The Simplon tunnel was begun in 1898 and completed in 1905. It lies between Brigue, Switzerland and Iselle, Italy. It has a length of 22.3 m. and is over 30% longer than the St. Gotthard. The greatest depth below the surface is 7,005 feet. A novel method was introduced by driving two parallel headings (56 ft. apart, connected at intervals of 66o ft. by oblique galleries), which greatly facilitated ventilation and resulted in increased economy and rapidity of construction, while also insuring the health of the men. One of the headings was enlarged at once to 16 ft. 5 in. wide by 19 ft. 6 in. high, for a single track railroad, but the second was left to be enlarged and similarly used at a later date. (This was undertaken in TOTS. during the World War.
and completed a few years later.) Had one wide tunnel been made instead of two narrow ones, it would have been difficult to main tain its integrity; even with the narrow cross section employed, the floor was forced up at points in the solid rock from the great weight above, and had to be secured by building heavy inverts of masonry. About 2.5 m. from the portal at Iselle, the "Great Spring" of cold water was struck. It yielded 10,564 gal. per minute at 600 lb. pressure per square inch, and reduced the tem perature to F, the lowest point recorded. A spring of hot water was met on the Italian side which discharged into the tunnel 1,60o per minute with a temperature of 113° F. The maxi mum flow of cold water was 17,081 gal. per minute, and of hot water 4,330 gal. per minute. These springs often necessitated a temporary abandonment of the work. Water-power from the Rhone at the Swiss and from the Diveria at the Italian end provided the power for operating all plants during construction of most of the work. The material penetrated was gneiss, mica schist, limestone and disintegrated mica-schist. The average progress per 24 hours was 35 lin.ft. and the approximate cost £49 7s. per linear foot. Among the able engineers connected with this work must be mentioned Alfred Brandt, a man of remarkable energy and ability, whose drills were used with much success. He died early in the work of injuries received from falling rock.
A group of tunnels—the Tauern, Barengraben, Wocheiner and Bosruck—was undertaken by the Austrian Government in con nection with new Alpine railroads to increase the commercial territory tributary to the seaport of Trieste, which at one time was greater than Hamburg.
The Loetschberg tunnel, in the Alps of Switzerland, between Kandersteg and Gopperstein, is 9.04 m. long and the maximum
grade 0.38%. It is a double track railway tunnel, and its con struction was begun in Oct. 1906 and completed in Sept. 1911. It was originally planned to be 8.5 m. in length and straight. It passed beneath the ancient glacial gorge now filled with detritus and occupied by the Kander river, but at a great depth and it was supposed it would be in solid granite. After driving the heading for nearly 2 m. it broke through into the gorge which was filled with sand, boulders and water under great pressure. In the space of a few moments about 8,000 cu-yd. of the material was carried into the heading. Twenty-five men, the drills and all equipment were lost beyond hope of recovery. It was bulkheaded off and the line bent to throw it farther into the mountains and beneath the gorge and was then successfully completed, the length being increased one-half mile. The tunnel is operated electrically, using 15,00o volts, single phase, alternating current of 16 cycles.
The Connaught tunnel at Rogers pass on the Canadian Pacific railway, pierces the Selkirk range of the Canadian Rockies. It is 5 m. long and replaces a surface line 54o ft. higher up. Its con struction saves 5 m. of distance and replaced 5 m. of snow sheds in a distance of 13 miles. It is a double track tunnel, operated electrically and has a maximum grade of 2.2%. It was built between 1913 and 1916 and was the first American tunnel in which a parallel pioneer tunnel was used. Progress on the pioneer heading reached as high as 817 ft. in 3o days.
Much important tunnel construction has been done in Japan by the Japanese government railways. Probably the most notable is the Tanna tunnel, between Atami and Mishima, which was started in 1918 and is not yet (1928) completed, as extraordinary difficulties have been encountered. The tunnel is 4.89 m. in length and passes under two mountains and the valley between them. The maximum depth below the surface is 1,300 ft. and below the valley 600 feet. It is partly in soft ground and partly in rock. The rock is andesite. Several methods of excavation have been tried but difficulty with water prevails. At the Atami side, 17 cu.ft. per second at a pressure of 240 lb. per square inch enters the work, and at the Mishima side 48 cu.ft. per second. The actual cost of construction up to the present (1928) has been $500.00 per linear foot.