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Manganese deposits discovered in Maine may solve one of the problems facing the steel industry today. Diamond drilling is scheduled to start in Aroostook County to determine whether the ore is of acceptable grade. The Bureau of Mines estimates the deposit contains several hundred million tons. If true, it means about a 30-year supply. The steel industry presently imports about 90 pct of its needs. Noranda Mines, Ltd., is planning a sulphur-iron plent for Ontario's Niagara Peninsula. Although contracts have not been signed, a substantial agreement has been reached with American Cyanamid, Ltd., whereby the Noranda plant would be constructed adjacent to Cyanamid's chemical plant at an estimated cost of million. The unit would treat approximately 100,000 tons of pyrite concentrate annually. San Manuel Copper Corp., wholly-owned subsidiary of Magma Copper Co., is asking the RFC for a $111.28 million loan for development of a copper orebody in Pinal County, Ariz. The property s said to be capable of producing 10 million tons of ore annually. San Manuel plans to construct facilities for processing 30,000 tons of ore and for smelting 800 tons of concentrate daily. An Aeromagnetic map covering 120 sq miles of the Wichita Mountain area in southwestern Oklahoma indicates a possibility of iron production from titaniferous magnetite deposits of the Raggedy Mountains, northwest of Lawton. The map shows an area in the north central part of the region which may prove favorable to further development.

Jan 1, 1952

By Orville Lyons

CENTRIFUGAL force has been utilized for the dewatering of fine coal for over 50 years by means of machines commonly called centrifugal dryers. In any centrifuge the coal and water are subjected to a spinning action which usually increases in intensity as the coal progresses through the machine. This spinning action, or the centrifugal force that it induces, tears water away from coal particles and produces a dewatered coal. The effectiveness of the dewatering action for any particular machine is governed by the size-consist of the coal and the centrifugal force imparted to the water on the coal.

Jan 5, 1951

By F. J. Menzer, E. M. Schern

The Morenci/Metcalf porphyry copper mining operation, located in southeastern Arizona, currently processes approximately 91,000 tonnes of ore per day and has copper ore reserves estimated to be in excess of one bill ion tonnes. Functional groups within the Geology Department (currently staffed with six professional and two support personnel include mine geology, project geology, and hydrogeology. The primary task of mine geologists is daily preblast bench face mapping with grade and mill amenability estimates. Auxiliary duties include detailed in-pi t metal distribution evaluation, mineragraphic work and flux quarry geology. Project geologists conduct exploration and preliminary development projects both within and outside the Morenci district and provide support to ore reserve block modeling and geotechnical work performed by the Morenci mine engineering group. Hydrogeologists handle exploration for and development of groundwater resources and groundwater flow modeling, mine dump leach solution penetration and recovery evaluation, and tailing dam water reclamation.

Jan 1, 1984

By Matti J. Saarivirta

Two new precipitation hardening copper-base alloys, Cu-1.5pct Ti-2.5 pct Sn and Cu-1.5 pct Ti-2.5 pct Sn-0.4 pct Cr were developed. High strength and medium conductivity are obtained by solution annealing and subsequent heat treatment. Combination of solution annealing, cold working, and heat treatment increases the strength further. Good elevated temperature strength and ductility makes these alloys superior to copper-beryllium-cobalt alloys. A considerable amount of research work is being done throughout the world to develop new and improved copper-base alloys. In many cases, the object is to develop alloys having a combination of high electrical and thermal conductivities, and high strength. The problem is complicated by the fact that any alloying element added to increase strength, invariably decreases conductivity. Among the few commercial precipitation hardening type copper-base alloys, the Cu-Be-Co alloys are best known. These alloys are used in many applications that require good spring characteristics cornbined with high strength and moderately high electrical conductivity. They can be formed readily after solution annealing, then heat treated to obtain high strength and conductivity. Because of the relatively high cost of the Cu-Be-Co alloys, considerable research has been aimed at developing new lower cost alloys having similar properties. As far as is known today, the binary Cu-Ti alloy is the only one whose properties are

Jan 1, 1962

By N. B. Gray, R. V. Culver, W. S. Boundy, N. W. Stump

The kinetics of sulfation of single crystals of lead sulfide to lead sulfate have been studied between 969" and 1073°K in gas atmospheres of known composition using a thermobalance technique. The data are described by an equation derived on the basis that diffusion outward through the Product layer is the major controlling step. The rate of sulfation is linearly related to the logarithm of the sulfur trioxide partial DESPITE its industrial significance the oxidation of lead sulfide has received limited attention. The oxidation reactions have been studied using beds, briquettes, single crystals, or thin films of lead sulfide. Lead oxide and lead sulfate (PbSO,) were formed when Mclntoshl and Gardner2 roasted beds of galena pressure and the temperature coefficient of reaction is 40 ± 5 kcal per g mole. Gold marker experiments show that the sulfate layer grows by outward movement of ions through the sulfate layer. Initially the PbSO, adheres to the PbS but later forms an irnpewious spheroidal envelope; PbS vaporizes and pb2' ions diffuse through the envelope to react at the external surface. in air at temperatures up to 800°C. In a more extensive investigation, Tchizhykov3 obtained Pb, PbO, and PbS04 in accordance with Eqs. [1] to [4], when a bed of -200 mesh galena was oxidized in O2-N2 mixtures at 700° to 900°C.

Jan 1, 1968

By J. E. Willson, N. K. Bohidar

An evaluation of internal stress distribution based on photoelastic studies and destructive testing of simulation models shows that pillar failure is a function of the internal stress distribution, and that stability can be changed by altering the internal stress pattern. Induced stresses in three-dimensional epoxy disks subjected to uniaxial forces were evaluated by photoelastic studies. Stress profiles across different sections perpendicular to the loading direction revealed two maxima for each profile. Based on the stress distribution for the entire column, an attempt was made to explain pillar spalling and the hour glass pattern of failure in a mine pillar. For maximum stability and optimum design of mine pillars, it is necessary to consider the external forces, the nature and distribution of induced stresses and the characteristics of the pillar material as determined in the laboratory. This paper summarizes the research done by N. K. Bohidarl and Ben L. seegrniller2 as partial fulfilment of the requirement for Master of Science degree in Mining Engineering, University of Utah. It is an evaluation of a study to determine the stress distribution in short columns in order that regions of high stress concentration in mine pillars may be found and their effect on pillar failure be ascertained. The ratios of the dimensions of the columns studied are representative of those found in mines located in flat-bedded deposits. The weight of the overburden generally constitutes the major external force. This force is calculated by taking into account specific weight and thickness of the cover. Determination of the distribution of this force on pillars may often require a complex analytical study. There have been many investigations of the strength

Jan 1, 1968

By Harold A. Krueger

FACILITIES and mining operations of the National Lead Co., St. Louis Smelting and Refining Division, near Fredericktown, Mo., are situated in a famous mining area. Copper, lead, nickel, and cobalt have been mined here for more than 100 years, work having been started on a high sulphide copper outcrop in 1847. Lamotte sandstone is characterized by differential compaction on a rigorously eroded pre-Cambrian surface. The Bonneterre formation was therefore a good host for minerals not generally found in mineable quantities in these midwestern areas. Unusually complex minerals, however, make beneficiation difficult, and because of irregular ore thicknesses and elevations many engineers and operators have not attempted to mine the property. Others have tried who failed. This paper deals with economic, efficient, and competitive methods of mining these highly irregular orebodies, as compared to the open-stope, room-and-pillar methods normally used for horizontal-bedded lead deposits. For the purpose of this study it should be understood that the ore is found in two distinctly different types of occurrences, one to be designated as basin ore and the other as contact ore. Mining of basin ore is complicated by many faults, fractures, cross faults, and breaks. Contact ore is complex because it is found on flanks or slopes of pre-Cambrian knobs or highs. The dip of the mining floor for the latter type varies between 18" and 45". Occurrences of both types of ore are complicated by water courses or solution channels which carry unconsolidated shale, lime, sand, and dolomite. This material is also found between the bedding planes of the members of the Bonneterre formation. The water found where there are fractures, faults, and channels makes it very fluid and tacky, see Fig. 1, particularly after it has been blasted and handled by loading and hauling machines. Much of the ore can be wadded and thrown without dispersing. During early operations by the Buckeye Copper Co. in 1861 and the North American Lead Co. from 1900 to 1910, conventional narrow-gage railroad and side dump mine cars were used with hand shoveling. The complications of mining the contact ore, the only type attempted at this time, can be appreciated when it is realized that operators were obliged to use mules for haulage. Haulageways constructed on these slopes were of necessity similar to wagon trails or goat trails up the side of a mountain. In other words, it was merely a matter of going from side to side of the strike length of the slope, gaining a little in elevation on each shuttle trip. Production totaled only one to two tons per manshift. A few years later, about 1913, the property was purchased by combined Canadian interests known as the Missouri Cobalt Co., and the use of trolley locomotives was initiated. Between 1900 and 1928 a land agent using churn and diamond drilling methods prospected scattered sections of the area. In 1928 the first property was purchased by the present company, then operating as the St. Louis Smelting and Refining Co. Check drilling and prospecting was carried out by the company at various times between 1928 and 1939 to correlate the erratic mineralization. Much information about both types of orebodies was accumulated, but it was still questionable as to whether money should be invested to work these occurrences. In anticipation of high lead and copper prices, about the time World War II started, it was decided to develop and bring into production some of this ore. In 1942 No. 1 shaft was put down on the largest basin-type orebody and in 1943 No. 2 shaft was put down on contact-type ore. Operations were expanded when No. 3 shaft was completed in 1943, and progressed further in 1948, when National Lead Co. dewatered and opened No. 5 and 6 mines, old workings of the North American Lead Co. and the Missouri Cobalt Co. Because of the differential compaction of Lamotte sandstone over the pre-Cambrian porphyry, in some instances mineable thicknesses of basin-type ore occurred 20 to 30 ft above the sand. This is the exception rather than the rule, since most of the mineralization starts at the sand and is variable in thickness. The ore was attacked, therefore, by development drifts and crosscuts at the lowest possible elevation, where the ore immediately overlying the Lamotte sandstone could be drained and made accessible for mining. It was planned to connect to the drifts and crosscuts with raises to mine ore deposited 20 to 30 ft higher. The higher orebodies were thus mined as slusher levels. Slusher hoists were used to drag the ore into the raises, which were made into hoppers. The ore was then loaded into 32x32-in. ore cans, hauled to the shaft by battery locomotives, and hoisted by the conventional Tri-State method. The rate of efficiency was 5 to 6 tons per manshift underground. The contact-type ore was attacked in a similar way, except that the orebodies were not nearly so wide, so that they were more flexible for slusher loading into cans. This advantage was offset, however, by haulage complexities, since the railroad was constructed on steep slopes. Through experience and ingenuity, many improvements were made in mining both types of ores. The two levels, so-called, in the basin-type ore-bodies were connected as previously planned, more efficient locomotives replaced the older ones, and a

Jan 1, 1954

DEPENDENCY on foreign sources for many mineral raw materials is a characteristic of our economy which is becoming painfully evident. Although investment in foreign mining projects has increased, it has not kept up with the growing demand for foreign minerals. The sphere of American investment capital in mining ventures abroad has been severely limited by the rise of nationalism in many underdeveloped countries. Consequently, we can look back over half a century in which mining investment, exclusive of petroleum, has increased by 50 pct whereas other American investments abroad have multiplied by better than 300 pct. Investment in foreign mining or petroleum encounters different problems than capital investment for other industries. It is rarely invested in industrialized nations. Most of it goes to countries with expanding frontiers, like Canada, or to underdeveloped nations like Liberia. It must be used for building communities, recruiting and training labor, and establishing lines of communication and transportation. These complications are an accepted part of the mining game. However, the most complex problem is in those countries which consider mineral exploitation a usurpation of the people's natural heritage. This is a characteristic of the young government existing by a tenuous balance of power in an underdeveloped nation. American mining capital understandably has shunned these nations as being poor investment risks. However, they possess minerals which are needed by industry. Our government has attempted to stimulate mineral supplies beyond those provided from abroad by private capital. ECA, now under DMPA, makes loans to foreign mining companies. Since the ECA program cannot be expected to continue indefinitely, Point IV seems to be the logical next step to encourage foreign countries to fill our shortages. However, only 1 pct of the $35 million budget provided in the first year for Point IV was alloted for mining programs. Considering the need for minerals and the difficulties of procuring them by private investment, a larger share is needed and justifiable. Those who have been engaged in foreign mining can vouch for the fact that it takes many decades to teach the complex technology and economics of mining to the natives of under-developed countries. For this reason Point IV must be considered a long range program. Mineral requirements for the present must be met by more direct measures. Encouragement of private investment in foreign mining by such incentives as tax relief on profits from foreign sources, international bank-borrowing facilities for private capital, and diplomatic assistance in encouraging foreign countries to cooperate are imperative for our future mineral security.

Jan 1, 1952

By Roy C. Kirkman

Dear Editor: It is with great pleasure that I read Mr. Howard M. Wells article in the December 1978 issue of MINING ENGINEERING entitled: "Optimization of Mining Engineering Design in Mineral Valuation." Mr. Wells very adequately presents the case and point that there are a great number of variables which must be analyzed during an economic evaluation of an FUND RESOURCE, such as copper or uranium. I wish to take this opportunity to suggest that, given today's economic climate, decision making takes place under conditions of uncertainty and that this uncertainty justifies our need to examine each one of the parameters entered into the evaluation model. It is my contention that the influence of the tonnages and grades as well as their distributions, have the most profound effect upon the results of an evaluation. Everyone concerned with the evaluation of FUND RESOURCES realizes that as metal prices decline or stagnate with sharply rising direct operating costs, cutoff grades (Gc) must increase according to the equation below which Mr. Wells uses: Gc = Total Operating Cost/(Market Price X 20 X Recovery) However, historically, we have seen cutoffs move dramatically lower in both the copper and uranium industries for the past decade. Henceforth, this established the metals industry most important argument for processing greater tonnages of lower grade materials from disseminated deposits (refer to paper by Kirkman, Roy C.). These disseminated deposits, created by either concentration processes (uranium) or dispersion processes (copper, gold, molybdenum), have log-normal grade distributions (Fig 1). Gross profits are rising, but unit profits are falling. The industry has created longevity through economy of scale, i.e., mining vast tonnages of low grade. In order to develop the great tonnages necessary to prove economic viability, we must examine alternatives at the low-end of the tonnage grade relationship. Notice from [Fig. 2] that as we move further to the right away from line A-B drawn tangential to the average grade curve at 45°, total profits will increase (given fixed annual production capacity) and unit profits decrease. The theoretical optimum operating point is where: [ ] At this point my observation is that slight shifts in production capacity bring about greater changes in profitability due to greater grade changes. Therefore, the best financial risk evaluation is obtained by totally revising the mining engineers methods and fixing the financial parameters such as discount and interest rates. A 10% shift in either of these two parameters will not cause near the same variance in economic viability as will a change on the GRADE-TONNAGE curve [(Fig. 2)].

Jan 1, 1980

By John Howe Hall

The recently announced run of three years, nine months and eleven days made by a crucible steel melting furnace of the Columbia Tool Steel Co., which is claimed as a world's record, brings forcibly to our attention the great improvements that have been made in the design, construction and operation of the Siemens regenerative crucible melting furnace since its introduction in this country. Credit for this advance should be given to the furnace designer, the manufacturer of refractories, and the operators, of the furnaces, whose persistent efforts and intelligent co-operation in attacking the problem have resulted so satisfactorily. There are three factors that determine the life of a crucible furnace, or any other furnace for that matter: Design, nature of refractories, and conditions of operation (including the nature of steel melted); and to some extent these factors are interdependent. Thus, for instance, if a crucible furnace is to be operated single turn and allowed to cool off considerably at night, in order to save fuel, the use of clay-brick melting holes may be advisable, since silica brick is not well adapted to endure repeated heating and cooling. But the total life of a clay-brick melting hole is necessarily short. Again, if local conditions such as danger of flood make necessary the building of the furnace largely above ground, so that the radiation of heat is promoted, the cooling down of the furnace over the week ends, when no steel is melted, will be considerable—and the contraction of the furnace that results tends to wrack it to pieces. The character of the metal being melted affects the life of the furnace to a great extent. Low-carbon steels and steels made from iron and charcoal require higher temperatures and much longer melting time than high-carbon steel or steel made largely from scrap; the life of the furnace will be shorter, and the number of heats melted will be much less, when such materials are melted. The figures available, showing the life of furnaces, are for this reason especially not strictly comparative, since the variations in the steel melted undoubtedly affect the life to a greater or less extent. Probably, however, the method of handling is as important a factor

Jan 1, 1914

By G. S. Hume

IN THE autumn of 1922, British Petroleums Ltd. found oil of 14° Baume in a sand 17 ft. thick in its No. 2 well at Wainwright, 120 miles southeast of Edmonton. This greatly encouraged drilling in the Wainwright-Irma area and this past summer several wells were started, three of which are now completed' and the others still being drilled. Of the three completed, No. 4 British Petroleums contains oil; No. 3 British Petroleums gave a show of oil but so far has not given much hope of becoming a commercial producer; and No. 1 Maple Leaf Co., as now finished, is a gas well with a daily flow of gas of about 2,500,000 cu. ft. at a closed pressure of 700 lb. An oil sand is reported . to have been encountered below the producing gas horizon, in the Maple Leaf well but has not been tested. Operations on this well have been suspended for the winter. The Geological Survey of Canada this past summer undertook a geological investigation of this area with the object of defining the structures with which the oil and gas are associated. The 'structure underlying this portion of the plains was supposed to-be a terrace with the western edge dipping into the Alberta syncline and with a monoclinal structure to the east. By accurate leveling on known geological horizons on this terrace, a number of gentle folds were located and it is in these folds that the oil land gas are found. At the British Petroleums Nos. 2-and- 4 oil wells, the western flank of the fold has a gentle dip of only a few feet to the mile to the southwest whereas the strata on the eastern flank dip to the northeast about 40 ft. in 1/2 mile, the strike of the fold being northwest and southeast. How far oil will be found down the gentle southwest dip is unknown but probably the productive part of the fold will not exceed 1 mile in width, and possibly less. No. 3 British Petroleums well is on the strike of the fold 1 mile southeast of the two oil wells. The sand that was productive in Nos. 2-and 4 wells was not present in this well or, if present, was very thin and unproductive. Two other sand horizons, however, were encountered. The upper of these

Jan 3, 1925

By E. Luttgen

The substance referred to in the title is the artificially prepared basic carbonate of magnesia, a compound of the carbonate with the hydroxide. It is the "block-magnesia " of commerce, the magnesia alba of the pharmacist. Its composition, though somewhat indefinite, may usually be expressed by the formula : 4MgCO3,Mg(OH)2, 5H2O; it is found to vary slightly with the details of the method of preparation. This substance has been employed recently with much reported success, as a non-conductor of heat. It is moulded to form coverings suitable for steam-pipes and their fittings and sectional jackets for boilers and cylinders; it is furnished also in forms suitable for lining refrigerators, walls and roofs of buildings, fire-proof safes, etc. It was with a view of ascertaining the efficiency of this material as a non-conductor, or, rather, its relative efficiency among the various non-conducting materials in use, that the writer made the experiments about to be described. A block of magnesium carbonate or magnesia alba exhibits some interesting physical qualities. It is a smooth, white, close-grained solid, in outward appearance resembling a block of Paris plaster. It possesses the lightness of cork, the porosity of sponge, and withal a degree of firmness and strength that, in view of its levity, is quite remarkable. To examine more closely the properties of this substance, a number of 1-inch cubes were sawed from the commercial block-carbonate, also some bricks, that is, blocks measuring accurately 2 x 4 x 8 inches, the dimensions of an ordinary brick. The cubes weighed from 2.2 to 2.7 grammes, the bricks weighed 140 to 175 grammes (5 to 6 ounces). The bricks were carefully measured and weighed, and placed in vessels containing distilled water, in which they became gradually submerged, owing to the displacement by water of the air inclosed in the structure of the magnesium carbonate. After twenty-four hours the blocks were removed from the water, dried superficially by contact with filter-paper and weighed. From the increase in weight, the volume of the water absorbed, and consequently that of the air displaced by it, were obtained. For example: a block which when dry weighed 155

Jan 1, 1887

By T. Prof. Egleston

How to interpret the composition of rocks has been a question which has caused a great deal of discussion and investigation among geologists and chemists. It is evident that that analysis will give the clearest results, which will give the relative proportion of the different minerals composing the rock as well as the weight of their different constituents. This, however, is a very difficult matter, and in those rocks which seem to the naked eye entirely compact, like obsidian and other rocks of that class, appears to be impossible. Cordier, in the early part of the century, invented a process which is known as the " mechanical analysis of rocks," which is really a method of mechanical preparation, and consists in crushing the rock to a certain fineness, and then, by virtue of their density, washing out the different minerals, so as to make a mineralogical analysis, separating completely the different constituents of the rocks. In the hands of so skilful a man, this was a comparatively easy matter, and Cordier found no difficulty in ascertaining the mineralogical composition of a rock. The ultimate chemical composition was ascertained from the sum of the elements contained in the different materials. In the light of to-day, it is very easy to see that the complete chemical analysis of the rock does not necessarily lead to the explanation of its character. It has been so difficult, however, to have any other kind of analysis made that most chemical examinations have been made as ultimate, and not as mineralogical analyses. The panning out of the different minerals composing the rock, which are often very nearly of the same specific gravity, is so difficult that a person of ordinary mechanical skill is scarcely able to do it; consequently the mechanical analysis which Cordier proposed, and was able himself so skilfully to effect, has never been practiced to any extent. A school was formed in France consisting of a very small number of Cordier's followers, which, in face of the difficulty of acquiring the method, very soon died out as a school, though some of his most skilful followers are still living. The next important step in ascertaining their composition was to out the rock into transparent sections and examine the minerals with

Jan 1, 1875

By Robert Pring

IN addition to the humanitarian aspects of a dust-control program, certain economic benefits are becoming more fully recognized and now furnish a greater incentive to the mill operator to eliminate the dust from his plant. It is well known that a favorable working environment promotes increased efficiency and improves the morale of em-ployees, with a consequent decrease in labor turnover rates. One progressive mining company estimates its direct and indirect labor turnover costs at from $40 to $50 per man; for skilled labor, such as machine operators, the cost may approach $100 per man. While these figures may not be typical of every plant, they do indicate a potential savings in operating costs. Dust signifies waste; its elimination de-creases maintenance costs of mechanical and electrical equipment; its recovery is often justified from the standpoint of values contained in the collected material, although in large-scale milling operations handling low-grade ore this may not be an important factor. Perhaps the most significant trend in industrial sanitation is that dust-control equipment and procedures are becoming recognized as integral parts of the mill flow-sheet. Exhaust ventilating systems are now afforded equal care in design and mainte-nance to that given other machinery more closely related to the process,

Jan 1, 1940

By M. R. Louthan

The susceptibility of titanium to stress orientation of hydride precipitates was investigated. It was determined that, when hydride precipitation occurred in titanium under an applied tensile stress of 30,000 psi, the hydrides precipitated on the titanium habit plane oriented most nearly perpendicular to the stress axis. Stress orientation of the hydride platelets occurred because the precipitation of the lower density hydride phase perpendicular to the stress axis caused expansion of the matrix in a direction that tended to relieve the applied stress. The Ti-H system has received considerable study in recent years, mainly because of concern over the effects of hydrogen on the mechanical properties of titanium. The amount of hydrogen present in commercial titanium is now quite low and should have no appreciable effect on its mechanical properties; however, many titanium applications require ex- posure to hydrogenous atmospheres under conditions in which hydrogen pickup is likely. In such cases continued exposures may cause the hydrogen content to increase to the extent that titanium hydride does precipitate as a second phase. The hydride phase has been shown 1,2 to have an adverse effect on the mechanical properties, particularly the impact properties, causing reductions in strength and ductility. BACKGROUND The behavior of titanium is often quite similar to that of zirconium and zirconium-base alloys, and the technology developed on one metal can often be applied to the other. Marshall and Louthan3,4 have shown that Zircaloy is susceptible to stress orientation* of zirconium hydride platelets, and that the platelet orientation has a pronounced effect on the mechanical properties of Zircaloy. They showed that when zirconium hydride precipitated in Zircaloy under an applied stress the hydride platelets tended to be aligned parallel to a compressive stress and perpendicular to a tensile stress. They also showed

Jan 1, 1963

By W. S. Gatley, F. C. Appl

This paper presents a combined analytical and experimental study of chisel penetration vs time during chisel impact on rock, a problem of fundamental importance in improving the performance of roller-cone bits or percussion drilling toots. For a given force-time relationship between chisel and rock, the problem of determining the penetration (displacement) vs time of the chisel is formidable. This is so because the rock is a nonlinear system with distributed mass and distributed damping (friction, dissipation of energy due to rupture, etc.). Since the literature does not contain adaptable solutions, the rock behavior to impact was simulated approximately by an "equivalent" lumped system, that is, an "equivalent" mass, spring, dashpot system. With this assumption, an analytical solution was found for chisel penetration vs time due to a sinusoidal load between chisel and rock. From this solution were found curves, in terms of dimension-less variables, for the maximum depth of penetration vs the frequency of the sinusoidal loading and for the energy transfer vs frequency. The results of this analysis were used to predict the penetration rate of rotary rock bits us rotary speed. The curve indicated that an optimum speed exists. To verify this analysis, an experimental apparatus was constructed and used to apply a sinusoidal pulse to a chisel penetrating a rock specimen under atmospheric conditions. Strain gauges were mounted on the chisel shank and a velocity transducer was mounted between the chisel and the rock surface. The velocity was integrated electrically and picked up simultaneously with the strain gauge signal on an oscilloscope. Permanent records were made photographically to provide simultaneous records of force us time and penetration us time. In comparing the experimental results for limestone and dolomite with the theoretical results, good agreement was found in the frequency range of the experiments. Unfortunately, the inertia effect (peak penetration) indicated by the theory occurs at a frequency much higher than could be obtained experimentally with the apparatus constructed. A "rate-of-loading" effect is indicated theoretically, but has not yet been verified experimentally. INTRODUCTION The process of drilling with percussion tools or rotary rock bits is basically related to the transient response of rock to surface impact. Each time a bit tooth contacts the rock, high stresses are developed which result in penetration and rock removal. As the tooth moves on, stresses are relieved and a new cycle begins as the next tooth contacts the rock. Thus the drilling process, which consists of an endless succession of these cycles, can be studied in terms of a single cycle. It is apparent, therefore, that the study of single-chisel impact on rock is fundamentally important in improving the performance of roller-cone and percussive-type drills. Previous studies in this area have been conducted by Simon1 and Hartman2 by means of drop tests. In these tests a chisel was attached to a weight and allowed to fall, due to the force of gravity, so that the chisel was driven into a rock specimen upon impact. Strain gauges were attached to the chisel shank and the resulting force-vs-time curves were recorded photographically from an oscilloscope screen. The depth of penetration and crater dimensions were also measured. These tests have provided much valuable information but, as mentioned by the investigators, have not provided complete information on the effect of "rate of loading'! This is partly due to the fact that the chisel motion during drop tests is not a controlled motion which can be varied in form and frequency. Therefore, it seemed that additional information could be obtained by studying chisel impact under conditions where both the motion and the frequency of loading could be controlled. This paper presents a combined analytical and exper-

By W. R. Strickler, P. Hazebroek, M. Prats

The pressure and production behavior of a homogeneous cylindrical reservoir producing a single fluid through a centrally located vertical fracture of limited lateral extent was determined by using mathematical methods to solve the appropriate differential equation. It is assumed that there is no pressure drop within the fracture — that is, that the fracture capacity is infinite. It was found that the production-rate decline of such a reservoir is constant (except for very early times) when the flowing bottom-hole pressure remains constant. The production-rate decline increases as the fracture length increases. Thus, the lateral extent of fractures can be determined from the production-rate declines before and after fracturing or from the decline rate after fracturing when the properties of the formation and fluids are known. The production behavior over most of the productive life of such a fractured reservoir can be represented by an equivalent radial-flow reservoir of equal volume. The effective well radius of this equivalent reservoir is equal to one-fourth the total fracture length (within 7 per cent); the outer radius of this equivalent reservoir is very nearly equal (within 3.5 per cent) to that of the drainage radius of the fractured well. The effective well radius of a reservoir producing at semisteady state is also very nearly equal to one-fourth the total fracture length. It thus appears that the behavior of vertically fractured reservoirs can be interpreted in terms of simple radial-flow reservoirs of large wellbore. INTRODUCTION An earlier report1 has considered the effect of a vertical fracture on a reservoir producing an incompressible fluid. That investigation of the fractured reservoir producing an incompressible fluid was started because of its simplicity. Thus, pertinent behavior of fractured reservoirs was obtained at an early date, while experience was being gained of value in the solution of more complicated fracture problems. One of these more complicated problems, and the one discussed in this report, considers the effect of a compressible fluid (instead of incompressible fluids) on the production behavior of a fractured reservoir. In the incompressible-fluid work mentioned, it was shown that the production rate after fracturing could be described exactly by an effective well radius equal to one-fourth the fracture length whenever the pressure drop in the fracture was negligible. Because of the simplification in interpretation, it is a matter of much interest to determine whether the production behavior of reservoirs producing a compressible liquid could be described in terms of an effective well radius which remains essentially constant over the producing life of the field. The details of the mathematical investigation are given in the Appendixes. IDEALIZATION AND DESCRIPTION OF THE FRACTURED SYSTEM It is assumed that a horizontal oil-producing layer of constant thickness and of uniform porosity and permeability is bounded above and below by impermeable strata. The reservoir has an impermeable circular cylindrical outer boundary of radius re. The fracture system is represented by a single, plane, vertical fracture of limited radial extent, bounded by the impermeable matrix above and below the producing layer (reservoir). It is assumed that there is no pressure drop in the fracture due to fluid flow. Fig. 1 indicates the general three-dimensional geometry of the fractured reservoir just described. When gravity effects are neglected, the flow behavior in the reservoir is independent of the vertical position in the oil sand. Thus, the flow behavior in the fractured reservoir is described by the two-dimensional flow behavior in a horizontal cross-section of the reservoir, such as the one shown in Fig. 2. Production is due to the expan-

By F. L. Bosqui

A. L. BlomFIeld, Denver, Col. (communication to the Secretary.*) — Mr. Caldecott says on p. 67: "The Dorr thickener shown, while a useful device when crushing with cyanide solution for removing surplus solution from slime pulp prior to air-lift agitation or vacuum filtration, is not adapted to effect as complete a separation of water from settled slime as the ordinary intermittent settlement and decantation." This statement might have passed muster in this country several years ago when. the Dorr thickener was a new device, but its use in hundreds of mills in the United States has demonstrated that as thick a product is being discharged from it as was obtained from the intermittent settling which it has supplanted. • It is interesting to note that recent investigation, especially the work of 11. 6. Coe and G. H. Cleveilger,' in the March Bulletin of the Institute, under the title: Laboratory Method for Determining the Capacities of Slime Settling Tanks, has developed the general theory of settlement and explains the results obtained in practice. Just as free settlement is a function of surface area, so thickening after the zone of free settlement is passed is a function of time. The time required is obtained by the capacity or volume provided in the settler for this thickening zone. Each pulp is a problem in itself, both in regard to free settlement and to time required to reach a commercially finished thickness. Some pulps require 48 hr. and more to reach a density of 40 per cent. solids; others no coarser to the screen test reach a density of 65 per cent.' solids in a fraction of that time. In thickening any pulp a point is reached where the increase in density is so slow as to be commercially unprofitable. When any part of the pulp has reached this point it should pass on for treatment—its place in the thickener should be occupied by pulp which has not yet reached the commercial limit. By doing this the whole volume of the settling tank is kept in active use. Thus the continuous thickener keeps the whole tank at work to its commercial limit, while the intermittent settler has much of its volume occupied at times by pulp which is either quite finished thickening or at least thickened past the commercial point. The mechanical efficiency of the continuous thickener can be the only argument for limiting this statement. In my own experience I have never

Jan 1, 1916

By J. W. Halley

Copper has frequently been recommended as an alloying element for steel and the precipitation-hardening of steels containing from 1 to 2 per cent copper has been studied by a number of investigators. The straight copper steels, however, have not been used extensively and little advantage has been taken of the precipitation-hardening of complex steels containing appreciable amounts of copper. It is difficult to produce a satisfactory surface on the straight copper steels and undoubtedly this has discouraged their use. During recent years a number of steels containing enough copper to make them susceptible to precipitation-hardening have been put on the market. These steels belong to the group usually referred to as "low-alloy high-tensile " steels. They were designed for use in the " hot-rolled" condition; transportation equipment and large structures that cannot be readily heat-treated have been their chief application. Little emphasis has been placed on the possibility of strengthening those containing substantial amounts of copper by precipitation-hardening. The present investigation was undertaken to determine the precipitation-hardening characteristic of one of the "low-alloy steels." Previous Work The first complete study of the effect of time and temperature on the precipitation-hardening of plain copper steels was made by Nehll in 1930. At about the same time Bucholtz and Koster2 studied copper-chromium steels but did not determine the relation between time and temperature to produce maximum hardening. Later, Smith and Palmer3 determined the rate of hardening at various temperatures for two I per cent copper steels containing different amounts of carbon. Their tests indicated that the higher carbon content decreased the rate of hardening. They made tests on many steels containing other alloying elements in addition to copper, but did not determine the time-temperature relationship for maximum hardening for any of the complex steels. Norton,4 in studying the limit of solid solubility of copper in iron, determined the time for maximum hardening of a 2.06 per cent Cu iron

Jan 1, 1940

By J. W. Halley

Copper has frequently been recommended as an alloying element for steel and the precipitation-hardening of steels containing from 1 to 2 per cent copper has been studied by a number of investigators. The straight copper steels, however, have not been used extensively and little advantage has been taken of the precipitation-hardening of complex steels containing appreciable amounts of copper. It is difficult to produce a satisfactory surface on the straight copper steels and undoubtedly this has discouraged their use. During recent years a number of steels containing enough copper to make them susceptible to precipitation-hardening have been put on the market. These steels belong to the group usually referred to as "low-alloy high-tensile " steels. They were designed for use in the " hot-rolled" condition; transportation equipment and large structures that cannot be readily heat-treated have been their chief application. Little emphasis has been placed on the possibility of strengthening those containing substantial amounts of copper by precipitation-hardening. The present investigation was undertaken to determine the precipitation-hardening characteristic of one of the "low-alloy steels." Previous Work The first complete study of the effect of time and temperature on the precipitation-hardening of plain copper steels was made by Nehll in 1930. At about the same time Bucholtz and Koster2 studied copper-chromium steels but did not determine the relation between time and temperature to produce maximum hardening. Later, Smith and Palmer3 determined the rate of hardening at various temperatures for two I per cent copper steels containing different amounts of carbon. Their tests indicated that the higher carbon content decreased the rate of hardening. They made tests on many steels containing other alloying elements in addition to copper, but did not determine the time-temperature relationship for maximum hardening for any of the complex steels. Norton,4 in studying the limit of solid solubility of copper in iron, determined the time for maximum hardening of a 2.06 per cent Cu iron

Jan 1, 1940