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By Edgar G. Hill

Much has been written and said recently about the methods used and materials and equipment employed in building the long tubes that criss-cross a great part of the United States, like the pattern of a spider's web. This paper will discuss the fundamentals of design of these lines from the economic as well as the engineering viewpoint, pointing out the effect of the volumes transported, and the load factor, on the unit costs of transportation, as well as the effects on costs of the character 01 the fluids the lines are called upon to handle. Generally speaking, crude-oil pipe lines carry oil from the producing fields to the refineries. Sometimes part of the journey is by pipe line to a coastal point and tank ships are employed for the rest of the trip. The main lines of directional flow of crude oil through pipe lines in the United States are shown on Fig. I, but this, of course, does not always show individual pipe lines. Basic Formula for Flow OF Crude Oil The laws governing the flow of crude oil through pipes are well known. The basic

Jan 1, 1942

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Jan 1, 1938

By Roy A. Koski

INTRODUCTION Cleveland-Cliffs Iron Company, and its subsidiary companies, operate and manage mining, beneficiation, and pelletizing operations in the Upper Peninsula of Michigan, the province of Ontario, Canada, and the State of Western Australia, Australia. The concentrates and natural ores vary mineralogically, physically and chemically. This paper describes the techniques employed in pelletizing the various concentrates and ore fines. The plant operations described are the Republic, Humboldt, Tilden, Empire and Pioneer in Michigan, the Adams and Sherman in Ontario, and the Robe River in Western Australia. Table 1 contains further details regarding design and operating capacities, commissioning dates, and participant ownerships. Allis-Chalmers grate-kiln systems are utilized in Michigan and Ontario, and Dravo straight-grate systems in Western Australia. Currently, the Empire and Tilden operations are being expanded. At Empire the additional pelletizing unit, identified as Unit IV, will have a design capacity of 8 996 metric tonne/d and is scheduled for startup May 1, 1979. The Tilden operation is being doubled with the additional pelletizing unit, identified as Unit 11, having a de- sign capacity of 12 599 metric tonne/d. Startup is scheduled for January 1, 1980. MINERALOGY OF CONCENTRATES AND NATURAL ORES In the Upper Peninsula of Michigan, the operations process ores from the Negaunee iron formation of the Marquette Range. The

Jan 1, 1977

By J. A. Collins

THE process of plastic extension of face-centered cubic single crystal-line rods is so well understood, since the notable studies of Taylor and Elam,1 that the change in orientation of any crystal by slip and rotation may be predicted from the measured elongation. It is customary to assume a very homogeneous deformation, wherein gliding lamellae are free to rotate so that their slip direction continually approaches the axis of the rod, until a second slip system comes into operation; whereupon conjugate slip proceeds quantitatively to an end adjustment with the [112] direction in the axis of the rod. This process has been checked in many face-centered cubic materials and readily permits the preparation of specimens that have been sub-jected to various determinable amounts of shearing action. It is clearly of interest to study in such measurably strained specimens the development of a recrystallized structure on annealing and if possible detect the source of nuclei from which the new crystals grow. Strain-annealing experiments of this character have been performed by others but not in detail sufficient to permit a study, for example, of the number of recrystallized grains vs, the amount of shear. In the experiments now reported, this was done with a wide variety of orientations covering nearly the entire range of slip on a single system and corresponding to amounts of shear (ratio of shearing distance to distance between lamellae) at the conclusion of a test of from 0.08 to 0.57. A particular point was made of determining the crystallite rotation, or small angular range assumed by the octahedral slip plane after these various amounts of shear. The mechanism of recrystallization and the magnitude and effect of recovery on the recrystallization process was investigated.

Jan 1, 1940

By E. O. Wagner, V. F. Parry, W. S. Landers

Development work has shown that the yield of primary tar from coal is proportional to the heat in the volatile matter of the coal and that the yield of tar from noncoking coals may vary from 10 to 45 gal per ton on the ash-free and moisture-free basis. Pilot plant operations have proved that 100 to 135 pct of the bench-scale carbonization-assay yield of tar can be obtained. FOLLOWING investigations by the Denver Bureau of Mines on drying fine coal in the entrained state,'. ' Texas Power & Light Co. employed the fluidized technique to upgrade Texas lignite for use in power plants. Because of the rapidly rising cost of natural gas in Texas the company agreed to cooperate with the Bureau of Mines in studying further the upgrading of lignite by low-temperature carbonization, since potential value of the tar would help offset the cost of fuel. Considerable interest was aroused, therefore, when Aluminum Co. of America decided to use dried lignite in its 240,000-kw power plant at Rockdale, Texas, operated by Texas Power & Light. Carbonization of coal before burning in a power plant is not new. Plants in Germany have been operated for many years on carbonized brown coal and lignite briquets produced in large integrated plants. Large-scale experiments in carbonizing pulverized coal with hot flue gases were made 30 years ago at Milwaukee," and many inventors have proposed other processes. In the U. S., technical and economic problems have prevented successful operation of large plants on carbonized coal. but new techniques of handling solids in fluidized beds may overcome these difficulties, particularly if the higher volatile noncoking coals are used. Any bituminous material will decompose when heated to about 900°F to yield primary tar, gas, and char. The quantity of tar obtained from various coals depends on their rank and volatile content and to some extent on rate and method of heating. The liquid products derived from thermal decomposition of peat, brown coal. lignites, oil shale, and noncoking bituminous coals can be easily liberated by rapidly heating these materials in a fluidized bed at about 500°C (932°F). Since it takes only a few minutes to heat small particles of fuel to carbonizing temperature in a fluidized bed, processing plants can be built to handle up to 50 tph at relatively low cost. The pioneering development work being conducted at Rockdale, Texas, by Alcoa and Texas Power & Light will solve many engineering problems of such operations. The Bureau of Mines at Denver has studied the carbonizing properties of several hundred coals by small scale assay at 500°C, deriving a simple correlation between the potential yield of tar and the proximate analysis. This correlation, shown in Fig. 1, compares the heat in the volatile matter of the coal with the potential yield of primary tar. The yield of primary tar varies from 12 to 50 gal per ton of pure coal." About the same amount of heat is needed to * MAF equals moisture-and-ash-free basis. distil any dry coal at 500°C, and the time required to carbonize a given particle size is about the same for any coal. It is therefore obvious that coals rich in volatile matter will show the greatest profits when processed. Texas lignites are rich in volatile matter, which contributes some 5700 Btu per lb of MAF coal, and the potential primary tar and oil yield from this lignite averages 12 pct by weight or 27 gal per ton from the pure lignite. Texas lignites are considerably richer in potential tar than lignites of North Dakota and Montana. During 1950 the Bureau of Mines conducted many experiments on carbonizing fine dry coal in the entrained state, publishing a report4 n major features of pilot and commercial-size units required to carry out the process. Additional experimental work has been done at Denver and the pilot plant has been improved, particularly the facilities for studying removal of fine dusts from tar vapors and gases at high temperatures by electrostatic precipitation. A number of materials have been carbonized, including sawdust, peat, brown coal, Brazilian oil shale, lignites, and the lower rank bituminous coals having noncoking properties. Straight coking coals cannot

Jan 1, 1957

By George M. Rigg, Samuel M. Cassidy

During 1937 a program was begun to mechanize and modernize the then 28-year old Isabella mine of the Weirton Coal Co., which is on the Monongahela River, in Fayette County, Pennsylvania, at one edge of what is generally known as the Coke Region. Weirton Coal Co. is a subsidiary of the National Steel Corporation, and produces metallurgical grade coking coal for the Weirton Steel Co., Weirton, W. Va. Improvements subsequently made included a cleaning plant for washing the entire mine output, shovel-action track-mounted machines for mechanically loading all the coal, universal-type track-mounted cutting and shearing machines, post drills, 8-wheel mine cars of 10 tons capacity, cable-reel gathering locomotives and other auxiliary equipment. This paper presents the factors, reasons and results of decided changes from the mining system generally prevailing in the region, as well as abandonment of selective mining practices in favor of complete seam extraction. Coal-seam Conditions Fig. 1 illustrates the Pittsburgh coal seam on the property. Cover over the seam averages 450 ft., and 675 ft. is the maxi- mum. Main roof varies from very weak to medium strong; usually it disintegrates rapidly on exposure to air. The "wild" coal makes a fairly strong immediate roof if supported by crossbars and if unbroken affords a seal to the main roof. The draw slate is very weak and treacherous. The floor is characterized by numerous irregular bottom rolls, or "horsebacks," protruding from a few inches up to 3 ft. into the coal. Some are soft, but many are hard and flintlike. Although the bottom slate usually is hard, the underlying fire clay causes it to buckle and heave readily with any moderate increase in roof pressure or where damp. As a whole, the bottom is weaker than the main roof. The coal is characterized by numerous closely jointed face and butt cleats and a woody, springy nature when shot, both having a decided influence on face practices. As shown in Fig. I, at both the top and bottom of the main coal seam is a layer of coal of higher ash and sulphur content than the body of coal in the middle. Factors That Influence the Mining System Equipment was bought and organization for mechanical loading was made on the basis of working each mechanical unit as near its full capacity as possible, to lessen investment cost and obtain best operating efficiency. This led to combination double and triple-shift operation at the start, and, very shortly, to all sections being triple shifted.

Jan 1, 1947

By Samuel M. Cassidy, George M. Rigg

During 1937 a program was begun to mechanize and modernize the then 28-year old Isabella mine of the Weirton Coal Co., which is on the Monongahela River, in Fayette County, Pennsylvania, at one edge of what is generally known as the Coke Region. Weirton Coal Co. is a subsidiary of the National Steel Corporation, and produces metallurgical grade coking coal for the Weirton Steel Co., Weirton, W. Va. Improvements subsequently made included a cleaning plant for washing the entire mine output, shovel-action track-mounted machines for mechanically loading all the coal, universal-type track-mounted cutting and shearing machines, post drills, 8-wheel mine cars of 10 tons capacity, cable-reel gathering locomotives and other auxiliary equipment. This paper presents the factors, reasons and results of decided changes from the mining system generally prevailing in the region, as well as abandonment of selective mining practices in favor of complete seam extraction. Coal-seam Conditions Fig. 1 illustrates the Pittsburgh coal seam on the property. Cover over the seam averages 450 ft., and 675 ft. is the maxi- mum. Main roof varies from very weak to medium strong; usually it disintegrates rapidly on exposure to air. The "wild" coal makes a fairly strong immediate roof if supported by crossbars and if unbroken affords a seal to the main roof. The draw slate is very weak and treacherous. The floor is characterized by numerous irregular bottom rolls, or "horsebacks," protruding from a few inches up to 3 ft. into the coal. Some are soft, but many are hard and flintlike. Although the bottom slate usually is hard, the underlying fire clay causes it to buckle and heave readily with any moderate increase in roof pressure or where damp. As a whole, the bottom is weaker than the main roof. The coal is characterized by numerous closely jointed face and butt cleats and a woody, springy nature when shot, both having a decided influence on face practices. As shown in Fig. I, at both the top and bottom of the main coal seam is a layer of coal of higher ash and sulphur content than the body of coal in the middle. Factors That Influence the Mining System Equipment was bought and organization for mechanical loading was made on the basis of working each mechanical unit as near its full capacity as possible, to lessen investment cost and obtain best operating efficiency. This led to combination double and triple-shift operation at the start, and, very shortly, to all sections being triple shifted.

Jan 1, 1947

By D. Gignac, P. A. Studemeister, H. Koza

Two epiclastic horizons in an Archean volcanic sequence host the gold occurrences on the Dunraine property near Wawa, Ontario, Canada. The Grace horizon of cherty and pelitic tuff strikes northnorthwest and dips east. Native gold occurs with arsenopyrite in bedlike and podlike bodies of quartz lenses and stringers set in a pelitic matrix. The Parkhill horizon of lithic graywacke with associated flow-breccia strikes southwest and dips south, Native gold occurs with minor sulfides in similar bodies of quartz erratic within the Parkhill horizon. The auriferous bodies occupy paleotopographic channels and troughs within the two horizons. The former producers are the Parkhill mine with 1689 kg (54,300 oz) Au, Darwin mine with 473 kg (15,200 oz) Au, and Van Sickle mine with 48 kg (1536 oz) Au between 1902 and 1944. The gold occurrences are syndepositional with the host volcanic sediments laid during a pause in explosive volcanism. Fumaroles along steep gullies on the flank of a subaqueous volcanic center precipitated aprons of auriferous silica-sulfide mud. Downslope slumping resulted in exhalative debris flows; gold concentrated in flexures and depressions along slumpage channels. Renewed explosive volcanism covered the auriferous sediments with pyroclastic tuffs, arresting the slumping of in situ fumarolic deposits.

Jan 1, 1986

By J. B. Dilworth

The word ".development," as used in connection with mining, is a rather general term and in most instances must be qualified or explained before the exact thought in the mind of the user is made clear. For instance, by the development of a mining district is often meant its entire facilities of mineral production, such as railroads, towns, mine plants, etc. In speaking of the development of a property its prospecting by test pits or diamond drill borings may be referred to; or it may be the mines, strip pits or quarries from which the coal, ore or rock is won. Rut, as a rule, when the development of an individual mine is spoken of the idea in mind is the system of underground workings by means of which the mineral is recovered and transported to the surface. It is this character of development that is considered here. The discussion will be confined to the ordinary room-and-pillar system of mining practically horizontal coal seams that is used in most bituminous coal mines in this country, and to only two phases of this subject; viz., what is properly included under the head of "Development" as it appears on the books of a coal company or the inventories of an examining engineer, and how its " value " should be determined by the accountant or engineer. No absolute rule or definite agreement covers these points, yet these questions are far more than academic. Development is often an important part of a mining company's assets, affecting the amount of its invested capital (and hence its rate of taxation under present Federal income tax laws) as well as the value of its total assets and the amounts chargeable to cost of coal and to depreciation. Mine Development Account Perhaps the majority of mine accountants will agree that the mine development account is that capital account which shows the extraordinary expenditures incurred in opening and expanding the underground workings of a mine until it has reached its normal production, the expenditures being those made for shafts, slopes, rock tunnels, drift mouths and such relatively permanent work; also payments over and above ordinary mining costs made for driving entries, air courses and break-through; for

Jan 1, 1922

By E. J. Schmitz

The following abstract of an unpublished treatise, prepared by me, on the geological formations and minerals of the State of Alabama, is deemed of interest to the Institute. This State, called after the river of the same name (which, formed by the junction of the Coosa and the Tallapoosa, waters, with its tributaries, more than half the State), is divided by its main watershed into a larger southern district, sloping south and southwest, and drained into the Gulf of Mexico, and a smaller northern district, sloping generally north and west, and drained into the Tennessee. Geologically the State may be divided (according to historical geology) according to the different formations it exhibits, among which I include the Azoic, the existence of which in Alabama has been doubted by some; or it may be divided (according to structural geology, as closely related to topography) into a north and northwestern, a middle, and a southern zone.

Jan 1, 1884

By E. T. Dumble

In continuation of the geological work begun in Sonora, Mexico, a partial account of which has already been given in the Transactions of the Institute,* a similar reconnaissance was made of Cochise county, Arizona, and a part of the Whetstone mountains. The investigation resulted in the identification of beds of similar age and character to those of the Sonora region, and in the discovery of interesting deposits, which, so far as I call ascertain from the literature at my command, have not been described heretofore. Route.—Starting from Nogales, we followed the railroad to Crittenden, and then drove to the southeastern slope of the Whetstones. After a brief examination of some reported coalbeds we continued our route, following the wagon-road between the Whetstones and the Mustang mountains to Huachuca, and eastward to Tombstone. Crossing the Dragoon mountains at South Pass, we traveled south and west by way of Turquoise and Antelope Spring into the road from Tombstone to Bisbee. Our route over the Mule mountains lay through Mule Pass and Bisbee, where we stopped a day or two. Thence, crossing Sulphur Spring valley, we drove around the southern end of the Swisshelms, and N. through the valley between these mountains and the Chiricahuas, to White river. From that point our way led through Rucker canon into the San Simon valley, then northward along the eastern face of the Chiricahuas, and by way of Fort Bowie to Willcox, Arizona, from which place we returned to Nogales. It was greatly regretted that the extremely wet weather prevented us from including in our examination the Huachuca

Jan 1, 1902

By William G. Pariseau

The flexure of geologic strata, a phenomenon of interest to geologists and mining engineers alike, is examined as a sheet bending problem in Coulomb plasticity. Fonnulae for the distribution of stress, strain, and displacement increments; volume change; change in the length of the central surface; and power of dissipation, as well as for the neutral surface shift are given. Strains of any magnitude are considered. The analysis shows that deeply buried strata may bend and develop "tensile" cracks under generally compressive states of stress. It is also shown that bed separation and high capacity props are desirable in mechanized longwall mining, a result in keeping with operating experience. Although speculative at this time, the analysis provides a rational working hypothesis as regards the problem of strata flexure and control. | he purpose of this paper is to present an analysis of the flexure of geologic strata as a problem in the bending of a sheet of material failing in accordance with a Mohr-Coulomb criterion. The flexure of strata has an obvious academic interest to the geologist concerned with the mechanics of folding. It is of interest to the economic geologist as it relates to the structural control of certain types of ore deposits. It has an intimate association with mine subsidence phenomena, and is of concern to the mining engineer. Strata flexure is also the dominant feature of roof behavior about longwall workings. An improved understanding of strata flexure through a rational mechanical analysis thus appears desirable not only from the academic view but from the economic one as well. In the field, the most commonly observed feature of folding, subsidence, and longwall roof behavior is the permanent and therefore inelastic nature of the strata movement. Fig. 1 illustrates the physical disposition of strata in the vicinity of a longwall face. Inasmuch as most rocks (with the possible exception of certain evaporites) do not exhibit significant viscoelastic behavior, at least not over time spans of engineering interest, a plastic analysis is indicated. The analysis is meant to apply to strata whose deformation is dominantly that of bending such as might be expected in the remote roof about a longwall face.

Jan 1, 1970

By P. V. Martin

SHORTLY after the middle of the nineteenth century, the invention of the regenerative open-hearth furnace and the development of the Bes-semer process stimulated a, rate of steel production whose magnitude created an unprecedented demand for pig iron. Revolutionary improvements in furnace design, auxiliary equipment, and operating technique enabled the blast furnace to keep abreast of the constantly increasing requirements of the steel mill. The development of improved blowing equipment, more adequate facilities for material handling, and particularly the general use of anthracite and coke to replace the physically weaker charcoal, led to a rapid expansion in both the height and volume of furnaces. Beyond a doubt,, however, the greatest single factor in blast-furnace improvement at this time was the use of the higher blast temperatures made available by the replacement of the recuperative iron pipe stoves by the regenerative Cowper brick stove. The increased blast tempera-ture not only resulted in greater output but also reduced fuel consumption far more than could be explained by the additional heat content of the blast. The progress of iron manufacturing was thus largely mechanical and thermal. Little attention was given tile chemistry of the process until the publication of the investigations of Sir Lowthian Bell.1 Bell's pains-taking experiments and investigations gave to the blast-furnace man his first real scientific conception of blast-furnace chemistry. Bell's recog-nition of the dual function of the carbon, the technical importance of reversible reactions and chemical equilibria, and his conception of the degree of oxidation of the carbon as shown by the analysis of the outgoing gases as a criterion of furnace efficiency, laid the foundation upon which has since been erected the structure of blast-furnace theory.

Jan 1, 1939

By Frank Tolonen

IRON-ORE beneficiation is becoming of vital importance to the Lake Superior region, since only a few decades will be needed to exhaust the direct shipping ores even if generous allowances are made for discoveries of new orebodies. If the region is to continue as the chief source of ore to the steel industry of the United States, it must concentrate or otherwise beneficiate the enormous tonnages of available iron formations. A beginning along this line has already been made. About one-fifth of the total shipment, even now, is the product of some sort of concentrating process, while another fifth is improved in physical structure by crushing, screening, drying, sintering, or some other similar method. The amount of material amenable to these processes is limited, however; and, in order to be able to utilize the billions of tons of iron formations that cannot be so beneficiated, an intensive study of their nature and concentration possi-bilities is necessary. As long as high-grade ores are available in ample quantities, ore dressing is economically impossible, but as soon as the supply nears exhaustion it becomes necessary. At first the products of ore dressing must meet as nearly as possible the same specifications as the rich ores in order to be adapted to the reduction processes already established. The future requirements as to quality will depend on the one hand upon the ability of the ore dresser to eliminate undesired constituents and charac-teristics in the material, and on the other upon the adaptation of the reduction processes to the product that can be economically supplied. A better understanding of the blast furnace and other reduction reactions, and improvements in the preparation of raw materials, should enable the Michigan districts to continue to supply ore for a long time to come. The study and testing of the iron formations necessary to bring a utilization of the low-grade ores, though requiring time and effort on the part of all concerned, should not be postponed, especially since the economic situation forces the use of the highest grade ore in preference to the leaner material.

Jan 1, 1933

By T. N. Williamson

The art of drilling tunnels is still in its infancy, although it is 70 years since the first tunnel driver was put into operation. (It was used to drive 6000 ft of tunnel under the English Channel.) But during the next 60 years neither government agencies nor private enterprise could find much of a future in tunnel drivers. It was difficult to justify the heavy investments, labor was opposed to the machines, and there had been some spectacular failures. In the last ten years, however, there have been changes. Tunnel drivers are being tried with increasing frequency-in spite of the fact that a large number of them have had to be abandoned on site.

Jan 7, 1965

By Samuel S. Arentz, Dorsey A. Lyon

Introduction % •................. 789 The Present Sources of Zinc ..:.......... 791 Zinc Ores.................. 791 Lead-Zinc Ores................. 793 Loss oF Zinc at the Mine.............. 793 Present Method oF Extracting Zinc From Ores....... 795 Class oF Ores Suited to Zinc Retort Smelting....... 795 Concentration Processes Used for Treating Zinc Ores .... 795 Hydro-Mechanical Processes............. 795 Electro-Mechanical Processes............. 796 Flotation Processes............... 797 Losses of Zinc in Lead and Copper Blast-Furnace Smelting .. 798 Possible Future Sources oF Zinc Supply.......... 800 The Problem oF the Metallurgist and the Present Status of New Processes................. 801 Introduction A great deal of attention has recently been given to the metallurgy of zinc, and much of that which has been said and written on this subject has been in the nature of a criticism. For instance, we are quite accustomed to hearing it said that the metallurgy of zinc has stood still, that it is antiquahed, out of date, etc. We are, however, inclined to agree with George C. Stone1 when he says that, although there have been no such spectacular and radical changes as were worked in the metallurgy of copper and iron by the introduction of converters, there has nevertheless been a decided and marked progress in the metallurgy of zinc, and especially during recent years. However, it must be admitted that, due to the fact that the chemistry of zinc is so different from that of the other metals, the retort process is the only process by which zinc is produced commercially; and, moreover, that losses which occur in the zinc industry— that is, in the mining, milling, and smelting of zinc ore—are very great, for it is stated2 that probably less than 50 per cent. of the zinc mined, even

Jan 1, 1915

By Frank R. Barnako

Coal mining is a hazardous occupation, but tremendous progress has been made in reducing accidental injuries and deaths in the mines. Let us take a look at the hazards in coal mining and the accident record. COAL MINE SAFETY TODAY Underground coal mining creates underground open areas, rooms, and haulageways. The roof (top) and ribs (sides) become highly stressed, and because coal and slate are very weak in tension or compression they frequently fail and fall from the roof and ribs unexpectedly. This is the most hazardous condition miners must cope with underground, and it has consistently produced the greatest number of fatal injuries in the coal mining industry. Only very sophisticated equipment, but which is not yet practical for use underground, is able to detect the buildup of stresses that may eventually lead to a roof or rib fall. Today's miner still looks for fresh cracks in the roof or rib, listens for the "drummy" sound, and feels vibrations from loose material in the roof, when tapped with a sounding stick, in order to find material which may fall. Once located, it is barred down, but if this is not possible, it is then secured to prevent it from falling. The next great& hazard is the equipment used to mine or haul coal. It is large, heavy, reacts quickly to its controls and is operated in con- fined areas with low lighting levels. The record of the last few years shows that fatalities attributable to mining and hauling equipment are about equally divided. Thorough training as part of a complete safety program is necessary to teach employees the hazards of loose roof, rib, and machine operation in order that they can work in the safest way possible. Unless there is such a program, the trade is learned by trial and error with a resulting tragic.

Jan 1, 1973

By James R. Dunn

The purpose of this chapter is to review the uses of sand and gravel by the construction industry. The specific intention is to give tech¬nical people the general perspective and frame¬work which they need to help in making tech¬nical and business decisions. In the sand and gravel industry such decisions are based on an understanding of sociologic, economic, and technologic factors. In order to discuss the sand and gravel industry intelligently, it is necessary to define sand and gravel. "Sand" as most often used by industry is not sand in an engineering or geo¬logic sense but should be called "natural fine aggregate." The expression "fine aggregate" is preferable to "sand" because fine aggregate in¬cludes grain sizes which, according to engineer¬ing or geologic classifications, are defined as pebble or grit size. Natural fine aggregate is distinguished from manufactured fine aggregate in that the manufactured material is crushed and screened to produce the required sizes and natural fine aggregate is only screened. Coarse aggregate is generally defined as aggregate which will not pass a No. 4 or %o-in. sieve. Coarse aggregate may be natural (gravel) or manufactured (crushed stone, crushed gravel, slag, or coarse lightweight aggregate). Gravel is usually considered sufficiently crushed to qualify as manufactured coarse aggregate when two or more sides are broken. Sand and gravel (crushed or uncrushed) is used in asphaltic and portland cement concretes, is subbase for pavements, as fill where good drainage is needed (such as around structures), and for many other uses. About 96% of all he sand and gravel produced is used in construction.

Jan 1, 1975

By C Gunther

Mining examinations are of several kinds and the scope of the investigation depends in each case upon the purpose for which the examination is made. A formal examination of a developed mine is an expensive undertaking; from one to several months are allowed for the work according to the size of the property; many samples are taken; investigation is made of the geological features, including, perhaps, a topographical and geological survey of the surface; the metallurgical treatment of the ore is studied; finally, a determination of costs is demanded. Formal examinations are made for prospective purchasers or as a basis for the consolidation of several properties, and occasionally, in the owner's behalf, to verify the work of resident engineers, or to determine the readiness of a mine for equipment and the kind and capacity of equipment it shall receive. A formal examination of a mine should not be undertaken until a preliminary examination has shown that it is justified. It is regrettable that some engineers are in the habit of prosecuting long and exhaustive examinations of properties whose lack of merit should be, and perhaps is, apparent from the start, or of continuing their investigation long after an unfavorable result is seen to be inevitable. This wasting of a client's money is a species of trickery difficult to prove, and therefore the more contemptible. Preliminary examinations are precisely what the term implies, and are undertaken to determine the advisability of making

Jan 1, 1932

By C. C. Miller, C. A. Hutchinson, A. B. Dyes

This paper presents a simple and practical method for the estimation of effective permeability and reservoir pressures from the rise in bottom hole pressure when a well is shut in. The equations on which the method is based consider a stabilized well producing from a uniform formation when flow is shut off at the sand face followed by the unsteady state flow of a compressible liquid from regions far from a well to points closer in during the build-up period. An approximation for extending the method for two-phase flow in the reservoir is also presented. In order to compare the effects of extremes in the conditions existing at the external boundary of the reservoir, two general equations defining the build-up characteristics of the reservoir are shown: first, for a reservoir with constant pressure maintained at the radius of drainage, and second, for a reservoir with no influx over the radius of drainage. These equations define the build-up characteristics for the shut-in well as functions of time, the permeability and porosity of the drainage area, the viscosity and compressibility of the fluid flowing, the production rate prior to shut-in, and the radius of drainage of the well. When a well is shut in at the surface, rather than at the sand face, flow will continue into the well bore after shut-in due to the compressibility of the fluids in the bore. The effect upon the build-up characteristics of this flow into the well after shut-in has been studied by means of the electrical analyzer. From the basic relationships and consideration of the limitations due to continued flow after shut-in, methods have been developed for the estimation of the effective permeability of an area from the plot of the build-up characteristics of the well producing that area. Likewise, equations are presented for the estimation of the reservoir pressure from an early portion of the build-up curve. By means of the electrical analyzer, studies have been made concerning the variations in the build-up characteristics resulting from damaged or improved permeability in the immediate vicinity of the well bore. These studies show that the permeability estimated from the build-up curves represents the average effective permeability of the majority of the drainage area and that the permeability in the immediate vicinity of the well does not affect this estimate. Since the major portion of the drawdown is in the immediate vicinity of the well, variations in the permeability of this area greatly affect the productivity of the well as expressed by the productivity index. From pressure build-up and productivity index tests the ratio of the permeability of some arbitrarily specified area immediately surrounding the well and the effective permeability in the majority of the drainage area can be computed. This ratio is a measure of any damage to the well incurred in drilling or reworking and likewise any benefits as a result of remedial measures. In build-up tests and many other tests that are made on a producing well it is at least desirable, if not absolutely necessary, that the well be stabilized prior to testing. A method is presented here for relating the time required to stabilize a well and the reservoir and fluid properties. An equation is also presented for approximation of the length of shut-in time required to obtain sufficient build-up data for the estimation of permeability and reservoir pressure.

Jan 1, 1950