Democratic Sentinel, Volume 15, Number 9, Rensselaer, Jasper County, 20 March 1891 — BORING A BIG TUNNEL. [ARTICLE+ILLUSTRATION]

BORING A BIG TUNNEL.

RAPID PROGRESS OF THE ST. CLAIR WORK. 4 Working: Under an Air Pressure of Over Twenty Pounds to the Square Inch—A Great Engineering Achievement Which Will Probably Be Duplicated Soon.

j\R E Grand ifTrunk • Railway under [■the River jßt. * Clair, near Lake t Huron, is a wonderful engineer- , ing achievei ment. It is an important link I in the commercial union of the United States and Canada. It will greatly facilitate the traffic over the several thousand miles of railways in the Grand Trunk system,

i,nd will be of immense importance in the transfers between Chicago, Milwaukee, Grand Haven, Muskegon, Bay City and Detroit to Buffalo, Toronto, Suspension Bridge, Wiarton, North Bay, Kingston, Montreal, Quebec, the White Mountains and Portland and intermediate points. In the summer of 1887 large and costly plants were erected for the tunnel machinery, in Ontario some 1,900 feet from the river, in Michigan about 1,800 feet back. In each plant were included three boilers, a pair of hoisting engines, a ventilating engine with a blower capable of 10,000 cubic feet a minute, a hydraulic pump, a drilling machine, a bolt-screwing machine, a planing machine with extra bed and table, a'water pump, two electric light dynamos and engines, a carpenter shop, a blacksmith shop, and a machine shop. The permanent plants are a small pumping house in Michigan, and in Ontario a brick engine and boiler house, containing at present boilers, four electric light engines and dynamos, two ventilating “blows,” and the two great pumps for draining the cut The great cuttings for tunnel approaches were begun on New Year's Day of 1889, says the Chicago Inter Ocean, The Canadian was begun somewhat narrow. At a depth of fifty-eight feet a landslide deposited about sixteen feet of ■soil in this cutting. Work was started again about ten rods farther back. At the portal the Canadian great cutting is sixty feet deep. It is 260 feet wide at Us broadest portion. From the portal it

rises one foot in fifty feet for 3,192 feet. The American great cutting is fifty-two feet deep, about 200 feet wide at its (broadest part, and rises one foot in fifty feet for 2,533 feet. An inclined track •was laid for flat cars lo haul out the tunaiel soil. In September, 1890, two steam shovels began work on each side of the river. jJEach shovel was attended by a ‘locomotive and train of flat cars. Hundreds of men are employed day and night. When the tunnel proper was ■commenced scarcely more than two layers of the soil had been removed. The -tunnel company grew impatient, 'and on Monday, Feb. 9, 1891, took the Canadian work from the contractors. Over 800 men are employed. As the tunnel will not be opened for traffic until after the approaches are completed the work on the cutting is being rushed. Mr. Alfred E. Boach, an American engineer, designed and used a shield in the Broadway tunnel, New York City, in 1868. Since then similar shields have been used in Chicago, Buffalo, Hudson River, London, and other tunnels. This excavating shield may be compared to a cylinder with no head. It is a circle of steel \platos. Inside these plates are braces, doors, and aids for thejworkmen. In the front end are knife-edges to penetrate the soil. In the rear portion of the shield, around the main walls,'are hydraulic jacks, each supplied with a valve, so that its action may be independent of others. The material of the tunnel walls, masonry, or cast iron, is built in the rear of the shield. Pressure is applied to the hydraulic rains, and thus the shie’d is pushed ahead the length of the jacks’ pistons. The soil is pushed into the front of the shield, and the men remove it by loading it upon cars, which are pushed out to the tramways, on which they are drawn by mules, or horses, to the entrance of the tunnel, where they ate hoisted to the regular .flat cars and taken to the dumping ground. While the men are removing -the soil in front the men in the rear are busy erecting the walls of the tunnel. In case of iron plates, a revolving crane lifts thg plate by means of a counterbalance height to the desired position, where itT§ bolted to the other plates. When the section of the tunnel is completed, and the pistons of the rams have been drawn back, the air is applied again, and the jacks pushed forward for another section of the tunnel to be put in. By this arrangement the workmen are always protected from danger above, around or below. The air pressure keeps the water back in front, and the ■comp’eted tunnel protects the rear. Two shields wore used in the St? Clair tunn 1. Each weighed eighty tons. "They were brought in sections to the Qorth bank of the cutting, where they ■were erected. Then came the problem of placing the shields in position. Wooden tracks were laid, huge ropes were placed Around each shield, and they were gradually lowered by men. In eighty min«tes they were in place at the proposed mouth of the thnnel. Each Shield was 16 feet long, and had an outside diameter of 21H feet The steel plates were l inch thick. Esch.skield had twenty-four hydraulic rams at equal distances apart. Each ram had a stroke of 2 feet and a diameter of 8 inches. Each iime the pistons were shoved ahsad the

shield moved enough to allow a section, or a foot and a half, of the tunnel to be made. The air could have been forced to press 3,000 tons on the shield, but the greatest pressure used was 960 tons. By regulating the pressure of any valve the direction bf the shield could be-varied at will. An observation of the shield’s direction was taken every morning, and by a diagram any variations, even to the smallest fractions of an*inch, were detected and regulated. The variation scarcely ever excelled a fourth of an inch. When the shields met they fitted exactly, which in itself was a marvel, for they had been burrowing farther and farther into unknown soil, yet controlled

by brilliant minds and wonderful inventions. The American shield started duly 11, 1889; the Canadian Sept 21, 1889; they met at nearly midnight of Aug. 30,1890. The Canadian had gone 2,686.10 feet, and the American 3,313v85 feet. Work had been pushed night and day, in shifts of. eight hours, for electricity lighted the shields and tunnel, and early completion of the tunnel was a great object. The average progress of each shield was ten feet a day; but one day twenty-seven feet and ten inches was accomplished, and the record of tunnel construction was excelled. Chief Engineer Hobson advised having these tunnel walls of cast iron. Each section was composed of a key and 13 segments, each segment being 4 feet 10 inches long, 18 inches wide, and 2 inches thick. Each had inside flanges C inches deep and an inch and three-quarters thick. In each segment were 4 holes in each end and 12 holes in each side flange. These 32 holes were occup ed by steel boits, each seven-eighths of an inch in diameter. Each section of the completed tunnel was a circle whose radius was 9 feet and 11 inches. Each section required for the longitudinal joints 56 bolts, and for the circular joints 15t bolts, a total of 213 bolts for each foot and a half of the tunnel. It required 828,150 bolts to fasten together the 27,000 tons ot the east-iron lining of this tunnel. Each segment was heated and dipped into a vat of coal tar. By the time it was cool the tar was dried in. This method was the happy thought of a workman. Another workman invented a tool which increased three times the rapidity of loading the clay upon the cars.

Tunneling was nearly stopped at tho line of the river by water and quicksand. Compressed air was tried. On each side of the river, beneath the shore lines, air-tight bulkheads of brick and cement were built across the line of the tunnel. Above each car-track and on each side of the bulkheads were erected two airlocks. each seventeen feet long and seven feet in diameter, with air-tight doors at each end. The outside door would be opened and men or mules admitted to the air-lock. Horses could not stand the pressure. The door being closed and tho air-valve opened, the air-pressure would bo increased until t le atmosp teres of the lock equaled the atmospheres inside tho inner portion of the tunnel, when the inner door could be opened, and the men or animals admitted to the works. It took several minutes to properlydn-

crease or docrease the air-pressure on a man. Certain rules had to be obeyed. The workmen had to have vigorous bodies, and be examined by the company’s physician before receiving admission to the compressed air. Two deaths resulted from the bad results of the air-pressure. The air caused terrible feelings, especially to strangers. In the beginning of the under-river section the three gangs, each of twenty-five men, worked under

an extra atmospheric pressure of ten pounds to the square inch. This was increased slowly and at interva’s, to twep-ty-two pounds per square inch, or abodt two and one-half times the usual atmospheric pressure. (The proposed limit in the Chicago Fourteenth street tunnel is forty pounds per square inch.) Quick

sands on tha Canadian side caused the highest air-pressures to be exerted upon that side. The compression of the air kept the quicksand and water from.overflowing into the tunnel. Leaks were Invisible. The viewless walls kept back the flood. Compressed air was used on the Canadian side from May 28,1890, and on the American side from April 7,189 a The completion of the hole was the beginning of the erfd. A vast amount of work had yet to be done. The tunnel was cleaned and the tramways’ beds of clay, about two feet thick, were removed. The cast-iron walls were painted with some anti-rust compound, hundreds of thousands of bolts were tightened, and

brick and concrete were placed in the lower half of the tunnel to prevent it being ousted by the brine from the meat cars. Above the cement are three drainage conduits, two thirty inches long, and one in the middle, eighteen inches square. Over these and their dividing timbers are wooden ties, nine feet long and eight by eight inches square. On these ties rest extra heavy steel T-rails, 100 pounds to the yard, of standard American gauge track, four and one-half inches wide. On each side of the T-rails are wooden guard rails, ten by twelve inches. Both sides of the track are planked. All the timbers are of pine, and have been soaked in dead oil of tar. Safety ladders and platforms have been placed for workmen and watchmen. The inside diameter is 19 feet 10 inches; 21 feet the outside diameter. In the top of the tunnel gre ttfo ventilating tubes, each 20 inches in diameter. It is constantly lighted by electricity. The tunnel will nearly drain itself.

The surface water in the cuttings will be taken caire of tho portals. It is estimated that not over fifteen gallons a minute of water escape into the tunnel proper. This is a small quantity for over a mile of linear surface. It will drain into a pump-shaft on the Canadian side, 112 feet deep, down to the rock, and fifteen feet in diameter. The portals are big limestone blocks, arranged 148 feet long, 36 feet high, and from 10 to 5 feet wide, with sloping comb. The tunnel entrance is flush with the lining, and is twenty feet in diameter. The portal’s only lettering is two lines—- “ St. Clair. 1890.” From the portals, on each side of the railway track, limestone retaining walls oxtend to the entrances of the great cuttings. At the

portals these walls are 6 feet high and 5 feet wide; near the beginning of the cutting they are 5 feet high and 3 feet wide. It was estimated that the tunnel would cost $2,500,000, plants, materials, and labor included. Not much will be left of that sum. It is likely that a second tunnel will be built beside this one. If so, this one’s plant and experience will be quite serviceable. If it is built it will be made of cast-iron, as that has been found to be better than masonry. The tunnel and its approaches have a total length of 11,725 feet, divided as follows; Canadian cutting, 3,192 feet; American cutting, 2,533 feet; from Canadian portal to water's edge, 1,994 feet; from American portal to water’s edge, 1,71 G feet; tunnel under water, 2,290 feet; total length of tunnel, 6,000 feet, Grades in the cuttings are one foot in fifty feet, in the tunnel, one foot in 1,000 feet The greatest depth of water above the tunnel is 40.47 feet; and the least depth of clay above the tunnel is 8.43. The number of feet from the level of the water to dhe top of the tunnel is 57.83 feet; and the number of feet from the level of ti>3 water to the rock, 86 feet. Considerable difficulty was met in selecting locomotives for the tunnel service, as most kinds emitted too much smoke and gas. Coke engines have been chosen. Each locomotive can haul two dozen loaded cars. One engine will be at each side of the St." Clair River, and another will be kept in steam ready for any break-down. The tunnel soil has been dumped in

the two switching yards until a level place has been graded off large enough for twenty-two miles of side-tracks. On the Canadian side a huge ice-house has been built for meat cars. It is B>ofeet long, 30 feet high, and the same wide. It is partitioned into twenty-seven bins, each twenty-eight feet square, and has a track on each side. Although the tunnel itself was completed in January, 1891, with perhaps the exception of a little plastering, the delay on the approaches prevents opening for traffic. There will be a grand celebration of this important international occurrence The leading officials of the Governments of Canada and the United States will be invited, besides many other distinguished people It is expected that the banquet will occur under the river. * It is probable tnat the Detroit River will soon be tunneled by the Michigan Central Railway at Detroit, and before long the Grand Trunk will put in another tunnel at Port Huron. Considering cost and subsequent expense, tunnels mav yet prove to be cheaper than bridges.

MAP SHOWING POSITION OF TUNNEL.

CANADIAN PORTAL TO ST. CLAIR TUNNEL.

THE SHIELD IN PLACE IN GRADE.

TUNNEL BUILDINGS IN MICHIGAN.

LOWERING OF THE SHIELD TO THE HEADING.