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By Normand Tassé

Reactive barriers, which consume oxygen, are prospective though unconventional alternatives to physical barriers for Acid Mine Drainage prevention. However, a reactive barrier implies a problem of duration. Pore gases were analysed in several wood waste piles in order to understand the factors which control wood degradation and help to determine the effective life span of such a cover. Long term efficiency seems to strongly depend on the degree of water saturation at the bottom of the pile, likely because the development of a microbial biomass in such an environment helps to keep the amounts of nutriments and readily metabolizable organic substrates at a high level, which in turn promotes oxygen consumption.

Jan 1, 2000

By S. S. Peng, V. Z. Sun

One of the major concerns of ground control in a coal mine is the prevention of roof, pillar and floor failures of the mine entry. To better design and evaluate the stability of a mine entry within a certain level of confidence, a reliability approach is introduced. The advantage of using the reliability approach, rather than the conventional safety-factor (SF) method, is that it not only takes variability of both rock/coal properties and stress into consideration but also assesses the stability of each component and the mine entry as a whole. Therefore, it is anticipated that by using this approach the current ground-control technology in a coal mine will convey a better sense of confidence. The results of a case study show that there is a significant difference in mine entry stability between the current design method and the reliability approach.

Jan 1, 1999

By David J. Hammel

This chapter will summarize some of the important applications in the geotechnical (pit slope, spoil pile and tailings stability, and hydrology), the environmental (including reclamation), and equipment selection and analysis areas. Virtually all aspects discussed are applicable both for planning of new mines and for evaluating existing operations. Probably the most influential item which has affected the areas discussed in this chapter and possibly most areas discussed in this book is and will continue to be, in the next decade, the myriad federal and state environmental, safety, and reclamation regulations affecting new mine development and continued operation of existing properties. Computer applications have been and will continue to be instrumental in assisting in planning to meet the challenges of the requirements dictated by these regulations.

Jan 1, 1979

On longwall coal faces in some Japanese coal mines more than half of the air coming from the intake gate road flows into the caved goaf and the air heated by the hot waste rocks in the goaf comes out through the latter half of the face. This still constitutes a major heat problem in spite of the introduction of gate and face air coolers. Therefore, in order to establish effective measures to improve the environ- mental conditions, it is essential to obtain information pertaining to the air flow pattern on the face as affected by the goaf conditions and the air flow regulating measures taken at the intake side of the face. Experiments for this purpose were carried out using a coal face model. The model was reduced to a scale of 1110th of the real face measuring 100 m long and 2.2 m high, equipped with self-advancing supports. The model design was also conceived to accomodate eventual modifications of the space of the caved goaf as imposed by the actual conditions.

Jan 1, 1980

By Steve Garcia

GEORGE WEINMAN: Our next speaker is Steve Garcia, operations vice president and general manager of mining at IMC-Agrico, Florida. Steve was born in Lakeland, Florida, to an IMC mining family. He has 17 years with IMC-Agrico and Freeport companies, including assignments in North Carolina, Nevada, Arkansas, and Indonesia. His work within the industry includes technical and operating positions including chief metallurgist, drying superintendent, and mines operations manager at Pane Creek. Other experiences include design of a grassroots phosphate facility in North Carolina; construction and start-up of a gold facility near Elko, Nevada; work in the Blytheville, Arkansas, ammonia urea facility; and three years managing engineering, construction, and support services in Irian Jaya, Indonesia. Steve's presentation is "Evaluation and Standardization of Multiple Slurry Pumping Systems."

Jan 1, 1998

By M. Karmis

The algorithms for the mathematical modeling to predict productivity of underground room-and-pillar mining systems are well known and documented. These algorithms consider the time-varying relationships between mining equipment for a given geometty of operations as well as other constraints. This paper presents WebConSim, a newly developed, Web-based, user-friendly computer simulation tool for the Windows environment. The simulator is easily customized for use by field engineers, planning engineers and management and will help mine operators plan the optimum mining sequence for different mine geometrie and equipment layouts. Program output includes production data and equipment utilization indices, as well as time driven event chains that can be used for virtual reality presentations.

Jan 1, 2002

By S. R. S. Sastri, D. K. Senguta, S. K. Bhaumik, G. V. Rao

The amenability of a calcite-bearing ore to the reduction of silica to below 0.2% by physical beneficiation was studied. The objective was to use the ore as a raw material for seawater magnesia production. The ore contains complex gangue minerals such as diopside, forsterite, phlogopite, clinohumite, graphite and quartz. These contribute to around 25% acid insolubles with 6% SiO2. Reverse-flotation studies using various cationic collectors with tannin as a depressant indicated the possibility of reducing the acid insolubles to around 5%. Direct flotation of calcite with anionic sodium oleate in the presence of sodium silicate and lactic acid as a depressant indicated the possibility of reducing the acid insolubles to below 3% and the SiO2 to from 0.2% to 0.3%. Lactic acid was found to be an effective depressant of the complex gangue minerals in the ore.

Jan 1, 2000

By Y. M. Jiang, D. W. Park, S. M. Lee

A vast majority of longwall operations in the US use shield-type hydraulic supports to provide ground control along the longwall face. The three-dimensional, finite-element technique combined with a progressive failure approach was utilized to simulate interaction between shields and surrounding strata and determine various loading conditions. In addition, a separate finite-element model of the shield structure was made to study responses of each longwall shield to the different loading conditions. Shield responses under various loading conditions and the shield characteristics, such as shield stiffness, the ability of resisting horizontal forces, and the effect of shield height, were studied based on the results from finite-element analyses. The results can provide the basis of effective shield design and be used for evaluation of the shield performance. It is suggested that a technique incorporating the finite-element method be developed to evaluate real-time shield performance for the purpose of effective ground control.

Jan 1, 1993

By Kathleen S. Smith, Katherine Walton-Day, James F. Ranville

Four different scales of observation were used to evaluate the potential effects of a fluvial tailings deposit on water quality along the flood plain of the upper Arkansas River south of Leadville, Colorado. First, we collected surficial material and subjected it to batch water-leaching test. Second, we excavated and leached an intact eight-inch diameter core. Third, we examined the water quality of the shallow ground water beneath the fluvial tailings deposit, and fourth, we monitored water quality along a 5-km reach of the adjacent Arkansas River. Leaching of surficial samples indicates that there is a reservoir of readily water-soluble material yielding elevated metal concentrations and high acidity. However, there are minimal measurable water quality effects of the fluvial tailings deposit on the adjacent reach of the Arkansas River.

Jan 1, 2000

By D. W. Fuerstenau, G. S. Sudhir, P. C. Kapur

Quartz-limestone feed mixtures were ground in a laboratory-size, choke-fed, high- pressure roll mill. As compared to individually ground minerals, the harder component (quartz) in the product mixture is coarser, and the softer component (limestone) is finer. An energy split index is introduced for quantifying the disproportionate split of the mill energy between the feed constituents. This index is incorporated into a grinding kinetic model for simulation of the product size distributions of the mineral components as a function of energy input to the mill. The self-similar character of the size distributions is analyzed and an energy-size reduction relationship for the roll mill is highlighted.

Jan 1, 1992

By F. F. Aplan

Estimations have been made of the tonnage of raw ores and coal treated by various beneficiation processes. The amount treated by gravity concentration is substantially greater than that treated by flotation, with coal representing the bulk of the material treated by gravity means. A discussion is given of the trends and anticipated improvements in gravity methods. Except for the concentration of iron ores, magnetic and elec- trostatic separation processes find their greatest use in the beneficiation of non-sulfide ores. Exciting new developments in magnetic materials and separation process (and, to a lesser extent, in the electrostatic process) indicate a substantial increase in the application of such processes to ores and a broad variety of non-ore uses.

Jan 1, 1989

By K. N. Han

The kinetics of gold dissolution in iodide solutions with oxygen in an autoclave was investigated. The leaching process was described by a gas-liquid-solid heterogeneous reaction. The effects of stirring speed, temperature, oxygen partial pressure and lixiviant, concentrations on the overall leaching rate was investigated. It was found that the dissolution of gold could be represented by a heterogeneous chemical reaction. Under the conditions studied, the apparent activation energy ranged from 34.7 to 54.3 kJ/mol. Experimental findings were in good agreement with the kinetic model proposed.

Jan 1, 1998

By Gary Schaffer, Anthony Stentz

Surveying of mines is a necessary step in coal mining to assemble maps which are used for tracking progress in the development of the mine and to plan future coal removal. A first approach for automatically building high-resolution two-dimensioml maps of underground coal mines is presented. The technique assembles laser rangefinder scans obtained from several locations within the mine into a consistent global map of the mine. Each range scan comprises thousands of data points collected in one second, thereby achieving higher resolution and much faster measurement compared to a human using a transit. The raw data (range scans) are processed to fuse them into a consistent representation. This paper describes a first approach to automated surveying and presents initial results of merging range scans. Improvements to the scan-merging algorithm are proposed.

Jan 1, 1993

By Robert W. Bartlett

Pretreatment of sulfidic refractory gold ore by biooxidation in coarse-crushed ore heaps is a promising new technology, especially for low-grade ores that cannot afford pressure leaching or roasting. An algebraic equation for determining the economically optimum biooxidation of the sulfide minerals in the ore is provided that is based on the empirical biooxidation rate constant for the ore, the project's financial discount rate, the ore grades of both refractory and non-refractory gold, and the gold price. Then, the economically optimum duration of bioheap pretreatment, t$, is determined from its logarithmic relation to the optimum fractional extent of ore biooxidation, F$, through the ore's biooxidation rate constant. In doing so, it is assumed that the ore is adequately crushed and amenable to bioheap pretreatment and that the cumulative oxidation of the ore with time is known from ore testing so that the rate constant can be determined.

Jan 1, 1995

Liebherr Mining Equipment Co., of Newport News, VA and Baxter Springs, KS, introduced the T282, a new two-axle, diesel-electric, AC drive haul truck with a payload capacity of 327-t (360-st). The T282 was unveiled at a press briefing in October 1998 at the company's Baxter Springs research and development1 manufacturing facility. In addition to an increase in pay- load capacity, the truck's AC drive system has been de- signed to allow for easy configuration to a trolley-assist system with minimal additional equipment. The T282 provides fuel savings, reduced maintenance requirements, and reduced downtime and maintenance costs, providing the mine operator with increases in productivity. Basic dimensions and weight of the T282 are: ? Overall length, 14.5 m (47.5 ft). ? Overall width, 8.7 m (28.7 ft). ? Loading height, 6.5 m (21.2 ft). ? Height - body up, 13.9 m (45.9 ft). ? Empty vehicle weight, 201 t (221 st). ? Operating weight - loaded, 528.6 t (582.6 st). ?Engine, Detroit Diesel 16V4000 at 2 MW (2,750 hp). ?Electric drive system, Siemens/Liebherr.

Jan 1, 1999

The application of Kirchoff's laws to two adjoining mine ventilation network meshes containing fans results in the construction of two general quadratic equations. These equations may be solved to give the resultant airflows and hence fan duties within the system for given network parameters and fan characteristics. This technique has a wide application for calculating the duties of fans in various combinations within a mine ventilation system. Recent difficulties in economically maintaining environ- mentally safe conditions in underground working areas distant from main ventilation fans has led to increasing interest in the use of controlled partial recirculation of ventilation. This paper develops a recirculation model which can be solved directly using mathematical techniques obviating the need for iterative techniques such as the Hardy-Cross method. The advantage of a direct mathematical analysis is that mathematical algorithms may be constructed to completely describe the ventilation system under a wide range of operating conditions. This technique is applied to controlled partial recirculation ventilation systems to demonstrate its advantages for mine ventilation planning.

Jan 1, 1989

By Frank F. Aplan, Robert S. Thomson

A placer ore jig, typically used to recover fine gold, tin and diamonds from alluvial ores, has been modified to remove fine pyrite from minus 6.4 mm (-114 inch) coal. In parallel tests, it proved to be far superior to two conventional coal jigs, the Baum and the Baum-feldspar, in removing fine pyrite from coal. The Pan-Am placer jig was found to remove essentially all of the +28 mesh pyrite and from 99% to 90%, decreasingly, in the 28 to 200 mesh range. This jig also showed a superior performance to the Baum-Type jigs in removing fine coal from its associated refuse. The superiority of the Pan-Am placer jig is related to the strong emphasis given on the suction stroke and, hence, on consolidation trickling, whereas the Baum jigs principally emphasize the pulsion stroke during jigging.

Jan 1, 1995

By J. Derwin King, Harrison R. Cooper

Applications of nuclear magnetic resonance (NMR) offer possibilities for on-line sensing of the concentrations of several elements in flowing sample streams. In addition to hydrogen, these elements, generally of low-order atomic number, include aluminum, phosphorus, fluorine, sodium, boron, and lithium contained in minerals having commercial importance. Many such elements have been difficult or impossible to successfully measure on-line using the more familiar X-ray fluorescence and neutron activation analysis techniques. The availability of practical on-stream analysis methods is essential to applying advanced controls to processes incorporating these elements. On-stream NMR instrumentation has been demonstrated in the past for several process applications including, as an example, coal flow and analysis; and the technology has recently been extended to the measurement of phosphorous BPL in Florida beneficiation plants. The technique involves simultaneous sensing of proton (hydrogen) and 31P intensities to provide data for continuous calculation of BPL in the phosphate through calibration to volume fractions of water and solids. Initial operating results are described using the PhospholyzerTM on-stream phosphorous analyzer designed for plant application.

Jan 1, 1990

By R. W. Hutson

One of the fundamental precepts of experimentation is the isolation of a single variable to quantify its individual effect. Unfortunately, the variability of natural rock joints has frustrated such isolation. This variability and the high cost of securing a large member of natural joints has lead to increasing experimental dependence on stage shearing, artificial tension fractures and/or model materials. The new apparatus described herein allows for the first time replication of real joints with field scale asperities. It employs a diamond band-saw blade with computer controlled feed table to cut joints with high precision. The feed system is capable of placement to tolerances similar to those of a high quality computer plotter. The accompanying software allows the table to cut any desired joint shape (repeating or non-repeating) within certain, over-all size limitations. Resulting joint surface dimensions and roughness as well as shear resistance indicates that the joint surfaces are reproduced with a precision similar to that possible for the control of other experimental variables such as normal and shear forces.

Jan 1, 1986

By Dwayne K. Rowlett

A lysimeter designed to measure suction and collect a pore water sample from unsaturated waste rock has been developed and its performance has been verified in two large scale column tests. The test columns were constructed to bracket the envelope of grainsize curves for waste rock from Northern Saskatchewan. The suction profile within the columns was measured under a series of infiltration rates using tensiometers and these were compared to the lysimeter readings. The rate at which pore water samples could be collected was also measured under each infiltration rate. Lysimeter measurements of suction were found to be slightly lower than the tensiometers.

Jan 1, 2000