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By Duk-Won Park, Syd S. Peng

INTRODUCTION More than five years have elapsed since the first shortwall panel was installed in a US mine in 1972. By the latest count, 11 mines have tried the shortwall method on 34 panels. Potentially, the shortwall method (see Figure 1) offers the combined advantages of longwall and continuous mlning. But just like any other mining method, shortwall is not a panacea. It is only applicable under a set of stringent conditions. Coal operators at eight of the eleven mines are satisfied with shortwall mining, though there are only five mines presently producing coal from shortwall panels.

Jan 1, 1981

By G. S. Rice, Clark H. H.

When mines in the interior coal fields of the United States began the practice of blasting the coal without undercutting, or what is known as…

Jan 1, 1915

By George Rice

WHEN miners in the interior coal fields of the United States began the practice of blasting the coal without undercutting, or what is known as "shooting off the solid," many explosions resulted, some of them of great extent and 'violence, and attended with large loss of life. One of the means adopted for preventing this large loss of life, though not preventive of explosions, was to employ shot firers to discharge the shots when all the other employees had gone out of the mine at the end of the day's shift. This system still prevails in most of the Central and Southwestern mines. Following the disaster at Winter Quarters mine, Utah, May 1, 1900, in which 200 lives were lost, a system of firing shots electrically from outside and when the men were out of the mine was adopted at the mines of the Utah Fuel Co.1 This system has also been used in France in certain mines that are subject to instantaneous outbursts of carbonic acid gas. These outbursts generally occurred at shot-firing time, on account of the blasts releasing the gas held in crevices under high pressure. The system was also adopted at a number of other mines in Utah, at the Cokedale mine, Colorado, at the Dawson mines, New Mexico, and in some mines of the Tennessee Coal, Iron & Railroad Co. in the Birmingham Ala. district; and more recently in certain mines in Iowa and Kansas. At first there was considerable trouble from misfires, and in a few instances from premature firing, while men were in the mine, through the shot-firing lines becoming crossed with power lines. Fortunately, however, no loss of life resulted from such premature firing within the knowledge of the writers, and latterly this danger has been reduced to a minimum by certain measures of precaution. The proportion of misfires, or failures of individual shots to fire, has also been reduced to a very small

Jan 10, 1914

Discussion of the paper of GEORGE S. RICE and H. H. CLARK, presented at the Pittsburgh meeting, October, 1914, and printed in Bulletin No. 94, October, 1914, pp. 2563 to 2571. NORMAN V. BRETH,* Pittsburgh, Pa.-It was my privilege to visit in the last two months on behalf of the U. S. Bureau of Mines 10 mines where electric shot-firing systems controlled from outside the mine are installed. I will describe briefly what I saw in some of these mines, which are located in Utah, New. Mexico, Oklahoma, Alabama, and Kansas. At a mine in Utah, 230-volt alternating current is used to fire the shots, which is taken from a small transformer in the substation. The shot-iring circuit is independent of all other wires and is tested for grounds every day. There are no lightning arresters on the firing circuit. Porcelain insulators are used inside of the mine, and glass outside. The switches are situated as follows: One in the substation, one in, the shot-firer's cabin, two at each cross entry; where the shot-firing circuit crosses the trolley wire a switch is placed on either side of the entry in series with the shot-firing circuit. The miners are checked in and out of the mine. The coal is undercut and is shot down with permissible explosive, the shots being connected in multiple. There are 75 to 110 shots fired each day. A great many times there are no missed shots. If not more than two or three are missed they are left until next day. The fan is kept running at full speed when the shots are fired. The shot-firing switch is closed only once and the whole mine is shot at once. At another mine in Utah, power wires are used for shot-firing circuits; 500-volt, direct current is used to fire the shots. The only sizes of wire used outside of the power wires are Nos. 8 and 14 B. & S. gauge. The return is connected to the pipe lines and track. Porcelain insulators are. used inside of the mine.

Jan 4, 1915

By N. S. Greensfelder

THE firing of explosive charges by electricity dates back to 1745 when a Doctor Watson is said to have used an electric spark for igniting gunpowder. His method failed in practical application because, to ignite blasting powder, heat must be applied for a period longer than the duration of an electrostatic spark; Wheatstone found that this does not exceed 14000 sec. The usual result, therefore, of an electrical discharge in gunpowder is to scatter the grains, without igniting them. Benjamin Franklin partly overcame this difficulty by confining the powder and crushing grains that lay in the line of discharge. In 1822, after the primary cell had been discovered by Volta, Robert Hare, professor of chemistry at the University of Philadelphia, noticed the heating of a short piece of wire placed in the circuit of a voltaic battery. Later work by Oersted, Faraday, Wheatstone, and Henley resulted in the development of the magneto blasting machines. Fulminates of gold and silver are thought to have been discovered by Cornelius Drebbel, about 1600. Pepys, in his diary for November 11, 1663, recounts a conversation with Doctor Allen, who told him about aurium fulminans "of which a grain ... . put in a silver spoon and fired, will give a blow like a musquett and strike a hole through the silver spoon downward, without the least force upward.1," This fallacious belief that explosives act downwards only, is still held by many who should know better. Fulminate of mercury was discovered by Howard in 1799. J. Shaw of Philadelphia is said to have invented a fulminate-of-mercury cap in 1814; his idea was later adopted by gunmakers in England and France. The principal advantages of

Jan 9, 1922

By M. D. Cooper

FOr the purpose of obtaining some first-hand data in regard to the shooting clown of coal in bituminous 'nines, it was the writer's good fortune to be employed as a shot-firer for almost one year. In all, 6,020 shots were fired by him during this period. All of the work was clone in what is known as the South Main section of the No. 2 Mine of the Ellsworth Collieries Co., Ellsworth, Pa., a subsidiary of the Lackawanna Steel Co. Position of Shot-firing in the Cycle of Operations The established practice of the Ellsworth Collieries Co. calls first for the undercutting of the coal by electric chain machines across the face of the entry or room. This is followed by replacing any posts removed by the machine-runners, or the setting of new posts or timber, as may be required. After this has been done the machine cuttings are loaded into cars. Then the coal is spragged, and a shot hole drilled to the depth of the undercut. Next in order, the shot-firer loads the hole and fires the charge. The working place is then cleaned up, timbered if necessary, the sides and face squared up, and loose material taken down. The face is again ready to be undercut.

Jan 1, 1917

By M. D. Cooper

LUCIEN EATON, Ishpeming, Mich.-It is not the custom in the Lake Superior region, as far as I know, to employ shot-firers. Each man, or pair of men (most of the contracts are given to two men) do their own firing; each contractor keeps his powder separately. The general custom is to distribute powder (dynamite only is used) to the mines 2 days a week. The boxes, marked with the contract number and the level, are taken underground and the men take them to their working places. They are kept in boxes, which must not be nearer together than 50 ft. and are usually away from the timber roads or traveling roads. When holes have been drilled, one man usually takes down the machine, and the other man makes up the charge. He cuts the fuse, puts in the caps, etc., at a distance from the powder box. He then carries the powder charges to the working place where both men charge the hole. They do their own firing and warn others coming from any direction that the holes are being fired.

Jan 4, 1917

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

By Jeremias K. Chitunda

Significant cost savings and improved ground stability are two initial indications from the current wet process shotcrete ground support program at the Lakeshore mine. The area of shotcrete for ground stability is not strange to the Lakeshore operation. Since the beginning of the project, various shotcrete techniques have constantly been experimented with, incorporating all the latest technological developments. Over the years, the use of shotcrete has been employed as a primary, temporary, or permanent support, singly or in combination with rockbolts and steel sets. The extent of shotcrete usage compared with steel sets and rockbolts has varied from time to time as dictated by the overall state of the art. In 1972, for example, the ratio of the linear drift footage supported with shotcrete to that supported with steel sets averaged 1.0. In 1973, that ratio was about 3.0. Overall, for the Lakeshore mine, there are about 8000 drift ft of shotcrete, 8000 drift ft of steel sets and timber, 750 drift ft of formed concrete, 21,000 drift ft of rockbolts, and 3700 drift ft of combined type support.

Jan 12, 1974

By AIME AIME

THE second session on geophysical prospecting at the February meeting of the Institute was a discussion of the mining law and the bearing of the new method of search on location of claims and assessment work thereon. Allen H. Rogers was chairman of the meeting, which he opened by reviewing the present law and the proposed changes. W. R. Ingalls commented (by letter) on the Arentz bill, as introduced into the House of Representatives in 1921 and the need for revision of the present mining law. L. W. Douglas explained (by letter) the bill that he introduced and which has been passed by the House. SAMUEL S. ARENTZ, Nevada: It is my opinion that if the American Institute of Mining and Metallurgical Engineers is to sell this proposition to the people in the West, they have to sell it to the lawyers, because, after all, they are heard loudly when it comes to speaking in Congress. One man tells the other, "This thing is a vicious piece of legislation"; it might not be, but they will pass it on if it affects them. If the Institute would impress on the people affected that we need a re-codification of the mining law and that such is necessary along certain lines; that things have changed during the past decade or two, so today instead of doing our prospecting alone through the sinking of a shaft, through a discovery that may be seen, we are now moving on to more modern means of discovery through geophysics, through the churn-drill, through geology, through geological inference, I think we could get somewhere.

Jan 1, 1929

By Charles Shamel

I FEAR most of the Institute members are already weary of the perennial controversy about the apex law. I feel that way about it myself now, though I have been guilty of considerable contribution to the discussion in the past. The discussion does not seem to perceptibly influence previously held views and I would not again break into print on the subject but for the urgent invitation of the Chairman of our, Law Committee. This energetic and able member has firmly determined to secure a revision of the mining law and among other things to eliminate the so-called apex provision from the U. S. mining statutes. He is, however, fair about it and has invited me to make "the strongest possible argument in its favor." I am suspicious that he is acting on the psychological principle that it is usually easier to convince an audience against a cause vigorously but unsuccessfully defended than against one wholly mute. Nevertheless, I realize that personally he wishes me no harm, much as he hates the apex law, and so am willing that the Institute have whatever benefit may accrue from my taking up again the unpopular side of the discussion. I say this because the attitude of a large part of our "articulate" membership seems irreconcilably hostile; their minds are made up; favorable consideration is foreclosed; and they become impatient and even sarcastic at any attempt to elucidate a favorable view of the apex law. The exact question for discussion at the present time is not whether on abstract, or any other considerations, the apex law is the best possible rule, but the very different proposition whether, after nearly 50 years of statutory life and much longer as a practically universal miners' custom, it is now just and expedient to repeal the apex law.

Jan 4, 1914

AT the meeting of the Board of Directors on Jan. 28, 1927, the tentative budget of this Institute for next year was discussed, and in connection with the evident necessity for a larger income to meet increasing demands for service, the advisability of in- creasing the dues of members, was brought up. W. Spen- cer Hutchinson advocated an upward revision of the dues "believing it necessary that the Institute have a larger income, in order that it may carry on necessary work and render adequate service to its membership." Since this is a matter that directly affects every member, .President Taylor was directed to appoint a committee, which he did, consisting of George D. Barron, W. H. Bassett, and R. H. Sweetser, with T. T. Read as secre- tary, to bring in a tentative outline of the main factors in the problem for discussion at the annual meeting, on Feb. 15, and to prepare, after they have had the benefit of the discussion at that meeting, a report for the board. The amount of the annual dues is fixed by the con- stitution and can only be changed by proposing an amendment to the constitution. This amendment would have to be submitted to the members by letter ballot at the time of the election of officers for 1928, so that no change can be made in the dues for 1927 in any case. WHY THE INSTITUTE NEEDS MONEY At the annual meeting past-president Reynders, as chairman of the executive committee made the follow-ing report, which since it admirably sets forth the rea-sons why an increase in the dues has been suggested, is included here. "The report of the president has covered the situation so fully that little is left for me to say. However, a word in regard to the functions of the executive com-mittee may not be out of place.

Jan 3, 1927

By H. C. Goodrich

AT THE Utah Copper mine, steam shovels were first used, in 1906, for the removal of overburden, and in June, 1907 for the mining of ore. Prior to 1907, the ore came from underground development work and from stoping. The use of the steam shovel gradually increased until 1914; since then all material, both overburden and ore, has been loaded by power shovels operating on the various benches of the mine. During FIG. 1.-SCENE OF UTAH COPPER MINE BEFORE OPEN-PIT MINING WAS BEGUN. these 19 years, there has been a great improvement in open-pit mining; largely in the use of equipment having greater capacity and dependableness. The history of the development of mechanical shovels and related equipment, as affecting the Utah Copper Co., would be interesting and would justify considerable space; but of greater interest at this time is the operation of the equipment now in use. The Utah Copper mine is in a great deposit of copper-bearing monzonite, which occurs as a prominent headland of the Oquirrh range of

Jan 9, 1925

Jan 1, 1886

Jan 1, 1885

Jan 1, 1884

Jan 1, 1887

A shrinkage stope is an overhand stope in which the broken ore accumulates until the stope is completed to, or near, the level above. As broken ore generally occupies at least 60 per cent. more space than ore in place, about a third of this must be drawn out as the stope advances to leave a working space under the back. The ore remaining supports the miners and gives temporary support to walls, and is all withdrawn when the stope is finished. The shrinkage-stope method is applicable to steep-dipping deposits of strong ore with strong walls. It may be applied to narrow or wide veins, and is simple and cheap. Five examples, which include important and varied types of deposits, are given: namely, Kennecott, Homestake, Jarbidge district, Mogollon district, and Cripple Creek district.

Jan 1, 1925

By Stephen Birch

The Chitina mining district of Alaska is located at the headwaters of the Chitina and Copper Rivers. At present, the only producing mining properties are the mines of the Kennecott Copper Corpn. and the Mother Lode Coalition Co., which are situated 196 miles from Cordova, the port of entry. The first claims, later acquired by the Kennecott Mines Co. and afterwards transferred to the Kennecott Copper Corpn., were discovered in 1900. The Copper River & Northwestern Ry., which connects the mines with tide water at Cordova, was completed in the spring of 1911. Contemporary with the construction of the railroad, aerial tram equipment was brought to the mines by pack train and a tramway, 3 miles long, connecting Bonanza mine with the proposed railroad terminal, was finished, enabling shipments of high-grade ore to be made immediately the railroad was completed. A mill to treat the lower grade ore was begun the same year. The Kennecott company's holdings consist of 111 mineral claims. The Mother Lode Coalition Mines Co., which is controlled by the Kennecott Copper Corpn., owns 73 claims adjoining the Kennecott holdings. All data on operations and geology refer equally well to the Mother Lode property. Geology The general geology of the district has been covered by the U. S. Geological Survey1 and the geological features of the mines have been carefully studied by A. M. Bateman, in his capacity as consulting geologist to the company.2

Jan 1, 1925

By S. J. Kidder

The Mogollon mining district is in the southwestern part of New Mexico near the southern end of the Mogollon range, from which the district takes its name. The town of Mogollon is but 371/2 miles in an air line northeast of Clifton, Ariz. The air-line distance from Silver City is 521/2 miles and from Tyrone, 57 miles. Supplies are transported by motor truck from Silver City. The distance by road is 75 miles, half of which is an improved highway of modern construction. Transportation has always been a large item of expense in carrying on operations in the district. Valuable ore is said to have been discovered in the Mogollon Mountains as early as 1870 but the first regular prospecting was carried on in 1875, by James C. Cooney, a sergeant from Fort Bayard. His discovery of rich silver-copper ores in the region of Mineral Creek led to the establishment of the Camp of Cooney. Remote from any settlements where there was a semblance of law and order, and harassed by the Apaches, development was slow and nearly 10 years elapsed before the village of Mogollon was established on Silver Creek. Prospecting in this section of the district had disclosed the outcrops of several promising veins containing silver-gold ores. Among the early claims located were the Last Chance, Top and Confidence, on what has proved to be the most productive vcin in the district. To the end of 1922, the Last Chance and Top claims had produced approximately 600,000 tons of ore and nearly 200,000 tons had come from the Confidence group of claims. The total value of the ore produced from this vein alone has amounted to about $9,600,000 in silver and gold. The Fanney vein was developed later and during its most active period of production contributed more than half of the output of the district. Other important locations, though far less productive than the above, were the Maude S, Deep Down, the Deadwood and the Pacific.

Jan 1, 1925