THE SIMPLON TUNNEL
IN order to reduce the distance between Paris and Milan to 979 kilometres is now being built the tunnel through the Simplon Pass, which, when completed, will be the most stupendous engineering feat of its kind ever performed— once thought impossible, because of the great depth which had to be reached. The distance between the French capital and Milan is 1,058 kilometres by the Mont Cenis tunnel, and 1,068 by the St. Gothard. (A kilometres is 3,280 feet.) The highest point of the Simplon tunnel is 705 metres; of the St. Gothard, 1,154 ; of the Mont Cenis, 1,294. The expense of building it at the time required to finish it will be much less than in the case of the other two tunnels. In that of the Mont St Gothard tunnel, with its costly approaches—nearly as costly as the tunnel itself—seven and one-halfyears were consumed in the construction ; that of the Mont Cenis took thirteen years;that of the Simplon is to occupy only five and one-half years (a seduction of twenty-five per cent, over that of the St. Gothard tunnel), while its cost will be $55,500,000. The approaches at each end are level; hence there is no need of such colossal works as in the case of the other two tunnels. It will be well ventilated during construction, as two-single track tunnels are to be built, instead of one of two tracks. One of these tunnels (a view of which, with two illustrations besides, accompanies this notice by courtesy of the Scientific American), when completed, will serve as a huge ventilating tube for the other, as yet non-completed tunnel Thus, instead of from one and one-half to two cubic metres of air per second being supplied to the workmen, as in the case of the St Gothard tunnel, the laborers are supplied with twenty-five cubic metres, fly the use of sprayers, also, the thermometers have never registered higher than 32° C.—the maximum temperature in the St. Gothard—instead of the 40°C. anticipated by many engineers The sanitary conditions (which include bathrooms entered by covered ways from the workings) are so good that, while the workmen in the St. Gothard tunnel were constantly being stricken down by disastrous epidemics, those in the Simplon tunnel are very rarely sick at all.
The work was begun in the fall of 1898. Sufficient power has been provided. Two thousand horsepower or thereabouts was available on each side of the mountain, the chief purpose of which was to drive the ventilating apparatus, hydraulic compressors, and workshop tools and dynamos. In the north, waterpower is obtained from the Rhone: in the south, from the Diverts (illustrated herewith) The water is led for for many miles from its source to the powerhouse through huge flumes, whose diameter exceeds one metre a half. (A metre is 39 37 inches.)
On the south side, the rock up to the 3,720th kilometer was perfectly dry; but. on reaching the 3,825th kilometre, springs were found yielding from four to five litres of water per second. (A litre equals 2,113 American pints) The galleries of schist were moist, yet not inconveniently so; but on reaching the 900th kilometre, springs yielding as much as 160 litres per second were found whose temperature varied from 25° to 30°. On this side (as on the north side, also, in the beginning), the progress made has been slow—five metres daily, as against six on the north, made in three reliefs of six and one-half to seven and one-half hours each. On the north side are required seven to eight drill holes sunk to the depth of 1.8 to two metres: on the south side, 1.2 to 1.4 metres are called for, needing five kilogrammes of dynamite as against four on the north. The consumption of dynamite, it may be noticed, is from 13,000 to 15,000 kilogrammes a month (28,000 to 33 000 pounds.)
The geological formations from north to south along the line of the tunnel are as follows: Calcareous mica schist and Antigoria gneiss, 6,330 metres; Teggialo lime, calcareous mica schist, mica schist and gneiss, Valle lime stone, 9,700 metres; mica and gypsum on the banks of the Rhone, 8,700 metres. The rock drills (illustrated herewith) used are the invention of Mr. Brandt, one of the engineers. According to the hardness of the rock, the water pressure on the north side at the drill varies from sixty to seventy atmospheres; on the south side, from ninety to 100. These drills are the efficient causes of the rapid progress made daily. So rapid is this progress that about one-half of the work seems already completed, and, barring unforeseen hindrances, the tunnel should be open for traffic before five and one-half years, the time set down in the contract. For every day between the actual day and the contracted day that the tunnel is ready for traffic, the engineers will receives bonus of $100; for each day it remaius unfinished over that appointed for the tunnel to be finished, a fine of the same amount will be inflicted.