Figure 44.—Opening of the St. Clair Tunnel, 1891.(Photo courtesy of Detroit Library, Burton Historical Collection.)
Figure 44.—Opening of the St. Clair Tunnel, 1891.(Photo courtesy of Detroit Library, Burton Historical Collection.)
The Hobson shield followed Greathead’s as closely as any other, in having a diaphragm with closable doors, but a modification of Beach’s sharpened horizontal shelves was also used. However, these functioned more as working platforms than supports for the earth. The machine was 21½ feet in diameter, an unprecedented size and almost twice that of Greathead’s current one. It was driven by 24 hydraulic rams. Throughout the entire preliminary consideration of the project there was a marked sense of caution that amounted to what seems an almost total lack of confidence in success. Commencement of the work from vertical shafts was planned so that if the tunnel itself failed, no expenditure would have been made for approach work. In April 1888, theshafts were started near both riverbanks, but before reaching proper depth the almost fluid clay and silt flowed up faster than it could be excavated and this plan was abandoned. After this second inauspicious start, long open approach cuts were made and the work finally began. The portals were established in the cuts, several thousand feet back from each bank and there the tunneling itself began. The portions under the shore were driven without air. When the banks were reached, brick bulkheads containing air locks were built across the opening and the section beneath the river, about 3,710 feet long, driven under air pressure of 10 to 28 pounds above atmosphere. For most of the way, the clay was firm and there was little air leakage. It was found that horses could not survive in the compressed air, and so mules were used under the river.
In the firm clay, excavation was carried on several feet in front of the shield, as shown in the model (fig. 42). About twelve miners worked at the face. However, in certain strata the clay encountered was so fluid that the shield could be simply driven forward by the rams, causing the muck to flow in at the door openings without excavation. After each advance, the rams were retracted and a ring of iron lining segments built up, as in the Tower Subway. Here, for the first time, an “erector arm” was used for placing the segments, which weighed about half a ton. In all respects, the work advanced with wonderful facility and lack of operational difficulty. Consideringthe large area, no subaqueous tunnel had ever been driven with such speed. The average monthly progress for the American and Canadian headings totaled 455 feet, and at top efficiency 10 rings or a length of 15.3 feet could be set in a 24-hour day in each heading. The 6,000 feet of tunnel was driven in just a year; the two shields met vis-a-vis in August of 1890.
The transition was complete. The work had been closely followed by the technical journals and the reports of its successful accomplishment thus were brought to the attention of the entire civil engineering profession. As the first major subaqueous tunnel completed in America and the first in the world of a size able to accommodate full-scale rail traffic, the St. Clair Tunnel served to dispel the doubts surrounding such work, and established the pattern for a mode of tunneling which has since changed only in matters of detail.
Of the eight models, only this one was built under the positive guidance of original documents. In the possession of the Canadian National Railways are drawings not only of all elements of the shield and lining, but of much of the auxiliary apparatus used in construction. Such materials rarely survive, and do so in this case only because of the foresight of the railway which, to avoid paying a high profit margin to a private contractor as compensation for the risk and uncertainty involved, carried the contract itself and, therefore, preserved all original drawing records.
While the engineering of tunnels has been comprehensively treated in this paper from the historical standpoint, it is well to still reflect that the advances made in tunneling have not perceptibly removed the elements of uncertainty but have only provided more positive and effective means of countering their forces. Still to be faced are the surprises of hidden streams, geologic faults, shifts of strata, unstable materials, and areas of extreme pressure and temperature.
BIBLIOGRAPHY
Agricola, Georgius.De re Metallica.[English transl. H. C. and L. H. Hoover (The Mining Magazine, London, 1912).] Basel: Froben, 1556.
Beach, Alfred Ely.The pneumatic dispatch.New York: The American News Company, 1868.
Beamish, Richard.A memoir of the life of Sir Marc Isambard Brunel.London: Longmans, Green, Longmans and Roberts, 1862.
Burr, S. D. V.Tunneling under the Hudson River.New York: John Wiley and Sons, 1885.
Copperthwaite, William Charles.Tunnel shields and the use of compressed air in subaqueous works.New York: D. Van Nostrand Company, 1906.
Drinker, Henry Sturgess.Tunneling, explosive compounds and rock drills.New York: John Wiley and Sons, 1878.
Latrobe, Benjamin H.Report on the Hoosac Tunnel (Baltimore, October 1, 1862). Pp. 125-139, app. 2, inReport of the commissioners upon the Troy and Greenfield Railroad and Hoosac Tunnel. Boston, 1863.
Law, Henry.A memoir of the Thames Tunnel.Weale’s Quarterly Papers on Engineering(London, 1845-46), vol. 3, pp. 1-25 and vol. 5, pp. 1-86.
The pneumatic tunnel under Broadway, N.Y.Scientific American(March 5, 1870), pp. 154-156.
Report of the commissioners upon the Troy and Greenfield Railroad and Hoosac Tunnel to his excellency the governor and the honorable the executive council of the state of Massachusetts, February 28, 1863.Boston, 1863.
Storrow, Charles S.Report on European tunnels (Boston, November 28, 1862). Pp. 5-122, app. 1, inReport of the commissioners upon the Troy and Greenfield Railroad and Hoosac Tunnel....Boston, 1863.
The St. Clair Tunnel.Engineering News(in series running October 4 to December 27, 1890).
FOOTNOTES:
[1]There are two important secondary techniques for opening subterranean and subaqueous ways, neither a method truly of tunneling. One of these, of ancient origin, used mainly in the construction of shallow subways and utility ways, is the “cut and cover” system, whereby an open trench is excavated and then roofed over. The result is, in effect, a tunnel. The concept of the other method was propounded in the early 19th century but only used practically in recent years. This is the “trench” method, a sort of subaqueous equivalent of cut and cover. A trench is dredged in the bed of a body of water, into which prefabricated sections of large diameter tube are lowered, in a continuous line. The joints are then sealed by divers, the trench is backfilled over the tube, the ends are brought up to dryland portals, the water is pumped out, and a subterranean passage results. The Chesapeake Bay Bridge Tunnel (1960-1964) is a recent major work of this character.
[1]There are two important secondary techniques for opening subterranean and subaqueous ways, neither a method truly of tunneling. One of these, of ancient origin, used mainly in the construction of shallow subways and utility ways, is the “cut and cover” system, whereby an open trench is excavated and then roofed over. The result is, in effect, a tunnel. The concept of the other method was propounded in the early 19th century but only used practically in recent years. This is the “trench” method, a sort of subaqueous equivalent of cut and cover. A trench is dredged in the bed of a body of water, into which prefabricated sections of large diameter tube are lowered, in a continuous line. The joints are then sealed by divers, the trench is backfilled over the tube, the ends are brought up to dryland portals, the water is pumped out, and a subterranean passage results. The Chesapeake Bay Bridge Tunnel (1960-1964) is a recent major work of this character.
[2]In 1952 a successful machine was developed on this plan, with hardened rollers on a revolving cutting head for disintegrating the rock. The idea is basically sound, possessing advantages in certain situations over conventional drilling and blasting systems.
[2]In 1952 a successful machine was developed on this plan, with hardened rollers on a revolving cutting head for disintegrating the rock. The idea is basically sound, possessing advantages in certain situations over conventional drilling and blasting systems.
[3]In 1807 the noted Cornish engineer Trevithick commenced a small timbered drift beneath the Thames, 5 feet by 3 feet, as an exploratory passage for a larger vehicular tunnel. Due to the small frontal area, he was able to successfully probe about 1000 feet, but the river then broke in and halted the work. Mine tunnels had also reached beneath the Irish Sea and various rivers in the coal regions of Newcastle, but these were so far below the surface as to be in perfectly solid ground and can hardly be considered subaqueous workings.
[3]In 1807 the noted Cornish engineer Trevithick commenced a small timbered drift beneath the Thames, 5 feet by 3 feet, as an exploratory passage for a larger vehicular tunnel. Due to the small frontal area, he was able to successfully probe about 1000 feet, but the river then broke in and halted the work. Mine tunnels had also reached beneath the Irish Sea and various rivers in the coal regions of Newcastle, but these were so far below the surface as to be in perfectly solid ground and can hardly be considered subaqueous workings.
[4]Unlike the Brunel tunnel, this was driven from both ends simultaneously, the total overall progress thus being 3 feet per shift rather than 18 inches. A top speed of 9 feet per day could be advanced by each shield under ideal conditions.
[4]Unlike the Brunel tunnel, this was driven from both ends simultaneously, the total overall progress thus being 3 feet per shift rather than 18 inches. A top speed of 9 feet per day could be advanced by each shield under ideal conditions.
[5]Ideally, the pressure of air within the work area of a pneumatically driven tunnel should just balance the hydrostatic head of the water without, which is a function of its total height above the opening. If the air pressure is not high enough, water will, of course, enter, and if very low, there is danger of complete collapse of the unsupported ground areas. If too high, the air pressure will overcome that due to the water and the air will force its way out through the ground, through increasingly larger openings, until it all rushes out suddenly in a “blowout.” The pressurized atmosphere gone, the water then is able to pour in through the same opening, flooding the workings.
[5]Ideally, the pressure of air within the work area of a pneumatically driven tunnel should just balance the hydrostatic head of the water without, which is a function of its total height above the opening. If the air pressure is not high enough, water will, of course, enter, and if very low, there is danger of complete collapse of the unsupported ground areas. If too high, the air pressure will overcome that due to the water and the air will force its way out through the ground, through increasingly larger openings, until it all rushes out suddenly in a “blowout.” The pressurized atmosphere gone, the water then is able to pour in through the same opening, flooding the workings.
Index
Agricola, Georgius,215,216Barlow, Peter W.,221,227Beach, Alfred Ely,224,227-229,231,237Brunel, Marc Isambard (the elder),204,205,217,218,221,224,229,231,236Burleigh, Charles,212,213Burleigh Rock Drill Company,212Burr, S. D. V.,236Cochrane, Sir Thomas,231,232Copperthwaite, William Charles,224Doane, Thomas,210,212,213,215Drinker, Henry S.,224,237Greathead, James Henry,204,218,221,224,229,231,235-237Gwynn, Stuart,210Haskin, DeWitt C.,204,232,234-236Haupt, Herman,204,209,210Hobson, Joseph,237Latrobe, Benjamin H.,208,209Law, Henry,218Mowbray, George W.,213,215Nobel, Alfred B.,213Putnam Machine Works,212Shanley, Walter,212Shanley Bros.,215Sommeiller, Germain,210Storrow, Charles S.,210Tweed, William Marcy (Boss),229Weale, John,218
Transcriber’s NotesAll obvious typographical errors corrected. Formatting inconsistancies and spelling were standardized. Paragraphs split by illustrations were rejoined. TheIndexwas extracted from the full publication Index.Transcription of the text inFigure 22. The text was transcribed with a slight modification to the figure description portion.OPEN TO THE PUBLIC EVERY DAY(Sundays excepted)from Seven in the Morning, until Eight in the Evening,THE THAMES TUNNEL.Fig. 1 shows a transverse section of the Thames, and beneath it a longitudinal section of the Tunnel, as it will be when completed; with the ascents in the inclinations in which they will be finished.Fig. 2 shows the two arched entrances of the Tunnel from the shaft.Fig. 3 is a representation of the iron shield, and shows a workman in each of the compartments.The Entrance to the Tunnel is near to Rotherhithe Church, and nearly opposite to the London-Docks. The nearest landing place from the river is Church Stairs. The Greenwich and Deptford coaches which go the lower road, start hourly from Charing-cross, and Gracechurch-street, and pass close by the works at Rotherhithe.Books relative to the Tunnel may be had at the works.The Public may view the Tunnel every day (Sundays excepted) from Seven in the morning until Eight in the Evening, upon payment of One Shilling each Person.The extreme northern end of the Tunnel is for the present secured by a strong wall; but visitors will find a dry, warm, and gravelled promenade, as far as to almost the centre of the river, and brilliantly lighted with oil gas.The entrance is from Rotherhithe Street, and by a safe, commodious, and easy stair case.H. Teape & Son, Printers, Tower-hill, London.
Transcriber’s Notes
All obvious typographical errors corrected. Formatting inconsistancies and spelling were standardized. Paragraphs split by illustrations were rejoined. TheIndexwas extracted from the full publication Index.
Transcription of the text inFigure 22. The text was transcribed with a slight modification to the figure description portion.OPEN TO THE PUBLIC EVERY DAY(Sundays excepted)from Seven in the Morning, until Eight in the Evening,THE THAMES TUNNEL.Fig. 1 shows a transverse section of the Thames, and beneath it a longitudinal section of the Tunnel, as it will be when completed; with the ascents in the inclinations in which they will be finished.Fig. 2 shows the two arched entrances of the Tunnel from the shaft.Fig. 3 is a representation of the iron shield, and shows a workman in each of the compartments.The Entrance to the Tunnel is near to Rotherhithe Church, and nearly opposite to the London-Docks. The nearest landing place from the river is Church Stairs. The Greenwich and Deptford coaches which go the lower road, start hourly from Charing-cross, and Gracechurch-street, and pass close by the works at Rotherhithe.Books relative to the Tunnel may be had at the works.The Public may view the Tunnel every day (Sundays excepted) from Seven in the morning until Eight in the Evening, upon payment of One Shilling each Person.The extreme northern end of the Tunnel is for the present secured by a strong wall; but visitors will find a dry, warm, and gravelled promenade, as far as to almost the centre of the river, and brilliantly lighted with oil gas.The entrance is from Rotherhithe Street, and by a safe, commodious, and easy stair case.H. Teape & Son, Printers, Tower-hill, London.
Transcription of the text inFigure 22. The text was transcribed with a slight modification to the figure description portion.
OPEN TO THE PUBLIC EVERY DAY(Sundays excepted)from Seven in the Morning, until Eight in the Evening,
THE THAMES TUNNEL.
Fig. 1 shows a transverse section of the Thames, and beneath it a longitudinal section of the Tunnel, as it will be when completed; with the ascents in the inclinations in which they will be finished.
Fig. 2 shows the two arched entrances of the Tunnel from the shaft.
Fig. 3 is a representation of the iron shield, and shows a workman in each of the compartments.
The Entrance to the Tunnel is near to Rotherhithe Church, and nearly opposite to the London-Docks. The nearest landing place from the river is Church Stairs. The Greenwich and Deptford coaches which go the lower road, start hourly from Charing-cross, and Gracechurch-street, and pass close by the works at Rotherhithe.
Books relative to the Tunnel may be had at the works.
The Public may view the Tunnel every day (Sundays excepted) from Seven in the morning until Eight in the Evening, upon payment of One Shilling each Person.
The extreme northern end of the Tunnel is for the present secured by a strong wall; but visitors will find a dry, warm, and gravelled promenade, as far as to almost the centre of the river, and brilliantly lighted with oil gas.
The entrance is from Rotherhithe Street, and by a safe, commodious, and easy stair case.
H. Teape & Son, Printers, Tower-hill, London.