h process simulator are presented. Characteristics of the end product are discussed. Process economics are reviewed along with plans for scaling-up the process to full commercial size.

Jan 1, 1993

By Qingwen Shi, Gang Xu, Shuwen Wang, Brijes Mishra

Pressure relief borehole is one of the most effective methods to treat coal burst in deep-buried coal seams. However, due to the large amount of randomly distributed fractures in the coal body and the varying stress environments in underground coal mines, there is no practical method to assess relief boreholes by far, which brings problems for borehole design and construction. This study focuses on the assessment of relief boreholes in a single driving entry wherein the impact of mining panels on relief boreholes is eliminated. A practical method, focusing on field monitoring of borehole deformation with a new device, is developed to evaluate the single driving entry’s relief boreholes. This method is applied to a Chinese coal mine. The application results showed that the convergence process of the boreholes showed a three-phase characteristic. Phase one involves the fastest deformation, reaching up to 8% in the first 3 to 4 days. Phase two lasts longer and converges more, reaching up to 30% in 4 months. Phase three stays balanced until the excavating face moves. The three-phase characteristic indicates that a large diameter of the borehole ensures relief efficiency because the borehole provides adequate space for deformation throughout its life span. In addition, it is verified that long boreholes and slow footage improve relief efficiency by providing adequate time for the boreholes to work. The application proposes that boreholes in the test coal mine need to be drilled larger and longer for optimization.

Oct 19, 2021

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