Mine (explosive)

“ This matter is also being investigated by the Survey mining engineers and others, by the actual use of such explosives in coal-mining operations.
Of the gases given off by explosives, those resulting from black powder are accompanied by considerable odor and smoke, and, consequently, the miners go back more slowly after the shots, allowing time for the gases to be dissipated by the ventilation. With the permissible explosive, the miner, seeing no smoke and observing little odor, is apt to be incautious, and to think that he may run back immediately. ”

“ Even at this distance from the explosive den, the blast is often so powerful, that it frequently tears the brattice walls of the shaft to pieces, and blows the corves suspended in the shaft as high up into the open air as the ropes will permit. Not unfrequently, indeed, the ponderous pulley-wheels are blown from the pit-head frame, and carried to a considerable distance in the bosom of a thick cloud of coals and coal-dust brought up from the mine by the fire-damp, whose explosion shakes absolutely the superincumbent solid earth itself with a mimic earthquake. ”

“ Inasmuch as no explosive manufactured for use in mining is flameless, and as no such explosive is entirely safe under all the variable mining conditions, the use of the terms ‘flameless’ and ‘safety’ as applied to explosives is likely to be misunderstood, may endanger human life, and should be discouraged. ”

“ The miner never touches either the explosive or the detonater. Then the shot-firer puts the primed charge in the hole, jams the hole full of clay with a wooden tamper—a steel bar might cause a spark and a premature explosion—tests for gas again, connects the electric wires from a portable battery around the rib corner, fires the shot, returns to the face and tests for gas again. Then, and not until then, does the miner begin to dig the coal. ”

“ A round of holes fired in this way, as for driving tunnels, sinking shafts, or in large surface excavations, produces better results, both in economy of explosive and effect of the blast, than when the holes are fired singly or in succession. Also, the miners are enabled to prepare for the blast with more care and deliberation, and then to reach a place of safety before the current is transmitted. Another advantage is that there is no danger of a hole “hanging fire,” which sometimes causes accidents in using ordinary fuzes. ”

“ Shafts are sunk, or tunnels driven, in the mass of rock to be blasted, and, connected with them, a number of chambers are excavated to receive the charges of explosive. The preparation for such blasts may occupy months, and many tons of gunpowder or dynamite are at times exploded simultaneously, breaking or dislodging thousands, or even hundreds of thousands, of tons of rock. This method is adopted for getting stone cheaply, as for building macadamized roads, dams and breakwaters, obtaining limestone for blast furnace flux, and occasionally in excavating large railway cuttings. ”

“ As it would have been impossible for the small fire in the winze to have generated such immense quantities of inflammable gases as must have been consumed in the two explosions that occurred during this last fire in the Yellow-Jacket mine, many men are of the opinion that a small quantity of the gas from pine-wood mingled with gases already in the mines, rendered the whole explosive. ”

“ The coal mine is the scene of a multitude of the most terrifying calamities, and these come directly from the selfishness of the bourgeoisie. The hydrocarbon gas which develops so freely in these mines, forms, when combined with atmospheric air, an explosive which takes fire upon coming into contact with a flame, and kills every one within its reach. Such explosions take place, in one mine or another, nearly every day; on September 28th, 1844, one killed 96 men in Haswell Colliery, Durham. ”

“ Blasting powder or explosives must not be taken into or out of a mine, or moved from place to place in a mine along any entry or haulway where there are electric wires, while the power is on such wires, except when such powder or explosive is conveyed in insulated cars or packages.
[Explosives and tools on cages or stairways.] Powder, explosives and working tools shall not be taken down or up a hoisting shaft in a cage when men are going down or up; nor shall they be taken down or up a stairway used for ingress and egress of persons. ”

“ In all cases, ample power should be possessed by the firing machine or battery.
The shattering class of explosives are very suitable for subaqueous-rock blasting. In many cases, their employment renders the boring of shot-holes unnecessary, an advantage of obviously great importance. When detached or projecting masses of rock have to be broken up, it is sufficient to place the charges upon them. Of course, when so applied, larger quantities of the explosive are required; but though the method is wasteful of explosive, it is very [170] economical of labour and time. ”

“ In connection with this may be mentioned the fact that under certain conditions coal dust may become violently explosive. When it is mixed with air, with or without the presence of fire damp, and is set into sudden and intense vibration by a heavy powder blast, a fall of roof, or other means, it may explode with greater destructive force than even fire damp is capable of. Happily such explosions are not frequent, all the conditions necessary being rarely present at the same time. It is obvious, moreover, that an accident of this kind could occur only in a very dry mine. ”

“ The buoyant are usually spherical, and contain from 400 to 500 pounds of explosive. They bring the charge near to the ship's bottom, but are difficult to manage in a tideway, and can be easily found by dragging. The ground mines can be made of any size and are not easily found by dragging, but are of little value in very deep water. They are either cylindrical or hemispherical in shape, and contain from 500 to 1,500 pounds of explosive in from thirty to eighty feet of water. ”

“ A barrier of high explosive across the North Sea—10,000 tons of TNT, 150 shiploads of it, spread over an area 230 miles long by 25 miles wide and reaching from near the surface to 240 feet below—70,000 anchored mines each containing 300 pounds of explosive, sensitive to a touch, barring the passage of German submarines between the Orkneys and Norway—this was the final five months’ contribution of the American and British mining forces towards bringing the war to a close. ”

“ In fiery mines, however, a very much larger amount must be provided in order to dilute the gas to the point of safety. Distribution of air underground. Even with the best arrangements a dangerous increase in the amount of gas is not infrequent from the sudden release of stored-up masses in the coal, which, overpowering the ventilation, produce magazines of explosive material ready for ignition when brought in contact with the flame of a lamp or the blast of a shot. ”

“ As the proportional part of the energy expended in each of the effects above named cannot be determined in any particular case, and as each case differs in some respect from every other, it is manifestly impossible to express in any mathematical formula a rule for determining the exact amount of explosive required for any particular mine. ”

“ Fire-damp is explosive when combined with certain proportions of air. Apart from ventilation, which dilutes the gas below the danger limit, the principal precaution against explosives is the use of safety-lamps, so constructed that the gas cannot come in contact with a naked flame. An excessive amount of coal-dust in the air of the mine may also give rise to explosions. Such explosions may be prevented by wetting the dust, moistening the air, or powdering the walls, roof and floor with a non-explosive “rock-dust.” ”

“ Sometimes listening galleries are driven underground and men posted to detect the sound of mining operations. Once the direction of the opposing tunnel is discovered a charge of explosive is laid across its approach and fired at a moment when it will cause the most damage. ”

“ Whilst all the explosives mentioned in this article are more or less suited to blasting in mines, so far as their propulsive force is concerned, yet the use of each and all is attended with great danger in a coal-mine, and for the following reason: coal, being of vegetable or organic origin, is constantly giving off numerous gases, the most dangerous of which, under ordinary circumstances, is methylic hydride or marsh-gas, known in mining districts as fire-damp. It is of an inflammable nature; and when it becomes mixed with from seven to ten times its volume of air, it is highly explosive. ”

“ As the pressure increases, the hot gases are forced more and more deeply into the grains, and combustion, consequently, proceeds more and more rapidly.
Detonation. —By detonation is meant the simultaneous breaking up of all the molecules of which the explosive substance is composed. Properly the term is applicable to the chemical compounds only. But it is applied to gunpowder to denote the simultaneous ignition of all the grains. The mode of firing by detonation is obviously very favourable to the rending effect required of blasting powder, since it reduces to a minimum the time of explosion. ”

“ Neither blasting gelatine, dynamite nor gun-cotton fulfills all these conditions; but they satisfy many of them and are more powerful than other substances. For the destruction of walls, trees, rails, bridges, etc., it is simply necessary to attach to them small bags of explosive, which are ignited by means of blasters' fuse and a cap of fulminate of mercury, or by an electric fuse.
We now come to the application of high explosives to warfare in the shape of bursting charges for shells. ”

“ The Government and the United Nations military observer group provided the necessary support to the operation. Upon its completion, on 18 April 1997, 378 mines and explosive devices had been lifted and destroyed.
24. While both parties have stated that the country is now free of minefields, the presence of unexploded ordnance (grenades, bombs, mortar rounds, etc.) left around the country in the wake of 36 years of internal conflict still poses a risk to the population in some areas.
E. Demobilization 25. ”

“ The silence which succeeds to this awful turmoil is no less formidable; for the atmospheric back-draught, rushing down the shaft, denotes the consumption of vital air in the mine, and the production of the deleterious choke-damp and azote.
Though many of the miners may have escaped by their distance in the workings from the destructive blast and the fire, yet their fate may perhaps be more deplorable. They hear the explosion, and are well aware of its certain consequences. Every one anxious to secure his personal safety, strains every faculty to reach the pit-bottom. ”

“ Fires and explosions attract a greater amount of public attention than other mining disasters on account of the large number of victims so often involved in a single occurrence of this kind. In the explosion at the Courrières colliery, in France, March 10, 1906, more than 1,100 miners perished. This mine had previously been renowned for its freedom from accidents. Coal mine explosions are due to two principal causes, which may act either separately or in combination—fire-damp and coal-dust. ”

“ When the crater radius is equal to the line of least resistance, the mine is termed common; when this radius is greater than the line of least resistance, the mine is termed overcharged; and when the radius is less, undercharged. A mine of small dimensions, formed by sinking a shaft in the ground, is termed a fougasse. The term camouflet is applied to a mine used to suffocate the enemy's miner, without producing an explosion. Small mines made in rock or masonry, merely for the purpose of excavation, without any considerable external explosion, are called blasts. ”

“ Countless, also, are the dangers to which they are exposed. To accidents as they come down or go up the shafts by the breaking of ropes, or the giving way of machinery, from the falling in of the roof or walls, as also from accidents in blasting, from spontaneous combustion, from explosion of fire-damp, suffocation from choke-damp, and eruptions of water, and even quicksands. Sometimes floods or heavy rains find their way down unknown crevices into the pit, where the miner is working, and forming a rapid torrent, suddenly inundates the mine and sweeps all before it. ”

“ Before starting work a miner often tests for gas by poking his lamp into all the corners. The gas may be touched off by a spark during blasting operations, or by a pick striking a spark from a stone, or by a defective lamp, or by ‘gob fires’ – spontaneously generated fires which smoulder in the coal dust and are very hard to put out. The great mining disasters which happen from time to time, in which several hundred men are killed, are usually caused by explosions; hence one tends to think of explosions as the chief danger of mining. ”

“ There are extensive coal mines about eight miles from us. Some of them are very deep under-ground, but others are not, but the coal is brought up a slope in wagons on wheels. I was up last winter, and saw the men and boys that work in the mines. They were terribly black with coal dust. Each of them carries a safety-lamp, which gives but a feeble light in such dark places. I was up two winters ago, and saw one of the places for myself. At one of the largest mines, about two years ago, there was an explosion, which killed forty men, and ruined the mine. ”