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By Borje Hjortzberg-Nordlund

THE great Swedish export iron ore mines are Kiruna and Malmberget in the north above the Arctic circle and Grängesberg in Central Sweden, see Figs. 1 to 3. These mines exported in 1951 about 13 million metric tons of high grade iron ore and concentrates. The origin of these three ore fields seems to be the same. They are of pre-Cambrian age and are regarded as typical instances of primary eruptive ore that has thrust up as glowing masses of lava flow between two somewhat older beds of porphyry. Apparently the ore and the porphyry became segregated from common parent magmas by a process of differentiation. Despite the fact that the Kiruna orebody belongs to the earliest pre-Cambrian formation, it has been influenced to an unusually small extent by later metamorphosisms, apart from its having been set on edge through folding and wrenching off by a number of later faults. The Kiruna ore occurs along a stretch of more than 4 miles as a series of slabs or lenses sloping steeply toward the east and sandwiched between two beds of porphyry. The main orebody has a length of about 3 miles and an average width of 300 ft with a maximum of 600 ft. The dip varies from 65° to 45° toward the east and the known depth is 3000 ft, although magnetic surveys indicate it may be at least 6000 ft. Malmberget has undergone a more thorough transformation, having been pressed and crumpled into a meandering band of disconnected layers and lenses. The largest of the more connected bodies of ore, the Great Ore Layer, outcrops on a low mountain ridge and has a total length of about 4 miles and a maximum width of about 300 ft. The dip varies from 30° to 70° towards the north. The main orebody in Grängesberg, the so-called

Jan 1, 1952

By H. Rush Spedden, A. M. Gaudin

ALTHOUGH the number of minerals that are ferromagnetic) or highly paramagnetic is strictly limited, it has been known for some time that many minerals have slight but supposedly characteristic magnetic susceptibilities. With the exception of pyrrhotite, however, sulphides have been thought nonmagnetic. A new magnetic separator has been made available recently in limited quantity to research laboratories. This device, the Frantz Isodynamic Separator, has been used for the separation of various nonsulphides from each other. Its application to the separation of sulphides, however, does not seem to have been reported. In the Richards Mineral Dressing laboratories, the success achieved through the use of this device in separating associated sulphides has been so startling as to lead us to believe that it constitutes a magnificent adjunct to heavy-liquid separation and to quantitative mineragraphy as a tool for the mineral investigator. THE SEPARATOR The separator (Fig. I) consists of: I. A powerful magnet, the strength of which can be adjusted by means of a rheostat; 2. A vibrating chute of nonmagnetic metal on which the mineral to be separated is made to flow (Fig. 2); 3. A feed bin and adjustable feeder; 4. Receptacles for the collection of products; 5. Means for changing, setting, and accurately reading the two slopes of the chute; viz., the cross slope and longitudinal slope. The separator is made operative by the special shape of its pole pieces, which ensures a strongly converging field. It is said by the makers of the machine that the pole pieces apply a constant mechanical force to a particle of given susceptibility, regardless of its position in the operating space of the separators.* Susceptible particles, therefore, behave as though of lower specific gravity than under ordinary circumstances. This effect, combined with the slopes of the chute and the action of the vibrator, causes a stratification not unlike that obtainable on a shaking table. The chute is of rectangular cross section, and shallow; it is broadened toward the discharge end and divided longitudinally by a partition into two compartments that lead to the collecting receptacles. Although the separator probably can be used to make separations at fairly coarse

Jan 1, 1943

By N. H. MacMillan, W. M. Mularie, R. E. Jackson, A. R. C. Westwood

The initial results of a study of the environment-sensitive microhardness and diamond rotary drilling behavior of granite and its constituent minerals quartz and feldspar (microcline)1 have established that many similarities exist between the environment-sensitive mechanical (chemomechanical) behavior of these materials and that of the simpler solids such as periclase, soda-lime glass, and alumina4 studied previously, at least as far as n-alcohol (straight-chain alcohol) environments are concerned. The results of this study (hereafter designated study I) also suggested that the rate of drilling of granite in these environments is controlled by the chemomechanical behavior of its quartz constituent, and is greatest in those environments which impart a zero l-potential to this phase, thereby maximizing its hardness. Now, cationic surface-active species strongly influence the l-potentials of silicate minerals. For this reason they are widely used in mineral separation operations. In particular, dodecyl trimethyl ammonium bromide (DTAB) was found in study I to produce f 0 for quartz at a concentration in water of 107 to 10-4 moles per 1. Accordingly, the influence of dilute aqueous solutions of this surfactant on the drilling behavior of granite also was examined in study I. This revealed that granite could be drilled three to four times faster in 10-° molar aqueous DTAB than in water, and confirmed by experiment the suggestion that granite is most effectively drilled with a diamond core bit in environments which impart a zero l-potential to quartz. According to O'Connor and Buchanan' however, the isoelectric point for quartz in aqueous DTAB solutions occurs at a concentration of .•.•2 x 10-° moles per 1, rather than [101 to 10-1] moles per 1. To confirm the results of study I, therefore, a more comprehensive investigation of the [ ]-potentials of quartz, microcline, and Westerly granite in aqueous DTAB environments has now been undertaken. At the same time an examination has been made of one of the basic assumptions of the current conceptual understanding of chemomechanical effects. In this view, although hardness changes occur essentially instantaneously following wetting of the solid, they are confined to a surface layer at most a few micrometers (µm) deep. Hence, to maximize the influence of chemomechanical effects on bit penetration rate only shallow cuts should be taken. Practical penetration rates are then obtained by increasing bit rotation speed. Experimental l-potentials were determined by the streaming potential technique using an automated rapid-cycling apparatus recently developed by Martin Marietta Laboratory from a design by Somasundaran and Kulkarni. The drilling studies employed 3.2-mm-OD 120-grit diamond-loaded core bits with a wall thickness of ~0.7 mm, and bit rotation speeds of 2200 and 25,000 rpm. The load applied to the bit was independent of the depth drilled in both cases. The 2200 rpm measurements employed the same drill press and puddle drilling technique as used in study I. The higher rotation speed was obtained using a water-driven dental turbine drill. In the case, the surface active fluid was pumped down the axis of the bit to ensure efficient wetting and flushing of the drilling debris from the hole. In both cases drilling rate was measured by the parameter D(200), defined as the average rate of bit penetration during the interval from 150 to 250 sec after drilling commenced.

Jan 1, 1976

By E. R. Parker, T. H. Hazlett

An understanding of the mechanism of creep of metals requires an accurate knowledge of shape of the time-deformation curve. An expression is developed which accurately expresses the creep curve for a number of structurally stable metals and alloys. VAST strides have been made in the development of high temperature creep resistant alloys; however, no sound understanding of the physical mechanism of creep exists to date. Consequently, creep resistant alloys are still developed by "cut and try" methods formerly so successful but now yielding returns at a continuously diminishing rate. It is apparent to all workers in the field that if the mechanism of creep were understood, much fruitless labor could be avoided. The dirth of fundamental knowledge has not discouraged the theorists. Speculation has flourished and numerous theories of creep have been proposed. A critical review of these theories reveals that, even though there are some general areas of agreement between the majority of the workers, there are many basic questions yet to be resolved.' It is generally conceded that theoretical speculation is far in advance of experimental evidence. The shortage of reliable creep data greatly hinders more rapid progress in this field. It is essential that the effects of different stresses and temperatures on the creep characteristics of metals be quantitatively determined. Once this has been accomplished, it will then be possible to evaluate the effects of alloying additions and, it is hoped, to provide a firm basis of facts for theoretical treatment of the creep phenomenon. The work reported herein was undertaken to determine the effects of such variables as stress, temperature, alloying, and structure on the creep characteristics of some metals. Material and Equipment Nickel was selected as the base material for the current investigation and an experimental program was initiated to determine the effects of temperature and stress on the creep characteristics of this material. Since a large quantity of high purity nickel was required for the proposed program and such material was not commercially available, it was decided to refine, cast, and prepare the required metal in our own laboratory. The resulting nickel test bars had the following composition, given in percentage by weight: Fe, 0.030 (1); Si, 0.003 (2); Ca, 0.001 (1); Mg, 0.020 (2); and S, 0.002 (2); to make total impurities of 0.056. The nickel (balance by difference) is 99.944 pct. The details of the purification process are described elsewhere.' This

Jan 1, 1954

By P. Majani, F. P. Kokesh, M. Grosmangin

Determination of the quality of cementation of casing in oil wells in the past has involved inflow and circulation tests to insure that the producing zones were adequately sealed off from the adjacent zones. Existing logging methods, such as temperature and radioactivity surveys, may detect the presence of cement behind the casing. However, the qualities of the cement (i.e., its hardness and particularly its bond to the casing) are not indicated. The new logging method described in this paper operates on the principle that the attenuation of a sonic pulse transmitted by a casing is greatly increased when that casing is bonded to an outer annulus of hard material (such as set cement) which has an appreciably smaller sonic-wave velocity than that of the casing. The down-hole tool contains a source of recurrent sound pulses which are detected by a receiver spaced a few feet from the source The amplitude of the detected casing-borne pulse is measured, and the resulting signal is transmitted to the surface where it is recorded vs depth. Since amplitude is a function of attenuation, the log is readily interpreted. Laboratory studies have shown straightforward relationship between attenuation and such variables as source-detector spacing and per cent of circumference bonded. It is shown that cement not set or not bonded to the casing has compara- tively little attenuating effect. Field examples show not only the cement top, but also the variation in cementation quality below the top. Further, the increase of bonding with time and after squeeze cementation is depicted. The detection of poor cement jobs is confirmed by production tests and by formation-test results. It is anticipated that the method will have wide application in evaluating cementation quality prior to formation testing in completions and recompletions. The analysis it affords may aid in further improving cementation techniques. INTRODUCTION The main purpose of oilwell cementing is to isolate a production zone from other undesirable zones. To investigate whether this purpose has been accomplished, several logging methods have been used such as temperature logs, radioactive tracer logs, etc. While these logs all respond to the presence of cement behind the casing, they do not indicate the degree of bonding of the cement to the casing. Early in the application of sonic logging, it was noticed that considerable attenuation of sound signals takes place in cemented pipe and is often made evident on the standard Sonic log by cycle skipping.' The development of a circuit capable of continuously recording the amplitude of the casing-borne sound signal has made possible an extensive series of laboratory and field tests, which gave the following results. The amplitude of a sound signal after it has traveled in a firmly cemented pipe is only a small fraction of that recorded by the same device in free pipe. This provides a wide spectrum of energy levels; for given local conditions, empirical values of the amplitude can be correlated with the quality of cementation. Interpretations made in this manner generally have been confirmed by production tests, circulation tests and squeeze cementation. The purposes of this paper are to give a general description of the new logging method and to present some laboratory and field results. CYCLE SKIPPING Early attempts to study the quality of the cement behind the casing were performed with a standard Sonic log, which measures the transit time At, and were based on the well known phenomenon of cycle skipping.' Cycle skipping normally is interpreted as being a manifestation of weak signals at the receivers. The log of Fig. 1 was run with the recording instrumentation adjusted to enhance cycle skipping. A mirror-image presentation was used for better visual interpretation. The transit time of sound in steel is about 58 microseconds/ft (corresponding to a velocity of 17,000 ft/ sec), and the portions of the log where this value is recorded are interpreted as zones with no cement bond. Where cycle skipping produces a higher value of At, weak signals (or a high rate of attenuation) are indicated, and a good cement bond may be present. The occurrence of cycle skipping, however, depends too much on instrument adjustment to give a uni-

By Robert Lepsoe

It is generally realized that in cyaniding the precipitation efficiency of zinc dust is due to the fine division or extended surface of its metallic particles; but frequently it is thought that the presence of other metals, say 2 to 3 percent. lead, is advantageous, causing more complete precipitation. The results of testing about fifty brands of commercial zinc dust have led to the conclusion that there is a distinct relation of precipitation efficiency to fineness and that the effect generally can be estimated by examining the size of metallic particles. The presence of lead was not found to be of any importance. Specifications Generally the term "97 per cent. to pass a 350-mesh screen, 95 to 97 per cent. uncombined metallic zinc" is used by the leading European exporters. Among the many methods of determination of metallic zinc, I have found the iodine test (iodine in potassium iodide) very satisfactory and rapid. It has been controlled by the other methods, samples of the same product having been sent to three different analysts: Iodine method................... 98.11 per cent. metallic zinc, Volumetric method.............. 07.63 per cent. metallic zinc, Ledoux Co., New York Bichromate method.............. 08.16 per cent. metallic zinc, Watson Gray, Liverpool. England Bichromate method.............. 98.20 per cent. metallic zinc, Norway Inst. of Tech., Trondhjem Determination of Precipitation Efficiency The method devised by W. J. Sharwoodl was used. The method proved to be satisfactory, the tests being merely for the comparison of different samples, hence the personal factor in manipulation was eliminated. As nearly all tests showed more zinc in solution than was accounted for by the silver precipitated, the term "dissolved zinc" was introduced—it means zinc dissolved by the action of cyanide and oxygen: Zn + 4KCN + H2O + O = K2Zn(CN)4 + 2KOH; or more probably, resolution of its equivalent precipitated silver, as tests stirred two hours showed more "dissolved zinc" than those stirred

Jan 1, 1925

By J. O. Mack, J. B. Russell

In recent years, solders containing 20 per cent tin with no bismuth or cadmium have been developed by a few companies, and personnel have been properly instructed in their use. In addition, since the tin shortage, a number of solders containing less than 10 per cent Sn, and some with no tin, are being used in special applications; however, a solder of this type has yet to be developed that is satisfactory for general use. Table i.—Composition Ranges Prescribed for a Commercial Substitute Solder Element Per Cent Tin............................ 18.0-20.0 Bismuth (maximum)a............ 0. 80 Silver.......................... O. 10-1. 25 Bismuth plus silver (minimum).... 0. 85 Antimony (maximum)............ o. 50 copper (maximum),,,,,,,,..,,,, 0. I3 Other elements, each (maximum)6 0.03 Lead........................... balance a When silver is present in excess of I per cent, the Bi content shall be 0.50 per cent or over. b Total not to exceed 0.10 per cent. The Purpose of this investigation was to develop an alloy containing a maximum of 15 per cent tin, with no cadmium or bismuth, having solder properties equivalent to or better than those of substitute solders now specified containing 18 to 20 per cent tin (Table I), or even approaching the properties of the standard 40 to 60 tin-lead solder. The wartime restriction of bismuth and cadmium, elements that have beneficial effects on fluidity, solidification range and strength, makes it increasingly difficult to develop a general-purpose solder containing a maximum of 15 per cent tin. In the course of this investigation, 11 elements were used in various combinations with the basic I5-85 tin-lead alloy. These elements were antimony, silver, copper, indium, thallium, lithium, calcium, barium, potassium, sodium and arsenic. In all, 116 low-tin solders were investigated, with the idea of developing a solder that will give satisfactory working properties, specifically in regard to "wetting" of copper, brass and iron, solidification range, capillarity and shear strength of a soldered joint. The relative importance of these various properties plays an important role in the search for substitute solders, since it is almost impossible to retain all of the desired qualities of a high-tin solder and still make drastic changes in the alloy composition. Because of the expected uses of a general-purpose solder, it is necessary that it have properties, especially in regard to wet-tability, that will enable it to be used on the metals in common use. Basic Considerations The maximum liquidus temperature of a solder is determined by the particular application involved and the temperature that can be obtained by the source of heat. If a soldering iron is used, it must not only

Jan 1, 1945

By H. J. Ramey

As fluids move through a wellbore, there is transfer of heat between fluids and the earth due to the diflerence between fluid and geothermal temperatures. This type of heat transmission is involved in drilling and in all producing operations. In certain cases, quantitative knowledge of wellbore heat transmission is very important. This paper presents an approximate solution to the wellbore heat-transmission problem involved in injection of hot or cold fluids. The solution permits estimation of the temperature of fluids, tubing and casing as a function of depth and time. The result is expressed in simple algebraic form suitable for slide-rule calculation. The solution assumes that heat transfer in the wellbore is steady-state, while heat transfer to the earth will be unsteady radial conduction. Allowance is made for heat resistances in the wellbore. The method used may be applied to derivation of other heat problems such as flow through multiple strings in a wellbore. Comparisons of computed and field results are presented to establish the usefulness of the solution. INTRODUCTION During the past few years, considerable interest has been generated in hot-fluid-injection oil-recovery methods. These methods depend upon application of heat to a reservoir by means of a heat-transfer medium heated at the surface. Clearly, heat losses between the surface and the injection interval could be extremely important to this process. Not quite so obvious is the fact that every injection and production operation is accompanied by transmission of heal between wellbore fluids and the earth. Previously, the interpretation of temperature logs',' has been the main purpose of wellbore heat studies. The only papers dealing specifically with long-time injection operations are those of Moss and White3 and Lesem, et al.' The purpose of the present study is to investigate wellbore heat transmission to provide engineering methods useful in both production and injection operations, and basic techniques useful in all wellbore heat-transmission problems. The approach is similar to that of Moss and White:' DEVELOPMENT The transient heat-transmission problem under consideration is as follows. Let us consider the injection of a fluid down the tubing in a well which is cased to the top of the injection interval. Assuming fluid is injected at known rates and surface temperatures, determine the temperature of the injected fluid as a function of depth anti time. Consideration of the heat transferred from the injected fluid to the formation leads to the following equations. For liquid, Eqs. 1, 1A and 2 are developed in the Appendix. These equations were developed under the assumption that physical and thermal properties of the earth and wellbore fluids do not vary with temperature, that heat will transfer radially in the earth and that heat transmission in the wellbore is rapid compared to heat flow in the formation and. thus, can be represented by steady-state solutions. Special cases of this development have been presented by Nowakl and Moss and White.3 Both references are recommended for excellent background material. Nowak' presents very useful information concerning the effect of a shut-in period on subsequent temperatures. Since one purpose of this paper is to present methods which may be used to derive approximate solutions for heat-transmission problems associated to those specifically considered here, a brief discussion of associated heat problems is also presented in the Appendix. Analysis of the derivation presented in the Appendix will indicate that many terms can be re-defined to modify the solution for application to other problems. Before Eqs. 1, 1A and 2 can be used, it is necessary to consider the significance of the over-all heat-transfer coefficient U and the time function f(t). Thorough discussions of the concept of the over-all heat-transfer coefficient may be found in many references on heat transmission. See McAdams5 or Jakob," for example. Briefly, the over-all coefficient U considers the net- resistance to heat flow offered by fluid inside the tubing, the tubing wall, fluids or solids in the annulus, and the casing wall. The effect of radiant heat transfer from the tubing to the casing and resistance to heat flow caused by scale or wax on the tubing or casing may also be included in the over-all coefficient. According to McAdams, on page 136 of Ref. 5>

By A. G. H. Andersen, A. W. Kingsbury

SILICON bronzes containing iron are used to a considerable extent in industry, under the trade name of P.M.G. alloys. Various classes of wrought alloys fall in the composition range 1.5 to 3.5 per cent silicon, and 0.5 to 2.5 per cent iron. Castings may contain as much as 6 per cent silicon and 3 per cent iron at present. The constitutional diagrams of these alloys are thus of considerable practical importance. Copper-silicon-binary alloys have been thoroughly investigated by a number of workers, the latest reports being those of C. S. Smith' and of A. G. H. Andersen .2 Although much work has been done on iron-copper alloys,3 recorded investigations on the copper-rich copper-iron binary constitutional diagram are not numerous. Tammann and Oelsen4 determined the solubility limits of iron in copper by means of magnetic measurements, and found that the solubility of iron in copper amounts to a fraction of one per cent at 400°C., increasing slowly to one per cent at 800°C. From 800°C., the solubility increases rapidly and attains 4 per cent at 1100°C. Hanson and Ford," using electrical resistivity measurements and the microscope, determined a somewhat different solubility limit. Of earlier X-ray works on the copper-iron system, very little has been published. The work by Bradley and Goldschmidt6 on copper-iron-aluminum alloys includes some information on the copper-iron binary. These investigators conclude that substitution of iron in the copper lattice decreases the spacings, which is contrary to the evidence of the present work. Hanson and West7 have investigated the ternary alloys of copper with iron and silicon. Although their diagrams are valuable contributions to the understanding of these alloys, they did not recognize the kappa phase,1,2,7,8 and their diagrams do not everywhere conform to the phase rule. The present work contains a check by means of X-rays of the solid solubility limit of iron in copper, and an X-ray investigation of the ternary-phase diagram, which, owing to present conditions, it became necessary to curtail considerably. PREPARATION OF SAMPLES Castings weighing about 75 grams were melted under vacuum. The charges were made up of ingot iron, copper cathodes from Laurel Hill, and refined silicon supplied by the Electrometallurgical Co. Alundum crucibles were generally used. The exceptions were alloys 77 and 78, which were melted in graphite crucibles. The ingots were annealed at 800°C. for one week, then samples were cut for chemical analysis. Longitudinal sections of the binary alloy ingots were hammered into plates h in. thick. Wherever possible, these plates were homogenized at temperatures ensuring

Jan 1, 1942

By R. D. Boddorff, R. L. Ash, C. T. Butler, W. W. Kay

DRILLING and blasting in anthracite open-pit mines is a continuous problem to contractors and explosive engineers because of the diverse conditions caused by the nature of the geological formations, the extensive mining of the portions of coal beds near the surface, and the proximity of many strip pits to populated areas. Pennsylvania anthracite occurs in four separate long and narrow fields totaling only 480 sq miles. The coal measures are rock strata and coal beds that are considerably folded and faulted. The crests of the anticlines are eroded extensively. The beds outcrop on the mountain sides and dip under the valleys. At first only the upper portions of the synclines could be stripped. Now stripping to increasingly greater depths is economically possible, as is indicated by the fact that the proportion of freshly mined anthracite produced by strip mining has increased from 3.7 pct of the total tonnage in 1930 to 29.6 pct in 1950. Much of the rock overlying the deeper beds now being stripped is so extensively broken that considerable difficulty is experienced in drilling satisfactory blast holes and in using explosives in such manner as to insure a uniformly broken material easily removed by the excavating machinery. Such breaking of rock strata has occurred because the bed now being stripped has been mined extensively in former years by underground methods, and tops of gangways and chambers have subsequently failed. Draglines are used to uncover coal where the overburden can be moved with little or no rehandling. These machines range in size from those having a 2 cu yd capacity bucket on a 60-ft boom to those handling a 25 cu yd bucket on a 200-ft boom. Draglines are also used to strip to the bottom of the coal basins if the depth and the distance between the crops are not too great. For this type of operation blast holes are drilled full depth to the bed. These holes are commonly 30 to 90 ft deep; however, in exceptional cases, holes may be as shallow as 12 ft or as deep as 130 ft. Drilling is normally done for blasts of 12,000 to 60,000 cu yd of overburden, 30,000 cu yd being considered an average blast if vibration is not the controlling factor. Where the stripping of wide basins or the exposure of a moderately pitching vein makes the use of draglines impractical, dipper front shovels equipped with 4 to 6 1/2 cu yd buckets load into trucks. Overburden is removed in benches of 25 to 30 ft with blast holes drilled 4 or 5 ft deeper than the planned floor of the bench. For shovels under 5 cu yd bucket capacity the volume blasted varies from 8000 to 12,000 cu yd, whereas a volume of 30,000 to 50,000 cu yd of overburden is frequently blasted at one time for the larger shovels where vibration is not an important factor. During the past decade the churn drill, generally the Model 42-T Bucyrus-Erie blast hole drill equipped for drilling 9-in. diam holes, has become the most common blast hole drilling machine. Electricity powers half the churn drills in use and is preferred on the large strippings where electric shovels are operated and the working area is concentrated. On these operations the cost of additional electricity for the drills is less than the cost of fuel to operate diesel units because of the existing large demand load of the excavating equipment. Moreover, electric motors start more easily in cold weather and generally are less expensive to maintain. Diesel driven units are employed where a higher degree of mobility. is required. The average drilling speed is 8 ft per hr, although in softer rocks a rate of 15 ft per hr is attained. Where rock is hard and strata is badly broken, drill speeds may ' be less than 2 ft per hr. Low drilling production results under these circumstances when loose material falling from the upper portion of the drill holes causes drill stems to be jammed. Rock formations vary so greatly in the region that a 9-in. diam churn drill bit may become dull after drilling only 2 ft or may drill satisfactorily for 56 ft; however, an average of 35 ft is usual in sandstone of medium hardness. Dull bits are hoisted to flat bed trucks by the sand line of the drill and are usually sharpened in the contractor's bit shop adjacent to the job. Care is generally taken to cover the thread end of the bit with a cap. To facilitate handling of bits around the drill, a heavy thread protector having an eye top is becoming more popular than the flat-top rubber or metal cap furnished with new bits. The 9-in. diam blast holes for a 25 to 30 ft bench are normally on 18x18 ft to 20x20 ft spacings, depending on the character of the overburden, although in broken ground 15x18 ft centers may be used to obtain better breakage and a more even bottom for the bench. The patterns of holes for shots

Jan 1, 1952

By J. W. Goss, M. J. Coolbaugh

Most grouting has been done to stop water flaw in mines and for stabilizing foundations of various man-made structures, a survey of the U.S. literature reveals. Apparently Sun Manuel is one of the first mines in this country to use grout extensively underground for strengthening and stabilizing ground in drifts, shafts, and stations. A comparison with other procedures as well as details of the Sun Manuel program are covered. The employment of pressure grouting as a ground stabilizer at the San Manuel Copper Corp. mine reduces delays in both development and production, lowers costs, and makes possible safer working conditions. It specifically reduces delays in haulage operations and permits the maintenance of normal ventilation. In development work this grouting allows faster excavation by cementing together highly fractured or broken ground that otherwise would require extensive cribbing or spiling. In drift repair, it consolidates the loose or fractured rock over the timber or steel drift supports, thus decreasing the frequency of repair, lessening the hazards from falling rock, and curtailing delays due to blockage of drifts by muckpiles and repair operations. Pressure grouting is the process of pumping an accurately controlled mixture of cement and water into loose, fractured, or porous rock. The ratio of water to cement varies according to the nature of the rock encountered, from the thinnest mixture of 30 gal of water per sack of cement, used to fill very fine fissures, to very thick grout of 5 gal of water per sack of cement, used to fill large fissures or extensive areas of loose, broken rock. The pumping pressures at San Manuel vary from about 100 to 1000 psi, depending upon the compactness of the rock, while at other mines the pressures sometimes go as high as 5000 psi. In order to grout an area in which ground water is encountered, the pumping pressure of the grout must be increased by an amount equal to the pressure of the ground water. GROUTING IN DEVELOPMENT WORK The areas under development at San Manuel include many sections of loose, highly fractured rock. Prior to the advent of the grouting program, drifts, shafts, and stations in these areas could not be excavated without utilizing extensive support such as cribbing, spiling, and breast boarding. This slowed down the development work and increased the costs considerably over that required for excavating in more competent ground. Now, when a particularly bad area is contacted, the mining is temporarily stopped while the bad portion of drift or shaft is grouted. After the grouting is completed, the excavating is resumed with an approximate decrease of 50 pct in lost time and costs. Grouting in Drifts and Turnouts: The grouting procedures and patterns used in drifts and turnouts are very similar. The standard procedure for grouting such a turnout is shown in Fig. 1. After the ground is supported as well as possible with cribbing or lagging, the gaps between the back lagging and side lagging are plugged with empty cement sacks or additional timber, if necessary. The ground surrounding the proposed turnout is then grouted in two stages. In the first stage, the broken and caved rock is drilled and grouted to a depth of 5 to 10 ft, depending on the depth of the broken rock. This stage forms a grouted seal that allows higher pressures to be used at depths beyond 10 ft without developing excessive leaks at the face. After a grout hole is drilled, a 10-ft long pipe is wedged tightly into it with empty cement sacks. Grout is then pumped into the hole until the pressure reaches 200 to 300 psi, and the pipe is subsequently removed if it hasn't become cemented in. No more than one hole at a time is drilled and grouted because the grout has a tendency to go from one hole into another, plugging up the latter. Five or six holes are usually adequate for the first 10 ft of grouting. Experience has shown bentonite to be a useful admixture to the grout, particularly when it is indicated that the grout is being lost into large fissures or voids. Bentonite increases the plasticity of the grout enabling it to remain in place more easily until it has begun to set. In the second stage, the longer holes are drilled through the previously grouted rock, after which the

Jan 1, 1961

By Samuel Lasky

FAULTING at Kennecott, with its attendant fracturing, is unusual, complex, and important. As study. and knowledge of the various fault systems have progressed, appreciation of that importance has helped in the selection of proper horizons for exploration and in the avoidance of useless crosscutting and drifting. During the study of this faulting and fracturing, a suggestion concerning the formation of the ore-bearing fissures occurred to me. Further study in the available portions of the approximately 45 miles of workings in the Kennecott mines for the purpose of checking up the the suggestion led to the hypothesis which this paper will attempt to present. Briefly, the hypothesis may be stated as follows: The formation of transverse faults that stop against a main, system is connected with changes in the strike or dip of the main fault, and such cross faults or fractures lie in the moving block of the main fault system and indicate a change in strike or dip of the main fault. It has been found that each kind of change tends to produce definite effects and that careful study of the evidence can often suggest the exact type of change.

Jan 1, 1928

By H. B. Muller

Single stage autogenous grinding of run-of-mine ore was selected by Broken Hill South Ltd., parent Company of Cobar Mines Pty. Ltd. for the concentrator to treat 60,000 tons per four weekly period of copper and complex copper-lead-zinc sulphide ores from the C.S.A. Mine at Cobar, Australia. Ore is mined by mechanised horizontal cut-and-fill stoping and is prepared for grinding by crushing under- ground in a 60 in. x 48 in. jaw-crusher set at 5 in. closed side setting. The ore is reduced to 80% minus 76 microns in two parallel sections each of one 22 ft. dim. x 7 ft. long autogenous grinding mill, powered by a 1,250 H.P. motor, operating in closed circuit with a single stage 20 in. dim. cyclone. Broken Hill South's original concept of the concentrator required the maximum use of reliable instrumentation, centralised control, and the minimum of manning. To achieve this objective the control room, housing the process recorders, alarms, closed circuit television monitors and all the control equipment, overlooks the grinding and flotation sections, and the whole plant is serviced by a public address system. The grinding units and associated equipment are located in the open and are serviced with the aid of a mobile crane and a mobile hydraulically-operated liner lifting device.

Jan 1, 1970

By R. G. Johnson

The prevailing system of locating wells on a rectangular basis, as shown in Fig. 1-A, has developed because of the exigencies of offsetting at boundary lines. When, however, a very large tract is being drilled, it is often possible to abandon this inferior method for the superior arrange- ment known as "staggering," which is illustrated in Fig. 1, B and C. The advantages of the triangular over the rectangular method are evident from Fig. 2, computed on the basis of one well to 10 acres (4 ha.). With the triangular system, no land is more than 409.4 ft. (124.8 m.) from a

Jan 1, 1920

By Sylvain J. Pirson

The number of seismograph field crews employed in the active survey of potential oil territories is still on the increase, owing to the ever pending threat of a shortage in the supply of crude oil. It is to be expected that for years to come the seismograph will be responsible for discovering many new oil fields, both in wildcat territories and in deeper formations, and that the seismographic campaign will go on unabated. Yet improvements in instrumental design, in the field and interpretative techniques, are brought about year after year, and lead to the reshooting of areas many times surveyed previously. Notwithstanding the experience gained by the past eight years of active work in reflection seismographic surveys, the results given by this method of mapping deep formations have in many instances been at variance with the information subsequently obtained by the drill. To overcome this shortcoming, geophysicists have used closer spacing of the shot points and closer control of the depth points. The method discussed here is being used actively in the Mid-Continent region and endeavors to reduce the interpretation work to a mere mechanical technique, leaving as little as possible to the opinion of the interpreter. The New Method Field Technique.—In sectionized territory where country roads are available every mile, shot points are preferably located every 1/4 mile when six detectors are available or every % mile when eight detectors are at hand. The disposition of individual spreads is represented on Fig. I; in each case a shot point is located at the section corners. Fig. 2a represents the layout of a spread between shot points, the vibration detectors being preferably equidistantly located. Normally in the 1/4-mile control, the distance between shot points is 1320 ft. and the distance between detectors 220 ft. When shooting from shot point S.P. I, detectors 1 to 6 are connected to the recording galvanometers and detector 0 (which indicates the vertical travel time of the wave corre-

Jan 1, 1940

By Sylvain J. Pirson

The number of seismograph field crews employed in the active survey of potential oil territories is still on the increase, owing to the ever pending threat of a shortage in the supply of crude oil. It is to be expected that for years to come the seismograph will be responsible for discovering many new oil fields, both in wildcat territories and in deeper formations, and that the seismographic campaign will go on unabated. Yet improvements in instrumental design, in the field and interpretative techniques, are brought about year after year, and lead to the reshooting of areas many times surveyed previously. Notwithstanding the experience gained by the past eight years of active work in reflection seismographic surveys, the results given by this method of mapping deep formations have in many instances been at variance with the information subsequently obtained by the drill. To overcome this shortcoming, geophysicists have used closer spacing of the shot points and closer control of the depth points. The method discussed here is being used actively in the Mid-Continent region and endeavors to reduce the interpretation work to a mere mechanical technique, leaving as little as possible to the opinion of the interpreter. The New Method Field Technique.—In sectionized territory where country roads are available every mile, shot points are preferably located every 1/4 mile when six detectors are available or every % mile when eight detectors are at hand. The disposition of individual spreads is represented on Fig. I; in each case a shot point is located at the section corners. Fig. 2a represents the layout of a spread between shot points, the vibration detectors being preferably equidistantly located. Normally in the 1/4-mile control, the distance between shot points is 1320 ft. and the distance between detectors 220 ft. When shooting from shot point S.P. I, detectors 1 to 6 are connected to the recording galvanometers and detector 0 (which indicates the vertical travel time of the wave corre-

Jan 1, 1940

by their overdogmatic picture of geology and their resulting drastic oversimplification and idealization of geologic features. I am in hearty disagreement with the recommendation that geophysics should be done by cooperative work between a geologist and a geophysi-cist. That arrangement would be comparable to doing petrography by having a physicist at the microscope and a geologist sitting by his side. The interpretation of the geological significance of geophysical data can be done efficiently only by a physicist who has become also a good geologist or by a geologist who is also a good geophysicist. Less Well-trained Men The rank and file, composing perhaps two-thirds of the personnel of exploratory geophysics, is not, and should not be, composed of highly trained men. The routine, stereotyped character of the work and the impossibility of promotion of more than a few from these lower ranks even under the best circumstances justify companies in filling the bulk of these rank and file positions with men having only a bachelor's degree at the most. There can be a wide range of training for such positions, although certain lines of study are preferred for certain kinds of work, and different employers have different preferences. For work in gravitational and magnetic prospecting, first preference will be for men having geological training and second for men with civil engineering training. In seismic work, men with geological training are preferred by some employers for computers; physicists, electrical engineers and all whose technical education has covered radio circuits are preferred for the other technical positions. Collegiate training in geophysical prospecting brings no preference and by many employers is given a slightly inferior rating. One large company seldom hires men who have just graduated with a major in geophysical prospecting. This prejudice is based on the reasoning that much of what is learned in college is obsolete or obsolescent, that most of the techniques learned in college will have to be unlearned, because different from those used by the employing company, and that in the long run additional courses in basic physics, mathematics and geology are of more value to a man than the courses on geophysical prospecting. DISCUSSION [This discussion refers to the five papers beginning on page 23 and ending on page 74.1 L. W. Blau,* Houston, Texas.—I have had some rather sad experiences with forecasting. For example, I could not foresee 10 years ago my present occupation, and I do not profess to be able to look ahead 10 years and tell anyone what he will be doing then. Referring to the point raised in the discussion, I do not know, for example, what the price of oil will be 10 years from now. If an appreciable number of

Jan 1, 1940

by their overdogmatic picture of geology and their resulting drastic oversimplification and idealization of geologic features. I am in hearty disagreement with the recommendation that geophysics should be done by cooperative work between a geologist and a geophysi-cist. That arrangement would be comparable to doing petrography by having a physicist at the microscope and a geologist sitting by his side. The interpretation of the geological significance of geophysical data can be done efficiently only by a physicist who has become also a good geologist or by a geologist who is also a good geophysicist. Less Well-trained Men The rank and file, composing perhaps two-thirds of the personnel of exploratory geophysics, is not, and should not be, composed of highly trained men. The routine, stereotyped character of the work and the impossibility of promotion of more than a few from these lower ranks even under the best circumstances justify companies in filling the bulk of these rank and file positions with men having only a bachelor's degree at the most. There can be a wide range of training for such positions, although certain lines of study are preferred for certain kinds of work, and different employers have different preferences. For work in gravitational and magnetic prospecting, first preference will be for men having geological training and second for men with civil engineering training. In seismic work, men with geological training are preferred by some employers for computers; physicists, electrical engineers and all whose technical education has covered radio circuits are preferred for the other technical positions. Collegiate training in geophysical prospecting brings no preference and by many employers is given a slightly inferior rating. One large company seldom hires men who have just graduated with a major in geophysical prospecting. This prejudice is based on the reasoning that much of what is learned in college is obsolete or obsolescent, that most of the techniques learned in college will have to be unlearned, because different from those used by the employing company, and that in the long run additional courses in basic physics, mathematics and geology are of more value to a man than the courses on geophysical prospecting. DISCUSSION [This discussion refers to the five papers beginning on page 23 and ending on page 74.1 L. W. Blau,* Houston, Texas.—I have had some rather sad experiences with forecasting. For example, I could not foresee 10 years ago my present occupation, and I do not profess to be able to look ahead 10 years and tell anyone what he will be doing then. Referring to the point raised in the discussion, I do not know, for example, what the price of oil will be 10 years from now. If an appreciable number of

Jan 1, 1940

The Institute maintains a dual relationship with students: (1) an individual relationship with a Student Associate; and (2) a relationship with local organizations of students, known as Affiliated Student Societies or Student Chapters. 1. The conditions of Student Associateship are set forth in Section 8, .Article 1 of the By-laws of the Institute (see p. 45 and following pages) During 1934, sundry amendments were made for the purpose of improving the student relationship. Post-graduate students are now eligible; and the associateship can be maintained, with the payment of the regular dues of $2 per gear, for 18 months following graduation in June. A Student Associate is given a subscription to MINING A ND METALLURGY: he is accorded the privilege of getting special publications such as "The Porphyry Coppers" and "Ore Deposits of the Western States" at the reduced prices applicable to Members; he has the privileges of the Engineering Societies Employment Service and the Engineering Societies Library; and he is not only invited but urged to attend all meetings of the Institute, its Divisions and its Local Sections. The Institute wants to extend the hand of professional fellowship to students following mineral industries curricula.

Jan 1, 1936

By T. Smales, P. L. Wright, K. Barron

The results of field measurements using an air injection technique to investigate the integrity of three pillars in the Mclntyre Mines Ltd. 114 seam at Crande Cache, Alberta, are reported. These pillars are shown to be stable and an estimate is made of the strength of these pillars. Using these results, together with Hustrulid's pillar strength formulae, a general pillar strength equation for the 114 seam is developed. This equation takes into account the probability of failure that may be deemed tolerable within the design requirements. The variation of the minimum pillar dimensions with depth below surface for uniform pillar layouts is then examined for a range of tolerable failure probabilities. A general equation of the form B = 2.60 +B Z relates the minimum pillar design width, B metres, with the overburden depth, Z metres, where B is a parameter related to the tolerable failure probability. This equation only applies for 3.05m high pillars with 6.lm wide entries. Finally, the question of what failure probability is tolerable within the design of mine pillars is discussed. This will depend on the support role required of that pillar and the anticipated period over which the pillar must perform that role. Five categories of coal mine pillars are defined, each with a somewhat different role to perform. Tentative design criteria in the form of "tolerable probabilities of failure" are suggested for four of these five categories of pillar. The fifth category of pillar has no reliable support function to perform and support must be obtained by other means.

Jan 1, 1983