Shaft (underground)

“ Vertical shafts may be either rectangular or cylindrical; when inclined they are always rectangular. The primary purpose of mine shafts is to act as hoisting and travelling-ways; incidentally they serve for ventilation, for pumping and for transmitting power underground by steam, compressed air or other means. Rectangular shafts are usually divided longitudinally into compartments. One or more of these are for the cages or skips, which run in guides bolted to the shaft limbering (see MINING) . ”

“ It is advantageous if a shaft connects with a tunnel, for then the miners and other workmen carry on more easily the work they have undertaken; but if the shaft is not so deep, it is usual to drift from one or both sides of it. ”

“ A shaft can be widened afterwards when it has been found worth while, but it is always well to refrain from shovelling out two or three tons of granite-like substance, as is done by most "new chums," merely for the sake of having more elbow-room during the trying process of sinking. ”

“ In sinking a shaft, danger is to be apprehended both from the falling in of loose and incoherent strata, and from the lateral springs, which sometimes empty themselves into the workings to an extent which it would at first appear hopeless to contend against. In such cases there is no safety to be obtained without walling the shaft with brick or stone, or securing it by timber or metal tubbing. ”

“ The excavation of the man-holes alone must have been a gigantic task, equal to, if not greater than, that of cutting out the horizontal tunnels. The cross-section of an average-sized shaft is, if anything, greater than that of the tunnel; and although in vertical dimension the man-holes near the mouth of the aqueduct are insignificant, the depth rapidly increases in the opposite direction, owing to the upward slope of the ground-surface towards the escarpment. ”

“ If one or more shafts reach the tunnel through intermediate drifts and shafts, the surveyor, starting from the nearest which is open to the air, measures in a shorter time the depth of the shaft which requires to be sunk, than if he starts from the mouth of the tunnel. ”

“ The water of the veins and stringers and especially of vacant workings, must be drained out through the shafts and tunnels. Air, indeed, becomes stagnant both in tunnels and in shafts; in a deep shaft, if it be by itself, this occurs if it is neither reached by a tunnel nor connected by a drift with another shaft; this occurs in a tunnel if it has been driven too far into a mountain and no shaft has yet been sunk deep enough to meet it ”

“ When the tunnel works are finally finished, the lining of the shaft should be carried up until it is 15 or 20 feet above the level of the surface of the ground, and a dome-shaped iron grating placed on the top as a protection against stones or other articles which malicious persons might attempt to throw down the shaft. ”

“ The shaft-alley is a strange place, hooded over with steel barely head high. Nothing lives there but the shaft, turning ceaselessly by itself, and the thrust-blocks working away. Mark had been in plenty of shaft-alleys on Resthaven freighters, but then the ships were anchored, the propellers still. ”

“ Considering the great labour necessary for securing the ground for the underlaying, the waste of planking, and of shores, and the time necessarily taken up in moving about, in securing and in baling out the water, and the many causes of interruption, and the imperfect way that things are done in underlaying, it is quite conclusive that the original plan of making a shaft, by sinking the structure, is the safest and the most economical. What is done is sound, and when once in place, may be secured with foundations in a very easy manner. The brickwork of the shaft is remarkably hard. ”

“ Shape of Shafts.-In Europe shafts are generally cylindrical, sometimes of elliptical cross-section, and are lined with masonry, concrete, cast iron or steel; in the United States and elsewhere throughout the mining regions of the world, rectangular cross sections are the rule for sinking in rock, the shaft walls being supported by limbering, occasionally by steel lining. For sinking in loose, water-bearing soils, the cross-section is almost invariably cylindrical, as this form best resists pressure tending to cause crushing or caving of the shaft walls. ”

“ The lagging on the sides of the shaft confine the vein, so as to prevent fragments of it which have become loosened by water from dropping into the shaft and terrifying, or injuring, or knocking off the miners and other workmen who are going up or down the ladders from one part of the mine to another. ”

“ When the required depth is attained a tunnel is pierced, mostly with the hands and a small shovel, in a horizontal direction, and seldom less than four feet high, two feet wide, just big enough to let the workman through. Then another shaft has to be made for ventilation's sake and to raise to the surface the displaced earth. Miles of these kanats are thus bored, with air shafts every ten to twenty feet distant. ”

“ On the arrival of Donald, Schwatka, and the ladies at the Company’s office, they were conducted to the brink of the shaft sunk by a countryman of Kate’s, which was the first successful attempt made in that direction.
Entering an elevator about six feet square, which was waiting to receive them, they slowly descended to the depth of two hundred feet. The earth had been probed to three times that depth, but the shaft had not as yet been sunk deeper. From the bottom of the shaft was a tunnel reaching to the mine, a distance of two hundred feet. ”

“ The second kind of shaft is very deep, sometimes as much as sixty, eighty, or one hundred fathoms. These shafts continue vertically toward the depths of the earth, and by means of a hauling-rope the broken rock and metalliferous ores are drawn out of the mine; for which reason miners call them vertical shafts. Over these shafts are erected machines by which water is extracted; when they are above ground the machines are usually worked by horses, but when they are in tunnels, other kinds are used which are turned by water-power. Such are the shafts which are sunk when a vein is rich in metal. ”

“ In shaft-sinking, I have known cases more than thirty years ago, where, when a depth, say 20 or 30 feet, had been sunk from the top, a curb was placed, carried by iron rods, and in some cases by chains from timbers laid across the top of the shaft, and the brickwork for lining the shaft was built upon this curb; and in some cases the brickwork has been built continuously on the top of the shaft, and the lining lowered away till it reached the required level. ”

“ SHAFT-SINKING, an important operation in mining for reaching and working mineral deposits situated at a depth below the surface, whenever the topography does not admit of driving adits or tunnels. Shafts are often sunk also in connexion with certain civil engineering works, e.g. ”

“ In principle, the sinking of the shaft was conducted much as Brunel’s shaft at the Thames [158] Tunnel, only it was built up of iron instead of brick. Imagine a big gasometer with a scaffold near the top, where men are busy building the walls higher and higher by adding on plate after plate of iron. On reaching the scaffold you find that there are two great cylinders of iron, one standing inside the other, and concrete is being filled in between them. Men also are down below digging out the earth which is being swung up in iron buckets ”

“ The method of working this great well is unique. As it would be impossible to raise the water to so great a height by one lift, the shaft is made in two divisions, the lower one being a little to one side. ”

“ A shaft may be made vertical or inclined, according as the vein which the miners follow in the course of digging is vertical or inclined. A tunnel is a subterranean ditch driven lengthwise, and is nearly twice as high as it is broad, and wide enough that workmen and others may be able to pass and carry their loads. It is usually one and a quarter fathoms high, while its width is about three and three-quarters feet. Usually two workmen are required to drive it, one of whom digs out the upper and the other the lower part, and the one goes forward, while the other follows closely after. ”

“ Therefore, if a tunnel is fifty fathoms long, it will reach the middle of the bottom of the newest shaft when it has been driven sixteen fathoms and four feet further. But if the shafts are then ninety-two fathoms deep, the last shaft will reach the bottom of the tunnel when it has been sunk a further eight fathoms. ”

“ Sundry modifications of shaft-sinking are adopted in excavating for deep foundations of heavy buildings, bridge piers and other engineering structures. If in solid rock, carrying but little water, shaft-sinking is a comparatively simple operation. But when much water is encountered or the formation penetrated comprises unstable, watery strata, special forms of lining become necessary and the work is slow and expensive. ”

“ Therefore the shaft, of whatever size, is always to be solid; and because the incrusted character of the rest of the building renders it more difficult for the shafts to clear themselves from suspicion, they must not, in this incrusted style, be in any place jointed. No shaft must ever be used but of one block; and this the more, because the permission given to the builder to have his walls and piers as ponderous as he likes, renders it quite unnecessary for him to use shafts of any fixed size. ”

“ It is as a consequence necessary to take some special steps to provide an efficient system of ventilation throughout the mine. This is effectually done by two shafts, called respectively the downcast and the upcast shaft. A shaft is in reality a very deep well, and may be circular, rectangular or oval in form. In order to keep out water which may be struck in passing through the various strata, it is protected by plank or wood tubbing, or the shaft is bricked over, or sometimes even cast-iron segments are sunk. ”

“ SECTION XXXIV. LAW IV. The shafts may sometimes be independent of the construction. Exactly in proportion to the importance which the shaft assumes as a large jewel, is the diminution of its importance as a sustaining member; for the delight which we receive in its abstract bulk, and beauty of color, is altogether independent of any perception of its adaptation to mechanical necessities. Like other beautiful things in this world, its end is to be beautiful ”

“ The verticality of the sides is determined by the plumb-line, and the size of the shaft by two gauge-sticks cut respectively to the outside length and width of the excavation, and distinctly marked at their centres.
To avoid the inconvenience of working under the top frame, the first interval is frequently marked out and excavated before the frame is fixed in its position. ”

“ As soon as the shaft excavation was deep enough, a drift was [Page 412] driven part way across the tunnels, and top headings were started both east and west to explore the rock. The heading to the west was divided into two drifts, as shown on Plate LXI. These two drifts were continued to the west end of the contract, and were then enlarged to a full-sized heading and timbered, as shown on Plate LXI and Fig. 3, Plate LX. The rock near the shaft contained many wet rusty seams, and settlement was detected in the segmental tunnel timbering soon after the widening of the heading was completed. ”

“ On arriving in shallow water or nearing a port the screw is raised, so that the bottom of it is above the level of the keel, and when the blades require examining or replacing, the shaft can be raised still higher, thus exposing the boss and allowing ready access when the ship is in light trim. The last two lengths of shafting are connected with an universal joint which works in a chamber in the after end of the tunnel and is at all times accessible to the engineers. ”

“ In building a drain-shaft it should be remembered that it may not only be subject to a compressive strain, but also to transverse strain and flexure from different pressures of the earth at various depths, especially when the soil is not the same throughout, and unequally damp. ”

“ The top of the working shaft at the colliery is 34 fathoms from the Shield Row seam. An incline bank leads northwards from the working shaft and ultimately reaches the day by a drift, and a little to the south is an up-cast shaft. ”

“ A shaft is sunk perpendicularly down for about four feet, and then a niche is hollowed to the side, so that the sack containing the corpse should not have to sustain any vertical pressure from the earth which is thrown in to fill up the grave. ”

“ Since the chance, in the one case, of horizontal dislocation, in the other, of irregular fissure, is much increased by the composition of the shaft out of joints or small stones, a larger bulk of shaft is required to carry the given weight; and, cæteris paribus, jointed and cemented shafts must be thicker in proportion to the weight they carry than those which are of one block.
We have here evidently natural causes of a very marked division in schools of architecture: one group composed of buildings whose shafts are either of a single stone or of few joints ”

“ About thirty years since, a man and a lad were engaged in sinking a shaft at Wheal Vor Mine, when the lad, through carelessness or accident, missed in charging a hole, so that a necessity arose for the dangerous operation of picking out the charge. ”

“ The sides of all shafts shall be properly secured for safety, and no loose rock or material shall be allowed to remain on any timber in the shaft after each blast. All loose timber, tools, and materials, shall be kept away from the top of the shaft, so as to reduce the danger of same falling down the shaft. ”

“ Where torrents, rivers, or streams have by inundations washed away part of the slope of a mountain or a hill, and have disclosed a vena dilatata, a tunnel should be driven first straight and narrow, and then wider, for nearly all the vein should be hewn away; and when this tunnel has been driven further, a shaft which supplies air should be sunk in the mountain or hill, and through it from time to time the ore, earth, and rock can be drawn up at less expense than if they be drawn out through the very great length of the tunnel ”