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By AIME AIME

AN outstanding session of the Annual February Meeting was one held under the joint auspices of several groups on Tuesday afternoon, Feb. 22, as a symposium on the question of preserving peace in the postwar era through the control of the supply of sundry minerals vital to the Axis nations. D. H. McLaughlin and R. C. Allen were associate chairmen. And C.K. Leith led the discussion.

Jan 1, 1944

Flag Day Celebrations Develop Practical Patriotism Among the hundreds of industries which celebrated Flag Day on June 14, were a number of mines, and a report- from the United States Smelting, Refining and Mining Co. tells how the programs were carried out at Mammoth and Chrome. In the first place, Flag Day was not observed by knocking off work, but by short exercises, after which work was resumed with re-doubled energy. In this crisis, that method of showing devotion to the flag and country might be termed "practical patriotism." In other words, it could be expressed as "Hats off to the flag and sleeves up for it." Harry Hunt, first-aid man at the Mammoth mine, reports that the flag raising was marked by the spirit of high enthusiasm, which included every man, woman and child belonging to the camp. "The miners in their working clothes, still wearing their carbide lamps on their caps, with faces covered with dirt, just as they came from the mine, and the ladies and children with their bits of bright color, made a picture worthy of the brush of a master painter. The program rendered was that arranged by the National Bureau of Education." First came a bugle call, "To the Colors," given by Assistant Superintendent C. W. Plumb. Then Foreman Carpenter W. R. (Bill) Young, raised the stars and stripes to the peak, and as the banner unfurled to the breeze, all heads were bared, and the salute was given by the workers, whose toil at home is strengthening our army in France. Then the miners joined in the singing of the "Star Spangled Banner," and repeated the "Pledge of Allegiance," and the "American's Creed." Shift-boss W. J. Phinazee then addressed his fellow workers, telling them how the flag stands for their protection and that of their loved ones, and how it should be loved and respected, not only by the native born, but by all who live here under its protection. Those of alien birth, who have come here because of the greater opportunities offered in America, owe a special honor to the stars and stripes, and the point was made that these men from other lands should not love their old home less, but their adopted country more. The majority of those present were foreigners, and their hearty applause showed that they appreciated the point made by their shift-boss, who, because of his position, was able to address them as man to man.

Jan 10, 1918

By David H. Y. Tang, Syd S. Peng

In general, the strata sequence of the immediate roof in the under- ground coal mine openings can be divided into three types. They are: (A) each stratum deflects independently, (B) some stratum (or strata) loads on the underlying stratum, and (C) each stratum loads on its underlying stratum. The flexural behavior of the immediate roof which is made up of multiple strata not only depends on the material property, geometry, and external loading of rock strata, but also on the strata sequence. A computer program based on the beam-column theory is written for determining the bending stress and deflection for the generalized immediate roof. The flexural behavior of the immediate roof in various strata sequences are investigated for the following effects: roof span, horizontal stress, thickness and Young's modulus of the lowest stratum. In addition, some of the results are compared with the results of the finite element method.

Jan 1, 1983

By Richard J. Mainiero

INTRODUCTION Because of the hazards associated with flammable methane gas and coal dust, the shooting of mudcaps (adobes) or other unconfined explosive charges in underground bituminous coal mines is prohibited; all explosives must be fired in stemmed boreholes. However, there are situations where it would be advantageous from a safety standpoint to fire open shots. This would be in the areas of dislodging loose roof slabs, overhangs, rock-fall leveling, slab or boulder breaking, crib removal, and crevice shooting. The Bureau of Mines, U.S. Department of the Interior, has been developing an explosive charge that is non-incendive; that is, detonation of the charge will not ignite a flammable atmosphere. This explosive charge could be applied to the blasting conditions mentioned above. As of this writing, the explosive charge has not yet been certified as "permissible" for use in flammable atmospheres, but the necessary protocol is being finalized with the Mine Safety and Health Administration (MSHA), U.S. Department of Labor. The explosive charge described in this paper is merely a prototype sheathed rock-breaker charge (sheathed permissible explosive rock- breaker charge) demonstrating the feasibility of such a device. Industry may modify the design and composition of the charge in producing a commercial product so long as it is still safe, as defined by a testing schedule being developed by the Bureau of Mines and MSHA.

Jan 1, 1984

The Library of the above-named Societies is open from 9 A.M. to 10 P.M. on all week-days, except holidays, from September 1 to June 30, and from 9 A.M. to 6 P.M. during July and August. The Library contains about 55,000 volumes, including sets of technical periodicals and the publications of scientific and technical societies. Members of the Institute, with few exceptions, are forced to spend a portion of their time in localities isolated from sources of information. To these the Library can render valuable service through correspondence; letters requesting information will receive special attention. The Library is prepared to furnish references and copies of articles on mining and metallurgical subjects; to determine the existence of mining maps, and to furnish general information as to the geology and mineral resources of all countries. All communications should be made as definite as possible so that. the information received may he what is desired and not include collateral matter which may not be of interest. The time spent in searching for such collateral matter will he saved, and the information will be sent more promptly and in more usable shape. The members of the Institute can be of service to the Library by forwarding copies of mining reports, maps privately issued, and similar material, which will be classified, indexed, and made available to other members. Suggestions for additions to the Library, either by, purchase or personal solicitation as gifts, will be welcomed. It is hoped that members while in the city will use the Library freely, and, assurance is given that most careful service will be rendered to them.

Jan 8, 1915

By J. H. Slater

There is nothing particularly new about the use of sinter in a blast-furnace burden. For many years flue dust has been sintered at the various blast-furnace plants to put it in a form that could be recharged to the furnace with some assurance that it would stay in the second time. This paper is not a compilation of scientific data but only an attempt to give our experience with sinter. There are some unexplained discrepancies in the tests given here, such as the flue dust produced and iron tonnages, but the results given are the results that were obtained. Sinter is not the cure-all for blast-furnace problems. A good coke is still the most important factor in good furnace operation. However, good sinter is a big help. As flue dust is produced under varying operating conditions and fluctuates greatly in carbon content, it is difficult to produce from flue dust alone a uniform sinter, which will give satisfactory blast-furnace results. Sinter made from flue dust alone will change in character with every carbon variation. Almost invariably flue dust contains carbon in excess of the amount necessary to make good sinter, and this excess must be burned out. This, of course, necessitates reduction of the speed of the sintering machine and thus a decrease in tonnage. An alternative is to dilute with a carbon-free material to use up the excess carbon. High-carbon material when sintered results in a very dense, undesirable product, since the excess heat melts the charge into a hard, nonporous mass, and tends to form refractory silicates. At the Republic Steel plant in Cleveland, there had existed since 1924 a continuous-type sintering machine having 224 sq. in. of grate-bar area, capable of producing 9 to 11 tons of sinter per hour from flue dust. Under a former management, it was the practice to sinter only the flue dust from the blast furnaces, no attempt being made to recover the gas-washer sludge. As the dust was limited, the plant operated only part time. In other words, there was a sintering plant representing considerable investment, with good facilities for screening and preparation of raw materials, and flue dust available for only part-time operation. The sinter produced was costly and not a very desirable product. The first step was to install equipment for the recovery of the gas-washer sludge. This was done in the form of two large thickeners and a filter, which have proved very satisfactory. It was then decided to screen out the minus 3/8-in. fines from the Mesabi ores, mix them with flue dust and coke breeze when necessary, and operate the plant at full capacity. The tonnage increased to 18 tons per hour and the product was much improved. Sintering costs fell and the product was a preferred blast-furnace material, which on an iron unit cost compared very favorably with good Mesabi ores. On the average, 40 per cent flue dust and 60 per cent fine ore was being used. The oversize from the ore screening also became a preferred product for the

Jan 1, 1941

By J. H. Slater

There is nothing particularly new about the use of sinter in a blast-furnace burden. For many years flue dust has been sintered at the various blast-furnace plants to put it in a form that could be recharged to the furnace with some assurance that it would stay in the second time. This paper is not a compilation of scientific data but only an attempt to give our experience with sinter. There are some unexplained discrepancies in the tests given here, such as the flue dust produced and iron tonnages, but the results given are the results that were obtained. Sinter is not the cure-all for blast-furnace problems. A good coke is still the most important factor in good furnace operation. However, good sinter is a big help. As flue dust is produced under varying operating conditions and fluctuates greatly in carbon content, it is difficult to produce from flue dust alone a uniform sinter, which will give satisfactory blast-furnace results. Sinter made from flue dust alone will change in character with every carbon variation. Almost invariably flue dust contains carbon in excess of the amount necessary to make good sinter, and this excess must be burned out. This, of course, necessitates reduction of the speed of the sintering machine and thus a decrease in tonnage. An alternative is to dilute with a carbon-free material to use up the excess carbon. High-carbon material when sintered results in a very dense, undesirable product, since the excess heat melts the charge into a hard, nonporous mass, and tends to form refractory silicates. At the Republic Steel plant in Cleveland, there had existed since 1924 a continuous-type sintering machine having 224 sq. in. of grate-bar area, capable of producing 9 to 11 tons of sinter per hour from flue dust. Under a former management, it was the practice to sinter only the flue dust from the blast furnaces, no attempt being made to recover the gas-washer sludge. As the dust was limited, the plant operated only part time. In other words, there was a sintering plant representing considerable investment, with good facilities for screening and preparation of raw materials, and flue dust available for only part-time operation. The sinter produced was costly and not a very desirable product. The first step was to install equipment for the recovery of the gas-washer sludge. This was done in the form of two large thickeners and a filter, which have proved very satisfactory. It was then decided to screen out the minus 3/8-in. fines from the Mesabi ores, mix them with flue dust and coke breeze when necessary, and operate the plant at full capacity. The tonnage increased to 18 tons per hour and the product was much improved. Sintering costs fell and the product was a preferred blast-furnace material, which on an iron unit cost compared very favorably with good Mesabi ores. On the average, 40 per cent flue dust and 60 per cent fine ore was being used. The oversize from the ore screening also became a preferred product for the

Jan 1, 1941

By C. F. Kelley

IT is no new experience for the distinguished subject of this presentation to be the recipient of honors conferred, to be eulogized for successful accomplish-ment, or to hear expressed with sincerity the admira-tion of his fellows. The objectives of his professional endeavor have taken him to many fields; the scenes of his labors have varied from the most remote corners of the globe to those which are close at hand; the universality of his experience is an epitome of modern life, impossible of occurrence in any other era. His career not only embodies to an unrivaled degree the opportunities of the contemporaneous epoch, but also exemplifies in the manner in which they have been transformed into successful accomplishments the pos-sibilities of our age. The many-sided career of our medallist is a composite. Tonight we deal chiefly with its phase for which this medal has been bestowed.

Jan 3, 1928

By J. P. Smith

Permian salt measures carry extensive lenses of soluble potash salts in north central Germany. Potash deposits of Oligocene age are found in the Upper Rhine Graben of Alsace (France), and in the Catalonian Basin of Spain. These deposits are found in a wide range of structural settings. Reserves are large, and the production of potash salts is an important phase in the economy of each of these countries.

Jan 1, 1950

By Donald F. Kennedy

During the past several years Climax Molybdenum Co. has been engaged in testing various types and sizes of hollow drill steel. The majority of tests have been on 7/8-in. hexagon st.ee1, inasmuch as it represents approximately 70% of total drill steel consumption at the Climax operation. Prior to December 1960, tests on 7/8-in. hexagon drill steel were conducted on steel with a forged collar and, in most cases, with a threaded bit connection. Through these tests and research, some improvement in steel life was achieved by making changes in heat treatment, design and alloying constituents. However, during that month, research and testing commenced on a rubber collar which was designed to replace the forged collar on 7/8-in. hexagon drill steel. Manufactured by the LeRoi Div. of Westinghouse Air Brake Co.. the collar. is very simple in design, consisting of a 1 ½ -in. diam steel cylindrical sleeve 2 in. long, containing a bonded rubber insert and attached to the steel with an epoxy cement

Jan 8, 1962

By E. C. Winegartner, A. A. Ubbens

The company attempting to sell coal to large utility plants is faced with a confusing array of quality parameters and specifications which are often poorly understood by both the utility company and coal supplier. While these specifications are placed on the coal by the utility company, many of them originate with the boiler manufacturer who must guarantee that his product will perform satisfactorily on the design coal. A proper understanding of these parameters by both the coal supplier and utility company can lead to a better understanding of their mutual problem. This paper brings together most of the parameters in common use today and attempts to show what the parameters mean to the boiler designer, particularly in the area of boiler slagging and fouling.

Jan 1, 1977

By I. Fatt

Laboratory relative permeability data on reservoir rock are obtained on samples which are not subjected to overburden pressure during the permeability measurements. These data are then used for calculating the performance characteristics of reservoirs in which the rock is under the pressure of the overburden. Recent observations have shown that the permeability and porosity of reservoir sandstones are decreased by application of overburden pressure. These observations led us to a study of the effect of overburden pressure on the relative permeability characteristics of sandstones. A previous note from this laboratory1 showed that overburden pressure, simulated by applying hydraulic pressure to the outside of a plastic mounted core. caused a reduction in permeability of the core by as much as 50 per cent at 10,000 psig. In a multiphase fluid flow system, the relative permeability at a given saturation will change if the permeability or the effective permeability changes but not if both permeability and effective permeability change by the same ratio. The tests described in this note were made to determine the effect of overburden pressure on permeability and effective gas permeability in the gas-oil system. The gas-oil system was chosen because the available equipment was best suited for studying this system. The resultant data can be applied to other systems of interest because the gas permeability in the gas-oil system is the permeability of the nonwetting phase and, as such, is equivalent to the gas permeability in the gas-oil-water system and to the oil permeability in the oil-water system. EXPERIMENTAL METHOD Cylindrical test plugs, one in. in diameter and one in. long, were cut from sandstone core samples from three different reservoirs. After extraction in toluene, the plugs were mounted in Lucite by conventional core mounting methods.3 The core properties are given in the legend in Fig. 1. The mounted cores were machined to fit the apparatus shown in Fig 4. Air permeabilities as a function of overburden pressure were measured by connecting lines (1) and (2) to a conventional air permeameter. To measure porosity changes as a function of overburden pressure, the lines leading to (1) and (2) and the core were saturated with kerosene; line (1) was capped and a small bore precision calibrated pipet was connected to (2). Changes in pore volume of the core as overburden pressure was applied were noted by reading the amount of kerosene produced into the pipet. To correct for the change in volume of the lines inside the hydraulic cell as a function of pressure, a pressure-vs-volume run was made with a solid Lucite cylinder substituted for the core. The change in volume of the lines was about 10 per cent of the change in pore volume of the core. No correction was needed for the permeability measurements because there was no measurable pressure drop in the lines at the maximum overburden pressure. Relative gas permeabilities were measured by the stationary liquid method described by Osoba, et al.' Gas saturations were obtained by allowing the kerosene from a kerosene saturated core to evaporate out. This procedure was followed

Jan 1, 1953

• Pellets of concentrated iron ore have been smelted in the blast furnace by Armco and the results proved satisfactory. Various percentages of pellet burdens were tried and it has been found that charges up to 70 pct pellets are workable. •In the reorganization of the Department of the Interior, two new assistant secretaries were appointed and the work divided between the four assistant secretaries. C. Girard Davidson will head a division of mineral resources including the Bureau of Mines, Geological Survey, Division of Oil and Gas and Division of Geography. •Germanium, one of the rarest of metals and a wartime strategic material, has been discovered almost in the shadow of the Capitol. The only catch is that the scattered nature of the deposits makes profitable recovery extremely doubtful. Nevertheless, experts have tabbed the concentration in the District of Columbia area the world's second richest known concentration of the element. • Cakes of mica, weighing up to 500 lb, have been formed at the Colorado School of Mines by a new "cool hearth" method. The process avoids use of crucibles and contains the molten mica in a basin of unmelted raw mixture from which the melt was derived. Crystallization takes place in this melting basin which forms a center pool surrounded by a solid cool mass of the unmelted raw mixture. • William 1. Baxter, of the International Economic Research Bureau, predicts a period of deflation because of war-essential restrictions on consumer credit and materials use. He stated; "the recent prosperity was based mainly on the sales boom in autos, homes, and household accessories." •Two subsidiaries of United States Steel have decided to build four new ships immediately to augment iron ore and limestone carrying capacity on the Great Lakes to meet demands created by the national defense emergency. •The Norfolk and Western Railway is making a complete change over to coal to drive its locomotives. •A national roster of scientific personnel similar to the one used in the last war will be established by the Office of Education, by agreement with the National Security Resources Board. The new unit, the National Scientific Register Project, will make studies of the Nation's scientific manpower supply and recommend steps to increase the numbers of skilled personnel where needed. •National Lead Co. will start construction immediately of new facilities at St. Louis, Mo., for production of titanium pigments for paints. Producers of titanium pigments have been under considerable pressure to meet all demands from paint manufacturers, particularly for titanium dioxide. •The basic criteria for deferment of reservists in civilian occupations are (1) the Department of Labor List of Critical Occupations, and (2) the Department of Commerce List of Essential Activities, both of which were announced Aug. 3. Fundamentally, the reservist deferred must be engaged in a critical occupation which is necessary to a highly essential activity, and he will be deferred only until he can be satisfactorily replaced in that occupation. A delay in call to active duty, it was emphasized, may not be considered as an indefinite exemption from military service.

Jan 9, 1950

By Joshua E. Clayton

This remarkable gold and silver bearing district is situated on the middle fork of Boise River, in Alturas County, Idaho Territory, about eighteen miles north of Rocky Bar, and sixty-five to seventy miles, as the crow flies, east of Boise City, the capital of the Territory. This district lies in the very heart of one of the most wild and mountainous regions of Idaho. For many miles in every direction nothing can be seen but bold granite mountains, with deep narrow gorges cutting into their sides in every direction, rendering them almost inaccessible except to .the hardy mountaineer and adventurous prospector. The mountain sides are covered, in most part, by dense forests of pine, fir, and spruce timber. In every canon there are clear streams of pure running water that empty into the principal forks of Boise River. The only line of approach to this mountainous region at present is from the southwest, by way of Rocky Bar, the county seat of Alturas County, to which place there is a good wagon-road. From thence to Atlanta City, eighteen miles, the road, or pack-trail, passes over the high, steep range that separates the south and middle forks of Boise River. During severe winters this line of approach is closed up by deep snows for months at a time, thus leaving the district isolated, in the bosom of the grand old mountains. The geological formation is granite, of a coarse, friable texture, and in many places is traversed by numerous dikes of syenite, and three or four varieties of porphyry, which cut through the granite in easterly and westerly directions. The metal-bearing reins also have an easterly and westerly trend, bat are occasionally intersected by the dikes. The largest number of the gold and silver lodes are confined to a

By George S. Ramsay

The Appalachian system contains the largest area of all known Carboniferous coal-fields. Beginning near the north line dividing Pennsylvania and New York, it extends southwest through West Virginia, southeastern Ohio, Kentucky and Tennessee and terminates in Alabama—a distance of about 950 miles. The northeastern part of this field will be considered in this paper. The general dips of the measures are toward a trough about parallel to the Ohio river, from the Allegheny mountains and ridges on the west. The Potonlac field is an exception; the dip in this case being northeast, the folding to the east of the Allegheny mountains in Pennsylvania being of a greater degree and diminishing southwestward. The cause of the general dip to the west of the mountains seems to be the westward movement of the thrust east of the mountains, with the large Nittany fold including other folds to the east of the escarpment, raising the mountains high above the coal-fields to the west, making a general slope toward the Ohio river southwest, and crossing waves of anticlinals west ward. The synclinals contain the coals, while in many cases on the top of the folds or anticlinals some of the veins (or, in some cases, all) are eroded. The Coal-Measures of this field are generally divided into three principal divisions, known as the Upper, the Barren, and the Lower Coal-Measures, but there is a tendency to divide them into five groups, which is more convenient. Beginning at the bottom, the first would be the Conglomerate ; second, the Lower Coal-Measures; third, the Barren; fourth, the Upper Coal-Measures, and fifth, the Upper Barren or Permian Measures.

Jan 1, 1896

By L. S. Reid, R. L. Huntington, Chen Chun Ku

The simultaneous adsorption of water and hydrocarbon vapor from natural gas by three grades of alumina has been studied at atmospheric pressure and temperature. Results of this investigation reveal that the presence of water vapor in the gas inhibits the adsorption of hydrocarbon vapor, although the presence of the latter does not have a pronounced effect upon the adsorption of water vapor. Adsorption of water-hydrocarbon mixtures from gas is divided into three phases. In the first, both water and hydrocarbon vapor are adsorbed; in the second, adsorption of water vapor proceeds while desorption of hydrocarbon takes place; in the third phase, the adsorbyt approaches complete saturation with respect to both water and hydrocarbon vapors. Both theory and experimental data can be applied to design and operation of commercial dehydration plants, and an illustration is presented. Introduction Dehydration of natural gas becomes increasingly important as the operating pressures employed in gas processing and transmission are increased above 500 ib. per sq. in. Gas produced from high-pressure wells is saturated with water vapor when it leaves the reservoir and it continues into the processing plant or transmission system in a saturated condition because of the substantial decrease in temperature due to expansion at the wellhead. Usually this gas is accompanied by liquid water and hydrocarbons that have condensed with the change in temperature and pressure. Without dehydration, gas temperatures must be held at relatively high levels to prevent solidification of gas hydrates. According to Hammerschmidt's data8 on the relationship of pressure to the freezing point of natural-gas hydrates, the minimum safe operating temperatures range from 55' to go°F. for pressures ranging from 500 to 3000 lb. per sq. in., respectively. Often it is difficult to maintain gas temperatures above the hydrate-freezing temperature because of climatic conditions, unless flow-line heaters are installed. Also, in processing gas for its gasoline content at high pressures, it is desirable to employ operating temperatures lower than the hydrate-freezing point. In distributing high-pressure gas, the large pressure drop from line pressure to town-gate pressure often prbduces sufficient cooling to freeze the regulators and disrupt consumer service. Therefore, it is highly essential to dehydrate high-pressure natural gas if smooth and economical operation is to be maintained at all times. Few published data are available on the simultaneous adsorption of water and hydrocarbon vapors. The literature contains many mathematical expressions for rate of adsorption in various systems but a rational correlation of the existing rate

Jan 1, 1944

By R. L. Huntington, L. S. Reid, Chen Chun Ku

The simultaneous adsorption of water and hydrocarbon vapor from natural gas by three grades of alumina has been studied at atmospheric pressure and temperature. Results of this investigation reveal that the presence of water vapor in the gas inhibits the adsorption of hydrocarbon vapor, although the presence of the latter does not have a pronounced effect upon the adsorption of water vapor. Adsorption of water-hydrocarbon mixtures from gas is divided into three phases. In the first, both water and hydrocarbon vapor are adsorbed; in the second, adsorption of water vapor proceeds while desorption of hydrocarbon takes place; in the third phase, the adsorbyt approaches complete saturation with respect to both water and hydrocarbon vapors. Both theory and experimental data can be applied to design and operation of commercial dehydration plants, and an illustration is presented. Introduction Dehydration of natural gas becomes increasingly important as the operating pressures employed in gas processing and transmission are increased above 500 ib. per sq. in. Gas produced from high-pressure wells is saturated with water vapor when it leaves the reservoir and it continues into the processing plant or transmission system in a saturated condition because of the substantial decrease in temperature due to expansion at the wellhead. Usually this gas is accompanied by liquid water and hydrocarbons that have condensed with the change in temperature and pressure. Without dehydration, gas temperatures must be held at relatively high levels to prevent solidification of gas hydrates. According to Hammerschmidt's data8 on the relationship of pressure to the freezing point of natural-gas hydrates, the minimum safe operating temperatures range from 55' to go°F. for pressures ranging from 500 to 3000 lb. per sq. in., respectively. Often it is difficult to maintain gas temperatures above the hydrate-freezing temperature because of climatic conditions, unless flow-line heaters are installed. Also, in processing gas for its gasoline content at high pressures, it is desirable to employ operating temperatures lower than the hydrate-freezing point. In distributing high-pressure gas, the large pressure drop from line pressure to town-gate pressure often prbduces sufficient cooling to freeze the regulators and disrupt consumer service. Therefore, it is highly essential to dehydrate high-pressure natural gas if smooth and economical operation is to be maintained at all times. Few published data are available on the simultaneous adsorption of water and hydrocarbon vapors. The literature contains many mathematical expressions for rate of adsorption in various systems but a rational correlation of the existing rate

Jan 1, 1944

By R. S. Hendricks

During the past two years, Hecla Mining Co. has used shotcrete for ground support purposes with substantial cost savings. Hecla's experience indicates that shotcrete is an extremely effective ground support material which can be successfully employed in problem areas where various conventional systems would fail. To date, Hecla's use of shotcrete has been limited to openings where long-term high-quality support was required, to specific areas where exceptionally difficult ground conditions were encountered [ ] and, occasionally, to stope support. It is anticipated that when the necessary engineering and procurement of the components of an efficient materials handling system have been accomplished, shotcrete will be used on a routine basis in stoping and development situations. The real future of shotcrete is based, however, on the fact that this form of support offers greater opportunity for mechanization than rock bolt, timber or steel. Unlike all other support operations, which are cyclic, shotcrete is a continuous process, and therein lies its potential for incorporation into an efficient rapid excavation system. Hecla has obtained and operated both wet- and dry-process shotcrete application equipment. The operational characteristics of the two processes are presented and discussed below.

Jan 1, 1970

Jan 1, 1948

Jan 1, 1939