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By N. Cruickshank

Gas outbursts occur as sudden eruptions of gas and minerals from the face of a mine heading as the heading approaches potentially burst-prone (or anomalous) zones of rock. Such outbursts have resulted in considerable damage to equipment and in some cases lives have been lost. Characterizing these anomalous zones and detecting their presence is therefore vital to safe mining. Certain significant characteristics associated with the outburst-prone zones are: (1) the presence of fluid inclusions, (2) unstable stress conditions, (3) characteristic geologic structures, (4) certain physical properties of the rock, and (5) micro-seismic activity. Geophysical and engineering methods for detecting these characterisitcs are discussed and are considered with respect to their past success and future potential for predicting gas outbursts.

Jan 1, 1985

By Paul H. Lu

This Bureau of Mines report summarizes the analysis and eveluation of the field measurement results of a comprehensive ground control study conducted in a mechanized longwall coal mine in West Virginia. Emphasis is placed on the three basic ground control parameters: ground pressure, ground movement, and geomechanical properties. Specific topics include premining ground pressures, front-abutment pressure in the longwall panel, histories of pillar loading, differential roof-strata movement and bed separation, differential floor strata movement, entry roof-to-floor convergence, in situ moduli of rigidity of coal seam and roof and floor strata, and mechanical properties of coal and coal measures rocks.

Jan 1, 1985

By L. Adler

When systematically compared to other engineering fields, mining engineering is distinctive in 1) having a total systems concern. 2) dealing with encumbered space and 3) requiring full spectrum practice. The total systems concern results from having to design and then co-ordinate in space and time several major systems: excavating and bulk handling, ground control, life support and normal support. This requirement favors a generalist rather than a specialist approach. In coping with encumbered space especially in underground coal mining, the uncertainties of geologic conditions are compounded by tightness, roughness, remoteness and hazards. Into this difficult setting the total systems * complex is "stuffed," adding congestion and interference. Because of significant ground deterioration a flexible "rapid in-out" approach is usually vital to mining. Full spectrum practice arises from the need to manage, as well as to plan and design, a labor intensive operation. Since market conditions can also fluctuate most aspects of administration are needed in many respects, mining engineering functions relative to civil engineering in a way similar to industrial to mechanical engineering, with encumbered space being crucial. On this basis stress is placed on: 1) personal relations, 2) field work and 3) entrepreneurship, viewing time as money. Specific recommendations for improving engineering, safety and management and leadership are made. Since most new deposits are marginal, by applying these recommendations with high technology they could possibly now be mined on a widespread basis.

Jan 1, 1985

By Tom Tallone

In the majority of metal and nonmetal mining operations, narrow vein deposits are being mined with slusher hoists. Thin; method of mucking is costly, due in part to its inherent labor intense operation and to its inability to muck 100 pct of the deposits. Mechanized equipment would greatly improve the material handling in narrow vein mining and would dramatically reduce the operational cost. The Compact Loader/Trammer, known as the "mini-mucker" has been developed to increase productivity of the load/haul/dump portion of the typical narrow vein mining cycle. This is Volume II of the final report and concerns the operation and maintenance of the mini-mucker. Volume I covers a general and design review of the activities on the subject contract and are available under separate cover.

Jan 1, 1985

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 H. Ewaschuk

"INTRODUCTIONRio Algom's Stanleigh Mill in Elliot Lake began production in June of 1983. The highly instrumented mill treats uranium ore at an average rate of 3900 metric tons per day. To help ensure a good start-up and low operating costs, an extensive training program was undertaken prior to and during start-up. This presentation describes how an unconventional operating crew were combined to form an operating unit with a high efficiency in terms of production and labour utilization. I would like to point out at the outset that the operating philosophy, and the role of the supervisors and the operators as set up at Stanleigh is not unique. Indeed, I have seen the same results at a couple of small plants where efficiency meant survival. However, these situations appeared to be the exception, and it was not readily apparent how similar results could be obtained in a larger plant. A factor that existed at the time was low labour turnover. As in most parts of Canada, jobs were easy to get in the Elliot Lake camp in the late 1970's. This, and other factors, contributed to an unusually high labour turnover. This changed dramatically in the early 1980's. Indeed, Rio's two other operating mills, Quirke and Panel reduced crew sizes at this time to reduce operating costs. As a result all of Stanleigh's operators came from Quirke and Panel with experience varying from 4 to 7 years. The experience that operators had was obviously of benefit and served to reduce the scope of the training program from what would have been required with inexperienced personnel."

Jan 1, 1985

By Gary P. Sames

Shale roof deterioration in coal mines. caused by ventilation air humidity fluctuations, is a common ground control problem. Shale roof deterioration often results in increased accidents, decreased production, inadequate ventilation, and increasing operating costs in maintaining haulage roads and airways. The results of Bureau of Mines research indicate that air tempering entries are an effective method of controlling deterioration prone shales. Some of the conclusions and recommendations drawn from Bureau research include (1) moisture sensitive shales will react adversely to moisture gains and losses, (2) the majority effect of specific humidity fluctuations can be concentrated in and absorbed by tempering entries, (3) tempering entry panels should be located as near to the main intake as possible, (4) tempering panels should be designed for a conservative recovery and provide a minimum of 20-to 30-min air residence time, (5) ventilation and escapeway requirements must be considered early in panel design, and (6) an efficient support and sealant plan can increase the life expectancy of a tempering panel.

Jan 1, 1985

By J-M M. Rendu

Geostatistics are increasingly recognized as powerful tools for reserve evaluation and grade control. It is also generally accepted that geologic input is required for the results of a geostatistical study to be meaningful. The role of the geologist is significant at all stages, whether it be to oversee the creation of the database, to assist in the statistical and semivariogran studies, to ensure appropriate block evaluation and kriging, or to review the results obtained. However the link between geology and geostatistics is often complex and not well understood. A presentation is made of the areas where geologic input is needed, and of the tools which the geologist should have at his disposition to ensure that his role is fulfilled. Organization of a Geostatisticel Study To be acceptable as the basis for financial investment, a geostatistical reserve estimation should be composed of four phases, the last phase being optional: Phase 1 - Background discussions, Phase 2 - Computation, Phase 3 - Reserve reporting, Phase 4 - Reserve audit. During the background discussions (Phase 1) the role of the geologist is primordial, as it is then that most decisions will be made concerning the geologic factors to be included in the geostatistical model.

Jan 1, 1985

By Robert A. Clifton

It seems probable that more and more minerals will be used in plastics as time goes on. This must occur because the minerals will; aid in processability, enhance the engineering properties, reduce the cost, and above all conserve large amounts of petroleum based chemicals. This paper examines the advantages and disadvantages of using the minerals and the ability of the domestic minerals industry to support this possibly very large undertaking. In the author's opinion, it can. This talk is excerpted from a forthcoming Bureau of Mines Information Circular.

Jan 1, 1985

By Dean S. Rogers

The conventional role of exploration, development and grade control is examined in this paper within the context of the many and varied types of gold occurrences which are found at the Dome Mine. The account endeavours to trace the development of the total ore evaluation process, from diamond drilling through the exploration and drifting stage, to the stope development and planning phase of the operation, with an emphasis on sampling techniques and assaying procedure. The concept of ore reserve calculations is developed and the practice of grade control is described. In summary, the role of the geological, the engineering and the mining department is presented in relation to the contribution each has to make in the evaluation and exploitation of ore from one of the world's classic Archean gold deposits.

Jan 1, 1985

By R. L. Wooten

When discussing what Coal Mine Safety in the future will be, it is important to examine three areas which at present provide significant parameters to the industry. These three areas are: 1) Safety improvements in mining equipment; 2) Labor-management relations; and, 3) The politics of coal mine safety. EQUIPMENT Over the past several decades significant safety improvements have been made in the types of equipment now in use in most operations. Many of these improvements have evolved through mandates from either the U. S. Bureau of Nines, MESA, MSHA; and in some instances, the states. Cabs and canopies are examples of federal mandates while the use of ATRS initially was a state mandate.

Jan 1, 1985

By Jon K. Ahlness

The Bureau of Mines investigated technologies for testing the integrity of in situ leach mining wells, as required by environmental regulations. To test for leaks, inflatable packers were used to seal the well casing. Laboratory testing determined that the packers could contain a casing pressure up to 50 to 60 psi (345 to 414 kPa) less than the packer inflation pressure. Single-and double-packer configurations were successfully field-tested in 32 wells ranging from 500 to 530 ft (153 to 162 m) in depth. A rigid pipeline and a hoist truck were used to run the packers in and out of the wells for the double-packer tests, which averaged 2-1/4 h each. In an effort to decrease the time of the rigid-pipe double-packer test. a self-contained trailer-mounted test system was designed and built. It utilizes a winch and steel cable to run the packers in and out of the well and high-pressure nylon tubing for packer inflation. This system was successfully field-tested in eight wells averaging 650 ft (198 m) in depth and resulted in a time savings of 13 pct and an operator-hour reduction of 42 pct.

Jan 1, 1985

By V. Svalbonas

With the occurrences of serious mill structural failures on both ball and primary mills, the mining industry has entered the era of detailed fabrication specifications. Such specifications, however, have been developed as individual entities, often by people not related to the mill design function. Therefore, there has been no effort to relate mill failure or safety to the existence or elimination of specific fabrication flaws; that is, no cause-effect failure relationships have been developed. The omission of this step produces a specification which can be termed uneconomical at best. The present paper attempts to fill this void, by reviewing methods for design consideration of flawed structures, and describing experimental tests used to tie such data to a meaningful quality assurance program in fabrication.

Jan 1, 1985

By W. H. Pomroy

Spontaneous combustion fires in deep metal mines, through relatively infrequent, are nonetheless cause for considerable concern because they pose a direct threat to the safety of miners and are quite disruptive to mine operations. They often occur in remote, inactive, or abandoned sectors of a mine where access for firefighting is difficult or impossible. Over half of all noncoal mine fires that last more than 24 hours are caused by spontaneous combustion. The most common means of fire control for spontaneous combustion fires is sealing and/or Flooding the affected zone. This process is never easy, but it is made especially difficult (and hazardous) if the fire grows in size and intensity to the point where underground fire- fighting crews must wear self-contained breathing apparatus owing to mine air contamination. The Bureau of Mines has developed and in-mine tested a mineworthy fire detection system capable of sensing the earliest traces of spontaneous combustion, thus enabling mine personnel to initiate fire control operations before hazardous atmospheres are created. This paper discusses system design within the context of the harsh mine environment, and describes laboratory and in-mine performance tests of prototype equipment.

Jan 1, 1985

By Madgwick J. C

Four manganese dioxide leaching microorganisms, an Achromobacter spp, Aspergillus niger, Elllerobacter cloacae and Elllerobacter agglomerails were purified from sucrose enriched crude mixed cultures which contained at least sixteen, non-leaching, morphologically different, colony types. Fastest leaching rates were obtained from the original enrichment's mixed cultures (1.26 g Mn++ I/d) while best yields of Mn++ m terms of sugar use came from Achromobacter and A. niger being 0.84 and 0.89 g Mn++/g sucrose respectively. The peak efficiency in manganese reduced, per carbohydrate used, coincided with the exponential growth phase for Achromobacter. The two Elllerobacter species performed better in stationary or senescent growth phases.

Jan 1, 1985

By M. F. Martin

Dewatering aids are chemicals which enhance the efficiency of mechanical dewatering equipment such as vacuum disc filters and centrifugal dryers. A new dewatering aid has been developed which significantly lowers the moisture content of the mineral concentrate and causes none of the undesirable side effects normally associated with dewatering aids. Highlights of product development from laboratory screening through field testing will be discussed.

Jan 1, 1985

By John H. Bassarear

Large scale equipment can reduce both capital and operating costs for concentrators. Large semiautogenous mills can be effectively utilized in big mills but they must be kept fully loaded to take advantage of their great potential. With varying hardness ores, controlling throughput is difficult and careful design must take this into consideration. A variable speed drive on large primary semi- autogenous mills can overcome this problem to a considerable degree. This paper provides a base case using standard accepted technology of two wound rotor single speed 4,476 kW (6,000 hp) motors to drive the primary SAG mills of a hypothetical 36,364 mtpd (40,000 stpd) typical porphyry copper mill. One other fixed speed drive will be described and five variable speed drive configurations will be reviewed. Capital costs for the entire grinding circuit, from crusher product to flotation feed, were developed for the base case and each of the alternatives. A technical evaluation comparing the advantages and disadvantages of each drive is presented.

Jan 1, 1985

By J. B. Czirr

MESA Corporation has completed a four-year program for the Bureau of Mines to develop a technique for measuring roof competence in underground coal mines. The preferred technique employs a tracer gas that is injected into a roof borehole drilled near the working face. The tracer gas performs the dual purpose of determining the pressure loss rate from the borehole and of marking the diffusion pattern of the the escaping gas. The primary detection technique relies upon observation of the rate of pressure drop in a hole drilled in the roof strata under test. If this measurement indicates a significant probability of roof collapse, the gas diffusion pattern is outlined with the Leak-gun tracer-gas detector. These two techniques provide a comprehensive method for predicting the relative probability of roof collapse in operating coal mines.

Jan 1, 1985

By R. A. Seitz

This paper presents a framework for analyzing the theory and industrial practice of coal flotation and gives some examples of its use for understanding flotation phenomena and optimizing/controlling flotation circuit performance. It is based on extensive laboratory and in plant test work conducted over the past several years by researchers at MTU as well as an analysis of the literature. Previous researchers have usually considered either the surface chemistry or the kinetics of coal flotation behavior, only rarely have these factors been considered together. However, these factors must be considered together in order to gain a clear understanding of the theory underlying coal flotation such that its practical application can be optimized. Fortunately, this complex objective can be achieved by considering the recovery and rate of recovery of the different types of particles present in the feed to coal flotation circuits and the fundamental mechanisms responsible for these recovery phenomena. The influence of three major groups of variables must be considered: control variables (reagent additions, aeration rate, etc.); disturbance variables (feed pH, percent solids, etc.); and circuit design variables (number of cells, circuit arrangement, etc.). Each of these groups of variables affects process kinetics in a clearly understandable manner, which, once determined, is extremely useful in circuit design and optimization. This paper includes a discussion of the use of the proposed framework to explain the effects of some coal characteristics on flotation performance. In addition, an example of using this analysis to optimize the performance of a coal flotation circuit using frother and collector addition levels is included.

Jan 1, 1985

By S. W. Thomas

One of the most difficult tasks associated with placer mining is the sampling of the deposit. More placer projects have failed due to inaccurate assessment of the reserves than to any other reason. Within the realm of placers, those containing valuable minerals with a high unit value .are more difficult to sample than those with larger bulk, lower unit value minerals. Some items to consider when sampling a placer deposit are as follows: A) A relatively large size sample is needed for accurate valuation of the ground being tested. Placers are composed of many sizes of gravel which makes a representative sample difficult to obtain. B) When sampling placers for high unit value minerals such as gold, any error in mineral content of the sample will be magnified in the calculation of reserves.

Jan 1, 1985