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By L. W. Saperstein, D. Yeung, L. B. Phelps

Introduction The success of preventive methods for the mitigation of coal mine drainage formation will require a marriage of the minimization of initial coal mine drainage formation, the minimization of toxic fluid formation after toxic material disposal, the minimization of the mobilization and transpor¬tation of formed toxic fluids, and the maximization of the rate of diultion and attenuation of the formed toxic fluids. This paper contributes to the understanding of factors af¬fecting mobilization and dilution and attenuation of formed toxic fluids. When water containing a salt content different from in situ pore water in the soil is passed through a body of soil, the concentration of salts in the outflow will gradually change composition in a manner that depends on the kinds of hydraulic processes that occur in the soil. These processes are molecular diffusion, lateral dispersion, longitudinal dispersion, chemical reactions or exchange, physical adsorp¬tion, and biological retardation. This note considers only the first three processes. These three microscopic processes can be analyzed statistically on a probability basis. Such results, confirmed experimentally, indicate that a tracer introduced instantaneously as a point source will tend to form a Gaussian normal distribution as it moves downstream (Todd, 1964). Dilution During Flow The closed-form soltuion for pulse or instantaneous injec¬tion of a tracer during confined flow in a homogeneous porous medium shows that the maximum tracer concen¬tration at a point in space, x, after the time interval, t*, is given by [ ] where Aa is the effective flow cross-sectional area; A is the column cross-sectional area; a is soil porosity; M is mass of the injected tracer; C is concentration of the tracer in the permeating fluid and is a function of x and t*; D is the longitudinal dispersion coefficient; and va is the interstitial fluid velocity (Klotz and Moser, 1974). Therefore, the following conclusion can be made: • For a medium with a constant longitudinal dispersion coefficient, D, a constant soil porosity, a, a constant cross¬sectional area, A, and a fixed mass of injected tracer, M, Cmax will decrease as the time of peak outflow concen¬tration t* increases. • For a medium with a constant longitudinal dispersion coefficient, D, a constant soil porosity, a, a constant cross¬sectional area, A, a fixed mass of injected tracer, M, and a constant interstitial fluid velocity, va Cmax will decrease as the distance of travel, x, increases. • For a medium of constant cross sectional area, A, con¬stant soil porosity, a, a constant mass of injected tracer, M, and a fixed distance of travel, x, Cmax will decrease as D/va increases. Klotz and Moser (1974) concluded that D is about proportional to no.3 where r) is the kinematic viscosity; D is about proportional to a-3 where a is soil porosity; D in¬creases with increasing grain size; D increases as grains become less spherical; D increases with greater grain rough¬ness and angularity; D increases with increasing uniformity coefficient; and D is significantly affected by grain size and uniformity coefficient. The remaining parameters are not significant. Numerical Simulation Studies Numerical simulation studies were used to investigate the nature of flow and the optimum length of a toxic package within a saturated porous medium of fixed dimensions and configuration (Fig. 1). The width and position of the package was maintained constant (Phelps et al., 1981). Results indicate that if the package extends throughout the length of the model, the flow is vertically downward and

Jan 1, 1984

By B. K. Larkin

Solutions to the diffusion equation for a line source located anywhere in a region bounded by a circular discontinuity are presented. Such solutions follow automatically from the Green&apos;s function presented by Jaeger.4 Petroleum industry applications of this problem would include transient compressible fluid flow in porous media bounded by a discontinuity. Since several recent papers have treated the subject in less general form, it would appear that many workers in this area of the petroleum industry are not aware of Jaeger&apos;s work. STATEMENT OF THE PROBLEM In several trearments1,2,3 of the transient flow of compressible fluids in porous media it was convenient to consider a region to be bounded by a circular discontinuity. In such a region (Fig. I), the properties in Region 1, r < a, are constant but different from the properties in Region 2, r > a. Hurst, l using the Laplace transform, obtained solutions for a line source located in the center of such a porous medium. The purpose of this work is to point out that a much earlier paper by Jaeger4 presents the solution for a line source located anywhere inside the discontinuity. The assumption is made that a line source may be used to approximate a well. In the following material it is convenient to use the terms source and well as being equivalent; however, the reader should remember the distinction in applications. SOLUTIONS Jaeger presented the Green&apos;s function for a line source, or well, in the composite region shown in Fig. 1. In the most general form, the solution for a system of j wells in Region 1, each producing at a time varying rate, qi (t), is

GWILLIAM H. CLAMER* (Philadelphia, Pa.).-Sulphur is not so detrimental in its effect if oxygen is also present, so that in sulphur-carrying bronzes and brasses, it is advantageous to maintain a certain percentage of oxygen. As a matter of fact, it would be possible sometimes to correct difficulties by actually adding oxygen. If the cathodes were charged directly into an electric furnace in a neutral or reducing atmosphere, a very high grade of copper would result by a simple melting operation. This would very largely eliminate the loss occasioned by melting in a reverberatory furnace. In such a furnace a large amount of slag is produced during the oxidizing stage of refining. Notwithstanding the fact that melting in an electric furnace might be somewhat more expensive than melting in a fuel furnace, the ultimate result would be a saving and the production of a very high grade of copper.

Jan 1, 1919

By J. A. Elias, A. J. Heckler

A simplified method is described for the prepauatior~ of comnposite samples for determination of one quadrant of an X-ray pole figure of a sheet material by the Schulz reflection method. Other special conzposite sampling methods were used to investigate specific areas of the pole figures. Plotting nets for these sampling plans were drawn by a computer. Step-scanning techniques were used to obtain detailed information about specific regions of a pole figure. Satisfactory pole figures were obtained for large-grained (0.5 to 1 in. diam) sheet materials. COMPOSITE sampling techniques for preparing one quadrant of an X-ray pole figure have been reported by a number of authors.&apos;-5 All of these methods are similar in that they use a composite sample prepared by stacking and holding together coupons cut from a sheet material. The schulze reflection technique is applicable to the composite sample so that only minor corrections are needed for defocusing and absorption effects. Also, a relatively large area of a sheet is sampled through the use of multiple cross sectional pieces. In general, sampling methods necessary to obtain a composite-type specimen have been formidable enough to discourage their use in routine pole figure determinations. This paper presents a versatile sampling technique which is simpler than those previously described along with an accurate method for obtaining stereographic plotting nets for any orientation of a composite specimen surface. A step-scanning technique is used to obtain more quantitative determinations of specific regions in pole figures, and the composite technique is satisfactorily applied to determine pole figures of very large grained sheet materials. REVIEW OF PREVIOUS TECHNIQUES Mueller and ~nott&apos; first proposed a technique for obtaining one complete quadrant of an X-ray pole figure by using a sheet sample and six different composite samples in which the individual coupons were aligned and held together by two types of jigs. Data from the seven different samples were overlapped to obtain a single quadrant. ~eieran~ and Lopata and ~ula~ obtained a complete quadrant of a pole figure from a single sample prepared by forming a cube from coupons cut from a sheet. These coupons were bonded together using an epoxy cement, and a cut was made at 54.7 deg to the normal, transverse, and rolling directions of the sheet, Fig. I. The normal direction of the cut face projects into one quadrant of a stereographic projection at equal angles to the three principal orthogonal reference directions mentioned above. X-ray reflection data obtained along a spiral path in physical space could then be plotted on a stereographic net offset 54.7 deg from the normal, as shown in Fig. 2. A rotation about an axis representing the surface normal is designated as a, and a rotation about an axis lying in the plane of the surface is 4. From Fig. 2 it is apparent that a tilting angle of no more than 55 deg @ is necessary to obtain the complete quadrant. ~eber~ devised an improved sampling technique by cutting coupons 45 deg to the rolling direction of a sheet, stacking and bonding these with an epoxy cement at an angle of 54.7 deg to a reference plane, and finally grinding and lapping a flat specimen surface parallel to this plane. An important consideration of this technique and that of Lopata and ~ula~ is variation in the diffracting power of the specimen surface due to the bonding medium. While any composite-type sample will have some such variation due to boundaries between coupons, the problem can be minimized by elimination of the bonding medium and by avoiding prolonged etching times which could lead to significant inter lame llar attack of the coupon faces. EXPERIMENTAL TECHNIQUE We were working concurrently though independently on a technique similar to ~eber&apos;s,&apos; but which does not

Jan 1, 1968

By P. Barnes

In a paper recently read before the Institute by Mr. W. A. Goodyear, a useful presentation was made of the subject of the production of&apos; water-gas on a large scale, by the use of a regenerative form of apparatus. By way of supplement to that paper, a brief statement of the details of a plan which was carried out at the works of the Elgin National Watch Company at Elgin, Ill., may be of interest, &apos;although the ultimate result of the working of the producer was not successful or satisfactory. This company had decided to build a gas-works for the supply of illuminating gas to their factory, on a much larger scale than that of the petroleum-works which had very successfully supplied the smaller buildings for many years, and in March, 1882, the material for a gas-making cupola furnace was purchased. A few weeks later it was decided to make the attempt to bnrn the gas under the steam-

Jan 1, 1884

By Bruce A. Kennedy

If it had not been for the persistent cold wind, the sun blazing out of a cloudless blue sky would have made it one of those warm, idyllic early spring days which attract the socalled "snowbirds" to Northern Mexico for a vacation at this time of year. At a drill site perched on top of a rather exposed mountain we were installing a number of borehole extensometers in diamond drill holes. A Threading Problem For the uninitiated in geotechnical instrumentation, a borehole extensometer is a series of anchors installed at various depths in a borehole, each anchor being independently connected by a tensioned wire to a measuring device set in the collar of the hole. Any movement of the rock at depth is detected by the anchors and transmitted by the wires to the measuring device. Flexible plastic tubing is used as a spacer between the anchors and the measuring wires are run up the inside of the tube. At this particular site we were installing an instrument string nearly 1000 ft in length. Threading wire only 0.041 in. in diam through 1000 ft of plastic pipe is almost as difficult as getting the proverbial camel through the eye of a needle.

Jan 1, 1971

By C. L. Colburn

THE statutory requirements of the States and the district rules are, broadly speaking, similar. There is just enough difference to make it tantalizing. DIFFERENCES IN STATE LEGISLATION GOVERNING THE LOCATION OF MINING CLAIMS Discovery Discovery is the first step in the location of the claim. The provision of the Revised Statutes (2320) is, "No location of a mining claim shall be made until the discovery of the vein or lode within the limits of the claim located." Strictly speaking, discovery may be defined as the finding of ore or metalliferous rock in place in a well-defined vein. This definition was too strict, so discovery extended later to cover such indications of the presence of ore, within rock in place, as would justify an experienced miner in spending his time and money with a reasonable expectation of finding ore in paying quantities. According to Colorado statutes a discovery must show a well-defined crevice; in Arizona, a lode, deposit, or mineral in place; in Montana, a well-defined crevice or valuable deposit; in Nevada, a lode or deposit of mineral in place. It is wrong to require a discovery. An honest prospector, wishing to obey the law, finds himself compelled, in most cases, to evade this point. In Clear Creek district, Colorado, a quartz seam will constitute a discovery; in Butte, a red capping; in Leadville or Ely, it is any place where a man can find a piece of vacant ground big enough upon which to sink a 10-ft. hole. If the vein or deposit outcrops a man can show a discovery, but if it does not outcrop it is foolish to compel him to show one; and this point has been gently side-stepped. Any hole 10 ft. deep now constitutes a discovery. It is no use having laws that the people cannot consistently obey. No sane man will dig unless he expects to find mineral, and he should be protected while digging. He should be required to show that he has mineral ground only when he comes to patent.

Jan 6, 1914

By J. B. Seabrook

The accompanying Fig 1 is a graphical scheme of intermediate accuracy for expediting interconversions of mol, weight, and volume percents. This chart consists of a family of curves of mol or atomic or volume percent plotted against weight percent, each curve in the family providing for a certain ratio of molecular or atomic weights or densities. Thus, the whole range of variations is presented in a very familiar format, and the conversion is effected simply by choosing the proper curve and reading off the required values. An entire series of conversions for a given binary system can be found by following the appropriate curve. It is interesting to examine the analytical geometry of the plots. The curves, which must fit into a square and all join at the 0 and 100 pet points, may be shown to be hyperbolas with their centers on the extension of the diagonal of the square which they intersect. Multiplying out the expression x A atomic fraction of A = y = ------ where x is the weight fraction of A, and A and B are atomic weights, we get xy+A/By- A/Bxy=x Upon rotating and translating axes and avoiding imaginaries, it is found that the angle of rotation is —45°, the origin moves upv2/2 units andv2/2(A/B+1/A/B-1) units to the right, and the standard form is Thus the curves are equilateral hyperbolas, their centers are units away from their intersection with

Jan 1, 1950

By G. G. Gunther, C. L. Boeke

THE zinc deleading processes at the Parral and Santa Barbara mills are described separately to provide a basis for comparison. Although the two procedures are fundamentally alike, there are some differences in application to meet specific conditions. The Asarco mill at Parral in the State of Chihuahua is a flotation plant treating 1450 metric tons per day of complex sulphide copper-lead-zinc ores. In general, the procedure used for selective separation of the minerals into a copper, a lead, and a zinc concentrate follows the usual practice. First, a bulk copper-lead concentrate is floated and then separated into a final copper and a final lead concentrate by the sulphurous acid process. A small tonnage of high grade gravity lead concentrate is tabled from the bulk copper-lead cleaner tailing before it is reground so as to avoid undesirable over-grinding and sliming of this portion of the lead mineral. Next, a zinc concentrate is floated from the lead rougher tailing and, as described later, is separated into a final lead product and a final zinc concentrate. Finally, the zinc rougher tailing receives a strong scavenger float to remove all recoverable middling values for regrinding and return to the flotation circuits. The slime is separated from the scavenger flotation product, and only the sand portion goes to the regrind section. The minerals in the separated slime are extremely resistant to all methods of selective separation and pose one of the major problems awaiting solution. Nevertheless, the slime shows a profit when mixed with either the lead or the zinc concentrate, except when metal prices are very low, so it is accepted as a final product for lack of a more profitable method of handling it. In contrast, the minerals in the reground sands of the

Jan 1, 1953

By G. G. Gunther, C. L. Boeke

THE zinc deleading processes at the Parral and Santa Barbara mills are described separately to provide a basis for comparison. Although the two procedures are fundamentally alike, there are some differences in application to meet specific conditions. The Asarco mill at Parral in the State of Chihuahua is a flotation plant treating 1450 metric tons per day of complex sulphide copper-lead-zinc ores. In general, the procedure used for selective separation of the minerals into a copper, a lead, and a zinc concentrate follows the usual practice. First, a bulk copper-lead concentrate is floated and then separated into a final copper and a final lead concentrate by the sulphurous acid process. A small tonnage of high grade gravity lead concentrate is tabled from the bulk copper-lead cleaner tailing before it is reground so as to avoid undesirable over-grinding and sliming of this portion of the lead mineral. Next, a zinc concentrate is floated from the lead rougher tailing and, as described later, is separated into a final lead product and a final zinc concentrate. Finally, the zinc rougher tailing receives a strong scavenger float to remove all recoverable middling values for regrinding and return to the flotation circuits. The slime is separated from the scavenger flotation product, and only the sand portion goes to the regrind section. The minerals in the separated slime are extremely resistant to all methods of selective separation and pose one of the major problems awaiting solution. Nevertheless, the slime shows a profit when mixed with either the lead or the zinc concentrate, except when metal prices are very low, so it is accepted as a final product for lack of a more profitable method of handling it. In contrast, the minerals in the reground sands of the

Jan 1, 1953

By G. G. Gunther, C. L. Boeke

THE zinc deleading processes at the Parral and Santa Barbara mills are described separately to provide a basis for comparison. Although the two procedures are fundamentally alike, there are some differences in application to meet specific conditions. The Asarco mill at Parral in the State of Chihuahua is a flotation plant treating 1450 metric tons per day of complex sulphide copper-lead-zinc ores. In general, the procedure used for selective separation of the minerals into a copper, a lead, and a zinc concentrate follows the usual practice. First, a bulk copper-lead concentrate is floated and then separated into a final copper and a final lead concentrate by the sulphurous acid process. A small tonnage of high grade gravity lead concentrate is tabled from the bulk copper-lead cleaner tailing before it is reground so as to avoid undesirable over-grinding and sliming of this portion of the lead mineral. Next, a zinc concentrate is floated from the lead rougher tailing and, as described later, is separated into a final lead product and a final zinc concentrate. Finally, the zinc rougher tailing receives a strong scavenger float to remove all recoverable middling values for regrinding and return to the flotation circuits. The slime is separated from the scavenger flotation product, and only the sand portion goes to the regrind section. The minerals in the separated slime are extremely resistant to all methods of selective separation and pose one of the major problems awaiting solution. Nevertheless, the slime shows a profit when mixed with either the lead or the zinc concentrate, except when metal prices are very low, so it is accepted as a final product for lack of a more profitable method of handling it. In contrast, the minerals in the reground sands of the

Jan 1, 1953

By F. I. Stalkup

Vapor-liquid phase equilibrium experiments have been conducted in a static equilibrium cell on mixtures of a light, 45 API stock- tank gravity reservoir fluid and a rich hydrocarbon gas containing approximately 55 mole per cent of intermediate hydrocarbons. Both apressure-vs-composition study of the gas and a simulated reservoir fluid, and a multiple-batch contact simulation of the condensing-gas-drive oil recovery process were performed. In the latter experiments equilibrium gas and liquid compositions were analyzed. Also, conventional, "condensing-gas-drive", long-tube displacement experiments of the reservoir fluid and gases of various richness were performed. The results of these experiments could not be satisfactorily interpreted by the conventional pseudo-ternary-diagram representation of multicom-ponent phase behavior. The results seem to be explained better by considering a bubble-point surface and a dew - point surface joined in a plait-point locus. Portions of the plait-point locus cannot be "seen" directly by the rich hydrocarbon gas because of curvature of the dew-point surface. In such a system, continuous injection of the rich gas over stationary reservoir fluid might form a zone of contiguously miscible compositions from pure rich gas to pure reservoir fluid by: (1) saturating the reservoir fluid with injected gas to the bubble-point surface; (2) creating by mass transfer with fresh injected gas a path of contiguously miscible compositions along the bubble - point surface to the plait-point locus; and (3) creating by mass transfer with additional injected gas a path of gas compositions along the dew-point surface up to the point where direct miscibility results between dew-point fluid and the injected rich gas. INTRODUCTION The use of the pseudo-ternary-phase diagram to illustrate miscible displacement phase behavior has been discussed by several authors.5,7 Such a representation of phase behavior is not rigorous, but the ternary diagram nevertheless gives a qualitative picture of what actually occurs in a miscible displacement process. Fig. 1 is a typical illustration of miscible displacement phase behavior by a ternary diagram. The multicomponent hydrocarbon system is divided into three pseudo-components: a light fraction containing methane and nitrogen, an intermediate fraction containing ethane through hexanes plus carbon dioxide, and a heavy fraction containing heptane and heavier components. A two-phase region is bounded by a dew-point curve and a bubble-point curve, which are joined at the critical point. The concept deduced from such a representation for miscible displacement by a condensing-gas-drive process is as follows: a rich gas G, which lies to the right of the limiting tie line through the critical point C, is injected into the reservoir and contacts reservoir fluid L, saturating the reservoir fluid to give bubble-point fluid L1 and equilibrium dew-point gas GI. Continued injection of rich gas changes the composition of the saturated liquid L1 through a series of liquid compositions lying along the bubble-point curve, until the critical composition C is reached, at which point direct miscibility with the rich gas is achieved. Some equilibrium gas with compositions lying along the dew-point curve from G1 to C is also formed in this process. Thus, continuous injection of rich gas forms a

Jan 1, 1966

By W. Mostowitsch, H. O. Hofman

In our investigation of the Behavior of Calcium Sulphate at Elevated Temperatures with Some Fluxes,&apos; we incidentally studied the decomposition of ferric oxide when heated in a current of dry air. We found that at 1,500° C., with 15-min. periods of heating, Fe²,O³, hardly changed in weight, the greatest loss being 0.23 per cent., and we therefore concluded that the compound remained unchanged at 1,500° C. in a current of dry air. In a more recent experiment we heated Fe²,O³, in a current of dry air and found that there was a decided loss in weight. A new investigation upon the behavior of Fe², O³, using a larger amount of substance and heating for a longer period of time, revealed the fact that a measurable dissocia-

Jan 1, 1910

By C. E. Birchenall, F. N. Rhines, L. A. Hughes

A. J. Shaler—I should like to congratulate the authors on the presentation of this paper, which we have been awaiting a long time. The view they have taken of the sintering process, namely that voids are comparable to particles of a second phase capable of dissolving to a slight extent in the metal phase, is an interesting but dangerous one. Pines has given a first-order solution of the problem and Has predicted a decrease in the concentration of pores near the surface. The authors of the present paper have experimentally demonstrated the second-order effects, that is, the diffusion of the space phase between voids of different sizes, and also the movement of atoms from highly curved parts of a void to less curved regions of the same void. I have recently calculated the rate of vapor-phase transport within odd-shaped pores in copper at 850 °C and found that probably at that temperature volume flow is the more rapid shape-changing mechanism. The authors of the present paper have found that at 1000°C, vapor-phase transport is dominant. There is no disagreement here, I think. The dominant phenomenon can easily be different&apos; in different temperature ranges and with different pore shapes: I used a cylinder going to a sphere, not a tricuspid going to a "triple cuspidor." But there is some danger in the other art of the explanation, that is, in the study of the diffusion of vacancies from a pore to its neighbors and to the outside. A vacancy is very different in dimension from an atom. When it moves, it carries a field of elastic strain. This has to be taken into account. A concentration gradient of vacancies can cause them to diffuse. But in the absence of such a gradient, they can be made to diffuse by a field of stress. What happens in some of our experiments, and it is most noticeable in the shrinkage of synthetic cylindrical pores, like the tubes we have been working with, may be broken down into the following steps. (1) The presence of a surface establishes a vacancy concentration gradient, as Dr. Kuczynski and the present authors have shown. (2) Vacancies then diffuse in order to decrease this gradient. (3) In so doing, they cause an elastic field to be built up in such a direction as to oppose the diffusion, so that it slows down until it reaches a steady-state rate. (4) The steady-state flow is due to the fact that the surface tension acting on curved surfaces applies a stress to the system which itself mechanically causes vacancy diffusion. What I have said is that the diffusive types of flow of the authors and of Dr. Kuczynski are transient phenomena which soon stop if the pores are large. We are then left with a mechanical problem only, and our researches have not yet disclosed just what the mechanism of flow is; it may be a slip process, or it may take place by a vacancy diffusion of the type Nabarro has de-

Jan 1, 1951

By R. W. Fenn, H. A. Lepper, W. R. Hibbard

A. J. Shaler—I should like to congratulate the authors on the presentation of this paper, which we have been awaiting a long time. The view they have taken of the sintering process, namely that voids are comparable to particles of a second phase capable of dissolving to a slight extent in the metal phase, is an interesting but dangerous one. Pines has given a first-order solution of the problem and Has predicted a decrease in the concentration of pores near the surface. The authors of the present paper have experimentally demonstrated the second-order effects, that is, the diffusion of the space phase between voids of different sizes, and also the movement of atoms from highly curved parts of a void to less curved regions of the same void. I have recently calculated the rate of vapor-phase transport within odd-shaped pores in copper at 850 °C and found that probably at that temperature volume flow is the more rapid shape-changing mechanism. The authors of the present paper have found that at 1000°C, vapor-phase transport is dominant. There is no disagreement here, I think. The dominant phenomenon can easily be different in different temperature ranges and with different pore shapes: I used a cylinder going to a sphere, not a tricuspid going to a "triple cuspidor." But there is some danger in the other art of the explanation, that is, in the study of the diffusion of vacancies from a pore to its neighbors and to the outside. A vacancy is very different in dimension from an atom. When it moves, it carries a field of elastic strain. This has to be taken into account. A concentration gradient of vacancies can cause them to diffuse. But in the absence of such a gradient, they can be made to diffuse by a field of stress. What happens in some of our experiments, and it is most noticeable in the shrinkage of synthetic cylindrical pores, like the tubes we have been working with, may be broken down into the following steps. (1) The presence of a surface establishes a vacancy concentration gradient, as Dr. Kuczynski and the present authors have shown. (2) Vacancies then diffuse in order to decrease this gradient. (3) In so doing, they cause an elastic field to be built up in such a direction as to oppose the diffusion, so that it slows down until it reaches a steady-state rate. (4) The steady-state flow is due to the fact that the surface tension acting on curved surfaces applies a stress to the system which itself mechanically causes vacancy diffusion. What I have said is that the diffusive types of flow of the authors and of Dr. Kuczynski are transient phenomena which soon stop if the pores are large. We are then left with a mechanical problem only, and our researches have not yet disclosed just what the mechanism of flow is; it may be a slip process, or it may take place by a vacancy diffusion of the type Nabarro has de-

Jan 1, 1951

By Howard R. Hume, Terry R. West, William R. Judd

One of the outcomes of a sector slope design in a large open pit in the western United States has been the scrutiny of the structural domain concept. These domains essentially define the area of influence of particular structural characteristics. In the present instance these structural characteristics are joint discontinuities. One of the major drawbacks of defining a domain is that unless large quantities of discontinuity data are available this process of definition is largely qualitative in nature. Viewed from a discontinuity analysis aspect the orientations of all the major joint sets at a given point are a concise descriptor of the structural geologic regime at that location. This is important to domain boundary definition, this in turn is extremely important for assigning which joint sets to use as input for slope stability analysis in a given discontinuity domain. An attempt has been made to develop a quantitative method for defining these discontinuity domains based on limited amounts of orientation data thereby reducing the subjectivity normally involved in such operations. Subjectivity is not always a problem if large quantities of joint orientation data are available, since the mean and variance of joint clusters always can be compared and then grouped to define these domains. However, even this method suffers from the problem that only a single joint set orientation can be considered at a time during the grouping process. On the other hand a discontinuity domain requires that all joint sets at a point be considered simultaneously to truly define the structural discontinuity character of that point. This provides a far more complete

Jan 1, 1982

By Hon. Charles McCrea

MINING taxation is a subject which bears definitely upon-the welfare of the mining indus-try. Every government must have a revenue but that revenue should be raised in such a way as to hamper as little as possible legitimate enterprise or industry. A mining tax should be fair, and one which appeals to the natural sense of justice. Our present system is a tax on net- profits after all expenses are met. On profits in excess of $10,000 the Mining Tax Act takes three per cent., one-half of which goes to the Govern-ment and one-half to the municipality in which the mines are situated, to meet local needs for roads, schools, etc. On profits from one to five million dollars", the tax is five per cent.; over five million, six per cent., and so on. The first $10,000 profit is exempt. The result is that if a mine is worked at a loss, it pays no tax at all; if it makes a small profit, it pays a small tax; if profits are large, the tax increases accordingly. It is difficult to imagine a fairer or less onerous method of taxation, or one better adapted to meet fluctuating conditions from year to year as profits rise or fall. A just and fair tax should be levied on profits, never on capital. There is, one branch of the mining industry upon which is levied a higher tax than upon other branches, namely, the nickel industry. I see no good reason why any branch of the mining industry should be discrim-inated against on a profits tax basis. A mining tax should not discourage development. The present tax meets this requirement. In the early years of a mine, when it is all outgo and no income, the mine pays no tax. Not until it reaches a productive and. profitable stage does the tax take effect, and then the mine can afford to pay it. Further, a tax on profits does not operate against the opening up of low-grade deposits, or those in which the chance of success is to a certain extent speculative.

Jan 10, 1923

By Earl R. Johnson

Ore broken at the mine or quarry face generally is loaded by power shovels into large trucks or rail cars and hauled to a primary crushing plant where it is reduced to a more workable size for ease in handling. The primary crushing plant is customarily located as close as possible to the center of gravity of the ore body and the projected limits of the mine pit to minimize the cost of hauling and to increase safety from flying rock as a result of blasting operations. A belt conveyor is used to transport the crushed product to a nearby ore treatment plant or, should this plant be located some distance away, the ore is loaded directly into cars and hauled by rail. Between trips the crusher product is accumulated in bins or stock piles. In all open pit mining and quarrying operations, the power shovel, the transportation equipment, and the primary crushing plant should work as a team, complementing each other. When establishing the design and selecting the equipment for these closely integrated operations, capital and operating costs for each unit operation must be weighed to achieve an optimum balance. Rising labor costs have given impetus to the universal trend toward greater efficiency, higher speed and larger equipment, and higher degrees of automatic control. The result is that power shovels have increased in size, haulage trucks are larger and faster, and only coarse crushers with feed openings adequate to receive run-of-mine lumps of ore with a minimum of secondary blasting are selected for new installations. These coarse crushers also have large through-put capacities, even when adjusted to produce a 6- to 10-in. size of product, thus making it possible to use a single stage of coarse crushing at the average mine. The use of a single crusher results in a compact crushing plant layout consisting of a dumping pocket for receiving loads of run-of-mine ore, a coarse crusher followed by a surge chamber for the crushed product, and a feeder to withdraw the ore at a uniform rate to deposit it on a belt conveyor. A

Jan 1, 1968

By Howard H. Fields

Any mining engineer with a desire to operate independently, with some financial backing, and with no fear of heavy responsibility and long hours, should be able to make a comfortable living in Mexico. Barring a few inconveniences such as a lack of satisfactory liability or accident insurance, the difficulty of obtaining repair parts for vehicles, and the length of time required receive returns from shipments, the operation of a small mine is not at all difficult. It is, in fact, a little easier to find a good prospect in Mexico than in the U.S.

Jan 11, 1950

By M. E. Fine

THE electrical conductivity (a) and the thermal conductivity (K) of metallic conductors, as demonstrated by Smith and Palmer1 and Hume-Rothery,2 are to a good approximation related by an empirical equation, K = A s T + B, in which T is the absolute temperature, and A and B are constants, the Lorenz constant and the lattice con- ductivity. Strictly speaking, the lattice conductivity is not a constant, but to some extent depends upon the electronic conductivity.3 By plotting K as a function of sT, this equation has been proved to a

Jan 1, 1951