Search Documents

By Wen H. Su

Extensive investigation has been conducted to determine the causes of a series of roof falls occurring in a room-and-pillar working located in southern West Virginia. Underground observation, along with laboratory testings and finite element analyses were conducted to search for possible mechanisms for the roof falls. Results of the investigation have led to a better understanding of the mechanisms involved in the roof falls. Necessary modifications of mine layout and roof support plan are proposed for improving safety and profitability at the mine.

Jan 1, 1984

By C. O. Brawner

INTRODUCTION My first major involvement on a rock mine slope stability project was in 1966 after I had become a principal of Golder Brawner & Associates in Vancouver, Canada. I received a request from Kennecott to evaluate two serious rock slope failures adjacent to the concentrator on their British Columbia molybdenum property near Alice Arm, BC, which was under construction. A rock slope up to 200 ft* high had been excavated at a design angle of 700. The inspection indicated that several large blocks of about 1000 cu yd each had failed on steeply inclined joint surfaces. Stability was reduced by extensive seepage caused by heavy rainfall. In addition, considerable overbreak had occurred, indicating excessive blasting had been used to excavate the slope. A program was developed to rock bolt potentially unstable blocks that could slide on dipping discontinuities. Some rock was scaled back to the inclined joints, and drain holes were drilled to reduce water pressures. The project was completed successfully and within reasonable economics. As a result of this success, enquiries were received regarding other mining projects. This indicated the potential demand for rock slope engineering. As a result, I took one month off to meet and discuss rock mechanics and slope stability with various people internationally. These included D. Coates in Canada, E. Hoek in England, K. John and L. Mueller in Germany, M. Rocha in Portugal, and the US Bureau of Mines in Denver, CO. Early misconceptions Based on involvement in projects during the next few years, it was concluded that there were a considerable number of misconceptions that existed among some geologists and mining engineers dealing with surface rock mechanics. Some of these included: • Water is a lubricant. This is incorrect. Water reduces the shear strength along discontinuities due to buoyancy, which reduces frictional strength. It also reduces the cohesion of clayey-type rocks. • The optimum pit slope angle in rock is 45°. The optimum slope angle for safety and economics is variable and is influenced particularly by structural geology, water pressures, mine blasting practices, and the depth and degree of weathering. • The flattest angle for slope stability is dictated by the angle of repose of broken rock, about 370. Where clayey-type rocks or clayey infill in discontinuities exists, failure can occur at much flatter angles, requiring flatter slopes or artificial stabilization. • Uniaxial and triaxial tests provide the necessary shear strength parameters to design rock slopes. Most failures in rock slopes are controlled by directional discontinuities. Therefore, the direct shear test is the correct test to evaluate strength parameters for most problems.

Jan 1, 1987

By E. G. Williams

Underclays and shales are two natural resources associated with the coal measures. Underclays are widely used as the raw material for refractory, semi-refractory, and face bricks. Shales are useful for sewer pipe and lightweight aggregate. This study concentrates on the geologic controls over the properties of shales for use in the manufacture of lightweight aggregate, and the geologic controls over the properties of underclays for use in the manufacture of bloating ladle refractories. The industrial processes are similar in that both involve the trapping of a gas phase to cause bloating. They differ in that the bloating of lightweight aggregate occurs at lower temperatures (1000-1200°C) than ladle bricks (1350°-1470°C). Lightweight aggregate bloats during an initial rapid firing. Ladle bricks are manufactured by slow firing at 1100°C for up to 80 hours. Bloating occurs when these bricks are reheated to 1350°C . Bloating shales are those which expand twice or more times their original volume during fairly rapid firing. Commercial bloating is usually done by rotary kiln processing or sintering; in both cases the firing rate is much faster than the experimental rate (5/8°C/minute). Bloating results from the entrapment of gasses which are evolved during firing. The material must have adequate viscosity to trap gas bubbles throughout the temperature range of bloating. The finished product contains a high percentage of closed pores with a bulk density between 35-75 pounds per cubic foot. Expanded shale finds its most important use as a substitute for heavy concrete aggregate (crushed stone, sand and gravel) where low bulk density is desired property. The extent of bloating in lightweight aggregate is a function of the mineralogy and chemistry of the shale. Figure 1 shows a corner of the three phase diagram, kaolinite-quartz-(illite and chlorite). Several areas on the diagram are outlined which contain predominantly marine shales, fresh and brackish water shales, and underclays. Each sample was rapid fired and the resulting expansion was plotted on the phase diagram.

Jan 1, 1973

By P-M. Dupond, S. Lowrie, C. Tauziéde, Z. Pokryszka, A. D. Jones

A physical model has been developed to simulate the flows and mixing of gases in the waste of a longwall retreat coalface. The model is used in conjunction with computational modelling, and the distributions of permeability and gas emission in the model waste follow those in computer simulations (Pokryszka et al 1996). The physical model represents at 1170th scale a 200 m long, 3 m high coalface with a waste extending up to 280 m to the face start line. The model is tilted to the same seam slopes as the real face, e.g. 22° ascensional ventilation along the face and 7" slope to the dip. The purpose is to investigate the flow of three components: ventilation seepage flow through the waste; methane; and nitrogen injected to quell spontaneous combustion. A heavier-than-air surrogate gas (SF,) is used in place of methane, and therefore the model is inverted so that gas layers form along the 'roof". The main forces driving the flows in the waste (pressure gradients due to ventilation and the density difference of gas layers) are kept in proportion by appropriate scaling of the permeability. Calibration and validation used data from a coalface at a mine in the Lorraine coalfield. The model is now in operational use.

Jan 1, 1997

By Robert J. Timko, R. Lincoln Derick

The Bureau of Mines evaluated the integrity of escapeways in a three entry underground coal mine. A center conveyor belt entry (secondary escapeway), was flanked by an intake (primary escapeway) and a return entry. Diesel equipment was used throughout the mine for material and personnel haulage. A carbon monoxide monitoring system, tied to a data recording computer on the surface, was deployed throughout the belt entry and at selected sites in the intake and return entries. Previously, the company had a fire of unknown origin in another mine, which prompted an interest in the performance of their escapeways. An initial, qua1itative evaluation was performed by burning approximately 14 kg of coal at the mouth of the intake entry. The first test was followed by a similar burn at the mouth of the belt entry. These initial trials showed a high quantity of leakage between entries. In several follow-up evaluations, simulated fires, using a tracer gas, were set in the intake and belt entries. Tracer gas concentrations were obtained in all entries at four different underground locations. The results of these tests showed that permanent stoppings could not guarantee isolated, contaminant-free escapeways.

Jan 1, 1989

By S. G. Malghan

This paper reviews uses of sodium sulfide in the flotation of oxide minerals of copper, lead, and zinc. The activation and depression effects of sodium sulfide are of particular importance because of their applications with oxidized lead and copper ores. In spite of its industrial importance, the nature of the heterogeneous reactions between sulfide ions in solution and the surface of oxidized minerals has not been fully understood. Hence, proposed mechanisms of the sulfide action in flotation, methods of measuring and monitoring sodium sulfide in flotation pulps, and variables influencing the sulfide addition are analyzed. Recent studies on sodium sulfide addition to flotation pulps, monitoring its concentration, and the optimum dosage control using platinum and/or sulfide specific ion electrodes are discussed.

Jan 1, 1987

By Jan W. Oberholzer, Jan J. L. Du Plessis, Gerard Appelman, Andrzej M. Wala

The use of on-board scrubbers on continuous miners is an important aspect in efforts to reduce the amount of dust that heading workers are exposed to. As part of the CSIR:Mining Technology's research programme to combat dust, a collaborative project with the University of Pretoria was conducted to evaluate scrubbers. Based on fundamental parameters that were identified to play a role in determining the efficiency of scrubbers, a protocol for testing scrubbers in the laboratory environment, as well as the working section, was established. Tests on various prototype scrubbers were conducted in the laboratory environment. These tests proved some of the fundamental premises according to which scrubbers were designed. By testing some of the newer scrubber types underground, insight into the effect of alternative design aspects on scrubber efficiencies was obtained. The importance of the factors which play a role in reducing the amount of dust in the air is illustrated, as well as the role which other non-design factors play in the reduction of dust levels.

Jan 1, 1995

By Winthrop F. Watts, Robert W. Waytulonis

During the 1980's. the Mine Safety and Health Administration (MSHA) proposed new regulations for the use of diesel equipment in underground coal mines, and the National Institute for Occupational Safety and Health (NIOSH) recommended that whole diesel exhaust be regarded as "a potential occupational carcinogen", and that reductions in exposure to exhaust pollutants would reduce excess risk. During the same time, the Bureau of Mines tested new emission control technology to minimize diesel emissions. The objectives of this paper are to discuss the major issues regarding diesel exhaust emissions. especially diesel particulate matter (DPM) , and to highlight emission controls that will be available. DPM is a potential health threat because it is respirable in size and is composed of nonvolatile carbon with adsorbed or condensed compounds. These compounds include potentially mutagenic or carcinogenic hydrocarbons such as polynuclear aromatic hydrocarbons and sulfates. DPM contributes to the degradation of air quality in mines with typical mean concentrations ranging from 0.2 to 1.0 mg/m3. In addition to adequate ventilation, control of DPM can be achieved by implemention of improved work practices, regularly scheduled engine maintenance, and emission controls.

Jan 1, 1991

By A. D. S. Gillies

The effectiveness of coal mine face ventilation and the ability of air flow to maintain satisfactory methane and respirable dust levels in the working face area has been studied through the use of scale modeling techniques and underground testing procedures. In particular, consideration has been given to examination of the effects of operation of a high air flow machine mounted dust scrubber unit on face air patterns. Results obtained through a cooperative study with the Peabody Coal Company demonstrate that new mining cycles can be considered which increase production efficiency while maintaining satisfactory ventilation conditions.

Jan 1, 1982

By R. Michael Craig

The flood basalts of the Columbia Plateau in eastern Washington State are under investigation for suitability in siting a deep geologic repository for high-level radioactive waste. To support safety and feasibility evaluations of the proposed repository construction and operation, an assessment is necessary of the potential for inflow of groundwater to the repository excavations from the surrounding saturated rock. Preliminary estimates of inflow are presented using simple models appropriate to the current understanding of available data. Both normal and bounding analyses are presented.

Jan 1, 1986

By L. W. Teal

The Paupers Dream Property is located in the northern Boulder Mountains, southwestern Montana, 30 km southwest of Helena. The property is situated in the central portion of the Butte-Helena gold belt, a NE trending lineament marking a zone of recurrent, late-Cretaceous to mid-Tertiary volcanic activity. Geology consists of a plutonic basement of late-Cretaceous quartz monzonite overlain by a pre-volcanic basal conglomerate and a complex sequence of Oligocene rhyolitic volcanics. Gold mineralization occurs in fracture-controlled quartz veins, silicified stockwork, and brecciated shear zones as auriferous pyrite, arsenopyrite, and disseminated free gold. An estimated 60,000 tonnes averaging 2.5 g/t was produced from the Porphyry Dike, Venus, and Paupers Dream Mines on the property. Current drill indicated reserves (May, 19861 are placed at 6,946,000 tonnes averaging 1.45 g/t gold.

Jan 1, 1987

By R. S. Das, A. K. Sinha

Modern mine ventilation systems have grown rapidly in recent years both in terms of complexity and value for human health and safety. Although computer models are now available to help the design and operation of mine ventilation systems, considerable differences often exist between the computer-based predictions and practical results. Research conducted to compare computer results with practical measurements made in ventilation circuits simulated in a physical model seems to confirm such differences. It is concluded that although a mine ventilation computer model is a very powerful tool, it can be utilized to its full potential only if reliable input data are provided.

Jan 1, 1987

By Lawrence F. Rooney

The wide distribution of limestone and dolomite and the decentralization of the depedent industries give the State Geological Survey a major role in the, development of these mineral resources. The amount of geological information necessary for efficient exploration is so large that few companies can afford to do the necessary basic field work or store the data. The state surveys fill these responsibilities and thus might be said to serve as the geological research departments of the limestone and dolomite industry. At the Indiana Geological Survey, the data of most value to limestone producers are in the form of unpublished measured sections, well records, cores, chemical analyses, directories, and geologic maps. Much of this information is published in summary form. The Survey also assists individual members of industry in exploration and evaluation of mineral deposits. In addition, a progressive State Survey provides the geological infor¬mation necessary for the development of new resources which do not appear to justify industry's own preliminary efforts.

Jan 1, 1966

By David H. Carrillo

HYL has developed a sticking tendency test which accurately predicts behavior of iron oxide feedstocks in the HYL III process. Test results together with pilot plant experimentation and commercial scale demonstrations permit the conclusion that lump ores will not agglomerate at 960°C (1233 K) in an HYL III Plant. Pellets may also be processed without agglomeration at 960°C (1233K) with the addition of no more than 5 percent lump ore. Using the HYL III process, the ironmaker can exploit feedstock market conditions without sacrificing plant productivity or energy efficiency.

Jan 1, 1981

By James W. Griffith, Sarah A. Riling

Bituminous coal dust was repeatedly placed into one lung lobe of anesthetized Macaca nemestrina monkeys using a flexible fiberoptic bronchoscope. Radiographs taken at 15 day intervals showed a focal radiographic density after 90 days time when a total of 1 gram of dust had been instilled. The radiographic density progressed slightly in size until 12 months by which time 3 grams of dust had been instilled and the animals were euthanized. At necropsy, the only significant gross lesion detected was the focal black pulmonary lesion located at the dust instillation site. Histologically, the lesion was composed of coal dust laden macrophages located primarily within interstitial tissue and interspersed with a slight amount of reticulum and connective tissue fibers. The distribution of coal dust was limited to the instillation site in the right caudal lung lobe based on radiographic, gross and histologic examination. Bronchoalveolar lavage of both right and left caudal lung lobes was performed 8 times during the 12 month long experiments without significant complications. More macrophages were found in lavage fluid from the right lung than the left, and most macrophages from right lung contained coal dust particles. Based upon a limited physical examination and complete blood count at 15 day intervals the animals remained normal during the experiment. We conclude that the primate lung's response to focal experimental bituminous coal dust resulted in a marked focal increase in pulmonary alveolar macrophages, which can be recovered regularly in high numbers by bronchoalveolar lavage. The model described has significant potential for investigating the pathogenesis of various respirable dust-induced pneumoconioses, for evaluation of new therapeutic approaches, and for refining experimental and clinical diagnostic applications of bronchoalveolar lavage. Key words: Coal Workers Pneumoconiosis, Disease model; Primate, Lung Lavage Fluids

Jan 1, 1991

By C. V. Deutsch, J. B. Boisvert, M. A. Cuba

The amount of information available for characterizing a deposit increases over time due to the continuous acquisition of data during mining. This additional information is collected from different sources, including geologic mapping, production data and infill drilling. Throughout the lifetime of a mining project, the block model and the mining sequence are periodically updated to account for this new data. In general, the acquisition of additional data increases the accuracy of the block model, reduces uncertainty in ore/waste limits and clarifies the optimal mining sequence. There has been extensive research on mine planning, but current techniques do not consider the decrease in uncertainty as additional information becomes available. Conventional paradigms assume either 1) the kriged model is correct and uncertainty due to multiple realizations does not change the mining sequence, or 2) the mining sequence is unrealistically adapted to each realization. A new paradigm is proposed for evaluating minable reserves of surface mining projects, which accounts for the acquisition of additional information in the design of the long term mine plan. Multiple scenarios characterizing the dynamic nature of mining and data collection are created. In the proposed methodology, the performance of the long-term mine plan depends on both mining and data acquisition strategies. Each scenario considers the same extracted volume for the first period, resulting in a set of scenarios that diverge from a common initial period, accounting for how the mine may develop over time as new data are acquired and provide a more realistic evaluation of reserves with an appropriate level of uncertainty. A synthetic example is presented to illustrate the implementation of the methodology and the benefits over conventional paradigms.

Jan 1, 2013

By J. D. Miller

On the basis of nonequilibrium zeta potential measurements by laser-Doppler electrophoresis, the sign of the surface charge of alkali halides in their saturated brines has been established. The results are generally as expected from simplified lattice ion hydration theory. This recent electrokinetic information coupled with the stability and prevalence of collector colloids in such soluble-salt flotation systems suggests that the selective flotation of alkali halides is due to the adsorption of oppositely charged collector colloids by heterocoagulation. Experimental flotation results confirm this surface-charge/collector-colloid adsorption model and are presented herein.

Jan 1, 1992

By James Wm. White

Mine management now recognizes the value of computer-based truck-shovel dispatching in open pit mines. The key tangible benefits are substantial productivity increases with a given fleet of equipment or, alternately, significant reductions in equipment required to meet production quotas. In this work, we review the literature, report on efficient, optimal algorithms for haul truck dispatching in real-time, and briefly discuss methods used by various mines to evaluate productivity improvements over manual methods. We also present actual results obtained at thirteen mining operations around the world.

Jan 1, 1992

By R. V. Ramani, J. Qin

During the mining process, the in-situ material is broken into different size ranges, from very large pieces to very fine particles. Some of the fine particles become airborne. In underground coal mining, airborne respirable dust is associated with health and safety of the miners. The amount and size distributions of airborne dust are important parameters to effective dust control measures. The design of underground mine experiments, including sampling procedures and sample analyses methods to determine these parameters are presented in this paper. A total of fifteen continuous miner cuts were sampled. The amount of dust generated during the cutting process and the relationship between total and respirable airborne dust concentrations and amounts are examined. The amount of respirable dust airborne is on the average only 0.016% of the respirable dust generated. On the average, 61% of the total airborne dust measured is in the respirable size range. The amount of respirable airborne is on the average 36% of the respirable size fraction in the total airborne dust. For equal proportion of rock and coal material cut, rock contributes about twice as much fines (=0.22 mm) as coal. Additional fundamental research is necessary to further the understanding of the airborne propensity of respirable dusts in mine atmospheres.

Jan 1, 1989

By P. Mousset-Jones, G. Danko

Rock thermophysical properties, i.e. heat conductivity and thermal diffusivity, were obtained for reference values at the Waldo Test Mine for mine fire simulation purposes. An in situ measurement method was chosen since it could include the effect of rock fractures. The REKA method (Rapid Evaluation of k and alpha) was used because it can measure conductivity (k) and diffusivity (alpha) simultaneously within an eight-hour measurement period. A total of six measurements were taken in three different holes, and at two different depths from the collar of the hole. Each measurement provided an averaged conductivity and diffusivity for a volume of rock of approximately one cubic meter. The boreholes were driven into the upper and lower limestone, two at right angles to and one parallel to, the stratification of the rock. Significant representative conductivity and diffusivity values were obtained for the whole mine by averaging the six measurement results. The thermal properties for the band of shale in between the two limestones were not measured in situ, but only in the laboratory. Problems were encountered in the evaluation because of unexpected heat conduction on one side of the symmetrically built probe. A modification was made to the previously developed evaluation method together with further testing and correction, before the final results were obtained. As expected, the in situ and lab- oratory measured values of k and alpha compared favorably, since the in situ rock was dry and relatively unstressed.

Jan 1, 1989