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By Jack S. Greber

The mining industry generates an estimated 2.3 billion tons of solid waste each year and the total accumulated mineral resource solid waste at both active and inactive mine sites, approaches 30 billion tons. Five industries generate 85 percent of mine solid waste: copper, phosphate, iron, uranium, and coal. Over the past several years, the Federal government has shown increasing interest in the proper disposal of solid wastes generated by the mining industry. Three new pieces of federal legislation have been passed recently beginning with the most comprehensive regulatory authorization passed in 1976, the Resource Conservation and Recovery Act (RCRA) which has been amended to the Solid Waste Disposal Act Amendments of 1980. RCRA is implemented and enforced by the Environmental Protection Agency (EPA) and intended to control municipal and industrial solid wastes. Next came the passage of the Surface Mining Control and Reclamation Act (SMCRA) of 1977 which is implemented and enforced by the Department of Interior to control coal surface mining and the surface effects of underground coal mining, and finally, the recent Uranium Mill Tailings Radiation Control Act (UMTRCA) of 1978 implemented by EPA and enforced by the Nuclear Regulatory Commission (NRC) to control uranium mill tailings disposal.

Jan 1, 1981

By J. A. Reizes, C. A. J. Fletcher, T. Jancar

Spirals play an important role in fine coal and mineral processing. To date, almost all spiral designs have been empirically based. Although many operational units have evolved utilising this approach, it does not necessarily lead to optimal spiral designs. This paper presents the preliminary results of a collaborative computational and experimental research program to understand the detailed separation process which will ultimately lead to a parametric assessment of alternative spiral designs through computational simulation. Unlike the empirical approach, a computational simulation is only subject to the fundamental physics of the fluid flow. No prior knowledge of the generic spiral flow is necessary. The computer code implements a robust finite volume technique to predict the three dimensional fluid motion. A height function method is used to model free surfaces and the code is capable of handling arbitrary spiral geometries. Preliminary validation of the computational simulation is carried out through analysis of an existing spiral design -the Mineral Technologies LD9 unit. Computational flow predictions are compared with experimental measurements obtained using a number of techniques, including sampling and flow visualisation, for flow test cases where no solid particulate is present.

Jan 1, 1995

By James J. Anthony

High-angle in-pit conveying is an idea that is being seriously studied by a number of important mining companies in North America. Its application in coal, iron ore, and copper mining is expected to reduce mine operating costs considerably compared with the conventional discontinuous methods, such as truck haulage, which are fuel, labor, and maintenance intensive. Therefore, a mine introducing high-angle in-pit conveyors will gain a competitive advantage over mines which continue to use conventional haulage. While the capital outlay for in-pit conveyor systems obviously varies depending on pit depth, the angle of incline, and the capacity required, it generally will not exceed that of truck haulage when all Factors are taken into consideration. These factors include the cost of excavation, as measured in relation to the volume of minerals mined, the cost of building truck ramps and roads, and the capital outlay for the trucks and maintenance facilities. In many cases, in Fact, the capital outlay will be less than for truck haulage. This cost advantage will best be realized by new mines, whereas in existing producing mines the switch from truck haulage may involve the abandonment of a substantial capital asset.

Jan 1, 1983

By Ryan C. Stephan, Zach Agioutantis, Christopher Mark

During the past 15 years, roof fall rates have fallen dramatically in US coal mines, particularly in regions where the roof is weakest. The remarkable reduction in the number of roof falls has been accomplished with more effective roof support systems. The purpose of this paper is to present a design methodology that builds on and quantifies the basic roof support concepts that have been successful in the USA. The methodology starts by defining three modes of roof support, based on the roof strength relative to the stress level: (1) suspension, where roof bolts mainly provide skin control for strong roof; (2) beam building, where moderate strength roof can be supported by roof bolts alone; and (3) supplemental support for weak roof. Next, a large database of roof fall histories at a number of mines is used to define the approximate boundaries of these three regimes based on the coal mine roof rating and the depth of cover. Finally, guidelines are presented for site-specific design of support systems within each regime. The new computer package, analysis of mine roof support (AMRS), implements the design methodology.

Sep 29, 2020

By Lawrence A. Engel

The idea of using apron feeders for in directly feeding crushers is not a new one, it has been used for many years. To the best of our knowledge, the first apron feeder was used for bulk material handling in 1893. Since that time many design innovations have been introduced, with perhaps the most effective one being, the application of crawler tractor components in the feeder construction. This design was first introduced to the mining industry in 1954 by, national iron company. These feeders were used in the handling of run-of-mine iron ore on the Minnesota iron range, at the rate of 1,000 ltph. The material was fed over a grizzly to a jaw type of crusher. The crusher output was also handled by an apron feeder. Today, the apron feeder is being used in hard rock surface mine operations feeding crushers at rates of 5,500 ltph and over.

Jan 1, 1983

By D. Kruse

Top-down constructed large-diameter (up to 90 m or 300 ft) shaft design and constructability issues present an interesting suite of challenges and opportunities highlighted in this paper. The study covers 2D and 3D finite element models used to analyze various failure modes, evaluate the shaft liner and internal structures' response to seismic loading, assist in segment design and assess final structural design tradeoffs. Efforts to achieve economic advantage over conventional heavy civil practices have prompted innovative solutions for ring and segment design, ring build assembly and annulus backfill grouting. Intended for soft ground conditions, relationships between soil parameters and structure design are also explored. Mining Engineering, 2011, Vol. 63, No. 9, pp. 81-88. Official publication of the Society for Mining, Metallurgy and Exploration, Inc.

Jan 1, 2011

By J. A. Ober

"In 2016, the estimated value of total nonfuel mineral production in the United States was $74.6 billion, a slight increase from the revised total of $73.4 billion in 2015 (Table 1). Increased construction activity spurred increased production of industrial minerals, especially those used in infrastructure and residential construction. Although starting the year relatively low, prices for several metals, especially for some of the precious metals, began to trend upward. Decreased production of most metals produced in the United States, however, contributed to an overall decline in the value of metal production.Several U.S. metal mines and processing facilities were idled or closed permanently in 2016, including iron ore mines in Michigan and Minnesota; three primary aluminum smelters in Indiana, Missouri and Washington; one secondary zinc smelter in North Carolina; a titanium sponge facility in Utah and titanium mineral operations in Virginia. In addition, in May, the weekly average rig count for oil and gas drilling reached its lowest level since the 1940s when that measurement was first recorded. The reduced drilling activity resulted in decreased production of some industrial mineral products used in the drilling sector. Trends in mineral-related sectors of the domestic economy declined or held steady, except in the manufacturing of nonmetallic mineral products and nonferrous metals excluding aluminum, which increased. Overall, mining trended downward as the result of significant declines in coal mining, oil and gas extraction and metal mining (Table 2). Discussion of mine production is frequently segmented according to the type of materials produced within the broad categories of metals and industrial minerals (also known as nonmetallic minerals). Industrial minerals can be further subdivided as construction aggregates and other industrial minerals. Metals tend to have higher unit values but very low production quantities compared with those of industrial minerals, which have higher production quantities but are lower-valued materials, such as crushed stone or construction sand and gravel. Therefore, for discussion and analysis of the performance of the nonfuel minerals industry, the value of production is used rather than the tonnage produced. Tonnages of construction aggregates are orders of magnitude larger than those for most other mineral commodities thus making direct compar"

Jan 5, 2017

By Jupneek Singh, Zachary A. Kiehl, Leila Safazadeh, Gareth Kennedy, Eleonora Widzyk-Capehart, Jeremy W. Ward

Mine workers are continuously exposed to a host of nonfatal stressors and potentially fatal hazards: noise exposure, excessive vibration, poor air quality, toxicant exposure, ignition of combustible gases, equipment-related accidents, and thermal heat stress. Wearable or portable sensors and contextual analytics provide a platform to unobtrusively collect and fuse multimodal health and safety data in real time to compute both acute safety and longitudinal health insights. This paper presents preliminary trial results, conducted by Simtars, VigiLife, Inc., and Queensland Mines Rescue Service, of the application of wearable sensors to monitor heat stress and other vital biometrics for mines rescue personnel.

Feb 1, 2024

By Liangguo Kang

Coal, as one of the vital sources of energy in China, has raised widespread concerns regarding its safety issues amidst the country’s economic growth driven by coal. To address this concern, this study employed the Kuznets curve, multiple linear regression, and data envelopment analysis models to investigate the impact of Chinese coal economic development on coal mine deaths from 1992 to 2021. The findings revealed a clear correlation between the Chinese coal economy and coal mine deaths. Specifically, per capita coal output, the death rate per million coal tons, and the death rate per hundred thousand persons exhibited positive, negative, and negative correlations, respectively, with the growth of coal income over the past three decades. Moreover, when the coal workers and coal output factors remained unchanged, the income of coal demonstrated a negative correlation with future changes in coal mine deaths. Notably, with three decades of coal economy development, substantial improvements in coal mine safety have been observed in China. Consequently, this research provides valuable insights for formulating safety measures and policies in coal mines across different economic levels, as well as a useful framework for assessing safety development in the coal industry.

Jan 20, 2024

By L. A. Alcorn, H. E. Camargo, G. Gwaltney

"One of the most pervasive diseases in the mining industry is noise-induced hearing loss. The exposure of miners to noise levels above the permissible exposure level results in hearing loss in approximately 80% of coal miners by retirement age. In this context, the U.S. National Institute for Occupational Safety and Health (NIOSH) is conducting research to develop noise controls for longwall mining systems, which are used to extract half of the national underground coal production.From field measurements, previous research determined that the dominant sound-radiating components at the shearer of a longwall system are the two cutting drums used to remove coal. Due to the dimensions and complexity of longwall mining systems, the NIOSH project developed a validated finite element model of the cutting drum to use in predicting the sound radiated by the drum due to the excitation forces experienced in underground operations. This same model will be used to develop engineering noise controls for the drum. The excitation forces arise from the interaction of the cutting bits and the coal and are transmitted to the cutting drum through the bit holders. Due to the adverse conditions at the face, and a lack of instrumentation approved for underground use, the operational coal cutting forces have not been assessed before. To this end, NIOSH, in collaboration with Michigan Technological University, developed a self-contained, intrinsically safe instrumented bit to measure these forces.This paper describes the development of the instrumented bit and the measuring of operational coal cutting forces at three working coal mines. The measurements revealed that the forces have a flat spectrum, representative of the impact nature of these forces, up to around 100 Hz. Above this cutoff frequency, the force magnitude decreases at a rate proportional to the inverse of frequency squared."

Jan 1, 2014

By T. Gelpe

A digital simulator of classification and grinding circuits is used to evaluate the performances of various flowsheets. For a given flowsheet configuration, unit processes dimensions and operating conditions, the simulator calculates the steady-state values of the process variables. A supervisory algorithm is implemented in the simulator to determine the conditions which meet the required criterion on operation, tonnage and product quality. Calculation illustrations are proposed for the design of wet and dry grinding circuits. The performances of various arrangements of cement clinker and sulphide ore grinding flowsheets are evaluated and discussed.

Jan 1, 1983

By Bob Munz, Ry Stone

To facilitate the installation of the longwall equipment for each extraction panel, West Elk mine develops set-up room roadways that are between 26.5 and 30.5 feet wide. Historically at the mine, the set-up room roadways have been driven in a single 20-foot-wide pass, then incrementally widened to the required width during installation of the longwall shields. The first pass roof is supported with a generic roof support plan consisting of partially encapsulated roof bolts and point-anchored cables. This ground support plan was utilized regardless of the geotechnical conditions encountered in the roadways or consideration of the required stand-up time of the roadway before the longwall shields were installed. This "blanket" approach tends to result in over-conservative or inappropriate roof support designs, particularly in changing geotechnical environments. Guided by the desire to optimize the ground support plans and increase mining efficiency for future set-up rooms, the West Elk mine and Agapito Associates, Inc. have developed and implemented a strata management program. Strata management, as a formal and structured process, allows ground support and mining methods to be tailored to the anticipated and encountered geotechnical environment in a con- trolled manner (Thomas 2007). To arrive at adequate site-specific ground support plans for the set-up rooms at the mine, several struc- tured processes were utilized. Firstly, the geotechnical environment was characterized by examining the roof lithology and geomechanical properties from nearby rock core obtained from exploration boreholes. To increase both mining efficiency and continuity, and to achieve longer stand-up times before the longwall shields are installed, a multi-pass approach was implemented into the design. During mining, the geotechnical conditions of the roadway are mapped, and the roof is strategically surveyed with a borescope. This process was used to ensure that the encountered ground behavior was in alignment with the design standards used for the roof support design. To support this process with measured data, roof extensometers were strategically installed throughout the roadway. This data was used to monitor the magnitude of roof displacement at various horizons and record displacement rates up until the longwall shields were installed. Lastly, a Trigger Action Response Plan (TARP) was used during mining to cater for any unforeseen changes in ground conditions that would warrant additional con- trols such as increased monitoring or the installation of additional ground support. This paper presents two case histories at the mine where the above strata management approach was implemented to arrive at a site-specific ground support plan. The main changes to the mine's ground control plan included a multi-pass mining approach, the utilization of fully encapsulated roof bolts, and the transition to a stiffer roof support system. The geotechnical mapping, the roof borescope results, and the roof extensometer data will be presented to demonstrate the effectiveness of the ground support system up until the longwall shields were installed in both presented cases.

Jun 25, 2024

By L. C. Lang

INTRODUCTION The introduction of 165-mm (61/z-in.) holes to underground mining operations has made possible the application of Canadian Industries Ltd's (CIL) vertical crater retreat (VCR) mining method, illustrated in the accompanying sketches. This unique and revolutionary new application of spherical charge technology (see the Appendix), when applied to primary stopes and pillar recovery, eliminates raise boring, slot cutting, and dilu¬tion of ore by backfill; greatly improves fragmentation; reduces labor and time requirements; eliminates uphole drilling and blasting; and minimizes or completely elimi¬nates damages by blasts to the walls and retreating backs of the stope or pillar. If vertical large diameter holes are drilled on a designed pattern from a cut over a stope or pillar to bottom in the back of the undercut, and spherical charges of explosives are placed within these holes at the calculated optimum distance from the back of the undercut and detonated, a vertical thickness of ore will be blasted downwards into the previously mined area. Repeating this loading and blasting procedure, min¬ing of the stope or pillar retreats in the form of horizontal slices in a vertical upwards direction until the top sill is blasted and the mining of a stope or pillar is completed. The VCR method is also applicable to drop raises and has the potential to replace all other raising methods under most circumstances. PILLAR RECOVERY Levack Mine Inco Metals Co., Ontario Div., provided the first opportunity for the method in pillar recovery. The Levack mine's high grade ore pillar No. 4800 on the 975-m (3200-ft) level was used for the production¬scale experiment (Figs. 1 to 3). The pillar was about 49 m (160 ft) long, 6 m (20 ft) wide, and 20 to 26 m (65 to 85 ft) high. The mined area on both sides of the pillar was backfilled with a 1:30 cement:sand mixture. The pillar was removed in two phases. In phase 1, the standard uphole method was used to blast down the 18-m (60-ft) long section of waste from the bottom of the ore into the undercut. From the pillar's top sill, 165-mm (61/a-in.) holes were drilled downward into the pillar, and by measuring the depth of the holes, the results of the uphole blast were determined and roof line 1 was established. The bottom of each hole was plugged, then filled with sand to place the center of gravity of each spherical charge (loaded from the top sill) at a predetermined optimum distance from the horizontal free surface. The charges were then detonated. After detonation, both draw drifts were full of extremely well-broken material. The depth of each hole was measured again, and the plot of these depths re¬sulted in roof line 2. The same blasting procedure was repeated and the resultant new back elevation was marked by roof line 3. The poor results of the initial uphole blast at one location (notice the peak in area 1) appeared to influ¬ence the subsequent new backs. A third blast success¬fully evened the back, and resulted in roof line 4. An unblasted slab averaging 6.3 m (20.9 ft) thick remained below the pillar's top elevation as the final sill. In all three spherical charge blasts fragmentation of the blasted material was extremely fine. The backfill was fully exposed on both sides of the now-blasted pillar. The backfill remained undamaged and the ore was not diluted by sand. The remnants of all the 165-mm (61/2 -in.) holes remained clean and undamaged, and the holes had well-defined bottoms that could be easily measured and plugged. Each blast took down a 3.9 to 4.2-m (13 to 14-ft) thick horizontal slab of ore. Productivity was three times greater than that of the previously practiced cut-and-fill method. Since this was the first such experiment, blasting the remaining 6-m (20-ft) thick final slab was the sub¬ject of some deliberation. If the described method was repeated, we could have ended up with a 1.8-m (6-ft) thick sill unsafe to work on. It was therefore decided to blast the whole sill using two spherical charges prop¬erly placed in each hole, but with the application of

Jan 1, 1982

By Fengmei Chen, Na Liu, Bingrui Li

A quantitative analysis method based on the airflow influence factors is proposed to evaluate airflow stability and discriminate airflow directions in complex ventilation networks. The law governing the changes in airflow caused by changes in branch resistance is revealed based on simulations of the airflow state in a ventilation network and a statistical analysis of the results. Then, three evaluation indices (airflow sensitivity, airflow influence factor, and critical airflow) are determined, matrices of the airflow influence factors and critical airflows are constructed, and a quantitative evaluation method for ventilation system stability and an airflow directional discriminant are proposed. The results show that the stability of a ventilation system can be reliably evaluated based on the airflow influence factors. The sensitive branches and dominant branches in the ventilation network can be determined based on the matrix of airflow influence factors, and the reversed branches, the trigger branches, and the reversal conditions can be determined based on the critical airflow matrix and the matrix of airflow influence factors. The proposed airflow directional discriminant is suitable for evaluating arbitrarily complex networks.

Nov 15, 2023

By d&apos, I. J. Agati

The stockpiling and reclaiming of bulk materials can be a challenging task for engineers seeking the optimum solution for plant needs, reliability, and at lowest unit cost. The objective of this paper will be to expose advantages, disadvantages and limitations of many storage and reclaiming systems to the responsible engineer and management. The paper will emphasize the practical aspect of stockpiling and reclaiming methods. Many valuable and interesting papers are available dealing with the theoretical viewpoint and application of a particular manufacturer's machine. Several of these are mentioned in the bibliography. As many practical parameters as possible will be given. After twenty years in the field of designing and selling bulk materials handling systems, the needs of the user and the plant are recognized and reasonably understood. This paper cannot give solutions to all problems In this vast field but will stress practical applications and examples of various installations. The evolution of advancements in materials handling is based upon not only technological innovations, but learning from many experiences of others and utilizing them as stepping stones to improved installations.

Jan 1, 1969

By J. Drelich

An improved experimental procedure to measure contact angle has been consolidated with coal surface preparation involving polishing with abrasive paper, alumina powder, and a cloth, followed by ultrasonic and mechanical cleaning. Specifically, the captive-bubble measuring technique has been compared with the sessile-drop technique and the former has been recommended for the examination of the hydrophobic properties of coal surfaces. Results of the research program, which is currently under way, on the examination of the effect of the nature, amount, size and distribution of mineral inclusions in coal on its wettability are briefly reviewed.

Jan 1, 1999

Ground falls (roof and rib) have historically been responsible for nearly 50% of all fatalities in bituminous underground coal mines. In recent years, the number of some annual ground fall fatalities has approached zero, indicating that significant progress has been made. On the other hand, the twin disasters at Crandall Canyon in 2007, in which nine miners perished in violent coal bumps, provided a stark reminder that complacency is premature. One important success has been a great reduction in the number of miners killed inby roof supports. Throughout the 1990s, these accounted for nearly half of all roof fall fatalities, but there have just been two inby incidents since 2005. Progress has also been made in pillar recovery, where there has been just one fatal incident since 2005. On the other hand, more than 300 miners continue to be injured each year by rock falling from between supports and 100 more are injured by rib falls. Together, these two categories also account for a large percentage of recent ground fall fatalities available technologies such as roof screen, rib bolting and inside control roof bolters could reduce injury and fatality rates if they were used more widely. Further advances in these areas will likely be the next big advance in ground control safety.

Jan 1, 2011

By H. W. Breathitt

World demand for phosphate rock has increased significantly in the past fifteen years. Prior to the early 1960's, most of the world production was obtained from Florida, North Africa, and Kola. As the 1960's arrived, new mines in North Florida and Eastern North Carolina, as well as expanded production in the Western United States, .increased domestic production. Many new mines overseas have also become significant. This includes countries such as Senegal, Togo, Israel, Spanish Sahara, and Jordan. Limited production, often as by-products, has been noted in South Africa, Brazil, and other countries. In recent years, and even recent months, we have learned of many new areas being considered as potential sources of phosphate rock. This includes Australia, Saudi Arabia, Mexico, Colombia, and Brazil. Many other developing countries have discoveries and are considering their new deposits, often with difficult beneficiation problems, as potential sources of phosphate. These factors all relate to expanded world, population and the demand for more fertilizer products to produce food. In this paper, four areas of the world with different types of phosphate deposits are briefly reviewed to contrast the ore beneficiation problems to Florida procedures--long considered the "standard" of the industry, at least for most of the United States' domestic production. Agrico has three large operating mines in Florida with total production capacity exceeding seven million tons per year. Here, pebble phosphate (+14 mesh material) is produced without the use of flotation, whereas all of the material finer than 14 mesh is subjected to flotation beneficiation to upgrade into high grade concentrates.

Jan 1, 1977

By O. A. Velasquez, A. R. Kumar

"Dust generated on underground mechanized coal mining faces is a health and safety hazard. Continuous miners deployed underground usually have an integrated flooded-bed dust scrubber mounted onto the machine that arrests the generated dust from close to the face and cleanses the air around it. However, the impingement screen might get clogged depending on the coal seam being worked. This necessitates the cleaning of the screen which in turn, reduces the overall availability of the scrubber and, hence the continuous miner. A novel non-clogging screen has been developed at the Department of Mining Engineering, University of Kentucky. The proposed impingement screen is built up of three individual aluminum screen units 1.5 mm thick and separated by 3 and 2 mm respectively. The screens have long vertical slits measuring 6 mm. A water spray continuously keeps the screen wet and provides for the filter element to arrest the dust particles. The slits force the dust-laden air to make sharp turns. The dust particles cannot change directions rapidly, impact one of the three screens and are separated out based on their momentum. Preliminary computational fluid dynamics (CFD) models have indicated significant cleaning efficiencies in the respirable range at the expense of much lower pressure drops. Results indicated by CFD models and supported by laboratory experiments have been discussed in this paper.ACKNOWLEDGEMENT The authors acknowledge the National Institute for Occupational Safety and Health (NIOSH) for funding this research. Dr. Thomas Novak, Professor of Mining Engineering, is also acknowledged for his continued support and encouragement. INTRODUCTION Continuous miners are ubiquitous in coal mining around the world. The miners are operated against bling headings, ensuring adequate flow of air at the face could be difficult. The minimum requirement of ventilation airflow quantities at those coal faces are legislated to dilute dust generated to harmless levels. New dust rules promulgated recently have further called for lower exposure levels of personnel working underground (Courtney) (MSHA, 2014) (NIOSH, 2010). Water sprays are also installed at strategic locations and serve as powerful air-movers. The sprays capture some amount of dust generated while cutting. In addition to this, usually, all continuous miners are equipped with a flooded-bed dust scrubber as shown in Figure 1 to capture the dust from close to the extraction drum (Chao & De-sheng, 2000) (Wala, Vytla, Huang, & Taylor, 2008) (Organiscak & Beck, 2010)."

Jan 1, 2018

By L. A. Alcorn, H. E. Camargo, G. Gwaltney

"Una de las enfermedades más extendidas en la industria minera es la pérdida de audición inducida por el ruido. La exposición de los mineros a niveles de ruido superiores a los niveles de exposición permisibles resulta en la pérdida de audición de aproximadamente el 80% de los mineros del carbón a la edad de jubilarse. En este contexto, el Instituto Nacional para la Seguridad y Salud Ocupacional (NIOSH, por sus siglas en inglés) está realizando investigaciones para desarrollar controles de ruido aplicados a los sistemas de minado de tajeos largos. Este método de minado es usado para extraer la mitad de la producción nacional de carbón subterránea. A partir de las mediciones en campo, se determinó en investigaciones anteriores que los componentes dominantes que generan sonido en el cizallador de un sistema de tajeos largos son los dos tambores de corte utilizados para extraer el carbón. Debido a las dimensiones y complejidad de los sistemas de minado de tajeos largos, el proyecto NIOSH desarrolló un modelo de elementos finitos validado del tambor de corte para utilizarlo en la predicción del sonido generado por este debido a las fuerzas de excitación experimentadas en las operaciones subterráneas. Este mismo modelo se utilizará para desarrollar controles de ingeniería para el ruido del tambor. Las fuerzas de excitación surgen de la interacción de la broca de corte y el carbón, y se transmiten al tambor de corte a través de los sujetadores de brocas. Debido a las condiciones adversas en el frente y la falta de instrumentación aprobada para uso subterráneo, las fuerzas operativas de corte de carbón no han sido evaluadas anteriormente. Para este fin, NIOSH, en colaboración con la Universidad Tecnológica de Michigan, desarrolló una broca instrumentada autónoma con seguridad intrínseca para medir estas fuerzas. Este artículo describe el desarrollo de la broca instrumentada y la medición de las fuerzas operativas de corte de carbón en tres minas. Las mediciones revelaron que las fuerzas tienen un espectro plano, algo característico de la naturaleza del impacto de estas fuerzas, hasta alrededor de 100 Hz. Por encima de esta frecuencia "cutoff", la magnitud de la fuerza disminuye a una razón proporcional al cuadrado de la inversa de la frecuencia."

Jan 1, 2014