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By S. K. Sharma

The Bureau of Mines' rapid method of dewatering fine-particulate slurries uses extremely high molecular weight polymers. These polymers form large, strong flocs which can be dewatered by sieving or sedimentation. However, sometimes these flocs deteriorate rapidly if water is not removed immediately. During field tests, clay slurries have been encountered that could have been dewatered economically if it were not for the rapid floc deterioration. A kinetics study was conducted to determine the rate of kaolin-PED floc degradation in which polymer addition, to bring the flocs back to their original condition, was used to determine the extent of floc decay. Results showed that the amount of polymer added, to replace polymer lost by spreading, was less for the lower PEO concentrations. For this clay-polymer system, floc breakage as judged by polymer additions followed first order kinetics. It was also found that the addition of fluoride ion stabilized the kaolin flocs.

Jan 1, 1992

By Thomas Camus

"STATE OF THE ART The current situation of ground prediction in TBM is of great concern for tunnelling contractors, and the subject has been quite widely addressed over recent years, for instance by the French Eupalinos 2000 programme, which tested a variety of technological approaches. A number of interesting projects were executed, such as the SOUND and OnSITE projects, part of the German Geotechnologien programme: these projects are focused on seismics, while other techniques such as radar are not considered. Little information and even less industrial applications have been released apart from lab simulations and numerical modelling. A number of field tests in different configurations have been carried out for compression waves, but the results were often not reliable or convincing, and therefore little has been reported in open literature. The advances seem somewhat promising as far as hard rock tunnels are concerned, but ignore the problem raised by concrete lined tunnels such as those bored by a TBM in soft ground. In such tunnels, sending and receiving seismic waves reliably through the lining (and the grouting behind) is quite illusory. A careful analysis of the seismic prediction research results show that the main problem is the source which is poorly controlled and poorly coupled (for instance in concrete lined tunnels, or in approaches that use the TBM cutter head vibrations as a source). Generating waves perpendicular to the tunnel axis is also a problem: aligning with the tunnel axis makes more sense. Radar (Ground Penetrating Radar - GPR) has been used in geotechnical surveys for decades, and also for tunnel inspection. Attempts have been made at using it on a TBM (for example in Japan by Taisei) but mainly using off-the-shelf GPRs, which are not adapted to work in the specific environment of a TBM (because of its huge mass of metal, to start with). Very few results have been published, probably due to the somewhat disappointing performance of such implementations. At present, no TBM has a GPR incorporated in its cutter head that is able to predict ground characteristics while drilling. Another characteristic and drawback of most current methods is that they require dedicated periods of time during which other tunnel construction activities must be stopped. Due to the duration of such operations this leads to performing ground prediction on a weekly basis only, and therefore to a requirement for an investigation range of 100 metres approximately (in order to cover the TBM advance over the coming week). This is not achievable with boreholes made from the TBM, even less if a reasonable accuracy is required, as is usually the case."

Jan 1, 2016

By Kent S. Roessler

The Bureau of Mines is currently investigating the geophysical application of Tomography to monitor leachate during in-situ mining. Determining the location of the leachate is important for both economic and environmental reasons. By analyzing a sequence of tomographic images, we can determine where highly permeable/fractured regions are located and hence, major flow paths. Since BOMTOM (Bureau Of Mines TOMography - Tomographic Reconstruction Program), and BOMCRATR (Bureau Of Mines Curved RAy Tomography - Tomographic Reconstruction Program) are sensitive to user-selected ray path arrival times, we are also investigating the use of neural networks to automate the process of recognizing this feature. This paper presents a technique for detecting fracture zones and their orientations in a region between two boreholes, by using a motion analysis study of a sequence of tomographic images. It also addresses the need for an automated/unbiased method to pick crosshole seismic arrival times using a trained neural network. In exploration geophysics, the picking of first break arrivals represents a pattern recognition task. The neural net paradigm has proved to be a good method of solving this type of task. To pick the first arrival peak of a trace, the network is trained with a set of known (user selected) first arrival peaks by creating a binary image of a set of traces. Once trained, the neural net correctly picked first arrivals of the remaining traces in the set.

Jan 1, 1992

By R. L. Wiegel

Several mineral process modeling and simulation packages are currently available for use in evaluating the performance of alternative process flow schemes. A critical link that has been missing from these packages is the ability to quantitatively model the effect of size reduction on the liberation of the valuable and waste minerals in the ore being processed. Although there have been several approaches taken to this problem over the past 25 years, none of them has led to a satisfactory conclusion. A technique was developed for measuring the effective liberation characteristics of magnetic taconite ores, and a program was constructed that makes use of these liberation characteristics in simultaneously simulating both size reduction and mineral liberation as it occurs in tumbling mills. This is an especially important step in the modeling of magnetic taconite processes, where magnetic rejection of low-grade wastes between grinding stages mandates that a predictive capability be available. The current application is specific to magnetic taconite, but it is possible that a similar approach could be used for other types of mineral systems. Key words: Modeling and simulation, Size reduction, Mineral liberation, Taconite, Magnetic concentrator

Jan 1, 2003

By L. G. Austin

Using an instrumented laboratory high-pressure grinding rolls mill, the grinding force, gap dimension, mass flow rate and net mill power were measured for six coals and a crystalline quartz. A technique was developed to estimate the compressive stress-strain curves for compression of the materials in the mill plus the effects of elastic decompression. To reconcile the mill power and grinding pressure results, it was necessary to allow for the energy recovery on decompression. No clear correlation was obtained between the form of the stress-strain curves or the variation of specific mill power factor with the Hardgrove grindability index (HGI), although coals with the lowest and highest HGIs (i.e., 44 and 106) gave results significantly different from the other coals. Feeds below 140 mesh (105 µm) flowed more rapidly than coarser feeds and would not build up high grinding pressures. This indicated shearing and fluidlike properties rather than compression as a locked bed.

Jan 1, 1998

By Fred D. Wright

In this paper the principal theories used to design roof bolting systems are presented and discussed. Then the characteristics of various types of roof bolts are presented and finally the interaction between rock and roof bolt characteristics on choice of roof bolts is discussed. Theories can be considered design tools which may or may not be appropriate for a specific situation. It is good for a design engineer to have a number of such tools available and also important that he understand their good features as well as their limitations. Hence, some of the principal theories and classification systems used for design of roof bolting systems are discussed first.

Jan 1, 1982

By K. Fotoohi

This paper presents a basic, and yet practical, three-dimensional finite element model that was developed by the authors for stress/stability analysis of mine structures. While the code is linear elastic at this stage, it has some practical features that make it an attractive tool for mine design. Such features include: simulation of mine backfill support, mining induced strain energy calculation, powerful out-of-core frontal solver and failure analysis by Mohr-Coulomb or Hoek-Brown failure criteria. Model development criteria are discussed, and the potential application of the model to mining is demonstrated by design examples.

Jan 1, 1998

By C. E. Capes

Reduction in the quality of resources and attendant increase in the quantities of fines to be processed present a major economic and environmental challenge for resource - based industries. It is becoming evident that agglomeration by immiscible liquid wetting will play a significant role in the treatment of these fines. Liquid phase agglomeration can be adapted to separate solids or liquids in highly divided form from liquid suspensions and emulsions. Diverse opportunities in coal fines recovery, novel fuels technologies and oily waste water treatment are cited here. The oil agglomeration of extreme fines from coal tailings, with consequent dramatic reduction in refuse for disposal, is now a commercial reality. It is suggested that this approach can serve as a prototype for the processing of extreme fines in an economical and environment ally sound manner.

Jan 1, 1989

By L. G. Austin

The use of crushed power station slags, both natural and coated, as granules for roof shingles shows some promise. Test shingles weathered for some years showed rust spotting and granule deterioration as serious problems. Chemical analysis on a particle-by-particle basis using a scanning electron microscope-energy dispersive spectroscopy system showed the wide variability of chemical composition of the granules within a given sample. Analysis of particles acting as sources of spotting within the weathered samples showed high iron contents but no rules could he developed for predicting the long-term stability of different compositions.

Jan 1, 1990

By Jacob Petersen, Jon J. Kellar, Samuel Kessinger, Kiran Green

 The paper demonstrates that Belle Fourche Shale (BFS), an abundant shale, can be transformed into a ceramic through careful characterization and thermal processing. The study explores the potential of BFS ceramics for use as refractories and thermal energy-storage devices, highlighting their high thermal storage capacity, good thermal shock resistance, and cost-effectiveness.

Dec 1, 2023

The ventilation of a mine is one of the key elements to a successful mining operation. It is, or should be, one of the primary concerns of the mining engineer at an underground mine. Too frequently, however, insufficient thought is given to future requirements. As a result, the mines suddenly find themselves with ventilation problems that cannot be corrected economically, or in short order, and have to suffer the consequences of being on the verge of having units shut down from time to time until the venlilaltion system can be improved. Insufficient ventilation in capital-intensive mining can cause production losses, the values of which far outweigh the significant costs of providing and operating an adequate ventilation plan. Many theories, and techniques in planning and control of underground ventilation systems have been developed over the years . It is the intent of this paper to point out some of the fundamental concepts, from the practical point of view, in the design and operation of a ventilation system, with special reference to underground mines using a room-and-pillar method.

Jan 1, 1986

By J. G. Groppo, D. J. Sung, B. K. Parekh

Hyperbaric filtration for the dewatering of fine coal cleaned by froth flotation was evaluated on a laboratory scale. A laboratory pressure filtration procedure designed to obtain a uniform cake structure from dilute slurries containing a significant amount of coarse material is described. Baseline tests were conducted to determine the optimum operating conditions for the eventual application of the process to a continuous pilot-scale hyperbaric filter. Investigated were filter operating parameters such as driving force, time, cake thickness, percent solids, viscosity and pH.

Jan 1, 1996

By S. A. Matthews, M. L. Nave

AC variable frequency motor drives are emerging technology for belt conveyors. The success of the application in mining depends on adequate and timely consideration of drive, motor, and conveyor features. The purpose of this paper is to familiarize and inform possible mining users of AC variable frequency drive attributes.

Jan 1, 1998

By K. V. K. Prasad

Stochastic simulation has been routinely used for performing risk and sensitivity analyses in a variety of fields. The commonly used means of generating the simulations has been the Monte Carlo approach, which usually employs a Simple Random Sampling (SRS) scheme of the variable distributions. This method is prone to sample clustering and requires a large number of samples to represent the distribution faithfully. This can become problematic for simulating complex processes where it is impossible to run an arbitrarily large number of replicate simulations. The Latin Hypercube Sampling (LHS) method uses a stratified sampling approach that assures representation of the input distributions for any given number of samples. In this paper the LHS and SRS approaches are compared, using a petroleum resource estimation example.

Jan 1, 1994

By Bo Forsman

The computer program SYGRISIS estimates number of units of equipment and operating costs on the basis of yearly production for different loading (wheel loader, LHD, digging arm loader) and transport (truck, train, conveyor belt, hoist, pump) equipment either individually or in any specified combination. Input data are yearly capacity, working time and technical data for the equipment. For the cost analysis input data are technical quantities and unit costs. SYGRISIS is written in TURBO Pascal and can be used on IBM compatible PCs with MS-DOS operating system.

Jan 1, 1989

By John Nadolski

Intensive hydrologic monitoring of the Powder river basin has been on-going since the early 1970's. Data were used in environ- mental assessments and for determination of hydrologic consequences associated with coal mining activities. For most coal mine operators, data collection has continued in this baseline mode with little or no statistical analysis of the data and with no statistical procedure established to detect changes in groundwater quality. For the past four years Powder River Coal Company has studied several statistical techniques to analyze groundwater quality. Three objectives were pursued: 1) to determine the baseline water quality for key aquifers; 2) to determine which wells could be deleted from the monitoring program without reducing monitoring effectiveness; and 3) to define a statistical test to determine water quality changes. Knowledge of the regional geo-hydrologic system was combined with an analysis of the water quality monitoring in order to identify homogeneous aquifer zones. All wells within an aquifer zone were treated as one population, and a t-test was used to determine the minimum number of samples needed to define the water quality for each aquifer zone. Results indicate that the data for each aquifer zone were nor- mally distributed and that groundwater quality could be defined using a fairly small number of samples. Because of the minimum sample size test, groundwater quality sampling was reduced by between 75 and 85 percent.

Jan 1, 1989

By A. I. Kalugin, A. A. Abramov, D. E. Kozlov

As a result of thermodynamic analysis of a mineral-sodium, oleate-water system, flotation and adsorption tests at various pH values, and sodium oleate concentrations, it has been established that due to regularities of phosphate-containing minerals (fluorapatite, hydroxyapatite, carbonatapatite) flotation cannot be explained by the formation of alkali-earth metal oleates on their surface. This paper presents a novel theory that connects optimal conditions for mineral flotation with zero charge of its surface, which can explain the regularity of minerals flotation observed. The quantitative physicochemical flotation models developed based on the theory are suitable for improving industrial processes, conditioning of recycling waters, and application in automatic control systems at the plants. Key words: apatite, oleate, flotation, modeling, control, and regulation.

Jan 1, 1999

By G. Granger, D. Malhotra

The paper briefly reviews the criteria employed in the selection of chemical reagents for testing and discusses the steps involved in laboratory and plant evaluation of these reagents. An example of successful implementation of reagent change in the plant is illustrated.

Jan 1, 1986

By J. D. Miller, D. M. Catarious, F. L. Stanley

The quality of cleaned products from coal preparation plants is often variable due to natural fluctuations in the washability characteristics of the plant feed. To combat this problem, many modern plants have installed on-line analyzers that provide feedback for the real-time control of product quality via the adjustment of circuit cutpoints. Unfortunately, optimization studies show that this approach may actually lead to increased losses of saleable coal. This paper discusses the problems associated with the real-time manipulation of circuit cutpoints and suggests alternative modes of operation that are better suited for plant optimization. A case study involving an eastern U.S. coal plant has been used to compare the economic impacts of these different approaches for plantwide control.

Jan 1, 2000

By T. Y. Yan

An effective elution technique has been developed for recovering uranium from ion exchange resins loaded in the carbonate leaching process. The procedure employs direct elution with acid. In comparison with conventional base elution, the procedure yields eluate of higher uranium concentration, results in a more complete elution, keeps the performance of the ion exchange resin at the fresh stage, reduces acid consumption, eliminates carbonate consumption, and reduces waste for disposal. The technique has been successfully demonstrated in the field and patented. It lends itself to commercialization.

Jan 1, 1987