Tunnel

“ The narrow passage appeared to extend and widen out before their advance, until it took the shape of a long railway tunnel, from which the pair emerged at length into the bright beams of day. The transit from what seemed to be the bowels of a high mountain range to a landscape fairer and more beautiful than our hero had ever seen, filled his mind with wonder. ”

“ Almost groping, and constantly pausing to inspect the floor beneath or the walls and the roof of this stone highway, we must have been walking for nearly an hour when we came to a halt. Our tunnel appeared to end in a most unexpected manner. It was as if we had stepped into the midst of a chamber devoted to huge, crude, archaic machinery consisting of stone levers, wheels, and weights. ”

“ It lay partly open; and sixty or a hundred feet above our head, we could see the strata propped apart by solid wooden wedges, and a pine, half undermined, precariously nodding on the verge. Here also a rugged, horizontal tunnel ran straight into the unsunned bowels of the rock. This secure angle in the mountain's flank was, even on this wild day, as still as my lady's chamber. But in the tunnel a cold, wet draught tempestuously blew. ”

“ At the bottom of this shaft, 163 feet below the surface of the ground, the mouth of the tunnel was reached, and the visitors took their seats on small tramcars which were drawn by workmen. So evenly has the boring machine done its work that one seemed to be looking along a great tube with a slightly downward set, and as the glowing electric lamps, placed alternately on either side of the way, showed fainter and fainter in the far distance, the tunnel, for anything one could tell from appearances, might have had its outlet in France. ”

“ The fall of earth did not extend many yards, and beyond it we found ourselves in the continuation of the tunnel. On, on, on we went, moving slowly, with only the uncertain light of the tiny lamp to warn us of any dangerous pitfall which might lie in our path. Contrary to my expectation, we encountered no further obstacle of a similar kind to that through which we had just cut our way. Now we were passing once more through solid rock, and now the tunnel was continued through earth, supported by rough-hewn beams, black with damp and age. ”

“ We drew a long breath when we emerged into the welcome blinking daylight at the other end of the tunnel, and soon after bade good-bye to our whilom friend the skipper.
I can imagine no place more calculated to quickly shatter the nerves and break the health of a human being than one of those foul, suffocating tunnels under the hills. ”

“ But out in the escape tunnels, we continued our explorations, now sure that no warnings could be broadcast to the tunnel exits, and mowed down contingent after contingent of the hated yellow men.
My register showed seventy-five miles before I came to the end of the tunnel, and drove my ball out into a vast underground city of great, brilliantly illuminated corridors, some of them hundreds of feet high and wide. The architectural scheme was one of lace-like structures of curving lines and of indescribable beauty. ”

“ A tunnel, defined as an engineering structure, is an artificial gallery, passage, or roadway beneath the ground, under the bed of a stream, or through a hill or mountain. The art of tunneling has been known to man since very ancient times. A Theban king on ascending the throne began at once to drive the long, narrow passage or tunnel leading to the inner chamber or sepulcher of the rock-cut tomb which was to form his final resting-place. Some of these rock-cut galleries of the ancient Egyptian kings were over 750 ft. ”

“ This exit, heading away from the concealed abysses, had in some ages past been made by man into a doorway.
Passing through this secret portal the passage is confined for some distance by narrow walls, and the low roof makes it necessary in places to crawl upon the knees. The tunnel ends by opening into a vast cavern similar to the one first entered; but on advancing the walls and ceilings grow invisible to the light of torches and it becomes like a vast field. ”

“ As you pass on the west side and are opposite the tunnel, the opening at a distance appears like a patch of snow upon the dark rock; approaching nearer you see the walls of the tunnel, with a view of the sky through the smaller opening on the east side, yet after advancing a certain distance in the steamer and looking backward, nothing is seen but a solid wall of rock, with no intimation of an opening. ”

“ The sophisticated stay inside and close doors and windows. We soon learn why, for in each tunnel we outsiders are subjected to a machine-gun fire of hot cinders and flue from Puffing Billy ahead. However, the glimpses of the Gorge, Cairns and the sea—'tween tunnels—are well worth getting smutty for. ”

“ Men have devoted their adult lives to promoting the cause of the tunnel, and such a powerful grip does the project seem to have had on the imagination of its various designers that just to look at some of their old drawings—depicting, for example, down to the finest detail of architectural ornamentation, ventilation stations for the tunnel sticking out of the surface of the Channel as ships sail gracefully [8] about nearby—one might almost think that the tunnel was an accomplished reality, and the artist merely a conscientious reporter of an existing scene. ”

“ The making of one tunnel so much resembles the making of another—the building of bridges and viaducts, no matter how extensive, so much resembles the building of others—the cutting out of "dirt," the blasting of rocks, and the wheeling of excavation into embankments, is so much matter of mere time and hard work, that it is quite unnecessary to detain the reader by any attempt at their description. ”

“ Through the very heart of this rocky mountain a tunnel has been constructed, of most admirable architecture, with a lofty arch and a spacious double-track; so that, unless the earth and rocks should chance to crumble down, it will remain an eternal monument of the builder's skill and enterprise. It is a great though incidental advantage, that the materials from the heart of the Hill Difficulty have been employed in filling up the Valley of Humiliation ”

“ In tunneling hard, firm rock, this is practically the entire compass of the work: breaking away the rock from the mother mass, and, coincidently, removing it from the workings. The opposite extreme in conditions is met in the soft-ground tunnel, driven through material incapable of supporting itself above [204] the tunnel opening. ”

“ When the tunnel for almost its entire length is driven on a tangent with a curve at each end.
(2) When the tunnel begins with a curve and ends with a straight line.
(3) When the whole tunnel is in curve from portal to portal.
(4) The helicoidal or corkscrew tunnel.
(1) The axis of every one of the great Alpine tunnels is a straight line, with a curve at each end. To range out the center line of one of these long tunnels from a curve, no matter how accurately laid out, will certainly cause an error, which, magnified with the distance, may produce serious results. ”

“ The tunnel being thus left dry, a man could crawl on his hands and knees through it, and once outside, walk upright on the top of the viaduct, along the empty bed of the river, until he reached the spot where the water had been diverted, and there find his comrades. ”

“ The guiding precept of the exhibit has not been to outline exhaustively the entire history of tunneling, but rather to show the fundamental advances which have occurred between primitive man’s first systematic use of fire for excavating rock in mining, and the use in combination of compressed air, iron lining, and a movable shield in a subaqueous tunnel at the end of the 19th century. ”

“ Gothard Tunnel.
Niches. —In short tunnels niches are employed simply as places of refuge for trackmen and others during the passing of trains, and are of small size. In long tunnels they are made larger, and are also employed as places for storing small tools and supplies employed in the maintenance of the tunnel. Niches are simply arched recesses built into the sides of the tunnel, and lined with masonry; Fig. 48 shows this construction quite clearly. Small refuge niches are usually built from 6 ft. to 9 ft. high, from 3 ft. to 6 ft. wide, and from 2 ft. to 3 ft. deep. ”

“ During construction, however, special means will have to be provided for removing the water from the excavation, their character depending upon the method of excavation and upon the grades of the tunnel bottom. When the excavation is carried on from the entrances only, unless the tunnel has a descending grade from the center toward each end, the tunnel floor in one heading will be below the level of the entrance, or, in other words, the descending grade will be toward the point where work is going on, while at the opposite entrance the grade will be descending from the work. ”

“ At the present day the word is sometimes popularly applied to an underground passage constructed by trenching down from the surface to build the arching and then refilling with the top soil; but a passage so con structed, although indistinguishable from a tunnel when completed, is more correctly termed a "covered way," and the operations "cutting and covering," instead of tunnel ling. Making a small tunnel, afterwards to be converted into a larger one, is called "driving a heading," and in mining operations small tunnels are termed "galleries," "driftways," and "adits." ”

“ So if the tunnel is sixty fathoms long, the remaining distance to be driven into the mountain is six fathoms and four feet. If the shaft is ninety-seven fathoms deep, the last one will reach the bottom of the tunnel when a further depth of three fathoms has been sunk. ”

“ At intervals of about 300 ft. throughout each tunnel, alignment pockets are formed in the concrete arch, also above the bench, on the south bench of the North Tunnel and the north bench of the South Tunnel. In each pocket is placed a graduated and verniered brass bar, so that, when the base line is projected on these bars, the lateral movement of the tunnel can be read directly. ”

“ It is formed of one long arch, or rather tunnel, some hundred feet in length, between twenty to thirty in breadth, and thirty to forty feet in height, cut through the wall of rock, which surrounds the town on the Bavarian side. On the outside the rock is handsomely sculptured, and forms a very elegant entrance into this long passage. ”

“ He bored holes in the bottom of the lining and drove steel legs right down to the next ledge of solid rock below. There’s that tunnel to-day, carrying 32,000 people between five and six o’clock every night perched down there seventy feet underground like a big caterpillar sprawled under the wickedest ledge o’ rock you ever see.”
It takes a real genius of an engineer for this sort of work. He who drives his bore into the unknown must be on guard for the unexpected. Emergencies arise upon [Pg 54] the minute, and the tunnel engineer must be ready with his wits and ingenuity to meet them. ”

“ This chap, back yonder, knows the hidden path. And now it seems he knows the tunnel, too. If I'm right in thinking that tunnel leads to the secret orchard enclosure, back of your house, then I fancy Standish may be visited during the next half hour. And, unless I'm mistaken, I heard more than one set of bare feet scurrying down that tunnel just now. Our friend with the bashed-in face was apparently the last of several men to slip into the tunnel, and we happened along as he was doing it. If he recognized you and saw you had a man as an escort, he must know we're bound for your house. ”

“ To reach the building at the nearest point to the object of our desires we shall have to steer nor’-west-by-north by the compass (I have allowed for the magnetic variation in the parallel of London) . I propose to construct a tunnel of the usual semi-circular form, three feet high by three feet six inches at the base. One hundred and twenty-seven yards of this tunnel will take us to the building. Now, in open ground, an ordinary navvy can shift seven cubic yards of dirt in a day. Each linear yard in our tunnel will measure in round numbers about a cubic yard. ”

“ This picture represents one of the difficulties of railroads through this rugged mountain range and shows elevation is overcome by the use of tunnels. A tunnel is cut through the rocks; a circuit is made leading back to the same point at a higher elevation and another tunnel is cut directly over the first one. The traveler will find this a most interesting view as the train winds its way through these mountains. ”

“ It chanced that winter that men were driving a railway tunnel beneath a corner of the Park. The tunnel ran for a short distance under the front of Last Bull's range, and passed close by the picturesque cottage occupied by Payne and two of his assistants. ”

“ Trains coming through the tunnel from France were to emerge into the daylight and the ordinary open air of England either from a four-mile-long access tunnel connected to the South-Eastern's railway line at Abbots Cliff or—this was a favored alternative plan of Sir Edward's—at Shakespeare Cliff via a station to be constructed in a great square excavated a hundred and sixty feet deep in the ground, which would be covered over with glass, lighted by electric light, and equipped "with large waiting rooms and refreshment rooms." ”

“ The time required to excavate a tunnel depends upon the character of the material penetrated and upon the method of work adopted. Tunnels driven through soft ground by hand require about the same time to construct as tunnels driven through hard rock by the aid of machinery. Tunnels can be driven through hard rock at about as great a speed as through soft or fissured rock, chiefly because the work of blasting is more efficient in hard rock, and because no time is required in timbering. ”