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By Wang Hongwei, Wu Yongping, Cao Peipei, Jiao Jianqiang

Fully mechanized top caving mining of steeply inclined extra-thick seams with variable angles has complex roof rock movement, failure, caving, and filling mechanisms. Moreover, the variable-angle coal seams make rock–equipment stability control challenging. We analyzed rock deformation and failure mechanisms, overburden bearing structures, and working characteristics of supports through physical simulations, field tests, and theoretical analysis of the no. 120210 working face of Zaoquan Coal Mine. Overburden rock movement has distinct regional characteristics, with a large caving height (to the main roof layer) in the upper area, and lower caving height (to the lower main roof) in the lower area. Support loading is regional and unbalanced along the inclined direction. The critical layer of overlying strata migrates, and bearing structures formed by breaking the critical layer exhibit cross-layer generalization along the inclination. The upper region has a cantilever beam structure in the basic roof rock layer; the lower region has an inclined masonry structure with multistage ladders in the breakage basic roof rock layer. Application of a false-inclined working face layout with the tailgate ahead of the headgate and an arc arrangement (radius 28.65 m, arc length 10–20 m) in variable angle areas, and regional control of support working resistance and top-coal caving amounts, control regional failure overburden. Safe and efficient mining was achieved, with the monthly production and recovery rates reaching 344,900 t and 85.86%, respectively. Our results expand the scope of fully mechanized top caving mining and have important theoretical and technological significance.

Nov 23, 2020

By Bo R. Arvidson

The strongest magnetic roll separator available on the market enhances certain industrial minerals purity to levels not reached previously. Exceptionally strong forces can also be utilized for processing relatively fine particles at feed rates several times greater than for prior art electromagnetic induced roll separators. Since the unique machine does not work with an air-gap, coarser particles than what has been considered practical can be separated at rates up to 20 tph per single machine unit and 40 tph for a double machine unit. Examples for all these three application areas will be given. While the roll separator can be used only for dry processing presently, the other new separator can be used for both wet and dry applications. It is a medium-intensity, high- gradient magnetic separator employing a filamentary matrix. It was primarily developed for recovery of weakly magnetic iron ore fines, but it is finding applications for cleaning of industrial minerals such as wollastonite, calcite, clay and talc. Its main advantage is a simple design resulting in a very lm cost machine both with regards to total capital investment and operation. A significant technical advantage exists also. The metallurgical performance is similar to conventional electromagnetic separators, while the cost per ton is about half of such separators.

Jan 1, 1985

By Todd Schrauf, James Scott, Mark Smith

"Cyanide heap leaching of gold ores in areas with extremely low winter temperatures requires special considerations to prevent freezing of the leach solution. Factors that impact the solution temperature include ore temperature at the time of stacking and during operation, burial of drip irrigation lines, use of geomembrane covers and heating of the leach solution. Thermodynamic modeling was performed to simulate expected ore and solution temperatures under different operating strategies for Kaminak Gold’s Coffee gold project in the Yukon Territory. Mean monthly temperatures at the site ranged from a low of -22.5 °C (-8.5 °F) to a high of 13.6 °C (56.4 °F), while in situ ore temperatures ranged from -0.5° to about -1.5 °C (31 ° to 29 °F). The modeling results were used to optimize the operational parameters and indicated that a combination of drip line burial and heating of the leach solution during the winter months was required to maintain solution temperatures above freezing during the initial years of stacking, although as the size of the heap increased, heating was no longer necessary.Modeling objectivesThe successful operation of a cyanide heap leach under extremely cold winter temperatures requires the implementation of operational strategies to prevent freezing of the leach solution and the ore within the heap. Thermodynamic modeling of the heap provides the means to quantify the effectiveness of these different operational parameters on maintaining the required operating temperatures to avoid freezing within the heap. The operational parameters that were evaluated with the model included:"

Apr 1, 2016

By S. J. Schatzel, V. Gangrade

A ventilation research study was conducted by the National Institute for Occupational Safety and Health and a cooperating trona mine in the Green River basin of Wyoming, USA. The mine operation uses the longwall mining method in trona bed 17, a commonly mined unit in the region. The longwall face length is 228 m (750 ft), and caving on the face occurred up to the back of the longwall shields. The mine is ventilated using a main blowing fan and a bleeder shaft. For this study, sulfur hexafluoride (SF6) tracer gas was released in two separate monitoring experiments. For the first experiment, tracer gas was released on the face, this test focused on airflow along the longwall face of the active panel. Face test showed the airflow patterns to be more complex than just head-to-tail flow in the main ventilation air stream on the active panel. For the second experiment, tracer gas was released 2 crosscuts inby the face on the headgate side, this test focused on gas transport in the mined-out portion of the same active panel. Gob test showed a pathway of movement through the front of the active panel gob that moved outby from the tailgate corner. The primary pathway of tracer gas movement in the active panel gob was towards the headgate and tailgate bleeders and out of a bleeder shaft. The rate of movement towards the back of the gob was measured to be 0.19 m/s (37 fpm).

By G. Richard Dreese

Most coal mining states have passed or amended laws restricting strip ruining in the past two years. In light of this and in anticipation of further restrictions by the states and the federal government on strip mining this paper attempts to show the Impact of these new laws on the structure of the coal mining industry in Ohio and specifically on one small stripping firm in Ohio. The implications of the study are applicable to other states under similar circumstances and to other industries which are being caught up in the ecological-economic struggle.

Jan 1, 1973

By J. E. Kulas

Red Dog is a Mississippian to Permian aged sulfide deposit located in the western Brooks Range north of Kotzebue, Alaska. It belongs in the family of black Shale hosted sedimentary exhalite deposits but lacks classic sulfide sedimentary textures. Pervasive silicification, and a significant portion of the mineralization, is replacement in nature. An extensive feeder vein system cuts the footwall and the exhalite package. A Jurassic to cretaceous age compressional event has repeated the ore section through thrust faulting and folding. The orebody contains 77,000,000 metric tons averaging 17.1% Zn, 5.0% Pb and 82 g per metric ton of Ag. Weathering has locally altered the sulfides to sulfates and formed elemental sulfur.

Jan 1, 1992

By J. L. Parks

Designs, installation procedures, and performance characteristics of martensitic cast steel concaves are reviewed. Longer wear life, fewer pieces to install, and eliminating the need to scarf joints are the principal benefits of using martensitic steel to replace austenitic 12% Mn (Hadfield's) steel, the traditional concave material for large gyratory crushers. Installation procedures that reduce the risk of breakage are described. Operating practices that affect concave performance are also discussed.

Jan 1, 1992

By I. A. Tinto

Labrador City is located in the southwestern portion of Newfoundland-Labrador, approximately 965 kilometers north-east of Montreal. The mine and beneficiation complex of the Iron Ore Company of Canada, known as the Carol Project, is situated 535 metres above sea level in a climatic region characterized by cold winters and short, cool summers. History The iron Ore Company of Canada commenced work in the area in 1949, however, it was not until 1958 that the decision was made to proceed with mining operations. The ore body consists of Specular Hematite (Fe203) and Magnetite (Fe304) with small quantities of Limonite and Geothite. The average grade of the ore bodies is 39% iron.

Jan 1, 1985

By Lance Rasband, Richard Hanke, John Starcevich

"Mining on Seattle’s SR99 tunnel began in July of 2013. Initial mining progressed slowly through a 4.5 m (14.9-ft) thick fiber-reinforced concrete headwall before immediately entering the first of three planned safe havens. Once through the headwall and safe haven the machine would move through roughly 122 lineal m (400 ft) of jet grout improved soil at a rate of slightly more than 1.6 m/d (5.3 ftpd). It was anticipated that once mining has passed through the improved area, “Bertha” – now the world’s second largest tunnel boring machine (TBM), would be moving at a rate of almost 11 m/d (36 ftpd). By the end of October 2013, Bertha had mined roughly 131 m (430 ft), averaging 1.4 m/d (4.7 ftpd), and had begun mining within native soils. By the start of December 2013, tunneling had reached the 244 m (800 ft) mark and Bertha was averaging 3.6 m/d (11.9 ftpd), achieving as much as 12.8 m (42 ft) of progress on given days. Unfortunately, on Dec. 6th, 2013, Bertha began to stumble and all progress quickly came to a halt.Initial reports stated an obstruction had stopped Bertha in her tracks. The preliminary investigation involved installation of 10 deep dewatering wells to reduce the hydrostatic pressure within the ground around the TBM, to allow the contractor’s personnel to inspect the cutter head from within and also to investigate for the presence of obstructions at the face of the cutter head. During inspection, the contractor’s crews found fragments of steel pipe entangled in the cutter head. The steel was apparently from an abandoned 254 mm (0.9 in.) diameter monitoring well casing, previously installed by the Washington State Department of Transportation (WSDOT) to monitor groundwater conditions for the design and planning of this tunnel project. After the steel was removed from the cutter head and cleared from Bertha’s path, she attempted to move forward but was only able to generate a slow crawl."

Jun 1, 2016

By D. S. Dinsmoor

Boron, estimated to comprise about 0.001 percent of the earth's crust (Fleischer 10), as an element is never found free in nature, although its compounds are found in many localities. the borates are the most important. Sassolite (B(OH)3) and boracite (Mg6C12B1406), non-borates, are-of-minor importance. The crystal structures of most natural borates are still unknown. A classification based solely on the ratio of boron to the total number of cations has been devised (Palache 28). This classification divides the borates into four, sub-groups; anhydrous borates, hydrated borates, borates containing hydroxyl or halogen and compound borates. Only four or five minerals of the hydrated borates group have ever been used commercially. In more recent years, the sodium borates have comprised all but a 'small fraction of all borates used. Borax, the hydrated borate compound, is the most important of all boron compounds. It has been used so long and so often that the layman often confuses borax and boron and, applies the terms synonymously.

Jan 1, 1958

By Rongdong Deng

A tower-like magnetic system comprising eight permanent magnets was installed at the center of a flotation column to separate chalcopyrite and pyrrhotite minerals. A cyclonic flotation was installed within the underpart of the column to separate the pyrrhotite from the gangues. A three-product magnetic flotation column was fabricated to create a magnetic field and a cyclonic zone. The products were Cu concentrates, pyrrhotite concentrates and tailings. The theoretical magnetic field strengths and the magnetic forces were calculated. The results of the flotation experiments showed that the Cu grade increased from 14.20% without the magnetic field to 26.40% in the presence of the magnetic field and that the S grade in the pyrrhotite concentrates increased in the presence of cyclonic flotation. The separation efficiency of this magnetic flotation column was evident. Therefore, this three-product magnetic flotation column may have a potential application, due to its high separation efficiency.

By W. Collingwood

As openpit mines continue to grow deeper and productivity continues to increase, the management of respirable dust and noxious gases can become a challenge. The natural wind flow in openpit mines is often recirculatory. This recirculation traps dust and gases in deep openpit mines. This problem is particularly acute in high-latitude openpit mines, due to a phenomenon known as atmospheric inversion. In the winter, arctic and subarctic regions experience short days and long nights. This deficit of solar radiation creates a situation in which cold, still air accumulates near the bottom of the pit. In openpit mines, this can result in unhealthy accumulations of gases and other contaminants. In this study, the natural wind flow patterns in and around openpit mines were investigated using a computational fluid dynamics (CfD) program. Two-dimensional models were created for a variety of pit geometries. The effect of depth, slope angle and wind speed on the recirculation pattern in the pit was examined.

Jan 1, 2012

By Kevin Vander Tuig, Tim O’Rourke, Rick Vincent, Doug Lopata, Kellie Rotunno, Dan Dobbels

"The Northeast Ohio Regional Sewer District (NEORSD) was required under the Federal Clean Water Act and U.S. Environmental Protection Agency’s (U.S. EPA) Combined Sewer Overflow (CSO) Control Policy to develop a Long Term Control Plan (LTCP) to reduce or eliminate overflows from its permitted CSO outfalls. The LTCP was completed in 2002. Key components of the plan include: 26 miles (42 km) of deep storage and conveyance tunnels providing a total CSO storage volume of 325 million gallons (MG) (1.2 billion liters); over 30 miles (48 km) of consolidation sewers to route CSO control flows to the tunnels; and associated diversion/inflow control structures and drop shafts. Final design and construction of the initial phases of the LTCP are completed or underway. Advanced planning of the final phases began in April 2013. This paper summarizes this advanced planning process and, specifically, how hydraulic performance and tunnel design and construction considerations were balanced to eliminate unnecessary projects and shafts, reduce implementation risks, and reduce program costs by approximately $650 million. BACKGROUND The Northeast Ohio Regional Sewer District (District) serves an area of approximately 350 square miles (SM) (907 km2), including combined (81 SM; [210 km2]) and separate (269 SM [697 km2]) sewer systems that discharge to three wastewater treatment plants in the greater Cleveland area. The service area, shown in Figure 1, is divided into three districts—Easterly, Westerly, and Southerly—each having its own interceptor system and treatment plant, ranging in wet weather treatment capacities from 100 to 735 million gallons per day (MGD) (378.5 million to 2.8 billion L/day). The system includes 124 permitted combined sewer overflow (CSO) outfalls overflowing into the region’s tributary streams, Cuyahoga River, and Lake Erie."

Jan 1, 2016

By Kallam V. K. Reddy, VADAPALLI SANJANA, Veerendra Singh, Gajanan Kapure

This work describes a leaching process for the conversion of high-magnesium peridotite rock, which is a chromite ore overburden, into two valuable products: magnesium salts and micro silica. Under normal leaching conditions, residue remaining after leaching is of a gelatinous nature and thus hinders the filtration process. To address this issue, oxidative leaching with the addition of H2O2 was employed, and it significantly improved the filtration kinetics. Four different approaches for H2O2 addition were tried, and they all proved effective in controlling gelation. The optimum oxidative leaching condition was 70 °C, 2 h time, 2 M H2SO4, 0.5MH2O2 and 400 RPM; under these conditions, 92% magnesium leaching efficiency was achieved. After leaching, the leach liquor obtained was purified and dried into Mg(OH)2 and MgSO4 salts. The leach residue contained mainly silica particles, with size in the 10–30 μm range. This material thus represents an attractive candidate for the production of highperformance concrete for the construction industry. The oxidative leaching process described here enabled the complete conversion of peridotite into valuable products, magnesium salts and micro silica.

May 5, 2020

By M. Dayne Aldridge

A description is given of an experimental ventilation control system designed, built, and tested by WVU under United States Bureau of Mines sponsorship. A description is given of the control, system used and the mine-wide microcomputer-based ventilation monitoring system used with it. Test results of experiments conducted with this system at Eastern Associated Coal Corporation's Federal No. 2 underground coal mine are presented. In addition, a brief description is given of a new microprocessor based system presently being tested.

Jan 1, 1980

By Nathaniel Arbiter

The increasing size of flotation cells as the use of flotation has increased is traced from the first United States application of the process in Montana in 1911 through the following eight decades, using data from the Taggart handbooks (1927) and (1945), from the SME Handbook (1984), and from recent manufacturers' catalogues and other sources for the 1980s and 1990s. With the earliest mechanical cells less than 1 m3 (359) in volume and the largest now available at 200 m3 (7,000ft3), three requirements are necessary: 1) demonstration of advantages in replacing smaller volume by larger volume cells; 2) estimating power requirements, impeller dimensions, and operating rpm by correlation equations; 3) considering effects of using larger cells, in necessarily much shorter rows, on process kinetics. The resulting seven tables that address these problems are presented, and their implications discussed.

Jan 1, 1999

By William D. Mayercheck

Beginning in 1974, the Bureau of Mines, U.S. Department of the Interior, sponsored R & D efforts related to further development and use of continuous face haulage in underground coal mines (Cowan, 1975). The U.S. Department of Energy continued this effort as of October 1977. This paper represents an update of an article previously published in Mining Engineering magazine (Mayercheck, 1979). Development progress is summarized for a variety of prototype systems or components now being built, surface tested, or tried underground.

Jan 1, 1981

By Tianzu Yang, Weifeng Liu, Lin Chen, BOYI XIE, DUCHAO ZHANG, HUI XIAO

In this study, the oxygen-rich bath smelting process of copper dross was simulated using Factsage software. It was found that the two-step simulation results agreed better with the industrial data, especially in the speiss. Bismuth (Bi), lead (Pb), antimony (Sb), arsenic (As) and copper (Cu) contents in the speiss by two-step simulation differed from the industrial data by 0.6, 0.8, 2.6, 7.2 and 8.6 weight percent, respectively. The two-step simulation results indicate that the speiss partitioning of Sb, As and Cu increased from 60.1, 32.3 and 27.5 percent to 81.6, 67.8 and 47.2 percent, respectively, with the smelting temperature increasing from 1,050 to 1,250 °C, while the metal partitioning of Sb and Cu increased from 0 and 2.7 percent to 15.2 and 13.3 percent, respectively, with the separation temperature increasing from 400 to 700 °C.

By JOHN R. HEBERGER, MAHIYAR F. NASARWANJI, Jonisha P. Pollard, Lydia M. Kocher

nt in the mining industry, and identifying factors associated with these injuries is critical for developing prevention efforts. This study identifies nonfatal injury incidence rates, nature of injury, work activities, glove usage, and sources of hand and finger injuries in the U.S. mining industry, as reported to the Mine Safety and Health Administration (MSHA) from 2011 to 2017. Hand and finger injuries occur at a rate of 6.53 per 1,000 full-time employees, which is nearly double the rate of the next highest affected body part, the back. Most of the hand and finger injuries were classified as cuts/lacerations/punctures (53 percent) followed by bone fractures/chips (26 percent). Materials handling and maintenance/repair were common activities at the time of the incident with miscellaneous metals — such as pipe, wire and guarding — and hand tools as the primary sources of hand and finger injury. Although the information on glove use was limited, leather gloves were most often worn when an injury occurred.

By Guangyao Si, Ismet Canbulat, Xun Luo, Yi Duan

Routine analyses of seismicity and event locations are essential for coal burst risk management, especially in the presence of unfavorable and complex geology. In an Australian longwall coal mine, a small-scale seismic monitoring network was installed to monitor a section of a major dyke intersected by the roadway, which was classified as a coal burst prone zone. The Deep Convolutional Neural Network (DCNN) technique was adopted for automatically discriminating seismic events to assess seismicity in this zone. The discriminated seismic events were located with the Shortest Path Method based on the Boundary Discretization Scheme (BDS-SPM) for temporal-spatial seismic event distribution analysis. The results demonstrate that the seismic events are discriminated with an average accuracy of 94%. Moreover, the seismic events are more accurately located using the BDS-SPM with a 3D heterogeneous velocity model compared with results obtained with a homogeneous velocity model. The temporal and spatial variances in seismic activities identify that the rock fractures in the dyke zone are closely related to the longwall mining process and a local dyke has a controlling influence on the stress concentration in its vicinity.

Apr 26, 2022