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By John W. Leonard

The typical tunnel boring machine in use on today's tunnel project uses 15'2-inch diameter cutters at a nominal load of 45 kips per cutter. The cutterhead rotates at a speed of 120 over D revolutions per minute where D is the cutterhead diameter in feet. The typical machine operates about 50 percent of the time. Delivery of a new machine takes 12 to 15 months. The TBM is a specialized tool and not applicable to all jobs. There is a range of job conditions that limit the economic use of a TBM. The machine should provide a thrust per cutter at least twice the compressive strength of rock in psi and up to three times the rock strength is required if in "granitic rocks." The rock strength in psi must be at least three times the cover above the tunnel in feet or the machine may stick. For example, 2,500 feet of cover requires at least 7,500 psi rock to avoid problems. When the RQD's over a significant distance of the project are less than 50, the TBM becomes support-bound. When a large percentage of the time is spent waiting while the ground is supported, the TBM cannot perform well (See Figure 1). This problem increased inversely with tunnel diameter. We are finding that increasing the RPM's does not significantly increase progress. The increased RPM results in a substantial decrease in cutter penetration. The explanation for this decrease appears to be vibration, cutterhead drag, or lack of stiffness in the cutterhead (See Figure 2).

Jan 1, 1981

By J. A. Organiscak

Two types of airflow splitting methods for improving longwall dust control were investigated by NIOSH's Pittsburgh Research Laboratory. These methods included a translucent mesh barrier and a staged spray barrier system to confine the shearer-generated dust to the coal extraction side of the long wall face while maintaining a cleaner split of airflow on the opposing worker walkway side of the longwall face. The translucent mesh barrier was shown to provide notable dust control effectiveness up to 60 m downstream of the shearer in both the laboratory experiments and a long wall field evaluation, provided the mesh barrier remains relatively parallel to the airflow. The staged spray barrier system showed marginal dust control effectiveness in the laboratory and subsequently was not field tested.

Jan 1, 1999

By E. F. Paski

Geological materials are likely the most complex and challenging substances to quantitate by ICPOES (inductively coupled plasma optical emission spectroscopy). For complex materials having widely varying compositions, spectral overlap interferences govern detection and quantitation limits attained by ICPOES based analytical methods.

Jan 1, 1993

By Cloyd D. McDowell

The Federal coal Mine Health and Safety Act of 1969 has been criticized by those who say it goes too far in controlling the activity of private enterprise and by those who say it does not go far enough in eliminating fatalities and accidents in an accident prone industry. Possibly a better evaluation of this legislation lies somewhere in between. From the viewpoint of the coal industry it can be said that through the efforts of those engaged in mining, both the operator and the miner, the year 1969 marked a record year in mine safety with only 190 fatalities and a frequency of 0.84 per million man hours exposure. This outstanding achievement compared to any previous was the result of a determined effort on the part of a concerned industry to improve its reputation as being the most hazardous industry in the nation. After the effective date of the Act, March 31, 1970, the Bureau of Mines assumed complete control of all safety and health activities of the mining industry. Unfortunately, there was no improvement in the safety record of underground mines in 1970 with the total of 255 fatal injuries and a frequency of 1.04 for the year. The number of fatalities declined to 177 in 1971 but the number of underground coal mines had declined from 5,955 to 2,268 during the two year period. Meanwhile, surface mined coal increased from about 38% of total production in 1969 to over 50% in 1971, keeping the annual production of coal at a normal level but involving fewer men.

Jan 1, 1973

By Steven Keim, Steven Stansfield, Kevin Andrews

Geotechnical, geological, and hydrogeological fieldwork and data collection for the mining industry is often conducted by younger, less-experienced staff members. In many cases, fieldwork personnel are recent college graduates or are otherwise relatively new to the mining industry. Due to busy schedules, staffing shortages, project budgets, and in some cases, poor management, new fieldwork hires often do not receive thorough training. In the past and the present, many workers in the mining industry learn(ed) by “doing.” While this is still considered to be the most practical approach and the easiest way for a company to determine the skill set of an employee, there is always some risk involved in the “feet to the fire” method. The reality is that field personnel are often collecting data on which major operational decisions will be made or on which regulators will base enforcement decisions. Inadequately trained or inexperienced field personnel may collect inaccurate data or fail to recognize key conditions that may influence decisions made by regulators, design engineers, mine managers, and corporate leaders. Even the best engineers may come to incorrect conclusions if they are starting with poor input data. Decisions based on inaccurate data often result in delays, budget issues, unsafe conditions, or even worse consequences. This paper provides numerous mining industry examples of incidences where inaccurately collected field information did, or could have, resulted in major adverse consequences. The paper also offers some simple approaches to minimizing the potential for such problems.

Jul 1, 2023

By Richard Louis Viner, William D. Leech, Walter A. Mergelsberg

With the construction management team established and a full funding agreement secured the Washington Metropolitan Area Transit Authority (WMATA) now has the manpower and the financial resources to continue Metrorail construction into the 1990's. This paper describes WMATA's new role as construction manager after the transition from Bechtel Associates and gaining the full funding agreement with the Urban Mass Transit Administration (UMTA) and regional governments to complete 84.7 Metrorail miles (136km). The authors review the most recent station and line tunneling projects. WMATA's contractors have employed the state of the art soft ground and hard rock tunneling equipment and methods - an earth pressure balance TBM, a closed face TBM, and the New Austrian Tunneling Method (NATM). In final, the paper previews future underground work to be let under the funding agreement.

Jan 1, 1987

By Edgar O. McAlister

Associated with cordilleran intrusives of intemediate to acidic composition, gold/silver ores are generally found in the intruded host rocks which are adjacent to these intrusives. Generally precious metal deposits lie further from the intrusives than allied base metal deposits. For vented intrusives, the associated volcanics may constitute the intruded rock and form the host for precious metal accumulation. Potential field methods, particularly magnetics, can help to define unseen boundaries of intrusive systems and thus can point to generalized prospecting targets. Other clues arise from the intrusive system type, its emplacement fracturing, the host rock type and local magnetic changes caused by mineralization processes.

Jan 1, 1984

By Colonel Oattis E. Parks

The quantity of coal recovered by diamond coring techniques is not sufficient in many instances to make meaningful coking and/or ash fouling tests. Quantities in excess of that obtained by conventional coring techniques, usually in amounts exceeding 500 pounds, has been designated bulk sampling. During the past three years, AMAX Coal Company has utilized five methods of bulk sampling. It was our desire to obtain a bulk sample that was diagnostic of the seam by the most expedient and economical method. From the beginning all of our efforts have been directed to methods which would extract the required coal from slim boreholes which provide quick and inexpensive access to the coal seam, regardless of depth, terrain and accessability. In our efforts and investigation several large diameter cores have been taken from thick coal seams at relatively shallow depths in easily drilled rocks. On the other hand, for deeper thin seams multiple large diameter coring is more expensive and time consuming. It is somewhat less expensive when multiple cores are taken from a single slim borehole utilizing deflection coring, although considerable skill is necessary.

Jan 1, 1973

By M. Kuchta

A linear integer programming (MIP) model to solve the long-and short-term production-scheduling problem for sublevel caving operations is presented. The MIP model is designed as a multi-time-period problem to provide monthly schedules that meet production, blending and sequencing requirements. One of the most important issues during the development of the MIP model was the requirement of sequencing between blocks. In this mathematical model, unique constraints that ensure sequencing of the production from sublevels are developed. A suggested method of handling a large number of variables is also given. The MIP scheduling model was implemented on a data set obtained from the Kiruna Iron Ore Mine located in northern Sweden. The initial MIP model implementation was successful and provided a solution that optimized resource recovery while meeting monthly and yearly production constraints. The scheduling results obtained based on the Kiruna Mine are further presented and discussed.

Jan 1, 2003

By M. Ziegler

The article deals with the use of a digital twin in the assessment and optimization of a conveyor system in the Chilean copper mine. This example shows that a digital twin is initially just a new (albeit powerful) tool with which the system behavior can be examined. The benefits for the customer arise through the system identification and automatic detection of critical deviations from the target state. This knowledge allows mine management to react and coordinate operational and/or maintenance counter measures to insure optimal performance of their conveyor system. The information derived from the BeltGenius digital twin also allows mine management to gain a clear perspective of the overall efficiency of their conveyors, which will be invaluable for future conveyor component selections.

Mar 2, 2022

By T. E. Wilson

An exploration bore core sample of coal ought to be reduced from its original cylindrical form to a particle size distribution and particle composition that reflects, insofar as possible, a process stream of? raw? coal it represents. Often, coal cores are reduced with a laboratory crushing machine, the product of which may not match the raw coal size distribution or size fraction composition. This study employs drop-shatter impact breakage followed by dry batch tumbling in a steel cylinder rotated about its transverse axis in order to characterize the core material in terms of first-order and zeroth-order breakage rate constants. These are indices of the propensity of the coal to degrade during excavation and handling. Initial drop-shatter and dry tumbling tests were done with synthetic cores, to reduce material variables and . conserve difficult-to-obtain coal cores.? Cores of three different coal beds --Illinois No.6, Upper Freeport, and Pocahontas No. 5 -were subjected to drop-shatter and dry batch tumbling tests to determine breakage response. Comparison of coal preparation plant feed with a crushed bore core and a bore core prepared by drop-shatter and tumbling (all from the same Illinois No.6 coal mining property) indicated that the size distribution and size fraction composition of the drop-shattered/tumbled core more closely resembled the plant feed than the crushed core.

Jan 1, 1998

By Lina Ospino Ballesta, Oscar J. Restrepo Baena, Juan Diaz Martínez

Artisanal and small-scale underground gold mining in Colombia plays a significant role in the country’s economy, but it faces persistent occupational hazards that threaten worker safety. Despite mining economic contributions, outdated technologies, limited risk management practices, and insufficient regulatory enforcement have led to recurring workplace accidents, many of which have been fatal. This study presents a systematic review of mining-related accidents over the last decade. Through geo-referenced analysis, high-risk municipalities were identified, and the frequency of accidents was correlated with the mining legal status and operational practices of these municipalities. The findings underscore the urgent need for evidencebased interventions that are tailored to the country’s unique mining context. Ultimately, this research contributes to the global discourse on mining safety by highlighting practical pathways to reduce occupational risks and promote safer, healthier workplaces in resource-constrained environments.

Feb 22, 2026

By Howard L. Hartman

Pardon my audacity, but I feel that this is the solution, not just a solution. Further, I will be so bold as to maintain that this is the last-ditch, eleventh-hour chance for the mineral industry to solve its critical technical manpower shortage. I am not being facetious. I am convinced that there is only one solution--just as there is but one real cause of the problem. My conclusion 'is reinforced by countless talks of endless hours with people both in and out of the industry, with employers and employees, and with educators and students. While I claim no originality for the idea and have no pride of authorship, I am concerned that the industry hear and heed in time. It is quite unlikely that the mineral industry and the mineral engineering profession will willingly subscribe to my thesis or gladly buy my proposal. I am convinced, however, that it is the only course of action open to us, and the only course of action which will succeed.

Jan 1, 1967

Small-scale flotation tests have been conducted to examine the effect of froth stability on the column flotation of finely pulverized coal. The results of this study demonstrate that the upgrading of coal in a column flotation cell can be significantly improved when froth stability is properly controlled through the manipulation of appropriate operating variables. Several important correlations have been established from the test data. These relationships should prove useful for the design and ore ration of column flotation cells for fine coal processing.

Jan 1, 1991

NICOR Mineral Ventures, Inc. retained Neyer, Tiseo and Hindo, Ltd. to evaluate the potential effects of a planned dewatering operation at NICOR's proposed, 258-acre silica sand mining facility near South Rockwood, Michigan. The ?orebody? is a horizontally extensive, friable, quartz sandstone from the Sylvania Formation which also serves as an aquifer for some of the rural, residential development near the site. We conducted an aquifer test on the site which identified the important aquifer properties. Using these data and an analytical model, we determined that the radius of influence would be expected to range up to 6000 feet from the quarry during its final development stage. An inventory of water supply wells revealed that most wells had sufficient available drawdown and would not be adversely affected. A long-term groundwater monitoring program was recommended to monitor the possible effects at some of the closest wells.

Jan 1, 1987

By T. S. McGahey

The southeastern region of the United States has long been a major market area for coarse and medium particle size natural ground calcium carbonate fillers. The primary market for calcium carbonate in the southeast traditionally has been as fillers in building materials such as carpeting, joint cement and roof shingles. In these applications the economic value of the calcium carbonate in the final product is weighted more toward lessening the cost of the final product, as opposed to contributing any desirable physical characteristics. For example, in carpet backing applications the calcium carbonate filler does little more from a physical standpoint than add weight and body to the backing adhesive. The important factor in the use of calcium carbonate in carpet backing is that it can be used at high loading levels to replace the more expensive latex binder, thus lessening the cost of the final product. It is estimated that calcium carbonate producers in the southeast sell in excess of 200,000 tons (181,436,000 kg) annually for use in latex compounds for carpet backing applications.

Jan 1, 1986

By I. Martinez-Dominguez

In September 1992, mining in Mexico was opened again to foreign investment by President Salinas-de Gortari, after thirty years of "Mexicanization" of mining industry which limited foreign participation up to a 49 % (or 34 % in case of national reserves) on a Mexican mining corporation. During said period mining in Mexico was controlled by four or five big mining companies and besides mining production was focused mainly on silver, lead, zinc, copper and fluorspar. Suddenly in middle of a big crisis on Mexican mining industry due to low prices of minerals in the world and also in a period on which it seems that mining industry in the United States and Canada has been condemned to die for environmental reasons, it appears a new Mexican Mining Law to permit foreigners to participate in mining in Mexico' trough Mexican mining corporations that they may control up to 100 %

Jan 1, 1994

By N. Damiano, J. Noll, C. Zhou, J. DuCarme

"Preventing machine-related injuries is one of the major safety concerns in underground coal mines. Severe injuries and fatalities occur when a miner is struck, crushed, or pinned by mining equipment such as a continuous mining machine (CMM), shuttle car, or a scoop. Proximity detection systems (PDSs) have been applied in mining to reduce these types of injuries and fatalities. All of the PDSs that are currently approved by the Mine Safety and Health Administration (MSHA) for use in underground coal mines are magnetic-field based and could be affected by metallic objects such as trailing cables. Researchers from the National Institute for Occupational Safety and Health (NIOSH) investigated the influence of trailing cables on the performance of PDSs. In particular, the magnetic field coupled from proximity system generators to a de-energized trailing cable were characterized. The results show that significant energy can be coupled from the proximity system generators to a trailing cable when there is a closed loop in the cable. The effect on PDS performance from the magnetic field radiated around an energized trailing cable was also quantified for different current amplitudes in the cable. It is shown that the magnetic field caused by the electric current in the trailing cable mainly consists of a 60-Hz signal and its harmonics which cause little interference to the PDS. The results presented in this paper can help PDS manufacturers to design better systems that are more immune to these effects. INTRODUCTION An average of 250 injuries occur every year during operation of Continuous mining machines (CMMs), and 43 miners have been killed by striking or pinning accidents involving CMMs in the U.S. from 1984 to 2015 (Mine Safety and Health Administration, 2015). In addition, there have been 10 fatal accidents involving mobile haulage equipped with trailing cables from 2000 to 2015 (Noll et al., 2017). In response to these fatalities and injuries the Mine Safety and Health Administration (MSHA) promulgated a regulation in 2015 requiring the use of a proximity detection system (PDS) on all CMMs except full-face machines and proposed a regulation in 2016 which would require a PDS on other mobile underground equipment. Current PDSs approved for underground use are magnetic-field based. The PDS contains machine-mounted magnetic field generators that create fields around the machine. The other part of the PDS is a miner-wearable component (MWC) that reads the flux density of the generators. These systems use the magnetic field strength readings from the MWC to determine whether a miner is at a safe distance from the machine. A stable magnetic field is essential for the accuracy of the system."

Jan 1, 2018

By T. Faulkner, S. A. Richards

"The Scale-Distance formula is one of the primary means of determining the maximum amount of explosives that can be safely detonated at one time by a single delay. This paper describes a method of applying the Scale-Distance formula to the entire mining area using gridded surfaces. Using this technique, the operator can better determine the economic impact of nearby structures on the mine plan. INTRODUCTION As the surface mining of coal and stone encroaches near populated areas, precautions must be taken to minimize blast vibration damage to protected structures. The common method employed to minimize vibration damage is not to reduce the total amount of explosive in the hole (which would negatively affect fragmentation), but rather to introduce delays to reduce the amount of explosive detonated at any point in time. The Scale-Distance formula, an industry-accepted standard, may be used to calculate the maximum weight of explosive that can be detonated at one time without damaging the structure. This information may then be used to determine the number of delays required for each hole. Detonators make up a large part of the cost of blasting. At roughly $15 per detonator an additional detonator in the hole can be significant. It is normal to set off hundreds of holes at in one shot. An additional detonator in each hole can cost additional thousands of dollars per shot. The number of detonators is also a function of the depth of the holes and the hole spacing. Being able to accurately forecast the economic impact of blasting near structures improves a company’s ability to make informed decisions on how to approach property owners. Operators basically have three options when dealing with property owners: 1. Buy the property and blast without restriction 2. Negotiate with property owner for a waiver to allow unrestricted blasting 3. Comply with the legal blasting restrictions This paper proposes a method for the engineer to forecast for all points in the proposed mining area the impact of nearby structures upon the blast design. Being able to create a contour map and ultimately estimate the number of delays required for the entire forecasted mining area, the engineer can create accurate economic forecasts of the cost of blasting. The objective is to reduce the level of uncertainty in the forecast of the blast component portion of the forecast."

Jan 1, 2016

By J. F. Mack, P. R. Michael, J. M. Shapaka, S. J. Self, M. W. Richmond

"On October 11, 2000, an estimated 306 million gallons of water and coal waste slurry drained from an impoundment in Martin County, eastern Kentucky into an adjacent underground mine. Approximately 230 million gallons of the water and slurry discharged from two underground mine portals and affected over 75 miles of streams in Kentucky and West Virginia. In response to this and several other similar events, the U.S. Office of Surface Mining Reclamation and Enforcement (OSMRE) commissioned an oversight study that evaluates how well state and federal regulatory programs established under the Surface Mining Control and Enforcement Act are ensuring that impoundment operators are minimizing the potential for impoundment-basin breakthroughs. The study focuses on slurry impoundments constructed in the hollows of Appalachia where numerous coal seams and steep topography combine to result in a large number of mined seams intersecting and underlying impounding facilities. Factors under consideration include: (1) full accounting of all mineable coal seams intersecting and underlying the impoundment; (2) identification and accurate location of underground mines close enough to the impoundment to potentially affect its stability; (3) assessment of the stability of coal barriers between the impoundment basin and adjacent mines, and stability of roof rock and pillars in mines subjacent to the structure; (4) determination of the flowability of the impounded slurry when expanding or undermining the facility are being considered; and (5) measures undertaken to reduce breakthrough potential when necessary. The oversight study began in 2012 after program-evaluation criteria were defined in an OSMRE technical position paper. The study is scheduled to be completed in 2017. BACKGROUND The Surface Mining Control and Reclamation Act (SMCRA) authorizes the disposal of coal mine waste by constructing a coarse coal mine waste embankment across a valley and pumping the fine coal mine waste (slurry) into the resulting basin (Figure 1). A concern shared by many engineers, geologists, and mine inspectors familiar with coal mine waste slurry impoundments is related to the common occurrence of underground mine workings adjacent to or beneath the impoundment: the potential for slurry “breakthroughs” into mine works and subsequent breakouts into the surface waterways (Figure 2). On October 11, 2000 a combination of coal refuse slurry and water from the Big Branch impoundment in Martin County, Kentucky broke through into an underground mine and subsequently discharged into the receiving streams. The location of the point of breakthrough, pathways of slurry/water flow within the mine workings, and two points where the liquid exited the mine are shown in Figure 3. An estimated 306 million gallons of water and coal refuse slurry drained from the impoundment into the adjacent underground mine. Approximately 230 million gallons subsequently discharged from the underground mine at two portals."

Jan 1, 2015