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By Tony Szwilski

A correlation between the rank, ash content and coal seam discontinuities and coal strength/stiffness is discussed. Rebound hammers were used to evaluate the strength properties of two coal seams. The coefficient of variability of the rebound tests are compared with those of laboratory compressive strength tests by other investigators.

Jan 1, 1985

By E. J. Haas

DISCLAIMER The findings and conclusions in this paper are those of the authors and do not necessarily represent the views of the National Institute for Occupational Safety and Health. Reference to specific brand names does not imply endorsement by the National Institute for Occupational Safety and Health. ABSTRACT Leadership is a critical component to an organization’s safety culture and influences the ways that health and safety is enacted on site. Therefore, it is not surprising that improving leadership will also improve safety. Worker perceptions of management practices are shaped through unique leader-employee interactions over time. However, few details are known about the communicative support (i.e., emotional, informational, and tangible) offered by supervisors and its impact on miners’ perceptions and performance. Using pre and post-interview data with 20 supervisors and 48 workers during six-week interventions, researchers identified positive and negative instances of supervisor support and its implications on worker performance. This paper highlights the common support tactics offered by supervisors and desired by workers to help practitioners identify ways to improve their safety culture and subsequently, the proactivity and compliance of their workforce. INTRODUCTION Supervisory leadership is a critical component to the effective implementation of an organization’s health and safety management system (HSMS). Specifically, supervisors serve as representatives of an organization and their actions are indicative of the organization’s safety culture (Eisenberger et al. 1986). Senior management has been shown to serve as a frame of reference for guiding safe behaviors in the workplace (Mearns et al. 1998) and, more recently, research has related supervisory enforcement to workers’ safety compliance (Petitta et al., 2017). Therefore, it is not surprising that by improving leadership, perceptions of management and subsequent safety outcomes are likely to improve as well (Zohar, 2002). Perceptions of management are shaped through unique leader-employee interactions over a period of time (Hofmann and Morgeson, 2004, 1999). How these unique interactions impact worker performance, however, remains unexamined. As a result, understanding how supervisor-employee relationships operate in high-risk environments is unclear (Mirza and Isha, 2017; Denis et al., 2010). A starting point to better recognize the idiosyncrasies of these relationships is by way of examining the communicative support offered by front-line management and received by industry workers. To this end, this paper uses pre- and post-interview data to study the communicative aspects of supervisor-employee interactions at mine sites. The analysis uses a social support framework to identify positive and negative instances of supportive communication. From interview data with 20 managers and 48 mineworkers, data emerged that shows how supervisors’ unique types of support contribute to workers’ perceptions, motivation, and follow-through of safe work behavior.

Jan 1, 2019

By Richard Klimpel

A common problem in mineral processing and chemical engineering is the need to estimate flow rates and/or weight ratios involved with engineering operations for which it is inherently difficult to directly measure stream weights. Simple examples of this situation include stream separators (a classifier operating on a particle flow) and stream mixers (the mixing of new feed and circulating load in a ball mill circuit). Often in these types of operations, it is possible to sample the streams involved to get approximate component analyses (e.g. size distributions of solid streams, chemical composition of chemical streams). In this paper various formulae are developed which can be used to estimate stream flow rates or weight ratios given information on the stream components. The type and level of experimental error present in the stream component analyses does have an important bearing on the numerical values (and reliability) of the weight ratios calculated by the various formulae. A simple but theoretically sound method is shown for selecting appropriate estimation formulae for any given engineering operation. The derived formulae are applied to sets of experimental classification data for illustration purposes.

Jan 1, 1979

By Leonard Sugin

As we approach the end-of the 20th century we are made more aware of the tremendous role that energy plays both directly and indirectly in our varied way of life. The industralized nations of the world have already established industries and economies which are greatly dependent upon the availability of energy. The underdeveloped and developing nations of the world are slowly and surely moving to the same utlimate requirements. The world wide need for distribution of energy sources is continuing to grow. At the present time there is a great imbalance between the sources of energy and the consuming economies In order to bring about greater equality between supply and demand major efforts and large capital expenditures are constantly being made. Industralized areas are seeking their own independent sources of energy whereas those areas of the world which contain great reserves of energy are limiting its export as well as developing its own industralized capacity. Nevertheless, energy bearing materials are still transported great distances in order to satiate the appetites of power hungry economies.

Jan 1, 1975

By Kailash Narayan

Atlantic Richfield Company began operating a commercial uranium solution mining project in April, 1975 in Live Oak County, 10 miles southwest of the town of George West (Figure 1). The operation is designed to produce 250,000 pounds of U303 per year and is jointly owned by Atlantic Richfield Company, Dalco and U. S. Steel. The proprietary process employed in this operation consists of injecting an alkaline leaching solution into the ore-bearing formation through a pattern of injection wells. The uranium-bearing solution is then removed through producing wells using submersible pumps in central production wells. The produced solution is pumped through a pipeline to the plant area where the uranium is extracted. The barren solution is refurbished and returned to the pattern area for reinjection. The injection field and plant site are located in the drainage of Spring Creek, a small intermittent stream tributary to the Nueces River. Land use in the area is primarily agricultural -- cattle ranching and farming -- but several producing gas fields are present in the areas as well.

Jan 1, 1976

By R. C. Gilmore, A. Juganda, Jr. Bogin, S. Saki, S. A. Lolon, J. F. Brune, Jr. Zipf, J. W. Grubb

"Methane-air mixtures form explosive gas zones (EGZs) in underground longwall coal mine gob ventilation systems. Such EGZs have caused a number of fatal mine explosions, including the 2010 disaster at the Upper Big Branch mine, where 29 miners lost their lives. Researchers at the Colorado School of Mines use Computational Fluid Dynamics (CFD) modeling to predict EGZ locations. In this paper, a model of a bleeder-ventilated gob system includes two adjacent panels, an active longwall and a mined-out gob. Boundary conditions for the simulations match statutory ventilation conditions for methane concentrations and air flow rates at common measurement points throughout the mine. The modeling results predict the persistence of EGZs in the gob that may compromise the effectiveness of the bleeder ventilation system. INTRODUCTION Mine operators must maintain statutory air flow and air quality requirements at various locations throughout the mine ventilation network. U.S. regulations generally require mine operators to establish bleeder ventilation systems surrounding longwall gob areas (30 CFR §75.334.) Gilmore et al. (2015) documented that explosive gas zones (EGZs) exist within bleeder-ventilated gobs and may extend into the bleeder entries that must be examined weekly, presenting an immediate fire and explosion hazard to mine examiners. In a project funded by the National Institute for Occupational Safety and Health (NIOSH) under contract 200-2009-31409, researchers at Colorado School of Mines have developed a tool for modeling gob air quality using Computational Fluid Dynamics (CFD). This CFD model is capable of examining a wide range of longwall mine ventilation systems. Marts et al. (2014a, 2015) studied progressively sealed gobs with U-type ventilation and using a back return. Saki et al. (2015) examined the impact of gob ventilation boreholes and face air quantity effects on tailgate methane concentrations. Gilmore et al. (2014) modeled bleeder-ventilated gobs and Gilmore et al. (2015) studied the effects of bleeder regulator settings on EGZ volume and locations in the gob. CFD studies for progressively sealed gobs were generally carried out using 5000 ft (1500 m) panels because the gob atmosphere remains largely unchanged from about 500 m (1,500 ft) inby the face. A modular meshing methodology (Gilmore, 2015) permitted researchers to extend bleeder models to 10,000 ft (3050 m) to include the full extent of bleeder entries. This paper further expands the bleeder CFD model to study the gob atmospheres of two adjacent longwall panels, each 10,200 ft (3100 m) in length, with the active face located 6,700 ft (2040 m) from the startup room."

Jan 1, 2016

By T. A. Oberhellmann

The Wobbler Feeder is a comparatively new materials handling and separating device. It is essentially a materials separating or scalping machine, particularly adaptable to separation of oversize particles from mine-run ore and to the separation of oversize materials from overburden, where the removal of oversize materials is necessary, as is the case in conveyor stripping. In construction, the Wobbler Feeder is simply a set of transverse bars of manganese steel, or other wear-resisting alloy steel, each having an elliptical cross-section with the major axes of adjacent bars displaced by ninety degrees so when rotating in unison, the pre-determined space between the bars remains constant.

Jan 1, 1959

By M. T. Ityokumbul

Experiments have been carried out to determine the efficacy of bubble column flocculation. An acid-base neutralization method was used to determine the mixing time in a 0.064 m x l.5 m bubble column equipped with a Mott porous sparger. The mixing times decreased as the tracer injection point approached the gas sparger. Preliminary flocculation experiments on two clay samples were carried out. The effects of frother addition and air flow rate are presented and discussed.

Jan 1, 1998

By F. J. Chernosky

In the past, a number of papers have been written on the use of various reagents as coal flotation frothers. For the most part, these papers have attempted to correlate the intrinsic chemical and physical properties of the reagents or reagent groups to the floatability of various fine coals. Because of the type or nature of evaluations made, chemically pure reagents were normally used. Generally, these reagents are unavailable in commercial quantities. Therefore, the results obtained with these reagents were usually limited in usefulness to the plant operator or metallurgist. This paper presents the results of a study in which commercially available forms of various reagents were used as flotation frothers. Flotation procedures which would conform in general to those employed in a large number of commercial coal flotation plants were utilized. The objective of the test was to compare these reagents on yield-selectivity-cost basis, that is, (1) the yields obtained, (2) the ash levels obtained, and (3) the reagent cost relating to these results.

Jan 1, 1962

By Harland E. Cofer

A computer-assisted resources and sedimentological study of the Andersonville, Georgia kaolin-bauxite district was begun in 1975 under a grant from the Office of Mineral Resources of the U.S. Geological Survey (Grant # 14-08-1110-G-173). A preliminary report on the kaolin and bauxite resources of the district has been placed on open file at the U.S.G.S. in Reston, Virginia; the Georgia-Geological Survey in Atlanta, Georgia; and Georgia Southwestern College in Americus, Georgia. In addition to a resources estimate, the objectives include the determination of the mineralogical variation, sedimentological parameters, and paleogeographic patterns of the deposition of the high alumina materials and their associated sediments. In the process of compiling data for the resources estimate, isopach maps were developed that provide information as to the shape, size, and distribution of the kaolin deposits and the kaolinitic sediments that contain them. These or similar maps developed for other districts can be useful exploration tools.

Jan 1, 1977

By P. Legast

Serpentinite minerals are available in large quantities from asbestos mining activity. The granular or fibrous serpentite, at temperatures greater than 700°C, will recrystalize into olivine, forsterite and enstatite. These minerals have been used and studied for decades and are environmentally safe. The thermal process changes the composition and properties of the original mineral. Therefore, the substitution of the original mineral cannot simply be made and the applications for these new synthetic minerals need to be redeveloped. The two original mineral forms allow a wide range of new synthetic raw materials which can be adjusted to specific applications or custom needs.

Jan 1, 1993

By D. Malhotra

Most primary-molybdenite producers use a selective-flotation process in which molybdenite is floated from the ore while other sulfide and non-sulfide gangue minerals are depressed in the same step (Figure 1). The process was developed at the Climax mill. Reagents used in the rougher-flotation stage include vapor oil (collector), syntex (surfactant), pine oil (frother) and occasionally sodium cyanide and Nokes reagent (depressant). Rougher concentrate is upgraded by cleaner flotation to produce market-grade molybdenite concentrates. Reagents used in the cleaner flotation stage are Dowfroth 250, vapor oil, sodium cyanide and Nokes reagent. The development of the flotation reagent scheme at Climax and the role of the reagents have been well described by Born, et al, (1976) and Malhotra, et al, (1976, 1977a, 1977b, 1977c, 1980). The hydrocarbon collector, vapor oil, accounts for approximately 50 percent of the total molybdenite-flotation reagent cost. Because vapor oil sources are limited, and the cost of vapor oil has increased significantly over the last decade, several studies have been done to evaluate alternate oil-based collectors and/or blends of collectors which would produce similar metallurgical results at a reduced cost, or increase the overall molybdenite recovery at the same cost (Smit and Bhasin, 1983; Hahn, 1969; Smith and Bhappu, 1971). The approach taken in the present study was to evaluate alternate non-oil based collectors and collector systems that are less expensive than vapor oil.

Jan 1, 1985

By R. C. Milici

Historical production data and reserve decline rates can be used both to predict future coal production rates and to estimate when the reserve will be depleted. Reserve estimates inferred herein from historical production data and decline rates are commonly lower than estimates made from geologic data. The latter include significant amounts of lower quality (deeper, thinner, higher sulfur) coal which may be mined when the better deposits are depleted.

Jan 1, 1997

By Miguel Angel Ibarra

This paper describes the results of a digital computer simulation study in which the impact of the proposed truck dispatching on the overall mine productivity was investigated for an operating open pit mine. In the study, the existing operation was first simulated for a one-month period, using both the actual time study data and the computed cycle times. By adjusting certain input parameters to the simulation program, the actual one month production was first duplicated through simulation. Afterwards, the operation was again simulated in a dispatch mode. Comparison of simulation results under the dispatch mode, with the initial base case simulation results, showed a definite improvement in overall productivity with dispatching; i.e., approximately 10% gain for the operation. As expected, the results also showed that the extent of possible improvement did vary with the particular pit configuration being investigated.

Jan 1, 1980

By Frank A. Jerabek

Pneumatic stowing was first introduced in longwall mining in the middle twenties. Since that time it has advanced through many stages of development, particularly abroad, which have greatly improved its efficiency and contributed to its growing use. Pneumatic stowing originated in coal mining but has also been adopted in metal mining. This paper discusses the techniques of pneumatic conveying of. stowing material and equipment and applications of pneumatic stowing.

Jan 1, 1966

By H. E. Grand

The purpose of this paper is to outline briefly some basic principles of ground- water hydrology that have application in mine hydrology. The development of a mine below the water table pleads for accurate values to answers of hydrology problems. Such problems involve both an inflow of water without adequate drainage facilities and a deficiency of water for the required use. Methods which give acceptable quantitative values for the solution of many ground-water problems depend on rather simple geologic structures, characterized chiefly by isotropic rocks of considerable areal extent. Unfortunately, mining operations are likely to be centered where isotropic rocks are not present. Consequently, methods that attempt to show values of the storage and transmitting capacity of rocks in mining areas must be applied with caution. In spite of complex geology and apparent uniqueness of individual mines and quarries, adherence to some concepts of ground water used by -hydrologists in the study of behavior of wells should be helpful to mine operators, The work of the Ground Water Branch of the U.S. Geological Survey through its history has been confined largely to the study of ground water as a resource, In view of the increasing number of problems relating to drainage of mines, the Branch started an investigation of mine hydrology in 1945 under the direction of W.T. Stuart, Mr. Stuart and other workers are making detailed studies of specific mine areas. In the present paper an attempt is made to synthesize some facts about ground water into usable form for the typical mine operator. Mining operations that extend below the water table disturb the natural hydrologic regimen, Prior to development, the water table slopes away from the site of a mine in at least one direction, but as soon as development begins and water is removed from the mine, the mine becomes the apex of a depressed cone in the water table, causing a convergence in the flow of water toward the mine. The behavior of the cone of depression, as it tends to deepen and increase in areal extent when the mine deepens, is related to the rate of withdrawal of water necessary to keep the mine dry. The significance and nature of the cone of depression in the vicinity of pumped wells has been studied by ground-water hydrologists for years, but the cone caused by pumping water from mines has generally been less systematically appraised.

Jan 1, 1958

By Albert H. Fay

The gypsum industry makes significant contribution to the wealth of our nation. This non-metallic mineral ranks in the highest order with America's most precious resources. Evidence of this is borne out by the fact that gypsum is a vitally necessary element in the building, industrial and agricultural industries. In 1967, the United States consumed 14 million tons of this valuable ore. Of .this amount 69% was required by the building industry for the manufacture of building materials. An additional 21% was directed to the industrial market, for the manufacture of Portland Cement and for other industrial uses. The remaining 10% was used for agricultural purposes.

Jan 1, 1969

By Eugene F. Casey

An immersed tube tunnel is one which is composed of elements that are prefabricated in a dry dock or on shipways, usually away from the actual tunnel site, floated into position and then lowered into a preexcavated and graded trench below a body of water. The elements or segments are then connected to each other under water, and the entire immersed tube tunnel covered with a protective blanket. Because water is essential, this method of construction offers advantages in a relatively limited field. By the very nature of the method, lowering elements to the bottom of an underwater trench, immersed tube tunnels are primarily used for crossing bodies of water, such as rivers, bays, straits, canals, etc. Although this method of construction was first used for a subaqueous railway crossing under the Detroit River in 1906-1910 and again in 1912-1915, for a four track subway tunnel under the Harlem River in New York, the reason immersed tube tunnels construction has not been used more extensively is simply a matter of economics. Bridges, compressed air tunnels and similar structures could be constructed at a lower cost.

Jan 1, 1970

By R. R. Beebe

Marcona Corporation produces about 3.5 million long tons of iron ore pellets annually on its two travelling grate pelletizing machines at San Nicolas, Peru. During 1969, these pellets will be shipped to customers in four marketing areas--Japan, the United States, Europe, and South America. All of these sales are on the open market, and product quality is a major concern. Typical chemical, structural, and quality test results for Marcona pellets are given in Table 1. [ ]

Jan 1, 1969

By Devraj Sharma

This paper presents technical issues in the design and management of a retorted oil shale disposal site. Major physical and geochemical mechanisms which affect the disposal are: heat transport, moisture migration, chemical species transport, auto-ignition, and mechanical behavior alterations of the retorted oil shale pile. The interaction of these mechanisms and their relative magnitude will affect the environmental behavior of the pile. The paper discusses the coupling between the mechanisms, presents a framework to quantify the processes by laboratory and field measurements, and in addition discusses the use of mathematical models to provide quantitative predictions.

Jan 1, 1981