Search Documents

By Richard K. Thorpe, Gordon D. Anderson, Merle E. Hanson, Ronald J. Shaffer

The propagation of pressurized fractures across a frictional interface is discussed, with emphasis on the case where an offset, or step, in the crack is produced. Theoretically, the steps can occur at regions of reduced shear strength along the interface. As a fracture is propagated toward a weak zone, extensional strain is concentrated at the edges of the zone where higher shear stresses can be sustained. Thus, when the fracture intersects the weak zone, it can be reinitiated at some small distance away on the opposite wall of the interface. The phenomenon has been studied through numerical modeling and laboratory experiments of the hydraulic fracturing process. Field observation of natural step cracks indicates that the mechanism is applicable to the genesis of jointing patterns in rock. Such features should not be confused, therefore, with steps caused by shear displacement of an interface.

Jan 1, 1982

By George M. Schwartz, Ian L. Reid

The Soudan mine in the Vermilion district of northeastern Minnesota is the oldest iron mine in the state. It has shipped ore every year since 1884 and still contributes a yearly quota of high grade lump ore. No comprehensive report on the Vermilion iron-bearing district has appeared since Clements' monograph,' but Gruner' discussed the possible origin of the ores in 1926, 1930, and 1932, and recently Reid and Hustad have added data on mining and geology." For many years geologists of the Oliver Iron Mining Div., U. S. Steel Corp., have kept up to date a series of plans and vertical sections of the Soudan mine. In connection with mine operation considerable diamond drilling has been done, and this, together with the mine openings, has permitted a reasonably accurate picture of the structure of the orebodies and wall rocks.

Jan 3, 1955

By Austin Park

More metal at a lower profit continued to be demanded from the mining industry during 1969. Correspondence with U.S. and Canadian mining districts and a study of the mining literature indicate that, a large majority of the mines are keeping pace and rising to the challenge. Continued research and better understanding of pneumatically applied concrete for roof and wall support was of top interest. Many mines are changing mining methods for the adaptation of load-haul-dump units. The most recent adaptation being the use of these units in cut- and-fill stoping and in various types of development headings. Boring methods and use of two- or three- boom drilling jumbos mounted on rubber tires for versatility continues to be the favorite approach to the demand for rapid excavation.

Jan 1, 1970

By John A. Church

In a recent paper read before the Institute it was said of faults that "the sensible expression of the fracture is an earthquake." This notion, which has been expressed before, though usually as a theory and not as an admitted conclusion, is based upon the early belief that faulting is a violent rupture of the earth's crust. Faults are of different kinds, from great dislocations of the earth —hundreds of miles in length—down to the still more mysterious displacements with which miners have to deal. The latter are usually quite short, from 1000 to 20,000 feet in length, but are distinguished even above their greater brethren by the excessive pro-

Jan 1, 1893

By James A. Soles

Concrete is a complex, multicomponent mass whose stability is dependent on three principal variables: quality of the mix, its composition, and environment of the site. The aggregate is only one component, but its constituent minerals may react in unfavorable regimes and, given sufficient time, destroy the concrete. Therefore, besides ensuring that a concrete will meet the strength requirements of a structure, the concrete engineer must be confident that the mortar and aggregates will resist destructive processes. This paper reviews the principal causes and effects of aggregate instability, notes reactions of certain phases, and suggests precautionary measures that can be taken to extend the useful life of concrete structures.

Jan 1, 1984

By J. Donovan Jacobs

An underground excavation project usually is a highly organized complex of different but interrelated construction activities. It is the whole effort, including the necessary tools, which will be referred to as the System. Tunnel-driving and shaft-sinking operations are among the most systematic of construction efforts. Systems are not new in the performance of construction. It is the Systems Concept which seems only recently to have been discovered and made the subject of much study and discussion. HISTORICAL From the seventeenth century, when explosives were first utilized for rock excavation, until the successful application of the rotary-head continuous tunneler in this decade, the cyclical drill-blast-muck-support method has been standard tunnel-driving procedure throughout the world. Whatever improvements occurred were the result of development of better tools for performing the various operations of the cycle. The electric locomotive replaced the mule and permitted the use of larger muck cars. The steam drill, which ended the day of the double jack, was itself quickly made obsolete when compressed air replaced steam as the source of drilling energy. Power shovels were introduced to save the time and money involved in the hand-loading of excavated materials. A cubic yard of rock tunnel muck can be excavated today for just half the man-hours of labor required in 1948. Developments over 20 years which cumulatively have resulted in this economy include: drifter drills mounted on hydraulically controlled booms and positioners; tungsten-car- bide-tipped bits; long feed shells on the drifters, making it possible to drill the full depth of a round without changing steel; better designed,

Jan 1, 1970

By P. Somasundaran

Processing of fine particles in suspension is markedly affected by their state of dispersion/aggregation. In addition, tendency for a given component of the system to undergo selective aggregation or selective dispersion is an important property which may be put to use for processing. In this paper, principles governing flocculation, dispersion, and selective flocculation of mineral fines are discussed and then the role of major solution properties such as pH, ionic strength, etc. is examined.

Jan 1, 1980

By Norman D. Fitzgerald

The growth of domestic requirements for motor fuel has been phenomenal, rising year after year in a fashion almost unique among commodities, resisting depressions and forging rapidly ahead in times of prosperity. Consumption advanced from 226 millions of barrels in 1925 to 522 millions of barrels in 1938; or 130 per cent. The economic influences generating and sustaining this demand are of vital concern to the petroleum industry. The general factors affecting utilization of motor fuel are well known but it is the purpose of this paper to employ the recently developed technique of economic dynamics to describe them mathematically. Such problems in economic analysis are complicated by the freedom of all the variables to fluctuate, their mutual interdependence, changing incidence upon one another, and the nonquantitative character of some of them. Economic quantities and relationships, unlike those of the physical world, are continuously changing and this dynamic characteristic is both a distinguishing and confusing feature in economic research. The complexities of the problems require application of the analytical devices of mathematical statistics to uncover the probable relationships between factors. The procedure employed is to formulate a logical relationship linking the dependent to the independent variables, and then simultaneously, rather than sequentially, determine their separate effects by multiple correlation. This transformation of common knowledge to quantitative terms makes it possible to measure the probable effects of changing conditions upon requirements, assisting in the sound interpretation of economic policies. The utility of the results of such dynamic analysis is in sharp contrast to the sterility of the trends and other simple empiricisms of descriptive statistics. It is not intended in this study to throw light on the reasons why any motor fuel at all is consumed; but to discover relationships explaining why more was consumed at one time than at another. Specifically the problem is confined to the measurement of the influences of statistically

Jan 1, 1940

By E. M. Boatman, S. J. Pirson, R. L. Nettle

More than a decade ago some theoretically derived relationships were proposed that permitted the prediction of the relative ability of reservoir fluids (oil, gas, water) to flow simultaneously within the porous structure of rocks. While many successful predictions of fluid-flow ratios from wells have been made from electric logs, the theoretical deductions have not been subjected to laboratory verifications. For the relative permeability to liquid and gas, simultaneous flow of water and air was used, employing the familiar external-gas-drive technique. While in the process or water desaturation, the resistivities of the test cores (Woodbine sand) were measured. Their permeabilities varied from 10 to 280 md. The laboratory results indicated the need for changing the values of exponents in the theoretically derived formulas, whereas the form of the functions of resistivities and saturations remained as derived by theory. For the relative permeability to oil and water, the three-core dynamic technique was used on six cores. In this case it was found that the formulas were valid with but slight modification as derived by theory, to a sufficient degree of accuracy for engineering use and for well productivity prediction from electric logs. INTRODUCTION Conventional quantitative well log interpretation generally stops after reasonable values for formation porosities and water saturations have been established. Yet such in formation is insufficient to predict either the outcome or the desirability of well tests and completion, let alone the economic aspect of producing oil- and gas-bearing sections which might have been established by conventional log analysis. To give an engineering answer to such questions, it is necessary to predict the expected fluid flow ratios, the productivity index and the ultimate recovery from potentially productive wells. This problem requires in part for its solution a determination of the relative permeability characteristics of the potentially producing formations, both to oil (or water) and gas, and to oil and water.

Jan 1, 1965

By Persifor Frazer

"The nebular theory is a noble speculation supported by plausible argument, and the verdict of science on the whole subject cannot be better expressed than in the words of Newcomb :—'At the present time we can only say that the nebular hypothesis is indicated by the general tendencies of the laws of nature, that it has not been proved to be inconsistent with any fact, that it is almost a necessary consequence of the only theory by which we can account for the origin and conservation of the sun's heat, but that it rests on the assumption that this conservation is to be explained by the laws of nature as we now see them in operation. Should any one be skeptical as to the sufficiency of these laws to account for the present state of things, science can furnish no evidence strong enough to overthrow his doubts until the sun shall be found growing smaller by actual measurement, or the nebulæ be actually seen to condense into stars and systems.' " Leibnitz2 is credited by Cuvier3 (who associates with him Descartcs) with " amusing their imaginations " by conceiving the world to be an extinguished sun or vitrified globe upon which the vapors, condensing in proportion as it cooled, formed the seas, and afterwards deposited the calcareous strata. Whiston4 believed the earth was crested from the atmosphere of one comet and deluged by the tail of another. The heat which remained from its origin excited the whole antediluvian population, men and animals, to sin, for which they mere all drowned in the deluge, except the fish, whose passions were apparently less violent. De Maillet5 held that the globe had been covered by water for many thousand years. The terrestrial animals were originally inhabitants of the sea, and man himself began his career as a fish. He adds it is not uncommon to meet with fishes in

Jan 1, 1905

By Norman D. Fitzgerald

The growth of domestic requirements for motor fuel has been phenomenal, rising year after year in a fashion almost unique among commodities, resisting depressions and forging rapidly ahead in times of prosperity. Consumption advanced from 226 millions of barrels in 1925 to 522 millions of barrels in 1938; or 130 per cent. The economic influences generating and sustaining this demand are of vital concern to the petroleum industry. The general factors affecting utilization of motor fuel are well known but it is the purpose of this paper to employ the recently developed technique of economic dynamics to describe them mathematically. Such problems in economic analysis are complicated by the freedom of all the variables to fluctuate, their mutual interdependence, changing incidence upon one another, and the nonquantitative character of some of them. Economic quantities and relationships, unlike those of the physical world, are continuously changing and this dynamic characteristic is both a distinguishing and confusing feature in economic research. The complexities of the problems require application of the analytical devices of mathematical statistics to uncover the probable relationships between factors. The procedure employed is to formulate a logical relationship linking the dependent to the independent variables, and then simultaneously, rather than sequentially, determine their separate effects by multiple correlation. This transformation of common knowledge to quantitative terms makes it possible to measure the probable effects of changing conditions upon requirements, assisting in the sound interpretation of economic policies. The utility of the results of such dynamic analysis is in sharp contrast to the sterility of the trends and other simple empiricisms of descriptive statistics. It is not intended in this study to throw light on the reasons why any motor fuel at all is consumed; but to discover relationships explaining why more was consumed at one time than at another. Specifically the problem is confined to the measurement of the influences of statistically

Jan 1, 1940

By K. A. Natarajan, I. Iwasaki

The meaning and the utility of redox potential (Eh) measurements in sulfide flotation systems are examined. Since some preliminary plant Eh and laboratory flotation data were available, experiments were made to establish the pH range at which a platinum electrode might be used for such measurements without much difficulty in aerated systems. Triangular wave voltammetry was used to study the surface conditions of the electrode immersed in pyrrhotite suspensions at different pH. The measured Eh both at the plant and the laboratory is interpreted in terms of the experimental water-oxygen line.

Jan 1, 1974

By C. W. Sherman, J. Chipman, H. I. Elvander

THE pronounced and usually deleterious effects of sulphur on all ferrous metals and the resultant necessity for its control in metallurgical processes have stimulated many investigations of the system iron-sulphur. The data required for thermodynamic study of the behavior of sulphur in molten iron and steel include the activity and free energy of the dissolved sulphur and its heat of solution. Such data are also of theoretical interest since there is all too little information available concerning solutions of nonmetallic solutes in metallic solvents. It was the purpose of this investigation to attack the problem very directly by a study of equilibrium at several temperatures in the reaction H2 (gas) + S = H2S (gas) [1] K1 = PH2S /PH2 as where the sulphur is present in the liquid iron in amounts up to several percent by weight. Such a method of attack is not new since several careful studies have already been reported. It is planned, however, to extend the study to other metallic solvents and particularly to determine the effects of the various alloying elements on the activity of sulphur in liquid iron. This paper presents the results on molten iron-sulphur alloys containing up to 4 pct sulphur in the temperature range 1530°-1730°C. Literature Review The significant researches on dilute molten solutions of sulphur in iron include those of Chipman

Jan 1, 1951

By D. M. Deason, G. Y. Onoda

Phosphate clay wastes, as currently produced, leave montmorillonite clay in a highly dispersed and disintegrated form. Alternative processing, where the extent of swelling and self-disintegration of such clays is controlled or limited, may result in improved settling and consolidation behavior. In this study, a method to control montmorillonite dispersion, through preservation of clay tactoids, was examined. Through this process, significant improvements in settling rates and sediment solids concentrations were achieved in both pure clay systems and on simulated phosphate clay wastes.

Jan 1, 1985

By C. H. Jacoby

Since salt, sodium chloride, is an essential mineral to animals and humans alike, the delineation of the salt deposits of the world has been continuous from prehistoric times. As man explores deeper into the crust of the earth, particularly in search of petroleum, numerous new deposits of salt have been recorded. This paper deals with the factors that equate the current economic value of a salt deposit. The value of a salt deposit is not only determined by the chemical purity of the sodium chloride, but also the method of extraction to be used, the use of the product, and/or the use of the deposit. Salt is basically an inexpensive industrial commodity where large tonnages must be available to conduct a successful mining operation. Therefore, not only must the deposit contain these large tonnages, but also it must be accessible and transported as low cost freight to a large market. The geological environmental conditions surrounding the deposit must be such that it will be conducive to low cost mining operations. These conditions include not only the depth, size, shape, and internal structure of the deposit, but also the characteristics and extent of the overlying ground water.

Jan 1, 1973

By J. Wayne Erickson

One of the major problems facing today's mining industry is how to manage people and control costs in the underground mine. It is a problem with a solution. Because of the concerted effort to find and mine minerals near the surface, open-pit mine opportunities for certain minerals are becoming more limited; the mining industry will eventually be forced to produce more and more from underground mines in order to obtain those resources necessary to sustain our civilization. Although much technical progress has been made towards solving problems associated with the underground mine, such as - mine design, ventilation, rock support, equipment, and blasting techniques, little has been written on managing mining personnel. Much of what is being taught and practiced today about human relations, motivation, incentives, etc., applies to the underground miner, but the uniqueness of his group dictates a different treatment from that associated with the typical construction worker or factory employee. The difference lies with the kind of man attracted to underground mining and his working environment. Anyone who has had the responsibility of managing an underground mine would agree it is a unique problem.

Jan 9, 1976

By L. G. Evans, W. W. Simpson, W. A. McKinney

In conventional dump leaching of strip wastes from open-pit porphyry mining operations, many years are required to extract a fraction of the copper from the contained sulfide minerals. Furthermore, none of the molybdenum, gold, or silver is recovered by current leaching practices. Because the copper sulfide minerals and molybdenite generally are distributed in the minute fractures throughout the host rock, the mineral values tend to concentrate in the finer fraction of the strip material. This suggests the possibility of segregating the enriched fines in as-produced or coarsely crushed strip wastes for blending with the ore grade flotation mill feed. In the past, extra handling or crushing of mine wastes to enable better leach extraction has been deemed uneconomical. However, recent articles on mobile crushing plants and conveyor haulage systems indicate possible cost improvements for these techniques over conventional truck haulage of ore and mine wastes. Another potential benefit from removal of the fines from copper-bearing mine waste derives from the increased permeability of the coarse dump material to leach solutions and air. Better permeability should result in faster oxidation of the sulfide minerals, less channeling of leach solutions, and fewer perched solution tables caused by compacted fines. Therefore, in addition to the metal values recovered by flotation, higher copper recoveries by leaching also might be achieved. The Salt Lake City Metallurgy Research Center of the U.S. Bureau of Mines undertook an investigation to determine the feasibility of removing enriched fines from strip waste material for separate treatment by froth flotation for early recovery of part of the copper, molybdenum, gold, and silver. Percolation leaching tests were made on mine-run and sized fractions of the dump material to determine the effect of fines removal on copper extraction. Samples Tested Three 10-ton samples of copper sulfide-bearing mine waste were obtained for the investigation. Partial chemical analyses of the samples are given in [Table 1] and the consolidated results of detailed screen analyses made on the samples are given in [Table 2]. The -1/4-in, fine fractions contain from 16 to 32% of the copper and 19 to 40% of the molybdenum in 11 to 18% of the total waste. The samples also were crushed to -3 in. to determine the feasibility of crushing to obtain a higher distribution of the metal values in an enriched fine fraction while providing a more leachable coarse fraction that could be transported by a conveyor system to a dump. The -%-in. fine fractions screened from the crushed mine waste were almost identical in grade to the natural fines. From 2 to 4% more1/4-in. fines were produced by crushing to -3 in. Copper distribution was increased by about 3% over that in the natural fines, while molybdenum distribution was increased by about 10%. The -1/4-in. fines screened from the mine-run and crushed strip waste were almost as high in grade as the ore being treated at the mills. In addition, the fines

Jan 1, 1974

A novel method of reconditioning vertical rock openings which are on the verge of collapse has been developed, ant1 a world patent applied for, by LKAB, the Swedish iron ore mining company. Without anyone descending into the dangerous opening, workers can place concrete reinforcement in the unstable section using sand-filled canvas tubes which LKAR development engineers are calling "stockings." First application of the new technique was in several inclined ore pockets which form part of the underground crushing and loading station at LKAB's Kiirunavaara mine in Swedish Lapland. LKAB experience demonstrated that with other methods it took about three months to repair a pocket, and neighboring pockets had to be closed while repairs were underway. With the new stocking method, the work was completed in three weeks with no disruption of nearby activities. Production losses amounted to 10% over the three-week period, as opposed to 30% with other methods. The simplified technique could save millions of dollars in underground maintenance, according to LKAB.

Jan 11, 1978

By Christopher Haycocks, Lawrence P. Johnson, George M. Neall, James M. Townsend

No method of roof control yet devised has proven to be universally acceptable for the wide range of strata conditions experienced in U. S. coal mines. However, a relatively new innovation, the roof truss, has proven itself capable of preventing roof failures which both conventional and resin bolting could not. Presently, the economics of roof trusses are not favorable when compared to bolting due primarily to drilling and installation procedures, but this is expected to change with improved truss and equipment designs. To realize the full potential of this new method of roof control, design criteria are needed which can optimize the effect of the truss for varying strata conditions.

Jan 6, 1978

By Robert P. Uhley, LeRoy Scharon

TEST gravity surveys were made in the Washington County barite district of Missouri on property owned by the Baroid Sales Division of the National Lead Co. This property is located just northeast of Richwoods in the northeastern corner of Washington County, Fig. 1. The area to which the surveys were confined comprised approximately 5000 acres, of which some 525 acres were surveyed gravitationally. Gravity observations were made at 2600 points within the area, observations being confined to relatively clear and gently sloping ground. Part of the area was heavily wooded, and the terrain too rugged for either the occurrence of a commercial barite deposit or a feasible gravity survey. The relief along the central drainage, Ditch Creek, was about 140 ft, the maxi- mum difference in elevation being 400 ft in a distance of 3 ½ miles.

Jan 1, 1954