Search Documents

By Xun Luo, Yi Duan

A field trial of by distributed optical fiber sensing (DOFS) technique was conducted at a longwall coal mine in Australia. This investigation was designed to assess the applicability of DOFS for microseismic monitoring in mining. The experiments used commercially available optic fiber cables, geophones and associated data acquisition instruments – a fiber interrogator and a seismic recorder. The fiber cable was deployed in a 300m deep hole and in trenches of approximately 3.5 km long on the ground surface around and across the longwall panel being mined. The results obtained from the experiments have shown that DOFS is able to acquire microseismic data with quality that is comparable to geophones. It has been proven that DOFS can achieve higher spatial resolution for seismicity sensing and higher accuracy for locating events than a geophone network. These characteristics are particularly useful for using DOFS to monitor ground vibrations associated with ground caving processes and rock fracturing events induced by mining and civil engineering. It was also found that far more additional seismic events were recorded by the fibers than by the geophones. Automated data discrimination and processing methods must be developed in order to utilize DOFS for real-time applications.

Apr 26, 2022

By M. Niinae, Y. Nakahiro, T. Wakamatsu

In some cases, the extraction and separation efficiency of metals with a combined extractant are better than those with either extractant alone. However, the extraction and separation efficiency of metals with a combined extractant are not always better than those with either extractant alone. As part of the fundamental studies on the extraction and separation of metals with combined extractants, the extraction and separation efficiency of Au and Fe(III) added as an oxidizer in the leaching of Au from a sulphuric acid solution containing thiourea, and the extraction and separation efficiency of Nd and Sm from hydrochloric acid and sulphuric acid solutions were examined. The combined extractants for Au and Fe(III) were di(2-ethylhexyl) phosphosphoric acid (D2EHPA)/tri-n-butyl phosphate (TBP), D2EHPA/trioctyl phosphine oxide (TOPO). tri-n-octylamine (TOA)/TBP and TOA/TOPO, and those for Nd and Sm were D2EHPA/TOA. D2EHPA/TOPO. 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (EHPNA)/TOA and EHPNA/TOPO

Jan 1, 1994

By J. L. Yordan

An induction time apparatus has been constructed in the present work which has a sensitivity limit of 100-150 micro-seconds. The basic unit is similar to the one used by Eigeles and Volova (1960) and Trahar (1983), but it operates with a micro-computer and has a greater sensitivity. Using this apparatus, the flotation chemistry of the quartz-amine system has been studied. It has been found that at a given dodecylamminium hydrochloride concentration, the induction time is at a minimum at approximately pH 10.5. At this pH, the collector hydrolizes to form neutral amine and the flotation recovery reaches a maximumy,suggesting that iono-molecular species are the surface-active species responsible for flotation. This finding confirms the earlier conclusions obtained using the surface tension (Somasundaran, 1976; Finch and Smith, 1973) and contact angle (Smith, 1963) techniques. The induction time measurements have also been conducted as a function of particle size, collector concentration, indifferent electrolyte concentration and temperature. The results are compared with flotation data, and the activation energies for the bubble-particle adhesion have been calculated.

Jan 1, 1986

By C. Ernst

The underground operation at Barrick?s Cortez Mine, located near Elko, NV, required the construction of a 12 foot diameter smooth-lined ventilation shaft. Barrick preferred to mechanically excavate from the ground surface without putting people in the excavation and considered blind drilling by Frontier-Kemper Constructors the best option. Design and construction challenges arose throughout both the excavation and lining stages. A large portion of the rock to be drilled was highly fractured. Important risks that were addressed included water loss into the formation, zones of squeezing ground, damage to drilling tools caused by blocky ground and fallout, and potential hazards during cast-in-place concrete lining. Detailed explanations of these challenges and the methods used to overcome them will be described.

Feb 23, 2014

By Phillip J. Maddex

After the presentation of a co-authored paper, "The Cost of Transporting Ores and Raw Materials in World Markets", at the February SME meeting, one questioner commented, "You have been talking about the large shipper and ship loads. What does the small shipper do?" This paper will attempt to answer that question, at least in part. Probably the questioner hoped to hear about specific new tools and new techniques that he could apply. But one paper could only scratch the surface of the vast fund of information available; so rather than talk specifics we should take basics, that is, people, management and technology.

Jan 1, 1967

By J. J. Bartels

The phosphate rock review did not arrive in time for publication in the. June issue. The world phosphate industry continued its slide in 1992 from the already depressed levels in 1991. The industry is locked into a 30-year fertilizer price low due to the worldwide fertilizer glut. Domestic production and imported, marketable phosphate rock decreased 1%, while domestic consumption increased by 1 % last year. The US Bureau of Mines reported a decrease in the domestic phosphate rock value from $25.42/t in 1991 to $23/t in 1992 ($23.06/st to $20.80/st). The diammonion phosphate (DAP) product price also dropped in value from $138/ t in January 1992 to $11 0/t in December ($125/st to $99.70/st). Continued declines in DAP prices is forcing the US fertilizer industry to develop cost-saving programs and reorganizations. Layoffs in 1992 resulted in a 7.6% decrease in the Florida phosphate workforce. Since 1980, the Florida workforce has declined by 35%. Small phosphate companies were forced to close operations or were sold to larger phosphate companies. Federal and state environmental regulations for byproduct waste disposal methods are being studied. The Environmental Protection Agency (EPA) approved phosphogypsum use in agri¬cultural and research applications as long as the radium 226 concentration is lower than 10 pci/g. The EPA is also reviewing regulations concerning air emissions at fertilizer plants. Industry publications reported the possibility of continued company sales and mergers in 1993. Industry expectations are optimistic while waiting for an upturn in the market. The US phosphate industry consolidation into three or four major companies should evolve into a stronger world market force.

Jan 1, 1993

By Raphael G. Kazmann

The predicted warming of the earth's surface, presently the subject of much debate, controversy and legislation, is based on what is termed "the greenhouse effect." This is the result of the property of certain atmospheric gases. These gases allow the passage of radiant energy to the earth's surface and reflect back, to the earth, the infrared radiation given out by the heated surface. Physicists have computed that if there were no greenhouse effect the average temperature of the earth, now about 15° C (60T), would be close to -18° C (OT). Just what gases have produced this salubrious effect? Water vapor is the most important. Then come carbon dioxide, methane and a number of minor constituents of the atmosphere, both natural and man-made. Climate change, its cause and its impact on human activities have been the subject of scientific and historical study for more than a century. Recently, some scientists have concluded that if the man-made increase in the carbon dioxide and other greenhouse gases continues, by the late 21st century the earth's global average temperature will rise between 2° to 8° F. This temperature rise would cause the water in the oceans to expand and the massive polar glaciers to melt. In 1980, it was predicted that the sea level would rise 7.6 m (25 ft) by the late 21st century. By 1985, the predicted rise was 1 m (3 ft); and by 1989, it was 0.3 m (1 ft) (Jastrow, Nierenberg and Seitz, 1990). Agricultural scientists have pointed out that an increase in atmospheric carbon dioxide would enhance biological growth including the production of foodstuffs.

Jan 1, 1992

By J. Hanna, H. R. Gonzalez

Discussion by N.L. Hargett Dear Dr. Hanna: As discussed in our phone conversation, we are enclosing a suggested revision to the paper, "Application of Bentonitic Clays in Suspension Fertilizer Formulations," published in MINERAL & METALLURGICAL PROCESSING, May 1990. The revision will replace the second paragraph in the article. The reason for the revision is that suspensions have decreased in market share since 1984 and at present comprise an estimated 25% to 30% of fluid mixtures. This represents 6% to 7% of all fluids and only 2% to 3% percent of all fertilizers. Based on national surveys conducted by the Association of American Plant Food Control Officials (AAPFCO), suspensions comprised an estimated 25% of all fluid mixtures in 1974, 33% in 1976, 35% in 1980, 40% in 1984, and 36% in 1988. Revision to "Application of Bentonitic Clays in Suspension Fertilizer Formulations." Suspension fertilizers are an important segment of the fertilizer industry in the United States. Suspensions allow higher concentrations of nutrients (N, P2O5, K2O) than clear liquid solution fertilizers. K20 content of solutions is limited to about 10%, while suspensions can contain more than 30% K2O. Suspensions can tolerate greater variations in temperature than solutions. In suspensions, if crystallization occurs, the crystals can remain suspended in a clay jell instead of settling as they would in solutions. Solubility is not a limiting factor in suspensions, since complete solubility of phosphate is not required. This allows a wider range of phosphate materials to be used. Also, materials commonly used in formulating suspensions are less expensive and more widely available than those for clear liquids (Getsiner et al., 1984).

Jan 1, 1992

A PDP 11/34 computer has been inter- faced to existing instrumentation in a 400 tph rod-mill/ball-mill grinding circuit and programed with a Kalman filter to estimate several unmeasured variables. A dynamic two-size- fraction model of the circuit is used to predict the complete state of the circuit including particle size distributions around the circuit, mass holdups and flowrates, the ball-mill grinding rate, water additions and cyclone parameters. Online measurements of sump level, slurry densities and product particle size are used to update the model values sequentially on a 20-second interval. This procedure results in optimal estimates of circuit variables given the relative reliability of measurements and the accuracy of the model.

Jan 1, 1983

By John E. Butler

Due to the present economic climate, particularly the depressed copper market, conventional mining, milling and flotation operations have been suspended. However, due to the apparent amenability of the ore to 'natural' leaching, investigations have been initiated into establishing an in-situ leaching operation as a preferred alternative to conventional operations. Cement copper production has been developed in parallel with the leaching trials and is presently at the rate of approximately 3,000 tonnes of contained copper per annum. Testwork includes controlled leaching of ore both in the laboratory and in-situ following blasting.

Jan 1, 1981

By Rudolf E. Greuer

Modeling a mine ventilation system is a formidable mathematical problem requiring the solution of twice as many equations as there are airways with half of these being quadratic equations. The addition of a mine fire to the problem adds many more complexities. The U.S. Bureau of Mines and Michigan Technological University attacked this problem in stages. During the 1970's and 80's, a series of computer simulation programs were developed which offered progressively increasing levels of modeling capability and accuracy. The current version of this software, MFIRE 2.0, was released in 1993. This programs provides for full dynamic state mass flow-based modeling of a mine ventilation system, and includes natural ventilation, mechanical ventilation, air reversals and recirculation, methane and fire contaminant spread, and moisture condensation and evaporation in the mass flow and heat exchange calculations. This program is a useful tool for routine ventilation planning and can significantly improve mine safety by enabling detailed quantitative analysis for mine emergency preplanning. This paper reviews the evolution of the MFIRE program from its infancy as a simple digital network simulator replacing analog computers to the present version.

Jan 1, 1994

By B. C. Paul, R. Q. Honaker, M. Huang

Froth flotation is now, the most commonly used method for cleaning fine-coal fractions in coal-preparation plants. Past research and industrial practice have demonstrated that froth flotation achieves excellent separation efficiencies for fine coals having only a small fraction of middling particles. However, the efficiency of froth flotation decreases sharply as the concentration of middling particles increases. This is due to the flotation of high-ash particles that have a small amount of hydrophobic coal present at the surface. Because gravity-based processes are much more efficient for the treatment of middlings, the application of centrifugal washing for fine-coal cleaning was studied with an emphasis on the primary cleaning of fine-circuit feed. Results are shown of a parametric study that used a semibatch Falcon centrifugal concentrator. The results of the study revealed that separation performance is a function of particle size, bowl geometry, feed solids content and feed rate.

Jan 1, 1996

By J. W. Currier

The compositions and natures of the materials charged to a blast furnace, as well as their respective distributions within the furnace, are known to int1uence furnace performance. However, fifteen years ago, there was little reason to believe that any significant variation of these parameters had been overlooked. Nor was there any particular reason to believe that olivine might be a particularly useful raw material for blast furnace applications.

Jan 1, 1989

By D. Stone, R. Pakalnis, B. Seymour

Most mines using backfill routinely carry out quality control (QC) testing of backfill mixes with unconfined compression test cylinders. This is true for paste operations, hydraulic fill operations, and cemented rockfill operations worldwide. However, a large number of mines simply do not prepare and test the backfill samples in a consistent manner and fail to properly analyze or interpret the test results. Conventional concrete test criteria are not applicable given the differences in the mix constituents and the fact that a large number of the backfill QC test cylinders typically fail to achieve the target strength. Standard industry practices are needed to improve the analysis and interpretation of QC test results and to provide a better means of determining if the backfill is achieving its intended target strength. This paper will attempt to lay the groundwork for standard industry practices and will address several key questions raised by operators, such as how laboratory test data compares to in-stope performance, and how many QC tests should fail before a red flag should be raised. INTRODUCTION Although paste backfill is widely used throughout the mining industry, cemented rockfill (CRF) remains as the backfill of choice in places like Nevada where very poor ground conditions mandate the use of underhand mining. The safety and stability of undercut entries beneath backfill is a function of the quality of the cemented fill, which is typically assured through routine quality control testing. In the absence of a backfill quality standard, most mines rely on concrete standards to design and interpret their backfill quality control programs. In the USA, these standards are developed and published by organizations such as the American Society of Testing and Materials (ASTM) and the American Concrete Institute (ACI). However, the application of these standards to cemented backfills can be very difficult owing to the high degree of variability in backfill mixes and the resulting variability in test results. To illustrate, the concrete industry standards denote that an acceptable (passing) test result occurs when the average strength of the duplicate test cylinders exceeds the target strength and no single test result deviates from the target strength by more than 10% (ACI 214R). Remedial measures must be taken if three consecutive tests fail. With mine backfills, it is safe to say that these criteria are rarely achievable. A further, more dramatic example is the accepted coefficient of variation for concrete QC cylinders. According to ACI 214R, the coefficient of variation (CV) should range from below 3% (excellent rating) to above 6% (poor rating). However, if this analysis method is applied to several backfill QC databases from operating mines, coefficients of variation are calculated on the order of 50%. Clearly, there is a need to develop better industry practices for assessing the quality of mine backfill and to assist mine operators with the interpretation of test results and the development of action plans in the event of undesired outcomes.

Jan 1, 2019

By Javad Sattarvand, Amin Moniri-Morad

Predicting equipment failure behavior plays a critical role in providing a safe operation. Although various reliability evaluation methods are available for estimating failure behavior profiles, these approaches are based on mathematical formulation, leading to actual operation simplification and improper estimation of failure trends. This study proposes a discrete-event simulation (DES) approach to model fleet failure behavior. This approach can model the maintenance strategies in multi-component systems with minimum simplifications. In this regard, the first step was to collect a historical failure time dataset (e.g., the time between failures). Then, the DES model is established to predict the severity of failure events and design maintenance strategy considering actual operation circumstances. Afterward, the maintainability analysis was performed to estimate equipment downtime and availability. The achieved results showed that the system availability was about 85%. Also, the findings demonstrated that the DES could efficiently predict the equipment failure behavior using various stochastic events.

Jun 25, 2023

By J. H. Rowland, R. A. Thomas, III, C. D. Litton

Atmospheric monitoring systems (AMS) are required when using air from conveyor belt entries to ventilate working sections in U.S. underground coal mines. AMS technology has the potential to increase fire safety mine-wide, but research is needed to determine the detection and response times for fires of a variety of combustible materials. To evaluate the potential of an AMS for fire detection in other areas of a coal mine, a series of full-scale fire experiments were conducted to determine detection and response times from fires of different combustible materials that are found in U.S. underground coal mines, including high- and low-volatility coals, conveyor belts, brattice materials, different types of wood, diesel fuel, and a foam sealant. These experiments were conducted in the Safety Research Coal Mine (SRCM) of the U.S. National Institute for Occupational Safety and Health (NIOSH) located in Pittsburgh, PA, using a commercially available AMS that is typical of current technology. The results showed that through proper selection of sensors and their locations, a mine-wide AMS can provide sufficient early fire warning times and improve the health and safety of miners.

Jan 1, 2016

By Fulian He, Jianhang Chen, Dongdong Chen, Shoubao Zhang

"The Wangjialing Coal Mine is the main colliery of the China Coal Huajin Energy Limited Liability Company. The average thickness of the coal seam in District 201 is 6.21 m. Fully mechanized longwall mining was used in this district. The ventilation roadway of panel 20102 was influenced by the retreat mining of the adjacent panel 20104. Therefore, large deformation and severe roof falls occurred in this roadway, seriously influencing the safety production of this coal mine. To support the roadway, cable truss was proposed to strengthen the reinforcement of this ventilation roadway. First, numerical simulation was used to optimize the reinforcement parameters, including the cable installation angle, cable length, and eccentric distance. Based on numerical simulation results, in-situ tests were conducted in the ventilation roadway of panel 20102 with the cable truss technology. In-situ monitoring results showed that the roof-to-floor convergence and the convergence of roadway on two sides were within the safety range. Furthermore, no apparent separations occurred in the roof. These indicate that based on the designed parameters, the cable truss system can effectively maintain the roadway stability under the severe influence of the adjacent longwall mining.INTRODUCTIONCable bolts are flexible tendons composed of multi steel wires, which are wound into a strand (Chen, Hagan, and Saydam, 2018). They were initially introduced in the hard rock mining industry in the 1960s. Later, they found rapid application in coal mines to maintain the stability of excavations (Wang et al., 2015).The standard cable bolt is composed of seven steel wires with a diameter of 15.2 mm. Laboratory and in-situ tests showed that there is a low bonding capacity between the standard cable bolt and the grout (Craig and Holden, 2014; Chen, Hagan, and Saydam, 2018). Then, modified cable bolts are developed based on the standard cable bolts. They are improved by changing the surface geometry of standard cable bolts, such as birdcaged cable bolts (Hutchins et al., 1990) or nutcaged cable bolts (Hyett et al., 1993). Further tests proved that modified cable bolts have better mechanical interlock and friction between the cable bolt and grout, leading to larger load transfer capacity of cable bolts.Although cable bolts have been used for many years, failure of the cable bolting system still occurs. A common failure mode is the damage of surrounding confining medium while the cable bolt is still hanging in the roof, which is caused by the bond failure of the cable/grout interface (Hutchinson and Diederichs, 1996). To prevent the cable bolting system from failing, the cable truss system is more widely used in mining engineering."

Jan 1, 2019

By G. Wayne Clough

During shallow tunneling in an urban environment, deposits or pockets of saturated soil or fractured, weathered rock are often encountered. Under such conditions, special problems with tunnel support, underpinning of structures adjacent to the tunneling, and/or flow of groundwater into the tunnel occur. If the ground conditions are appropriate, i.e., the soil is sandy, silty or fissured, or the rock is weathered or fractured, the solution to these tunneling problems may be chemical stabilization of the ground. Injection stabilization as an aid to tunneling is practiced extensively in Europe and its use is increasing in the U.S. The advantages of this technique over conventional solutions can be substantial in terms of cost and time, especially in mechanized tunnel boring where even a small zone of soft ground can bring the tunneling to a complete halt. In this paper European practice in using chemical ground stabilization for urban tunneling will be reviewed. In contrast to previous papers which have dealt with specific applications (1,5,8,9) this paper will broadly cover the subject, addressing itself to grouting techniques, costs, the reasons for grouting, philosophy of the users towards grouting, design of grouting solutions (or lack thereof) and methods of quality control. Differences with U.S. grouting practice are also noted. The information presented is derived from several visits to Europe, discussions with European and U.S. grouting personnel, and the available literature (2). The author's most recent European trip was made under the auspices of the U.S. Department of Transportation in conjunction with a research study being performed at Stanford University; a detailed report of this visit is available in reference (6).

Jan 1, 1976

By Atmesh K. Sinha

The market for thermal coal has recently been growing rapidly and it is projected to continue to do so in the foreseeable future. Both the national and international markets often demand high Btu low sulfur thermal coal in order to minimize the cost of utilization and meet the environmental restrictions. High quality thermal coal can be prepared to compete in the utility market by desulfurizing the high Btu midwestern coal and blending it with low sulfur western coal which is usually low in Btu content. The methods that can be used for optimizing the coal preparation plant operating parameters for physically desulfurizing coal is presented.

Jan 1, 1984

By R. R. Klimpel

The use of froth flotation as a means of separating and upgrading sulfide mineral concentrates is standard industrial practice throughout the world. It is ap-parent from observing the industrial practice of sulfide mineral flotation over the last decade that progress is being made in optimizing the operating aspects of flotation. Examples of this are the availability of improved instrumentation and related computer control devices, the modification of mechanical flotation cell designs, the introduction of column cells, better reagent dosage control, blending of feed ores, increasing attention to coarse and fine particle separations, the successful introduction of new frother chemistries, etc.

Jan 1, 1989