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By V. Ogarlaci

Over 90% of the Romania's lignite reserve is located in the region of Oltenia, which is why this area is given special attention in the country's coal resources. Because the lignite deposit of Oltenia is comprised of 1-8 exploitable coal layers, their capitalizing calls for urgent arrangements to ensure rational exploitation under conditions of total safety, minimum losses and efficiency. The technology used the coal pits of North-Western Oltenia is the technology of excavation, transport and dumping in a continuous flow by using the complexes of excavation, transport and high-capacity dumping. The theme of this paper is of particular importance because the rhythmic operation in complete safety, is necessary both for sizing and keeping within the bounds of acceptable values, throughout the process of excavation of the geometric elements of the coal faces, marked by: the height of benches, slope angle and width of berms. Geometric dimensions of the benches of the open pits, the height of benches, slope angle and width of berms shall be calculated and shall be based on: the massif structure that forms the benches; physical-mechanical characteristics of rocks from the bench; working conditions, characterized mainly by mining and extraction methods applied; functional parameters of the mechanical equipment used to perform various operations on the coal face etc. For this study it was necessary a broad field for task tracking, measurement, research and design elements of the coal face, for land survey and a desk activity by: processing of topographic data, laboratory analyses on physical and mechanical properties of rocks and numerous specialized studies. In the final part, we bring some contributions to elucidating the issues of special importance for the lignite coal pits of Oltenia, coming up with data, graphics, formulas, solutions and concrete dimensioning of coal faces in terms of using technology in a continuous flow.

Aug 1, 2013

By Harry Roeser

Short cuts for determining the constants of oil decline curves, with the method of least squares as a starting point, are presented and applications made to practical examples. The nature of the raw data does not justify rigid adherence to the orthodox theory but does lend justification to convenient methods of approximation within reasonable limits. If the conventional form y = kxn were changed to y = k(x + c)', methods of determining the curves would be simplified and greater uniformity in calculated results would probably follow. As A result of the publication, several years ago, of some articles on determining the constants of empirical formulas, the determining the constant's of types of curves used for estimating the production decline of oil wells was brought to the writer for study. Methods requiring a minimum of time and labor and a maximum of rigor were sought, as it appeared that the nature of the data from which such curves are computed and the relative uncertainty of occurrence of the events predicted from them did not justify close adherence to the theory on which the solution of such problems is ordinarily based. The technical deficiencies of the solutions presented in this paper, from the standpoint of the method of least squares, are readily apparent to those familiar with that method, but their presentation in detail here is irrelevant to the subject matter. However, it is the author's conviction, after a rather exhaustive study of the problem, that the value of the solutions lose little by the approximate application of the conventional theory. It must be understood by those who use these formulas that the solutions herein given, and the formulas based on them, are merely facilities to aid the valuation engineer in forecasting future events. It is assumed, also, that before application is made of them, prescient judgment based on the circumstances in each case, shows that the forecast has some probability of realization. On this basis only will these formulas be found useful.

Jan 6, 1924

By P. Mattar

The geotechnical importance of studying fluid flow through porous media and soils in particular, becomes evident when dealing with groundwater movement in surficial geomaterials that can be initiated by hydraulic gradients that develop during construction activity, groundwater extraction, impounding of reservoirs and groundwater recharge during adverse climatic events. In a geotechnical context, rocks are regarded as virtually impermeable materials, with comparatively greater resistance to flow of water through their pore structure. The importance of the permeability of rocks comes to the forefront when deep geologic formations are used in geoenvironmental activities for disposal of hazardous and toxic materials. The permeability of the rocks encountered is of critical importance to these geoenvironmental activities since the movement or transport of the hazardous materials during their eventual release will be largely governed by the permeability characteristics of the geologic formation. The estimation of the permeability characteristic of geologic formations is a non-trivial exercise since the measure of permeability can be influenced by the scale at which the measurement is made. Regional-scale and borehole-scale estimates of the permeability can be greatly influenced by the inhomogeneities, including fractures, fissures, solution channels and other anomalies that are present in naturally occurring geologic media. These anomalies are considered to be site specific and can only be determined in a reliable fashion by either conducting tests at the appropriate scale or in the regional-scale through inverse analysis of tracer movement patterns in rock masses. The estimation of the permeability of intact units of a geologic medium has important geoenvironmental applications in connection with storage of wastes since the units in which repositories will be located should be sparsely fractured and the sealing of the fractures and fissures are a prerequisite to developing an efficient solution for storage. The intact permeability of geomaterials is therefore regarded as an important property that influences efficiency and reliability of geoenvironmental solutions for deep geologic disposal. The permeability of geomaterials such as concrete and cementitious grouts are also important to many geoenvironmental and infrastructure applications where durability of structural materials in general and cements used for sealing deep boreholes and other access shafts employed in waste management endeavours is influenced by the permeability characteristics of these materials

May 1, 2009

By Martin Harper

This paper concludes a five year program on research into the use of a portable X ray fluorescence (XRF) analyzer for analyzing lead in air sampling filters from different industrial environments, including mining, manufacturing and recycling. The results from four of these environments have already been reported. The results from two additional metal processes are presented here. At both of these sites, lead was a minor component of the total airborne metals and interferences from other elements were minimal. Nevertheless, only results from the three sites where lead was the most abundant metal were used in the overall calculation of method accuracy. The XRF analyzer was used to interrogate the filters, which were then subjected to acid digestion and analysis by inductively coupled plasma optical emission spectroscopy (ICP OES). The filter samples were collected using different filter holders or "samplers" where the size (diameter), depth and homogeneity of aerosol deposit varied from sampler to sampler. The aerosol collection efficiencies of the samplers were expected to differ, especially for larger particles. The distribution of particles once having entered the sampler was also expected to differ between samplers. Samplers were paired to allow the between sampler variability to be addressed, and, in some cases, internal sampler wall deposits were evaluated and compared to the filter catch. It was found, rather surprisingly, that analysis of the filter deposits (by ICP OES) of all the samplers gave equivalent results. It was also found that deposits on some of the sampler walls, which in some protocols are considered part of the sample, could be significant in comparison to the filter deposit. If it is concluded that wall deposits should be analyzed, then XRF analysis of the filter can only give a minimum estimate of the concentration. Techniques for the statistical analysis of field data were also developed as part of this program and have been reported elsewhere. The results, based on data from the three workplaces where lead was the major element present in the samples, are summarized here. A limit of detection and a limit of quantitation are provided. Analysis of some samples using a second analyzer with a different X ray source technology indicated reasonable agreement for some metals (but this was not evaluated for lead). Provided it is only necessary to analyze the filters, most personal samplers will provide acceptable results when used with portable XRF analysis for lead around applicable limit values.

Jan 1, 2007

By J. M. Lovejoy

Various estimates have been made as 60 the percentage of oil left in a field after the wells have become so small that it is no longer practical to produce them. Engineers have given the matter much study and can substantiate their figures by data taken from fields from the Appalachians to California. The average oil sand has a porosity of about 20 per cent., which gives a capacity per acre-foot of approximately 1500 bbl. The sand thickness in Oklahoma pools averages 20 ft. With 20 per cent, porosity and a 20-ft. sand thickness, the capacity per acre is 30,000 bbl., yet these pools will seldom yield more than 5000 bbl. to the acre. These figures gupport the theory that at least 50 per cent. of the oil remains in a sand after all known methods to recover it have been used. Certainly we can never recover all the oil, unless in years to come oil becomes so rare and yet so necessary that the price will justify sinking shafts into the abandoned fields and regular mining methods of drifting and stoping. However, with improved methods of production and conservation of the natural agencies of expulsion, we should be able to increase recovery. It is with this in mind that this paper, relating to the effect of back pressure on wells, is presented. Except in the fields where production is caused by hydrostatic pressure, the chief agency for getting oil out of the sand into the hole is the gas that occurs with the oil. After the pressure has declined, probably gravity also is a factor, but not an important one. With a given amount of oil in a sand and a given amount of gas occurring with the oil, the ratio of gas volume per barrel of oil is the key to the ultimate recovery from that sand. Our efforts should be along lines that will lower this ratio and make the gas, the agency given us by nature, do its work better and yield more of the oil, of which it is a part. T. E. Swigart,' of the U. S. Bureau of Mines, has published an extract of the paper he is preparing under the title "The Effect of Back Pressures. on Wells." The experiments described were made on two

Jan 1, 1924

By L. G. Huntley

The entire production of Colombia for 1927 was that from the Tropical Oil Co. concession. Production was approximately 14,000,000 bbl., of which 12,081,000 bbl. were exported from the Mamonal terminal of the Andian National Corp. near Cartagena. The balance represents that refined and used or marketed within Colombia. As production in 1926 was only 6,443,540 bbl., the increase has been more than 100 per cent. This is partly due to the looping of the pipe line from the concession to the coast, and the resultant increase in capacity to 50,000 bbl. per day, and also to increased domestic sales. The refinery at Barranca has been doubled in capacity, and it is understood is now handling 5000 bbl. of crude daily. This gives the producing field a potential outlet of 55,000 bbl. daily. The Tropical Oil Co. completed 82 wells in 1927, with one abandoned for drilling difficulties. The average daily initial production was 1136 bbl. per well. The largest well is reported to be No. 173 La Cira, rated as 5000 bbl. initial. Most of the wells were drilled on the Infantas and La Cira structures, the latter located en echelon to the northwest of the main Infantas anticline, and separated from it only by a low saddle. Drilling operations on the Llanos fold, also en echelon with Infantas but to the southeast, and at San Luis, bearing about the same relationship to the Umir Hills uplift, are still more or less in the exploratory stage. The four structures mentioned cover approximately 15,000 acres, on which there are at present 223 producing wells. Drilling has been better than 92 per cent. successful since starting operations on this concession. Allowing 15 acres per well, which is 50 per cent. more than good practice in the Mid-Continent fields, there is thus room for 1000 wclls, which at the recent rate is a 10-year drilling campaign. This does not take into consideration the known deeper oil zones, which have not been prospected, but which are uniformly petroliferous at their outcrops to the eastward. It is estimated that with the enlarged pipe line capacity, as well as increased domestic consumption, the production for this country will be about 20,000,000 bbl. for the current year of 1928. It is possible that

Jan 1, 1928

By H. E. Doerr

The writer has been unable to find much information relative to tests made to determine the effect of forging on the specific density of steel. The opinion, however, among men engaged in the business, seems to be that forging greatly compresses or consolidates the steel. While such is doubtless the case with spongy or porous steel, the following experiments indicate that there can be little or no change in the density with steel initially free from cavities. Ten ingots of basic open-hearth steel cast as shown in Fig. 1 were used in the experiments. All the specimens were 0.53 carbon with all other elements the same, the analysis being determined from drillings taken midway between the center and outside of the upper end, as shown in Fig. 2. The specimens were selected from over one thousand ingots so that the tests could be comparative for the work done in forging only, but no two of the ingots were cast in the same heat. Each ingot remained in the mold approximately 30 min., when it was removed and sir-cooled. About 12 hr. later, when the temperature had been reduced to approximately that of the surrounding atmosphere, the head was discarded and the ingot heated in an oil furnace to approximately 2250" F. (1235" C). Approximately 1 min. was required to forge under the steam hammer to 1 1/4 in. (31.75 mm.), rough diameter, as shown by the dotted lines in Fig. 2. All ingots were allowed to air-cool after forging. Cylinders 1/2 in. (17.7 mm.) in diameter and 1/2 in. high were then turned from the forged and unforged parts of the ingots and numbered. The ten pairs of specimens were submitted to Louis E. Endsley, Professor of Railway Mechanical Engineering, University of Pittsburgh; A. N. Talbot, Professor of Applied Mechanics, University of Illinois; L. Z. Slater, chief chemist, Scullin Steel Co., St. Louis, Mo. NO information was furnished as to which specimens were forged or unforged and each laboratory used the same specimens, submitting the average of three independent determinations, a tabulation of which is shown in the accompanying table in which the laboratories are designated by the letters A, B, and C. While there is considerable difference in the individual determinations for a number of the specimens, the averages

Jan 1, 1920

By Irving Crosby

ELECTRICAL prospecting by potential methods has been applied to mining problems for some years and determinations of the depth to bed rock have been made, but so far as is known it has not been used previously in the solution of civil engineering problems, such as investigating the foundations of dams. During the past winter and spring the senior author has been engaged as consulting geologist in studying the site of a large darn on the upper Connecticut River and has had the satisfaction of introducing electrical prospecting to foundation problems. The valley across which the dam is to be built is underlaid by a deeply buried preglacial gorge which is filled with glacial deposits. An extensive drilling campaign was in progress, but the work was unusually slow and expensive on account of the number of boulders in the overburden. The necessity of speeding up the work was pressing and it was decided that much of the needed information could be obtained by geophysical methods. After investigating the various methods and conferring with the company engineers and with the consulting engineer, Albert Crane, a contract was made with the Schlumberger Electrical Prospecting Methods, and an observer with apparatus was sent to the dam site the first of April, 1928. The problem was to determine the depth to rock at various points in order to prepare a contour map of the bed-rock surface and outline the buried gorge in the vicinity of the dam site. Over one hundred determinations of depth have been made and the bed-rock topography, is now known in considerable detail. In addition, some information has been obtained about the nature of the overburden. The drilling has been continued; in fact, two additional drills have been put to work, and the electrical determinations have been checked at several points. At one of these the depth to rock given by the electrical work was 142 ft. and the drill found rock at 147 ft., an error of less than 4 per cent. The electrical work has also been checked by the geological study, and it has been found that when the electrical determinations are in agreement with the geological expectations they are probably reasonably accurate. When the electrical interpretation of the sub-surface topography is incon-

Jan 1, 1928

By M. L. Fuller

MOST commercial alloys undergo changes in phase composition after casting. This is a natural result of the fact that the alloys are not in a state of phase equilibrium as cast and phase changes will therefore take place, with more or less rapidity, in an attempt to attain equilibrium. The practical aspect of aging in zinc-alloy die castings concerns the changes in physical properties and in dimensions that may accompany aging phase changes. Harmful alterations have been reduced to a minimum and zinc-alloy die castings are being produced today that are so stable with respect to dimensions and physical properties that they are entirely suitable for most practical purposes1. In the first paper' of this series, and in this paper, aging phase changes of zinc alloy die castings have been investigated and the possible influence of these changes on dimensional changes of the castings has been evalu-ated and compared with the dimensional changes actually experienced. The change of dimensions has been selected for practical comparison in these papers because the effect of phase changes on the dimensions of a casting is directly calculable; from X-ray crystal-analysis data of the phase structure. The die-casting alloys considered contain, in addition to zinc, 4 per cent of aluminum, about 0.03 per cent magnesium, and from 0 to 3 per cent of copper. It was shown in the former paper that the eutectoidal decomposition of the beta aluminum-zinc phase, while intrinsically capable of causing a considerable shrinkage, can have very little effect on the observed shrinkage of die castings because it takes place within a few days of aging, whereas the observed shrinkage continues for five weeks. It was therefore concluded that the other existing phase change,

Jan 1, 1936

By John W. Rozelle, David S. Bolin

INTRODUCTION During the normal course of a mining project, a feasibility study will be prepared that addresses all the aspects of the project including geology and mineral inventories, mining and geo- technical, metallurgical processing, infrastructure, environmental considerations and economic analyses. These studies are prepared for various reasons. Occasionally, a feasibility study will be prepared solely for use within a company as justification for development expenditures, however, these documents are frequently submitted outside the company either to raise funds from financial institutions or from public financing on one of the various securities exchanges. Mineral industry consultants are often called upon to participate in the preparation of feasibility studies or to conduct an independent audit and review of an internally prepared study. As the recoverable mineral resources form the foundation upon which the balance of a feasibility study is based, including the economic analysis of the project, the resource aspect of the study is examined very carefully by financial and securities organizations. The balance of this discussion is directed toward the various geological and resource estimation aspects of feasibility studies that experience has shown to be of particular importance. Much of this discussion will be directed toward open pit gold operations, although the principles are applicable to any type of deposit. 2.0 GEOLOGIC RESPONSIBILITIES IN FEASIBILITY STUDIES The principal geological effort in the preparation of a feasibility study is generally dedicated to the following areas: - Preparation of Geologic Reserve/Resource Estimates - Condemnation of Sites for Facilities, Access Roads, Leach Pads, Waste Dumps and Tailings Disposal - Collection of Geotechnical Data - Provision of Mineralogical and Petrological Data Pertinent to Metallurgical Processing - Selection of Appropriate Bulk Sampling Sites for Collection of Metallurgical Samples Each of these items will be addressed in detail in the following sections. 3.0 RESERVE/RESOURCE ESTIMATION An ore reserve estimate consists of the determination of a volume, or tonnage, and a grade for the deposit. There are numerous cases in the mining industry of projects that have experienced severe difficulties when operational ore grade, tonnage or metallurgical amenability have proven to be deficient compared to predicted estimates. An error in estimation of tonnage generally leads to more long term problems affecting mine life and production schedules. However, a significant error in the estimation of grade, particularly if mined grade is lower than anticipated, can have an immediate, and often disastrous, effect upon a project. The geologic preparation leading to an ore reserve estimate generally follows a logical sequence familiar to

Jan 1, 1987

For the last decade Australia has been the leading exporter of both steam and coking coal. In the ten-year period 1989 - 1998 steam coal exports increased by 93 per cent and metallurgical coal exports increased by 50 per cent. However, profitability of the steam coal sector has been disappointing. The coking coal sector, especially the hard coking coal segment, has fared better but its profitability was more because of its ability to maintain relatively high prices rather than its inherent productivity. Until quite recently the Australian coking coal sector was widely expected to be able to maintain this comfortable state without undue effort for the three major æpartnersÆ; the companies, the State Government and the unions. But coking coal could now be heading down the path followed by steam coal that ends with long-term over-supply and, despite steady improvements in productivity, poor profitability. Steam coal entered the ænewÆ era of long-term over-supply some years ago. Over-supply was due to the rapid increase in production in Indonesia, often from new mines and Australia. AustraliaÆs production rise was underlain by the apparent belief that the best way to lower costs was to increase production. In the first couple of years costs didnÆt fall much but the additional tonnage was sold at lower and lower prices into the spot market. By mid-1998 the difference between the contract price set with Japanese utilities and spot sales was often in excess of $US12 per tonne. Japanese contract prices and tonnages have since fallen significantly. Steam coal has moved from being a product to being a commodity. Any profits are due more to the low Australian dollar rather than inherent mine productivity. Seaborne coking coal trade has been dominated by Australia, Canada and the USA, with the USA becoming less competitive. Unfortunately, when the Queensland capacity expansion was well down the pipeline, the Asian financial crisis occurred and the Japanese economy entered what appears to be a long-term recession. Contract prices fell 18 per cent, tonnages decreased and some mines have been reclassified as supplying lower priced coking coal. The paper analyses past and expected future trends in labour and mine productivity, rail freight and FOB export port cash and total costs of the Australian steam coal and coking coal sectors and discusses the market outlook for Australia. The future economic viability of the industry is analysed and discussed in the light of the rapidly changing global environment.

Jan 1, 2000

By H. C. van Elst

Ultrahigh-speedphotographic and electronic meth-ods were applied to an investigation of details of brittle-fracture propagation in steel. The brittle fractures studied were obtained in steel plate with the aid of a Robertson apparatus. It was found that a brittle fracture proceeds by discrete steps ranging from 30 mm near the stop temperature to less than 2 mm at lower temperatures. The halting FROM prior metallographic observations of brittle fracture in steel' it could be concluded that the distribution of mechanical twins along a brittle fracture was similar to the distribution of mechanical twins induced by explosive deformation. It was therefore assumed that a running brittle fracture created stress waves, cf. Refs. 2-7. An emission of stress waves by a brittle fracture, however, seems only conceivable if the fracture propagates by discrete steps. For this reason a study of the details of times between successive steps drop in this tem-perature region from 20 usec to about 1 psec. The stepwise propagation mechanism is accompanied by an intermittent emission of stress waves of the order of 100 to 200 kg per sq mm. These stress waves seen1 to play an important role in the mechanism of brittle fracture as will be discussed. brittle-fracture propagation was undertaken to investigate the possible determination of the fracture steps and the emitted stress waves associated with the assumed mechanism. The more practical object of this work is the development of a test method for the determination of the ductile-brittle transition in small specimens. This has special advantages for the study of irradiation damage in steel. In this test method, which will be published in a following paper, the stress waves emitted by an actual brittle fracture are reproduced with explosive or electrical means and are then transmitted through small specimens at various temperatures. In the present paper only the results of the brittle-fracture study will be reported.

Jan 1, 1964

By T. C. Desollar

The group of iron-ore mines known as the Red Ore Mines, owned and operated by the Woodward Iron Co., is on Red Mountain approximately ten miles southwest of Birmingham, Ala. At the present time NO. 1 and No. 3 mines are active, No. 2 mines having been abandoned in 1928. Ore from this group of mines was first mined in 1882, and originally came from open cuts along the outcrop, but, when the "soft ore" (weathered hematite) was mined out and the harder ore was encountered, it became necessary to develop the orebody by means of slopes driven in the ore formation. The three mines to date have produced more than 22,000,000 tons, and the two operating mines now have a capacity of over 1,000,000 tons per year. Geology The U. S. Geological Survey has described the features of the district. It places the hematite of Red Mountain, commonly called "red ore," in the Clinton formation of the Silurian system. This formation varies from 200 to 300 ft. in thickness, and is composed largely of shale (slate) and sandstone. There are four iron orebeds in the formation, known as the Hickory Nut, Ida, Big Seam and the Irondale seams. The strike of the orebeds is northeast and southwest, and the dip is southeast, the outcrops being on the west side of the mountain. The two seams that have been worked at the Red Ore mines are the Big Seam and the Ida. The Big Seam, which is and has been the principal source of the ore mined, is approximately 20 ft. thick and consists of hematite and ferruginous bands of sandstone. It is separated into "upper" and "lower bench" ore by a slate parting that is about 30 in. thick. All present mining is confined to the "upper bench" ore, which is uniform in texture and drills and breaks fairly easily when the holes are placed so as to take full advantage of the face of the ore. Typical analyses are shown in Table 1. The presence of two water-bearing formations, the Fort Payne chert and the Hartselle sandstone, lying respectively 160 and 300 ft. above the Big Seam, make it essential that in mining the ore any movement of

Jan 1, 1934

By Bernard MacDonald

The writing of this paper was prompted by the discussion by H. M. Chance of the paper written by Thomas M. Chance,l and by the remarks of the editor in which he stated that while the matter contained in discussion did not refer to the original paper it " was presented as of interest to the operators of cyanide and other lixiviation processes dealing with fluid mixtures of varying specific gravity." For some years past the principle enunciated in the discussion referred to has been known to the writer and demonstrated by him to be an efficient and economical way of separating water or solution from solids in the cyanidation, lixiviation or acid leaching of ore pulps. In utilizing this principle in commercial practice he has invented a method whereby not only the separation of solution from solids may be effected in any given tank, but also the counter migration of the solids and solution may be effected continuously through a series of tanks in which the hydro-metallurgical treatment of ore pulps is being carried on. In effect this method is analogous to the counter-current system, but is different physically in that it is carried on throughout a series of tanks on practically the same level, continuously and automatically, by hydrostatic pressure and gravity-flow, without the aid of intervening pumps or elevators, at the same time that agitation is being carried on in the same tanks. In the Parral system, agitation is effected in tanks by a number of air lifts of comparatively small diameter through which the pulp is continuously transferred from the bottom of the tank and spouted horizontally on top of the charge. The spouting force of the several streams thus discharged maintains a rotary flow in the pulp charge which extends from top to bottom of the tank. This continuous transfer of pulp and the spiral flow from top to bottom of the tank maintains the pulp constituents in uniform proportions and meets the requirements of efficient treatment in a most economical manner. The quantity of compressed air required is very small, as the pulp is not lifted but simply transferred from the bottom to the top of the tank charge under hydrostatic balance. Fig. 1 gives a bird's-eye view of two adjoining tanks in any series equipped with the apparatus for producing the separation of

Jan 1, 1919

By P Hawkes

Within the mining industry computers have made their most significant impact with 3D design, visualisation and resource modelling/ optimisation. Recently, the application of computers to data gathering and accounting functions has also started to reap benefits. These two areas of application cover the beginning and end of the mining process. There has been limited use of computers on the middle section, the actual mining process. This is interesting when considering the relative proportion of overall mining costs that this section produces. There is a certain amount of irony in the lack of mining application software for developing accurate budgets compared to the systems/software then used to review performance against budget. Computers have been used extensively in the manufacturing industry to design, model and simulate the manufacturing process. This has not been extended to the mining process. But, we all strive to have an open pit that replicates a manufacturing plant û smooth, efficient, optimal production. If we could model mining operations with the confidence of plastic box makers we would reduce risk by an order of magnitude, improve planning and focus on value drivers. Cost û benefit analysis would be easy. The extrapolation of manufacturing to mining process models is difficult. The variables in the manufacturing process are fewer in number, have low volatility and are highly predictable. The time between a box falling on a conveyor belt and falling off is very consistent. Mining is quite the opposite. It has large numbers of variables, some of which are unpredictable and volatile. The time to fill an excavator bucket could vary by 30 per cent and the frequency distribution is unlikely to be a mathematically simple normal distribution. Further, each of these variables can be distorted by one-another û they are interrelated. The mining process is a disjointed flow of parcels whereas manufacturing is a controlled continuous feed. A loaded truck might join a ramp and follow a slow water cart up. This is the equivalent of a localised voltage drop on equipment in a manufacturing plant. The manufacturing plant is quite likely to rapidly recover to full capacity. Whereas the slow truck might throw the mining fleet cycle out of balance for hours û trucks queuing at the ROM bin and so on. A mining process simulation has been created that addresses these mining variable issues to produce a highly accurate model of the open pit mining process. The number of uses for such a model is growing rapidly as it is being utilised for a variety of projects within the industry. This paper discusses the need for and application of mining process models.

Jan 1, 2003

By L. D. Jaffe, D. C. Buffum

The importance of temper brittleness in alloy steels has long been realized in Europe. In the United States recognition of its importance has developed within the last several years. Many brittle failures encountered in parts made of alloy steel are undoubtedly attributable, wholly or in part, to temper brittleness. These failures have occurred particularly at low temperatures, under shock loading, and in the presence of notches, restraints and combined stresses. It has been almost universally accepted that plain carbon steels are not susceptible to temper brittleness. As a result, considerable effort has been expended in attempts to discover the manner in which alloying elements introduce temper brittleness. It is desired to raise the possibility that plain carbon steels are not only susceptible to temper brittleness, but are much more susceptible than alloy steels, in the sense that they embrittle much more rapidly. It is suggested that previous views, (that plain carbon steels are not susceptible), are based upon an erroneous interpretation of the experimental results. Interpretation of Previous Data For many years the standard criterion for susceptibility of a steel to temper brittleness consisted of comparison of the energy absorption, in a notched-bar impact test at room temperature, of specimens that had received two heat treatments.' One specimen (or group of specimens) was quenched, tempered, and quenched from the temper. The other specimen (or group) differed only in having received an embrittlement treatment, which might consist of a slow cool from the tempering temperature, or of an isothermal hold in the range 45w550°C subsequent to quenching from the temper. If the energy absorption of the specimen receiving the embrittlement treatment was lower than that of the specimen not given this treatment, it was said that the steel was susceptible to temper brittleness. If the energy absorptions were the same, it was said that the steel was not susceptible. Several investigators2J found that plain carbon steels showed negligible difference in energy absorption in such tests (at least when their manganese content was below 0.60 pct), and concluded that plain carbon steels are not susceptible to temper brittleness. Recently the deficiencies of the criterion mentioned above have been pointed out.'-= The criterion now generally used for susceptibility to temper brittleness retains the heat treatments used in the earlier scheme, but instead of the notched-bar impact tests being made only at room temperature, they are made over a range of temperatures, covering the transition from ductile to brittle fracture. If the transition temperature of the specimens receiving the embrittlement treatment is higher than those

Jan 1, 1949

By John H. Melvin

The Omaha District, Corps of Engineers, has been doing subsurface exploration work for a number of years, both by contract and with its own forces. Certain practices and procedures concerning the recovery of large diameter cores have been developed which will be described in this paper. Geology Most of the drilling to date has been in connection with structures on the main stem of the Missouri River above Sioux City, Iowa. A wide variety of subsurface conditions has been encountered. The bedrock formations appear in regular order from the oldest to the youngest, traveling upstream; or in other words, the general regional dip is to the northwest. The oldest formation is the Carlile shale, a compaction or noncemented waxy shale of Cretaceous age. Because of its unce-mented, soft nature this shale has a tendency to grind or wash away when drilled. It also has a tendency to rebound or expand when the overlying pressures are removed. A 25-ft bed of sharp, friable sandstone called the Codell member is present near the top of the Carlile shale. This member is a cemented sediment, but in drilling, many of the sand grains are broken loose and exert extensive abrasive action on the core barrel and bit. Above the Carlile shale is the Niobrara chalk, a soft calcareous deposit with shaly horizons and some thin beds of bentonitic clay. The average thickness of this deposit is about 145 ft. It is soft enough to be sawed or bored with ordinary woodworking tools, yet is compact enough to be used as building block. The Pierre shale, the formation above the Niobrara chalk, is over 800 ft in thickness and is the most widespread material in the area. It is a dark colored, compaction shale containing numerous thin bentonitic clay seams and at certain horizons, hard manganese concretions. The shale has numerous faults and in addition, along the valley walls, has undergone considerable slumping. Joints, fault planes and slickensided surfaces are common features encountered in drilling and add to the difficulties of high core recovery. East of the Missouri River the bedrock is generally covered with from 100 to 200 ft of glacial till, composed of clays, silts, sands, gravels and boulders. The valley itself is filled with alluvial deposits, mostly of the sand and gravel sizes, and contains a buried preglacial or interglacial channel over 100 ft in depth. The overburden deposits require sampling in connection with engineering studies and must also be cased before the underlying bedrock can be cored. The diameter of the required overburden samples can thus have an indirect effect on the size of core recovered from the bedrock. West of the river, which in most cases is the western boundary of glaciation,

Jan 1, 1949

By Gerald Sherman

IN the southern field of the anthracite region of Pennsylvania, many of the coal seams dip at angles of 40° to 50° from the horizontal. For transportation purposes, "tunnels" are driven across the coal measures and, occasionally, "rock gangways," beside the seams and parallel with them. The use of gangways driven in country rock appears to be increas-ing, as they avoid the maintenance' of long gangways in coal, which eventually are driven to the colliery boundaries, and permit mining from a number of intermediate blocks without interference. The rock consists of slates or sandstones of moderate hardness, which may range into very hard, highly siliceous, fine-grained conglomerates. In this distinctly bedded formation,' the direction of the heading, whether parallel with or across the structure, makes it necessary to distribute the drill holes in a different pattern to break the ground, but does not change loading conditions. In 1932, practically all the mucking was done by hand, and it was the established custom to use four men on two drills for drilling and breaking the ground, and five for loading it, out. A driver and mule was needed in addition, to assemble the rock cars at a siding or branching track in the rear, pending their final disposal. This might occupy the driver's whole time, or if the length of haul were short, he might be able to do other useful work. It was thought possible in 1932 to reduce the cost of driving such headings in rock by mechanical loading, and to investigate this subject a scraper loader was used in a section of tunnel then being driven. Opera-tions while driving 195 ft. of this tunnel using a scraper loader were care-fully observed. Time studies were made of the loading, and records made of the routine of breaking ground, but not in such detail. Tunnels or gangways in the colliery are 7 ft. high above the rails, by 10 ft. wide, which requires a minimum of 8 ft. in height, broken to allow for rails and ties. This cross section is of sufficient size to permit the use of any one of several types of power loaders, but for this demonstration if was found most convenient to use a scraper loader.

Jan 1, 1936

By Stanley C. Herold

Only two years ago there appeared in our technical magazines articles wherein it was shown that the application of back-pressure increased the ultimate production of a well, that edge water can be stopped in its encroachment by the injection of gas into the productive formation, with the consequent conservation of energy within the pool, that gas is the source of all energy involved in oil production, and that each pool has a definite minimum-valued gas-oil ratio to be attained for the most economical operation of wells. Today we are not so certain of these matters. Probably in some fields, under special circumstances, these ideas are correct, but certainly they must not be correct in all fields, under any and all circumstances. The nature of the productive structure, the location of particular properties on the structure, the existence of adjoining neighbors, whether these are higher or lower on the structure, and the methods of production followed by all operators on the structure, sand for sand on depth, make these subjects worthy of full consideration. Our difficulties in analyzing and comparing the performance of reservoirs in various parts of the world do not rest solely upon structural features and property lines. We do not complete the list of causes for these difficulties if we add lithologic features and correlation of strata encountered by the drill, with the magnitude of pressures exerted by fluids within any of these strata. A further cause, one which the author believes will complete the list, is one involving the theoretical mechanics of fluids within porous formations—porous in the nature of interstices in sandstones and some limestones, networks of fractures in shales, and cavities in otherwise compact limestones. The confusion of ideas concerning reservoir mechanics still with us today seems largely due to our failure to recognize among all wells three great divisions of theoretical mechanics, three great systems which are distinct in themselves, and according to which each well, or better, each group of wells, must be analyzed separately. These systems have been named by the writer Hydraulic Control, Volumetric Control and Capillary Control, respectively.' Wells in these controls behave dif-

Jan 1, 1930

By Richard Moldenke

One of the little-known characteristics of cast iron, which nevertheless has an important bearing on results where accuracy in machining is essential, is the ability of this material to ease up internal strains when allowed to remain quiescent for a more or less extended period of time. It seems as if the molecules in such a casting, by virtueof their "mobility," can adjust their relative positions to an extent sufficient to overcome some of the existing stresses. The following instance will perhaps give a fair idea of the condition a casting may be in when just shaken out of the sand. A very large sheave-wheel, after shaking out, was taken outdoors to be cleaned and made ready for turning up. It was leaned against the side of the building, but before much could be done an arm tore apart with a loud report. Investigation showed that the sun had been shining on the upper rim, thus adding a slight strain to those already existing within the arm and thus overbalancing the strength of the metal in tension. Had this sheave been kept under cover for a while, or at least until machined, the strains would have eased off sufficiently to allow the sun to look upon it without disaster. It will not be necessary to multiply examples. Every engineer knows the danger of water-hammer in pipe lines, particularly if the latter are of cast iron. Every mechanic knows, or should know, that it is not good to strike a fitting that is under steam pressure. It will be necessary to say a few words on the "internal strains" in castings—the so-called "casting strains" we hear so much about. We all know that to get a casting reasonably true to the dimensions wanted requires a slightly larger pattern. The usual allowance for gray iron is 1/8 in. to the foot (1 cm. per meter) and 1/4 in. to the foot (2 cm. per meter) for white iron (all dimensions). This reduction in length, breadth and thickness in a casting is erroneously called "shrinkage." It should be called "contraction," as for practical purposes it is simply the difference in dimensions of the casting red-hot and cold. The real "shrinkage" covers an entirely different situation. When a

Jan 1, 1917