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By T. P. Oxford, G. Y. Onoda, E. D. Whitney

Disposal of phosphatic clay waste slurry has been a problem since the advent of hydraulic processing of phosphate rock in Florida. Alternatives to the present practice of storing slimes behind earthen dikes have been earnestly sought for more than a quarter of a century. Seepage dewatering is a promising technique intended to increase waste clay solids content to a level sufficiently high to permit clay disposal in mine cuts, in lieu of above-grade impoundment. An experimental array of vertical seepage columns containing mine tailings sand was constructed. Significant improvement in waste clay dewatering relative to that occurring in a control test was observed when approximately 1800 m3 of waste clay was disposed of in the presence of the seepage aids.

Jan 1, 1983

By Horace Pops, J. F. Libsch

THE discovery of SAP alloys (sintered aluminum powders) by lrmannl has stimulated investigations in other alloy systems.23 Not only do such alloys have good room-temperature properties, but they maintain high strength after prolonged service at elevated temperatures. In addition, they show high structural stability, including unusually high recrystallization temperatures. These characteristics are secured by dispersion hardening. For this investigation, Zn-ZnO alloys were selected. Practically, the fact that commercially pure zinc recrystallizes near room temperature prohibits strengthening and hardening by cold deformation and therefore limits the application of zinc where mechanical strength is important. Similarly, the poor

Jan 1, 1961

By V. Rajaram, H. W. Earnest, A. W. Jenike

Mine backfilling is a desirable method for the disposal of retorted oil shale. Hydraulic, mechanical and pneumatic transport and stowing methods were investigated, and the mechanical transport and stowing method using conveyors was selected as the most promising system. Transport of retorted oil shale at the rate of 2700 t/h (3000 stph) to the backfill level, situated about 610 m (2000 ft) below surface, with skips or conveyors is uneconomic. Hence, borehole transport utilizing gravity flow was investigated. This Paper describes the theory of flow, flow properties of retorted oil shale, and the design of a borehole and hopper system.

Jan 1, 1980

By H. M. Howe

One of the little electric-resistance magnesia crucible-furnaces which I designed for the metallurgical laboratory of the School of Mines of Columbia University is shown, in vertical section, of full natural size, in Fig. 1. The furnace itself consists of two semi-cylinders of magnesia, A A, with a cover of magnesia, B B, and a stopper, C, also of magnesia, which is perforated to admit the leads x, y, of a thermo-electric couple. The furnace is heated by the spiral of platinum wire, D D (entering and departing by the openings I and K), through which a current of any desired strength is passed, bringing it to incandescence, and to ally temperature, not above the melting-point of platinum, which may be desired. The crucible E, actually used in this furnace, is also of magnesia. I have heard of some unsuccessful attempts with furuaces of this general class, and have attributed these failures to the use of siliceous materials for the furnace-walls. Of course such a result is what we should expect, since the silica mould readily be electrolysed by the current, and the resultant silicon would alloy with platinum ; but the little magnesia furnace here clescribed seems to be wholly free from this objection. It has been used in my laboratory for some months, and temperatures, up to 1100° C, hare been developed in it over considerable periods of time—indeed, it has been held near 1400" C. for about two hours—without indication, thus far, of any deterioration of the platinum. In the section shown, F F are a pair of steel disks, bound together, but separated by the inverted thermo-junction, N, of the thermo-electric pyrometer. This arrangement permits the observation and record of retardations in the heating and cooling of F F—in other words, the determinations of the cooling curves of steel—a purpose for which the furnace has been used, thus far, more frequently than in the determination of meltingpoints. For the latter operation, however, it is also suitable.

Jan 1, 1902

By Clarence Fenner

THE manufacture of optical glass is a process that demands careful regulation and control at all stages in order that satisfactory results may be obtained. The product, to serve its purpose, must meet stringent requirements, which can be assured only by careful procedure in manufacture. During the greater part of the time that a pot of glass is in the furnace, temperatures should be kept within certain rather narrow limits; a departure on either side is likely to be detrimental to the glass and may result in total loss. If the temperature during melting and fining be low, the melt is likely not to fine properly and the glass will contain quantities of bubbles, or "seed," or it may become milky and unfit for use; too high a temperature, on the other hand, is severe on the pot and may cause it to leak or cast stones, or the increased solution of pot material in the melt may acid to the color of the glass and decrease its transmission. Moreover, variations in the working temperature will mean variations in the amount of selective volatilization and, consequently, variations in optical properties from pot to pot. Furthermore, in the closing stages of furnace treatment, the melt is cooled until a certain degree of stiffness is attained, when the pot is withdrawn. The quality of the glass-its freedom from striae and bubbles-will depend in large measure on whether the temperature to which cooling has been carried is suitable. For each type of glass there is a narrowly restricted range of temperature to which each pot of the given type should be cooled before withdrawal. A quick and reliable method of measuring temperatures is, therefore, of the first importance. In the optical-glass work conducted by the staff of the Geophysical Laboratory during the period of the war, much attention was given to the clatter of determining what methods would meet the requirements. This article will deal with these investigations and with the application of the results to actual practice at various plants. At the. time that the work of the Geophysical Laboratory was begun at the Bausch & Lomb plant, each melting furnace was equipped with

Jan 7, 1919

Discussion of the paper of WALTER 0. SNELLING, presented at the New York meeting, February, 1915, and printed in Bulletin No. 100, April, 1915, pp. 695 to 704. A. F. LUCAS, Washington, D. C.-Are the results of the experiments in practical operation? WALTER 0. SNELLING.-There have been no large-scale operations up to the present. The necessary conditions of temperature are easily arranged for, but the required condition of pressure, 800 lb., is not so simple a matter. The company has been working on this problem, and at the refinery in Oklahoma work of this kind is now being carried on. The way in which an ordinary still will leak at 50 lb., and more at 100 lb., leaves some doubt in the mind of many as to what can be clone at a continuous working pressure of 800 lb. On the other hand, the fact that they are making ammonia abroad by a method which employs higher pressures and temperatures than anything involved in this method, leads me to believe that the difficulties, which will undoubtedly arise when this is attempted on a commercial scale, can be overcome. WILLIAM N. BEST, New York, N. Y.-Is there any change in the calorific value of these oils?

Jan 5, 1915

By G. Kinder, R. Gilges, W. Stoker, R. Davey

The Bingham Canyon Mine, located 48 km (30 mi) southwest of Salt Lake City, Utah, is operated by Kennecott Copper Corporation's Utah Copper Division. This operation is the world's largest open-pit copper mine and produces 96 000 tons (106,000 st) ore and 327 000 tons (360,000 st) waste each day. This material is loaded by large electric shovels and transported by both truck and rail haulage. To meet the requirements of the Clean Air Act of 1970 (as amended), new facilities for the control of smelter emissions were required and are now nearing the final stages of construction. The facility will be capable of treating all the output from the mine, some 2,530 tons (2,789 st) per day of combined concentrate and precipitate. Costing $280 million and necessitating the replacement of reverberatory furnaces with continuous smelting vessels, the plant, with its massive and complex gas handling and acid-making facility, is required to remain on-stream with the minimum of pollution control equipment outages to conform with Federal Regulation 52.2325. As part of this giant effort, the smelter planning team and supervisory staff considered that new, well organized, highly flexible, readily available maintenance information was essential to assist the maintenance personnel in the performance of their duties.

Jan 1, 1979

By B. B. Zavoico

Considerable progress has been made during the past year throughout the Russian petroleum industry. Perhaps the most remarkable achievement is the execution of the programs set out by the Central Planning Bureau of the Department of Commerce. These programs have been increased twice during the past operating year, necessitating drilling the richest reserves, instead of developing gradually as originally planned. The fulfillment of the set-out programs during the past few years makes therefore the present five-year plan of considerable importance to the international oil statisticians in approximating actual supply conditions up till 1933. The production of all Russian fields increased by 14,200,000 bbl. as compared with the 1927-1928 operating year, while the next year's program anticipates a further increase of 15,700,000 barrels. It appears therefore that production for 1932-33 will total 187,000,000 bbl., or approximately double that of the operating year just closed. It is also evident that the old fields are counted upon to produce only about 67 per cent. of the total, the new fields, not yet discovered, to furnish the balance of 33 per cent. The Soviet oil leaders therefore are hoping to have new fields discovered and developed by 1932-33. However, as in the past wildcatting

Jan 1, 1930

By M. R. Tek, K. H. Coats, D. L. Katz

In natural gas storage operations, seasonal pressure fluctuations in the gas reservoir cause the water from the surrounding aquifer to flow into and out of the gas sand. The theory of unsteady-state liquid flow through porous media developed by Van Everdingen and Hurst' has been applied to predict the water movement into and out of the gar bubble for .several .postulated pressure cycles. Those cycles with as many pound-days above the original aquifer pressure as pound-days below, may cause the gas reservoir to slowly grow or shrink rather than hold to a constant volume. Applications to an actual field case study give the predicted gas reservoir monthly pressures and volumes as compared with the observed monthly pressures and volumes. INTRODUCTION A large number of natural gas storage reservoirs are bounded by or adjacent to large water-saturated formations called aquifers. The presence of these aquifers is usually evidenced by the production of water from wells delineating the gas-hearing sands. Some gas storage reservoirs in use today have been purposely developed on aquifers. Cyclic pressure variations in a gas storage reservoir cause water influx and efflux from the surrounding aquifer. This, in turn, results in a varying gas reservoir volume. The prediction of the effect of this aquifer fluid movement on the size and size variation of the gas reservoir can provide information valuable in the study of several reservoir engineering problems. The economics of gas storage operations are directly influenced by the influx of aquifer fluid into the reservoir since a shrinking storage reservoir requires increasing pressures for the storage of the same quantity of gas. Material balance and reserve or recovery calculations also obviously require knowledge of reservoir volume. Various other reservoir engineering calculations such as interpretation of well interference data, evaluation of physical characteristics of porous media, water coning, gas injection and pressure maintenance studies are typical problems where variations of volume due to edge or bottom-water encroachment becomes important. The solution of equations describing influx and efflux of water in the gas sand, application to gas storage reservoir behavior and interpretation of results are the main objectives of this paper. While this work was directed toward gas storage reservoirs, it applies equally well to repressuring of partially depleted oil reservoirs with an active water drive. MATHEMATICAL ANALYSIS As just mentioned, the cyclic pressure variations in an aquifer-surrounded gas storage reservoir cause water movement and varying gas reservoir volume. Prediction of this volume variation from the reservoir pressure cycles or the injection-production schedule requires adoption of a flow model, certain assumptions concerning reservoir and fluid properties, and formulation and solution of the governing differential equation. The flow model used in this study is a gas bubble located on a very large aquifer (Fig. la). Gas bubble radius and aquifer sand thickness are denoted by rr and h, respectively. Fig. lb shows the horizontal, radial two-dimensional porous reservoir attended by the unsteady, compressible motion of the aquifer liquid. Volume variation of the gas bubble is determined from aquifer water flow across the cylindrical boundary, r = r0

By Morris Muskat, J. M. McDowell

In both production and refining operations of the oil industry many processes are controlled by the gas-liquid phase relationships of the hydrocarbon mixtures of interest. The quantitative behavior of fractionating or distillation columns and stills depends on the changes in the equilibrium distributions of the hydrocarbon components between the gas and liquid phases as the pressure or temperature conditions may vary along the length of the column or as the gross operating parameters and compositions are varied. In oil producing operations the nature and amount of gas phase developed within an underground reservoir as it is being depleted and its pressure declines also involve the basic equilibrium gas-liquid phase interactions. The influence of surface conditions of temperature and pressure and various separation procedures on the nature and amount of stock tank oil and natural gas recovered from a given well stream is likewise determined by the same basic phase equilibrium characteristics of the hydrocarbon systems. Such equilibrium separation of the gas and liquid phases in a well stream is of importance both in establishing optimum separator conditions for obtaining maximum stock tank oil yields and in the general problem of crude stabilization. The phenomena involved in these problems and their quantitative aspects can, of course, be established in each individual instance by appropriate laboratory experimentation. It has been found, however, that by associating with the individual hydrocarbon components functional characteristics de- scribing their individual gas - liquid phase equilibrium behavior, the phase properties of the composite mixtures can be predicted by mathematical computation. These characteristics have been termed "equilibrium constants", or "equilibrium ratios"," and are defined by the general equation: where K, is the equilibrium ratio for the jth component, y, is the rnol fraction of that component in the gas phase, and xj is the corresponding mol fraction in the coexisting liquid phase. Considering the Kj as representing available and measurable properties of the individual components of a mixture, and as defined by Eq. (l), it is readily shown that in a coexisting gas-liquid system the rnol fraction concentrations of the individual components in the gas phase, y,, and those in the liquid phase, x,, are given by the expressions: where the nj are the corresponding rnol fraction concentrations in the composite system, and ng is the mol fraction of the whole which is in the gas phase. The basic unknown in Eq. (2) is n,: which gives the gross separation between the gas and liquid phases. This may be determined in principle by imposing the requirement that the sums of the mol fractions in both the gas and liquid phases are unity, i.e. by the equations: The solution of the equivalent Eqs. (3) lying between 0 and 1, when inserted into Eqs. (2), provides a complete description of the compositions of the coexisting gas and liquid phases. While the Eqs. (3) are essentially equivalent to polynomial equations, such transformations are of little value when dealing with multicomponent sys-

Jan 1, 1949

By J. M. McDowell, Morris Muskat

In both production and refining operations of the oil industry many processes are controlled by the gas-liquid phase relationships of the hydrocarbon mixtures of interest. The quantitative behavior of fractionating or distillation columns and stills depends on the changes in the equilibrium distributions of the hydrocarbon components between the gas and liquid phases as the pressure or temperature conditions may vary along the length of the column or as the gross operating parameters and compositions are varied. In oil producing operations the nature and amount of gas phase developed within an underground reservoir as it is being depleted and its pressure declines also involve the basic equilibrium gas-liquid phase interactions. The influence of surface conditions of temperature and pressure and various separation procedures on the nature and amount of stock tank oil and natural gas recovered from a given well stream is likewise determined by the same basic phase equilibrium characteristics of the hydrocarbon systems. Such equilibrium separation of the gas and liquid phases in a well stream is of importance both in establishing optimum separator conditions for obtaining maximum stock tank oil yields and in the general problem of crude stabilization. The phenomena involved in these problems and their quantitative aspects can, of course, be established in each individual instance by appropriate laboratory experimentation. It has been found, however, that by associating with the individual hydrocarbon components functional characteristics de- scribing their individual gas - liquid phase equilibrium behavior, the phase properties of the composite mixtures can be predicted by mathematical computation. These characteristics have been termed "equilibrium constants", or "equilibrium ratios"," and are defined by the general equation: where K, is the equilibrium ratio for the jth component, y, is the rnol fraction of that component in the gas phase, and xj is the corresponding mol fraction in the coexisting liquid phase. Considering the Kj as representing available and measurable properties of the individual components of a mixture, and as defined by Eq. (l), it is readily shown that in a coexisting gas-liquid system the rnol fraction concentrations of the individual components in the gas phase, y,, and those in the liquid phase, x,, are given by the expressions: where the nj are the corresponding rnol fraction concentrations in the composite system, and ng is the mol fraction of the whole which is in the gas phase. The basic unknown in Eq. (2) is n,: which gives the gross separation between the gas and liquid phases. This may be determined in principle by imposing the requirement that the sums of the mol fractions in both the gas and liquid phases are unity, i.e. by the equations: The solution of the equivalent Eqs. (3) lying between 0 and 1, when inserted into Eqs. (2), provides a complete description of the compositions of the coexisting gas and liquid phases. While the Eqs. (3) are essentially equivalent to polynomial equations, such transformations are of little value when dealing with multicomponent sys-

Jan 1, 1949

By C. M. Marquardt

Tramp iron and steel moving on a conveyor belt cause small currents to be generated in a coil situated in a strong magnetic field, which are converted to an alternating current and are amplified. The output voltage from the amplifier fires a thyratron with a relay in its anode circuit, which actuates a howler and simultaneously drops a spot of marker material on the belt. THE problem of tramp iron removal from moving ore belts is a long standing one. When heavy ore streams are carried on a belt, magnetic pulleys and strong surface magnets fail to remove tramp buried in the ore stream. Tramp iron buried in the ore stream cannot be pulled from the bed by surface magnets and is carried past the magnetic pulley by the falling ore stream. With the increased use of detachable bits the problem of the detection and removal of tramp has become more necessary and difficult. Several types of tramp detectors have been developed. It would serve no practical purpose here to review exhaustively the literature on the subject. Methods of tramp detection used are: (1) The magnetic method, wherein the small current generated by the magnetized tramp passing a Coil is used. (2) The unbalanced oscillator method wherein the tank circuit of a stable radio- or audio-frequency oscillator is unbalanced causing a change of frequency or a change in plate current due to changes in eddy currents, hysteresis, or dielectric because of the presence of tramp. (3) The bridge methods wherein the impedance of one leg of an alternating current inductive bridge is changed due to the presence of conducting tramp. Each of these methods of tramp detection has its field of usefulness. The second and third methods are excellent for oxide iron ores, coal, sand and gravel, grain, etc. However, these latter methods are not suitable for use on ores that contain rich conducting sulphides, since a large piece of pyrite or galena will cause the same detector response as a piece of tramp iron. At the Caselton, Nevada, plant of the Combined Metals Reduction Co., sulphide ores are treated; therefore, it was necessary that a tramp detector operating on only the magnetic properties of the tramp iron be used. Tramp iron detectors of this type operate on the principle that if a piece of tramp iron moves near a coil in a high intensity, steady magnetic field, the presence of the moving tramp iron causes the magnetic flux lines through the coil to change. This induces a mall current in the Coil. In series with the Coil is generally placed a relay sensitive to currents of 1 to 3 microamp. When the tramp iron passes near the coil the flux linkages change, causing this very sensitive relay to actuate. Since the contacts of such a relay are very small it must actuate a second relay capable of breaking a larger current

Jan 1, 1951

By C. M. Marquardt

Tramp iron and steel moving on a conveyor belt cause small currents to be generated in a coil situated in a strong magnetic field, which are converted to an alternating current and are amplified. The output voltage from the amplifier fires a thyratron with a relay in its anode circuit, which actuates a howler and simultaneously drops a spot of marker material on the belt. THE problem of tramp iron removal from moving ore belts is a long standing one. When heavy ore streams are carried on a belt, magnetic pulleys and strong surface magnets fail to remove tramp buried in the ore stream. Tramp iron buried in the ore stream cannot be pulled from the bed by surface magnets and is carried past the magnetic pulley by the falling ore stream. With the increased use of detachable bits the problem of the detection and removal of tramp has become more necessary and difficult. Several types of tramp detectors have been developed. It would serve no practical purpose here to review exhaustively the literature on the subject. Methods of tramp detection used are: (1) The magnetic method, wherein the small current generated by the magnetized tramp passing a Coil is used. (2) The unbalanced oscillator method wherein the tank circuit of a stable radio- or audio-frequency oscillator is unbalanced causing a change of frequency or a change in plate current due to changes in eddy currents, hysteresis, or dielectric because of the presence of tramp. (3) The bridge methods wherein the impedance of one leg of an alternating current inductive bridge is changed due to the presence of conducting tramp. Each of these methods of tramp detection has its field of usefulness. The second and third methods are excellent for oxide iron ores, coal, sand and gravel, grain, etc. However, these latter methods are not suitable for use on ores that contain rich conducting sulphides, since a large piece of pyrite or galena will cause the same detector response as a piece of tramp iron. At the Caselton, Nevada, plant of the Combined Metals Reduction Co., sulphide ores are treated; therefore, it was necessary that a tramp detector operating on only the magnetic properties of the tramp iron be used. Tramp iron detectors of this type operate on the principle that if a piece of tramp iron moves near a coil in a high intensity, steady magnetic field, the presence of the moving tramp iron causes the magnetic flux lines through the coil to change. This induces a mall current in the Coil. In series with the Coil is generally placed a relay sensitive to currents of 1 to 3 microamp. When the tramp iron passes near the coil the flux linkages change, causing this very sensitive relay to actuate. Since the contacts of such a relay are very small it must actuate a second relay capable of breaking a larger current

Jan 1, 1951

Improvement of drilling operations through the development of new, unconventional drill bits is a prime research target at Sandia Laboratories, Albuquerque, N.M. Sandia is currently focusing efforts on four new bit designs which its engineers believe may eventually improve penetration and reduce operating costs. The Energy Research and Development Administration (ERDA) has budgeted $500,000 in support of this program to date. Two of the drill bits-one that chips rock with high voltage spark discharges, and another which fires small projectiles into the rock ahead of a regular roller bit-are designed to increase both penetration rates and downhole bit life.

Jan 8, 1975

By P. T. Carter, A. B. Murad, H. B. Bell

The distribution of manganese and oxygen between molten iron and FeO-MnO-SiO2 slags not saturated with SiO2 has been determined and used to calculate activities of MnO and SiO2 in MnO-SiO2 slags. These were found to be intermediate between the corresponding activities in FeO-SiO2 and CaO-SiO2 slags. THE equilibrium constant for the reaction between molten iron containing manganese and slags containing FeO and MnO, namely: FeO(slag) + Mn = MnO (slag) + Fe(1iquid) is most conveniently represented by: (MnO) Kmn== (FeOHMn] [Fe] is omitted, since for dilute solutions of manganese in iron, afe is approximately constant. When activities are used for (MnO), (FeO) and [Mn], Kmn is a true equilibrium constant and will apply to all types of slags, but when weight percentages are used, the values obtained for Kmn for different slags vary considerably. The equilibrium between iron containing manganese and relatively pure FeO-MnO slags has been investigated by several workers;1-4 the most recent investigation reported is that of Chipman, Gero, and Winkler.4 Their results, corresponding to slags containing up to 4 pct SiO2, were represented by the equation: 6440 log KMn = +2.95 In this case both slag and metal may be assumed to be ideal solutions, therefore the values of Kmn so derived represent the true constant for the manganese reaction. As the molecular weights of MnO and FeO are almost equal, weight concentration of these oxides may also be used in the above expression. Acidic oxides such as SiO2 and P2O5 affect the activities of FeO and MnO differently, so that when total concentrations by weight of FeO and MnO are used in the above expression for Kmn the values obtained are no longer constant. These will be denoted by K'mn. Körber and Oelsen5 investigated the manganese reaction using silica-saturated iron-manganese-silicate slags and found: 7940 logK'mn =3.172 This corresponds to Kmn values much higher than those obtained for pure oxide slags. The results of Körber and Oelsen, and Chipman, Gero, and Winkler are summarized in Table I. In the present investigation it was decided to study the manganese reaction using iron-manganese-silicate slags not saturated with silica, and which fell mainly between the orthosilicate join 2FeO . SiO2 - 2MnO.SiO2 and the FeO-MnO side of the ternary system FeO-MnO-SiO2. It has been shown" that the phases present in solidified slags of this part of the diagram are (FeO, MnO) and (2Fe0.Si02, 2Mn0-SiO,) solid solutions. Such an investigation would be of interest in deoxidation and also gives information on activities in liquid slags. This equilibrium has not as yet been investigated successfully. Hilty and Crafts7 attempted to examine this reaction in a rotating crucible furnace, but were unable to obtain suitable slag samples. In the present investigation one series of experiments was carried out in a rotating crucible furnace, because the success of Taylor and Chipman8 with such a furnace in their study of oxygen distribution between molten iron and (CaO, MgO) — FeO-Si0, slags suggested that it would minimize contamination of the slag by the crucible material. A second series was carried out using a wire-wound resistance furnace. Rotating Crucible Furnace Experiments In all cases the metallic charge consisted of 800 to 1000 g Armco iron containing 0.02 pct C, 0.03 pct Mn, and traces of Si. Manganese and silicon additions consisted of electrolytic manganese (99.9 pct)

Jan 1, 1953

By Michael P. Richardson

INTRODUCTION This paper is intended to be a summation of the state-of-the-art i n draw theory and draw- point spacing. Knowledge of this very important factor in the successful design and operation of a block caving mine is scarce and nonconclusive. It is hoped that the presentation of this paper will stimulate interest and discussion which will lead to a stronger understanding of these a1 1 important factors. Please note that block caving as used here- in refers to block, panel, and mass caving systems in general, not just to the specific system of block caving where discrete blocks of ore are prepared and caved as a unit. DRAW THEORY The knowledge of draw theory as related to the practice of block caving mines is, unfortunately, very limited. In recent years much work in draw theory has been done in respect to sublevel caving systems and an understanding of draw mechanics relating to sublevel caving seems to be emerging. This work is certainly helpful to those of us interested in block caving but the question of "what goes on up above" still hounds us since we are more interested in the region of draw which begins just above the area where sublevel caving interest ends. Herein is presented a brief summary of draw theory with an attempt to look at the factors which can help our understanding of the area of draw influence in block caving mines. Nature of Gravity Flow An understanding of the flow of granular material (rock, sand, grain, or prill as examples) is the first step toward understanding block caving draw. If we take a supported column of granular material and allow gravity flow through an aperture at the bottom of the column, an ellipsoidal shaped zone of disturbance of the in-place material will form and grow with extraction of material through the aperture. The volume of this zone of disturbance or loosening is about 15 times the volume of material extracted at any given time (Kvapil, 1980). Figure 1 shows the development over time of the zone of disturbance. The ellipsoid of disturbance represents a future ellipsoid of extraction which will equate to the volume of materia1 extracted by that future time. Extraction involves the movement of the particles located vertically over the drawhole directly downward while material outside this direct vertical volume moves radially inward and down toward the drawpoint as shown in Figure 2a. Figure 2b shows the result of this motion on originally horizontal strata within the ore column. Increased draw increases the eccentricity of the ellipsoidal volume or, in other words, the ratio of the height over the width of the disturbed area increases as ore is withdrawn from the column (Kvapil , 1980). This becomes important to block caving since eventually a vertical cylinder of draw will be approximated as this ratio increases without bounds. Figure 3 shows this result. The width of this draw cylinder is a critical dimension for the determination of draw point spacing in relationship to block caving mine design. McCormick (1968) for one, felt that within this cylinder of draw, mass flow would take place. This is the

Jan 1, 1981

By Michael F. Dunn, Francis S. Kendorski

The fall of rock from strip coal mine highwalls continues to be the largest single source of fatal accidents, so methods to improve highwall stability through improved blasting practices were investigated in the field. This paper covers the results of a project to improve, using existing and proven technology, unstable highwall conditions through better blasting practices in Appalachian strip coal mines. Better borehole blasting agent distribution and optimization of burden, spacing, and delay periods allowing satisfactory breakage with minimal backbreak were the objectives. At a selected field site, geologic conditions were closely examined with regard to joint orientation and spacing, and resulting slope stability considerations. Utilizing surface blasting concepts of trying to achieve flexural failure of the rock mass both horizontally and longitudinally by appropriate relationships between burden, spacing, and hole length, as well as delay time sequence to achieve optimal confinement and breakage, successful results were achieved. A test series of eight blasts was completed and the resultant highwall monitored by repetitive photography. Actual blockfalls could be measured and the stability for each blast design thus quantified. The study of drilling and blasting economics along with equipment performance led to an economic model of blast parameters and the identification of blast design cost benefits. The work demonstrated that small strip mining companies are able to achieve a more stable highwall excavation utilizing presently available technology, equipment, and explosive products at improved operational cost and safety.

Jan 1, 1983

By Ralph Wilcox

The diamond drilling of certain characters of unstable rock formation, as, for example, the copper-bearing schists of the Miami district in Arizona, is rendered most difficult by what is known as a caving " of the sides of the drill holes. As this caving is very greatly increased by the action of flowing water, it occurred to me, after experiencing a great deal of difficulty with caving in diamond-drill holes which I was drilling for the Miami Copper Co., that if I could substitute air for water, much of the caving—with resultant difficulties, such as decreased speed of sinking and increased consumption of diamonds—would be overcome. After some experimenting, I found that it was perfectly practicable to substitute air for the water; forcing the air down the hollow rotating rods in the same manner as is done with water, the air passing out around the bit, which is thus cooled, and ascending on the out~ide of the rods to the collar of the hole, carrying the borings in just as satisfactory a manner as had been done by the water, but without the accompanying destruction or caving of the sides of the drill holes such as had been so generally experienced with the water. When water was encountered in the drilling this water was forced up to the collar just as it would have been had water been used in the drilling, but with the correspondingly decreased flow there was relatively less washing or caving of the sides of the drill holes. The only change necessary in the arrangement of the drill is that a cross instead of a tee is used at the collar of the hole. A tightly woven jute bag is attached to one arm of the cross, for collecting and filtering the sample; and when drilling in dry ground a jet of water is attached to the opposite arm of the cross, to collect the dust and wash down the sample into the bag. The rods rotate through a stuffing box attached to the upper opening of the cross. The distention of the jute bag by the issuing air indicates the operating conditions as sufficiently as did the flow of water when using water in the drill hole. The small percentage of core recovery rendered it necessary to

Jan 1, 1914

By Edward C. John, Wilbur H. Smith

At the Bingham Canyon pit operated by Kennecott's Utah Copper Division, the demand for geology has recently grown and diversified so rapidly that it has necessitated a revolution in geologic mapping techniques. The most significant changes in method have been in the preparation of the base map and in the computer application of collected data. Formerly maps were prepared by surveying with a transit or plane table. Now, however, a photogrammetric map with a scale of l in. to 200 ft is prepared semiannually and updated continuously to keep pace with the removal of more than 350,000 tons of material a day. Larger-scale bases of areas with specific problems such as un- stable slopes are prepared with aerial and terrestrial photography and photo-mosaics. Note sheets designed for computer application speed the processing of data. The multiplying applications of geology at the Bingham mine now include studies of the effect of structure, rock type, and alteration on slope stability, the relationship of sulfide mineral distribution to concentrating results, the effect of rock and mineral types on waste dump leaching, and the requirements of a reliable internal source of silica flux for smelting, as well as many others.

Jan 9, 1969

By John Birkinbine

An item of considerable importance to the producers of pig-iron is the disposition of the slag or cinder from the blast-furnace; and various plans have been adopted at different works to care for the rapid accumulation of this generally waste material. The charge per ton of iron made which must be allowed for the care of cinder is sufficient in times of business depression to give plants having facilities for disposing of their slags an advantage over others less favorably arranged, and to allow iron to be produced profitably in the one case and prevent a profit in the other. The varied methods employed and the means of conveyance utilized need not be detailed. It is sufficient to say that the large outputs of American blast-furnaces, and consequent rapidly augmenting dump-piles, have brought into general favor the use of cars carrying the slag in a liquid condition. The advantages of this method are the prompt removal of the slag, the reduced space occupied by the dump-piles, and the facility of converting the slag into such forms for use as may be desired. The progress in iron-manufactlire is also marked by a more general adoption of methods by which molten metal is carried in vessels away from the point of its production; and, anticipating the prospective advance in pig-iron manufacture, it does not seem unreasonable to prophesy the early abolition of casting-houses at blastfurnaces, particularly where several are grouped together; or the casting of steel ingots away from the converters or furnaces. In some large blast-furnace plants, the iron is carried molten from the blast-furnaces to the converters or other furnaces. Even where it is cast into pigs, casting-sheds removed from the immediate vicinity of the furnace-stack would, perhaps, be superior to casting in beds in front of the furnaces. The idea of casting-sheds appears to present the following advantages : 1st. The equipment of boilers, hot-ovens, and blowing-machinery could be closely grouped around the blast-furnace stacks, permitting

Jan 1, 1887