Tunnel boring machine

“ We sink the shaft to within twenty feet of the tunnel level and then quit sinking until the tunnel is completed. We use a tunneling machine, boring a tunnel six feet in diameter at the rate of one hundred feet per day. We run the tunnel directly under the shaft and then withdraw all the men and machinery from the tunnel, put a six-inch drill into the shaft that makes a hole into the tunnel, and quickly drains the mine. Then we begin to stope out at the lowest level, filling in the waste upward, and taking out only ore to be conveyed to the mill or smelter. ”

“ Several such machines have been invented and constructed with reference to this very work, and one or two of these have been found successful in practice, though the immense strain caused by the boring is such as to require corresponding strength in the borer. To give the necessary ventilation, and now and then light to the tunnel, both when in the course of construction, and especially when finished and in use, it is proposed at proper intervals to sink dry wells, or openings from the top of the mountain, down to the tunnel itself ”

“ All things that live and breathe, miners among the number, require air for their sustenance; and, in order to supply it in sufficient quantities for the support of the human moles within the interior of the tunnel, it has been necessary to resort to special appliances for this purpose. Immense machinery, moved by water-power of an aggregate force for each end of about 400 horses, erected at both entrances of the tunnel, works not only the boring machines, but, at the same time, furnishes the miners with the necessary ventilation. ”

“ The work begins with the 'machine-men,' who operate the 'chain-machines.' In order that the blast may dislodge by gravity an even block of coal, of the dimensions of the cross-section of the tunnel, these men cut with their machines a 'sump-cut,' or, in other words, carve out an opening level with the floor, about six inches high and six feet deep, at the end of the tunnel. The machines—which are propelled by electricity—consist of a motor and a large oblong disk, about which travels an endless chain containing sharp steel 'bits' or picks. ”

“ The reason they have not gained more favor among American tunnel builders is due to some extent perhaps to prejudice, but chiefly to the great cost of the machine as compared with percussion drills, and to the expense of diamonds for repairs. Those who advocate these machines for tunnel work point out, however, that under ordinary usage the diamonds have a very long life,—borings of 700 lin. ft. ”

“ First, it is well known that compressed air is used to work the perforating machines used in boring the tunnel; then, by the employment of compressed-air locomotives, ventilation of the galleries would be produced, as these machines would allow only pure air to escape; and then these motors would be more powerful than horses, and effect more rapidly the clearing away of the débris. ”

“ I could think of nothing but these ventilation shafts. Had they been destroyed by all the food-tubes and medicine-tubes and music-tubes that the Machine has evolved lately? Or did traces of them remain? One thing was certain. If I came upon them anywhere, it would be in the railway-tunnels of the topmost story. Everywhere else, all space was accounted for.
"I am telling my story quickly, but don't think that I was not a coward or that your answers never depressed me. It is not the proper thing, it is not mechanical, it is not decent to walk along a railway-tunnel. ”

“ Huge wood fires are made up against the face of the rock, which becomes shattered and traversed by cracks, and when cooled, it is easily detached with a pick or fork. Of late years, however, machines have been devised for boring or breaking the rock. Some form a hole by the continuous motion of a rotating drill, others by means of intermittent blows. One of these rock-boring machines, manufactured by Messrs Turner, of Ipswich, performs its work by a combination of both these operations. By the employment of these machines, the formation of the tunnel under Mount Cenis was greatly facilitated. ”

“ The introduction of the first machine into the tunnel, before its capacity, strength, and expense of working had been fully tested, was unfortunate, inasmuch as its use there delayed the progress of the work. The second machine gives such promise of success, that it will be continued in use in the tunnel until a fair test has been made. But should the Burleigh machine prove unsuccessful, and further attempts with machines be attempted, the Committee recommend that their usefulness be tested outside of the tunnel, and meanwhile the excavation with hand drills be resumed. ”

“ Actual work on the Hoosac Tunnel began at both ends of the tunnel in about 1854, but without much useful effect until 1858 when a contract was let to the renowned civil engineer and railroad builder, Herman Haupt of Philadelphia. Haupt immediately resumed investigations of improved tunneling methods, both full-area machines and mechanical rock drills. At this time mechanical rock-drill technology was in a state beyond, but not far beyond, initial experimentation. There existed one workable American machine, the Fowle drill, invented in 1851. ”

“ The completed tunnel was to be lighted throughout by electric light—a novelty already being tried out in the pilot tunnel by the well-known electrical engineer C. W. Siemens—and the trains that ran through it between France and Britain were to be hauled by locomotives designed by Colonel Beaumont. Instead of being run by smoke-producing coal, the locomotives were to be propelled by compressed air carried behind the engine in tanks, and, like the Beaumont tunneling machine, the engine was supposed to keep the tunnel ventilated by giving out fresh air as it went along. ”

“ Under present conditions, therefore, the engineer is limited either to air or water under compression for the transmission of his power. Steam-power may be employed directly to operate percussion rock drills; but owing to the heat and humidity which it generates in the confined space where the drills work, and because of other reasons, it is seldom employed directly. Electric transmission, which offers so many advantages to the tunnel builder, in most respects is largely excluded from use by the failure which has so far followed all attempts to apply it to the operation of rock drills. ”

“ They accomplish double the work without repairs that those do which were made after the previous pattern. There is a further advantage in using the Burleigh machines; their breaking, when it occurs, is not very serious, the injured parts consisting mainly of cams, can generally be replaced at the tunnel; whereas for the repairs on the Brooks, Burleigh and Gates machine, the dependence to a very great extent has been upon the machine shop at Fitchburg. ”

“ The machine, striking a blow far more rapidly than can be done by hand, reduces the number of operators to one man, and perhaps his helper. So durable is the metal of these wonderful little mechanisms that the delivery of 360,000 blows daily for months, even though each is given with a force of perhaps half a ton, fails to wear them out; or at the most only necessitates the renewal of some minor and cheap part. The debt that civilisation owes to the substitution of mechanical for hand labour will be fully understood by anyone who is conversant with the history of tunnel-driving and mining. ”

“ The steam hoisting engine is the standard machine for the rapid lifting of heavy vertical loads. Recently oil engines and electric hoists have also come to be used to some extent, and under certain conditions these machines possess notable advantages.
The construction of hand windlasses is familiar to every one. In tunnel work this device is located directly over the shaft, with its axis a little more than half a man’s height, so that the crank handle does not rise above the shoulder line. ”

“ The loads which can be carried in single skips are also smaller than those possible where elevators are used; and this, combined with the slower hoisting speed required, reduces the capacity of this method, as compared with the use of elevators. Where elevators are employed, however, the plant required is much more extensive and costly; it comprising not only the elevator cars with their safety devices, etc., but the construction of a guiding framework for these cars in the tunnel shaft. ”

“ The longer the plant is to be required, the nearer the construction may economically approach that of a permanent plant. As regards the machinery itself, whose further usefulness is not limited by the duration of any single piece of work, true economy always dictates the purchase of the best quality. Speaking in a general way, a steam-power plant for tunnel work comprises a boiler plant, a plant of air compressors with their receivers, and an electric light dynamo. When hydraulic transmission of power is employed, the air [86] compressors are replaced by high-pressure pumps ”

“ This means of illumination is very poor for mechanical work. The fumes and smoke from blasting, added to the smoke from torches and lamps, render the atmosphere underground, especially when the barometer conditions were unfavorable to ventilation, very offensive and discomforting to the workmen. An investigation of the subject of lighting the tunnel by other means, more especially at the locality where the mechanics were at work,—brick and stone masons, and the workmen on the iron lining,—resulted in the selection of acetylene gas as the most available and economical in this special emergency. ”

“ They never quite removed the machine from the heading when they were finished, but it was maintained right up to the outbreak of the Second World War, when it became derelict."
Adams and I walked back to the car. As we did so, he revealed himself as being pro-tunnel. "It's a tragic thing, this tunnel business, I think. If the tunnel had been built forty or fifty years ago, just think of what an asset to Europe it would have been," he said. We packed ourselves in, and Burgess drove us down a very rough, narrow road to the level of the railroad line. ”

“ The power-house, the foundations for the machinery, and the general construction and arrangement, should be the least expensive which will satisfy the requirements of economical and safe operation for the time required. It will often be found more economical as a whole to operate the machinery with some loss of economy during the short time that it is in use than to go to much greater expense to secure better economy from the machinery by design and construction, which will be of no further use after the tunnel is completed. ”

“ In 1919 he asked permission from the Board [111] of Trade to drive a new heading from the old Number Three ventilating shaft at the eastern end of Shakespeare Cliff a little way under the foreshore, and got it, but he changed his mind and decided to try the machine in the chalk down here. The Whittaker machine cut a tunnel twelve feet in diameter, and some time between 1921 and 1924 they drove a heading into the chalk, just at the point where it's sticking out now, for some four hundred feet. ”

“ Space limitations did not permit treatment of the many interesting ancillary matters vital to tunnel engineering, such as the unique problems of subterranean surveying, and the extreme accuracy required in the triangulation and subsequent guidance of the boring in long mountain tunnels; nor the difficult problems of ventilating long workings, both during driving and in service; nor the several major methods developed through the years for driving or constructing tunnels in other than the conventional manner. ”

“ In working them, no process is more costly than that of tunneling. It is also not unfrequently the most discouraging. This is especially true of those mines that can only be prospected by means of a tunnel, as was the case with the Blue Gravel Mine. ”

“ Its number of strokes is about 300 per minute, and its blow somewhat lighter than that of the other. This machine is not entirely automatic; the feed-motion not working regular; when it does not, it is fed by hand, which is a simple process.
These machines stand the work much better than those first made at Fitchburg. Their average time in the tunnel without repairs in the interval, is about five days ”

“ EXCAVATING MACHINES AND ROCK DRILLS: EXPLOSIVES AND BLASTING. Earth-Excavating Machines. —Comparatively few of the labor-saving machines employed for breaking up and removing loose soil in ordinary surface excavation are used in tunnel excavation through the same material. Several forms of tunnel excavating machines have been tried at various times, but only a few of them have attained any measure of success, and these have seldom been employed in more than a single work. ”

“ Instead of climbing far up and then coming down in long, slow curves, the train can run quickly straight through.
Tunnels are hard to dig. They often have to be blasted out of solid rock. So the builders don’t make them any bigger than they have to. Of course, there’s not room for a man to stand up on top of a freight car{61} as it goes through a tunnel. To protect brakemen who might forget, there is a device called a tell-tale close to the mouth of a tunnel. It is simply a fringe of cords hanging down from a tall bar across the track. ”

“ Three 8-hour shifts carried the work forward: drilling occupied half the time and half was spent in running the carriage back, blasting, and mucking (clearing the broken rock) .
The tunnel’s 1028-foot central shaft, completed under the Shanley contract in 1870 to provide two additional work faces as well as a ventilation shaft is shown at the far right side of this half of the model. Completed so near the end of the project, only 15 percent of the tunnel was driven from the shaft.
The enormous increase in rate of progress was not due entirely to machine drilling. ”