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By A D. Campbell, G R. Power

The objective of the draw strategy in a caving mine is to maximise economic return by minimising waste dilution3 and maximising ore recovery4. The draw strategy must also include suitable controls for air blast and mud rush hazards and is highly constrained until continuous cave propagation has been achieved. This paper details a three-year project at the Ernest Henry Mine (EHM), which used cave flow simulation software to develop a draw strategy that increased the mine value by 32 per cent.Dilution and ore loss can be significant in sublevel cave (SLC) operations and result in poor recovery and considerable economic losses. To minimise dilution and ore loss, cellular automata software was used to simulate cave flow over the mine life. The optimisation project required mining footprints for various cut-off grades to be developed. Draw strategies for each mine footprint were then generated using a range of shut-off grades. Economic assessment of each scenario was then conducted to determine the mine footprint and corresponding draw strategy that generated the highest NPV (net present value). The iterative simulation process was improved by developing automated software functions in the flow modelling software to reduce time taken to generate and assess life-of-mine (LOM) draw strategy scenarios.In addition to improving the NPV of the mine, the optimisation project also enabled a decrease in the mine cut-off grade which increased the ore reserve and extended the mine life. Overall, an iterative process of mine planning, cave simulation, economic evaluation and geotechnical analysis was used to significantly increase the economic return of the SLC whilst ensuring caving risks were controlled to an acceptable level.CITATION:Campbell, A D and Power, G R, 2016. Increasing net present value by a third at an operating sublevel cave mine using draw strategy optimisation, in Proceedings Seventh International Conference and Exhibition on Mass Mining (MassMin 2016), pp 167–174 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2016

By P. A. Vukmanic, M. Gensamer

Only recently has it been realized that preferred orientations are common in hot-rolled steels. In a recent paper, N. P. Gossl stated that hot-rolled mild steel exhibits a texture different from that characteristic of cold-rolled steel. No complete study of these hot-rolling textures has been reported using the pole-figure method of Wever. The material used in the work reported in this paper was the same material used by Gensamer and Mehl2 in a recent study of preferred orientations in cold-rolled steel, to which reference may be made for the composition and thermal history of the steel. Automobile-body sheet bar 1/4 in. thick was hot-rolled at two temperatures, 780' and 910' C. (1436' and 1669' F.). These temperatures refer to the temperature of the furnace in which the steel was heated; after each pass the steel was returned to the furnace and held there long enough to return to temperature. Although no accurate method was used to measure the temperature after each pass, it was estimated by color that only a slight drop in temperature occurred. In order to determine the effect of any preferred orientation that might have persisted through the normalizing treatment, one specimen at each temperature was rolled in the same direction as the original working direction and the other at right angles to it. The total reduction in each case was 85 per cent, the specimens having been reduced from 0.250 to 0.0375 in. in five passes. Final cooling was in air. Pinhole reflection photograms were taken of all four specimens, with the rolling direction vertical and the X-ray beam at an angle of 7' with the transverse direction (the transverse direction is defined as that direction in the rolling plane perpendicular to the rolling direction). These photograms, taken with a Mo target at 35 kv., are reproduced in Figs. 1, 2, 3 and 4. They show that a more pronounced texture was developed by the low-temperature rolling (780' C.), and that of the two

Jan 1, 1937

By S. D. Hill

To help insure the continued viability of the minerals and materials sector of the U.S. economy, the Bureau of Mines is conducting research and disseminating technology that will result in more efficient minerals extraction. As part of this effort, a process is being investigated that involves an aqueous chlorine-oxygen leaching procedure to treat complex sulfide concentrates to produce ZnCl2. Subsequent fused-salt electrolysis of the ZnCI2 produces high-purity zinc metal. Previous reports described preliminary, small-scale research on the chlorine-oxygen leaching system and fused-salt electrolysis of ZnCl2. This report discusses the details of design, construction, and longterm, continuous operation of both monopolar and bipolar fused-salt cells. The effects of temperature, electrode gap, current density, electrolyte composition, and electrode configuration on current efficiency and energy consumption were determined for a ZnCl2-KC1-NaCl electrolyte system. Zinc metal was produced at the rate of about 50 lb/day in a monopolar cell which was operated continuously for 60 days with current efficiencies from 85.8 to 98.6 pct and an average power consumption of 2.1 kwhr/lb. Bipolar cells with several different electrode configurations were operated for 90 days. A current efficiency of about 70 pct and power consumption of about 1.7 kwhr/lb of zinc were achieved using a three-electrode-pair, bipolar assembly with a chlorine gas lift pump to circulate electrolyte.

Jan 1, 1981

By T. M. Siew

"This paper begins with a brief discussion of the geology of the Newfoundland Zinc Mine area. The results of groundwater studies and pumping tests are then presented. It was decided that groundwater in the mine could best be controlled by conventional sump pumping and grouting. The system is fully described, as well as plans for improvements on the method. LocationThe Newfoundland Zinc Mine is located in the Great Northern Peninsula of Newfoundland, six miles northeast of Daniel's Harbour. The mine is situated at an elevation of approximately 350 feet above sea level, 5 miles farther inland , west of the long range of mountains which rise abruptly with elevations of over 2,000 feet above sea level.GeologyThe ore deposits occur in lower Ordovician carbonate rocks that form part of the stable St. Lawrence platform, which is mainly composed of (1) the lower Cambrian Labrador group, (2) the upper Cambrian to lower Ordovician St. George group, (3) the disconformity overlying Middle Ordovician limestones and shales of the Table Head formation and, (4) two overlying klippen composed of Cambrian and lower Ordovician rocks.The ore deposit is a Mississippi Valley type of the Tennessee variety, having proven are reserves of 5.3 million tons averaging 9.70/0 zinc from eleven ore zones which exist in an area of 5.5 square miles.Among these ore zones, the L zone is the major underground mining area, and is by far the largest of the known deposits. It has proven are reserves of 3.4 million tons with 11.5% zinc; this underground development has been inprogress since 1974.Stratigraphically, the orebody, which occurs about 300 feet below the disconformities between the Table Head and St. George formations, is situated in the upper St. George formationof lower Ordovician age.The upper St. George formation of the L zone is divided into three main units (Fig . I) : the underlying lower limestone the middle grey dolomite pseudo breccia unit and the overlying siliceous dolomite unit. In this area of the mine, the beds of the St. George formation dip gently west to northwest to 10 to 15 degrees. The orebody, which is generally strata controlled with a southwesterly plunge and which has the form of thin, narrow, but elongate, en-echelon ore bed s, is contained in grey dolomite pseudo breccia. Its dimensions vary from 50 to 900 feet in width and 8 to 120 feet in thickness, and the over-alllength exceed s 6,000 feet.The surficial deposit of the area is a till comprising a heterogeneous mixture of sand, gravel, cobbles and boulders, with an average depth of 20 feet."

Jan 1, 1980

By C. Navalkar

Systematic drilling & blasting techniques are currently being viewed in the mining & construction industry as a correct 8z scientific approach for optimization process in rock excavation, as drill & blast costs usually represent major share in total cost of production and also the environmental impacts plays an important role in designing of the operations. Designing a blast is a complex planning task, which for optimization, includes deciding the bench geometry with respect to the rock properties & geology of the area, capacity of the excavators, choice of explosives & detonation method, tiring sequence, etc. Optimization of blast design needs a detailed comprehensive study of all the above intersecting elements. Preblast & Post blast surveys are required for further improvements in blast designs. However, the choice of blast design depends upon the the requisite blasting results opted for and the cost you are ready to pay for the same. The blasting operation, in general, also involves numerous side effects namely, ground vibrations, fly rocks, dust, noise & gas pollution, air blast effect etc. Again these effects can be made tolerable up to a certain extent depending upon the limitations of the environmental obligations as may be specified by the concerned authorities.

Jan 1, 2001

By Bill M. Stewart

Since 1974, a large amount of data has been developed concerning the physical properties and stability characteristics of waste generated by the mining and preparation of bituminous coal. However, very little information has been developed on the properties and characteristics of anthracite waste. During this Bureau of Mines research project, coarse anthracite breaker refuse from five sites in eastern Pennsylvania was sampled and the physical properties, which indicate stability characteristics, were determined in the laboratory. Coarse anthracite breaker refuse is quite similar to coarse bituminous refuse in chemical and mineralogical composition. However, the physical properties of the anthracite waste materials tested are different from those of coarse bituminous refuse. For the coarse anthracite breaker refuse tested, the average maximum laboratory density is 113.2 lb/ft3, the average angle of internal friction (direct shear) and average cohesion are 30.2° and 2.6 psi, respectively, and the average permeability (four sites) is 1.24 x 10-2 cm/sec. Stability analyses were conducted on six theoretical anthracite waste embankments. These analyses show the effects on minimum safety factors of geometry, phreatic surface level, and physical properties.

Jan 1, 1983

By David Colloby, Darelle T. Janse van Rensburg

Premature coating failures of new and refurbished structural steelwork of clarifiers have been a common occurrence at power generation plant in recent years. Several of these failures have ended in disputes regarding which party was actually to blame for the early degradation of the coating system, i.e. quality of the power station?s water, poor application, substandard materials, outdated corrosion protection specifications, etc. Having investigated several of these premature failures, it is clear that the corrosion protection of clarifier steelwork is a highly complicated process and that the painting work needs to be closely monitored in order to ensure long-term protection by whichever product that is applied. The need for quality control inspections during the painting of the plant is often underrated during the project planning stage, also the importance of detailed corrosion protection specifications that consider not only the practical application of the materials, but also the quality control responsibilities of the Contractor, End User and Third Party Inspectorates that may be involved. This paper considers the application constraints of coatings to clarifier structural steelwork and importance of stringent quality control procedures in order to ensure the long-term performance of the corrosion protection systems.

Jan 1, 2006

By David C. Uhrin

Two improved methods have been developed to transfer microfilmed mine maps to suitable base maps showing surface features. The methods provide for (1) positioning and orienting maps; (2) merging adjacent maps; and (3) plotting maps at a common scale. One method produces an overlay mosaic of mine maps using an Integrated camera-processor. This photographic method shows the details of mine workings and is most useful for specific limited-area projects. In the second method, outlines of mine maps are digitized, manipulated, and plotted as overlays using a computer. This computer method can plot mine outlines and spatially index large numbers of microfilmed maps. Microfilmed mine maps used in this Bureau of Mines study are on file in the Mine Map Repository of the Eastern Field Operations Center. The base maps are U.S. Geological Survey 7.5-minute topographic maps. The demonstration area is located in the New Kensington East and West quadrangles, Pennsylvania.

Jan 1, 1977

By C. C. Walden, A. Bruynesteyn

"Chemical and biological aspects of the formation of acidic effluents from sulfide waste materials are discussed. Test procedures to determine the acid producing potential of waste materials, as well as the characteristics of such acidic effluents, are presented. Practical applications of the test procedures are discussed with reference to predictior of environmentally unacceptable drainage and to estimation of metal recovery by dump leaching.INTRODUCTIONNatural leaching of sulfide minerals, exposed to the atmosphere, has been occurring for geological time. For centuries, man has been aware of the acid drainage originating from coal workings, copper mines and waste dumps. With the advent of the technical sciences, the processes involved in acid mine drainage production were considered to be solely chemical in nature. However, in 1947, it was shown (1) that a specific microorganism, called Thiobacillus ferrooxidans, was responsible for acid mine drainage from coal workings. It was demonstrated that under suitable conditions - this bacterium oxidized pyrite and marcosite in the coal to ferric sulfate and sulfuric acid. Numerous studies have subsequently demonstrated that - under suitable conditions - Thiobacillus ferrooxidans can attack most sulfide minerals, producing weak sulfuric acid, oxidizing ferrous to ferric iron and solubilizing other metals present (notably copper and zinc) as their sulfate salts."

Jan 1, 1980

By J. Chilton

The fact that methane ignitions continue to occur at the mining face indicates that monitoring with machine-mounted methanometers does not always indicate the presence of high methane concentrations. Methane concentrations at the face change quickly due to changes in airflow. By measuring these changes in airflow, it may be possible to predict changes in face methane levels more quickly. Currently there are no techniques or instruments to accurately measure airflow in by the mouth of the ventilation curtain or tubing. Tests conducted in the NIOSH ventilation test gallery compare the data provided by one-, two-, and three-axis ultrasonic anemometers. The effects of changes in airflow direction and turbulence on instrument readings are discussed, and guidelines are given for selecting the type of instruments to be used for monitoring airflow near the mining face.

By L. Nahai

THE OUTPUT ff the mineral industry in 1964 in both non-Communist and Communist Europe showed an upward trend for most countries in keeping with the higher index of overall industrial production. Comparable indexes of mineral industry production for non-Communist and Communist Europe (including the U.S.S.R. in Asia) are not available, primarily because the U.S.S.R. does not report details of its industrial production by industrial sectors. However, available data both in the form of index numbers on production published by the United Nations and based on data as reported to the United Nations by the various countries, and actual production data for selected major commodities published by the various European countries reflect generally expanded output by both the extractive sector and the processing sector of the mineral industry in most of the 26 nations of Europe.

Jan 1, 1966

The seams of black coal occurring in Victoria are so disturbed by faulting, wash-outs, thinning, etc., that it is necessary, for the prevention of costly errors in development, that close boring be undertaken so that the correct positions of the shafts, tunnels, main and auxiliary roadways can be set out in order that the area can be economically worked. The State Coal Mine has two boring plants continuously at work, which have given good service for the last twenty-five years.The information supplied herein is merely our experience in boring at the State Coal Mine over an extended period. The type of plant in use is that known as the Victoria Drilling Plant, equipped with an 11 h.p. portable oil engine, using power kerosene as fuel. It was purchased in 1914, complete with mechanism for cable drilling, capable of boring to a depth of 1500 ft. with a guarantee of 1000 ft., with Calyx cutters, boring rods and all necessary equipment for the sum of £1473. The chief mechanical features of the plant are as follows:-The derrick is in the shape of a tripod (see Fig. 1), two of the legs being of steel channel built together to form a frame which, when lowered on to two sets of road wheels, forms a carriage for the transport of a portion of the boring equipment. The third leg is made of oregon in the form of a double bow, with bolts and distance pieces between the wooden sides. The top of this is hinged on to the steel frame, and the bottom is fitted into a cast iron block, having two small wheels to facilitate erection. A rope attached to the cast iron block and to the winch easily...

Jan 1, 1936

By William J. Rothschild

Ground water at construction sites can be controlled by properly placed wellpoint dewatering systems. Care must be taken in planning cofferdams to have adequate space for and access to pumps, headers and the points. A most important part of dewatering is protection of adjacent structures from movement. A checklist gives items to consider in bidding.

Jan 1, 1984

By Ian Martin

A precious metals refinery’s switch to personal computer-based, three-dimensional piping design saved many hours in the design of a South African precious metals refinery. Bateman Minerals and Industrial provided engineering, procurement and construction management services for Impala Platinum Limited-Refineries’ new $60 million refinery in Springs, South Africa. This project is one of the largest platinum refineries in the world. Bateman evaluated a new design method during this project that involved developing a three-dimensional model for the project. The new method saved time by reducing the man-hours required to generate complete project documentation, including plans, sections, isometrics and material takeoffs. The new method also saved design and construction time by allowing designers to detect clashes before construction began.

Jan 1, 2000

By J S. J van Deventer

Geopolymerisation is a new technology that processes and transforms aluminosilicate minerals into mechanically strong and chemically stable products. In this investigation, minerals such as fly ash and kaolinite were used as the solid raw materials for geopolymerisation. Inorganic salts were added to the geopolymeric pastes to simulate ionic contamination during processing for building and construction applications. The resultant products were examined and characterised physically. It was found that the early strength development of geopolymeric pastes could be changed according to the nature as well as the extent of the contamination. At a small dosage, the effect of the contamination on the early geopolymeric system depended heavily on the nature of the artificial surfaces that were created in the geopolymeric solution through the addition of the chemical additives. For example, the samples containing MgCl2 and Mg(NO3)2 had shown the same yield stress developments due to the similar surfaces that were formed. The cations of these salts were expected to hydrolyse and form magnesium hydroxide precipitates immediately after the addition to the early geopolymeric systems. The calcium cations of CaCl2 also precipitated upon addition, but the nature of the surfaces of these hydroxides was quite different to those of the magnesium hydroxides and gave rise to different yield stress development. The samples that contained the insoluble salts (in water) demonstrated different yield stress development when compared to each other because of the different nature of the additive surfaces that were exposed to the geopolymeric solution. These results suggested that heterogeneous nucleation could be responsible for the change of the rheological behaviour upon inorganic salt addition. When the extent of the ionic contamination was large, the anions released from the insoluble salts (in water) changed the nature as well as the concentration of the geopolymeric solution and the setting processes were retarded. Oxides, in general, behaved very differently from other salts, indicating the uniqueness of the oxygen anions in a system rich in hydroxyl and silicate anions. The inorganic salt contamination in geopolymers did not show any significant signs of structural change according to the XRD diffractograms collected. The seven-day compressive strength was not lowered by the inorganic salt contamination and it could sometimes be beneficial to the product performance, for example, an increase of 20 MPa was induced by the addition of calcium oxide. Inorganic salts as chemical additives have demonstrated the potential to modify setting times of geopolymers without sacrificing much of the productsÆ strength and integrity.

Jan 1, 2000

By D. W. Tuckwiller

Electroplating is a widely utilized but little understood process. The fact that the average person is in contact with dozens of plated items daily without even being aware that they are electroplated is evidence of the success of the process. Although a complete explanation of electrodeposition involves thermodynamics and modern theories of bonding and catalytic reactions, in its simplest form the process conforms to the following description. A metal salt dissolved in water partially dissociates into negatively charged and positively charged ions. In the case of nickel sulfate dissolved in water, for example, a portion of the salt dissociates into positively charged nickel ions and negatively charged sulfate ions. If an electrical potential is applied between two electrodes in this solution, the nickel ions migrate toward the cathode and the sulfate ions toward the anode. The negatively charged cathode has a high concentration of electrons, which combine with the positively charged metal ions to form neutral metal atoms with a stable electron configuration. These insoluble atoms thus form a deposit on the cathode.

Jan 1, 1970

By Raymond J. Pichette

"Aeromagnetic data can be useful in helping to delineate structures and rock types in gold exploration. Magnetic anomalies associated with Archean volcanic belts in northeastern Ontario can be quickly and effectively analyzed in profile form with the use of model curves. The model curves help to locate contacts between strata. They also help to estimate the magnetite content of the rocks and their depth beneath overburden.An aeromagnetic map of part of Catharine Township, Ontario has been analyzed with the aid of model curves. Several magnetic rock types, potential fault zones and areas of relatively thick overburden were delineated.IntroductionIn any exploration program, a good understanding of the stratigraphy, rock types and structure enhances the possibility of success. For example, environments which host gold deposits in the Abitibi Volcanic Belt may be characterized as follows (Jensen, 1980; Pyke, 1980):(I) They have major faults, especially as tectonic boundaries between volcanic piles which include mafic and ultramafic rocks and clastic sedimentary rocks or gneisses.(2) They have subvolcanic felsic intrusions.(3) They have extensive carbonitization, with or without carbonate and sulphide-facies iron formation.In all cases, delineation of structure and rock type should be a major objective in exploration. The analysis of magnetic data can be a useful tool in this task. This paper is presented with the purpose of describing the application of the magnetic method to gold exploration in Archean volcanic terrains.Magnetic AnalysisTotal-intensity magnetic contour maps can be used to discriminate rock units according to differences in magnetization. However, because of smoothing of texture resulting from the compilation procedure and the fact that survey lines are widely spaced, contours should not be directly used for quantitative analysis. A much more definitive means of magnetic analysis is provided by the use of the original profile or chart recordings. Model curves provide a basis for analyzing these profiles both accurately and rapidly."

Jan 1, 1982

By M. G. Pelipetz

High-pressure, high-temperature hydrogenation of coal has been known and practiced for many years. A full' understanding of the mechanism in this process by which coal is converted to oil and gas must rest on a critical interpretation of the manner in which external variables influence the rate and the course of the coal-hydrogenation reactions. Same Bureau of Mines studies on the effect of temperature, catalyst, and rank of coal on these reactions have been published. The effect of pressure was not studied in this earlier work, and the effect of reaction time was complicated by the interruption of long reaction periods in order to refill the autoclave with hydrogen. It is the purpose of this paper to present data from more recent autoclave experiments that extend the results of Storch, et al, on the kinetics of coal hydrogenation. These data must be explained by any comprehensive theory of coal hydrogenation; their detailed evaluation, however, will be deferred until a later publication.

Jan 1, 1949

By Gerald G. Griswold, Allan G. Provost

INTRODUCTION The Norad Expansion Project was located 10 miles southwest of Colorado Springs, Colorado, within Cheyenne Mountain. The expansion areas to be excavated would be adjacent to the existing underground Norad complex, which would remain in operation during the work on the expansion. The original complex had been constructed approximately eight years earlier and had been in full operation for approximately five years. Phase I, Excavation was awarded the Tiro Construction Corporation, a subsidiary of Harrison Western Corporation, Denver, Colorado, in the fall of 1970. Notice to Proceed was given to Tiro on 28 December 1970. The project owner was the U. S. Air Force, design was performed by the U. S. Corps of Engineers, Omaha District, who would also serve as the construction agency. [ ]

Jan 1, 1979

By J. M. Ortiz

Grade control and short-term planning are usually based on the samples obtained from blastholes. These samples may carry a large sampling and sample preparation error. At El Tesoro copper mine in northern Chile, an advance drilling grid is used for short-term planning and grade control. These drill holes are sampled well in advance, and a short-term model that incorporates several variables and sophisticated estimation methods can be prepared for decisionmaking. An additional advantage of the advance drilling samples is that reverse circulation can be used instead of conventional down-the-hole equipment, and a very careful sampling and sample preparation process can be implemented, reducing the total sampling error. Advance drilling can be performed on a wider grid than blasthole drilling, hence the decision about the grid requires assessing the economic benefit of different sampling grids. Furthermore, this process allows the cost of poor sampling and the effect of different estimation procedures to be quantified. We demonstrate the optimization of the drilling grid for short-term planning and grade control at El Tesoro mine by means of the economic evaluation of the performance of different drilling grids, with different drilling techniques (which differ in the sampling error). The methodology is based on creating dense (exhaustive) geostatistical simulations of the grade distribution over a volume defined for a production period in respect of the geological model, and assuming each simulation as the true grade distribution. Then, samples are obtained from the exhaustive simulations at a spacing similar to the advance grid to be evaluated, and a sampling error is added. The short-term estimation procedures used on the mine are applied to determine the destination of each block and the profit obtained. This profit can be compared with the maximum profit (unachievable) and with the profit under different sampling errors and grids. The results show that the current 8 x 8 m drilling grid is appropriate and by reducing the sampling error, misclassification is also reduced, leading to an increase in profit of about US$ 5 million in 4 years.

Jan 1, 2012