THE BORING MACHINE USED IN THE PRELIMINARY CONSTRUCTION OF THE ENGLISH CHANNEL TUNNEL.
In cutting the Mersey Tunnel, which was completed in 1886, machinery was used for some of the work. The machine bored partly to a diameter of seven feet four inches, but hand labour had to be largely depended upon. The plan pursued was to sink a shaft on either side of the river and drive a heading, sloping upward through the sandstone to the centre; this heading acting as a drain for any water which might appear. The thickness between the arch of the tunnel and the river bed is thirty feet at its least, and the tunnel, which occupied about six years in construction, and of which the engineers were Messrs. Brunlees & Fox, is provided with pumps raising some thirteen million gallons of water daily. As in the case of the Severn Tunnel, ventilation is provided for by huge fans.
A boring machine was also used in the preliminary efforts for the construction of a tunnel under the English Channel. Holes, seven feet across and to the length of 2000 yards, have been bored by a compressed air machine, working with two arms furnished with teeth of steel. The construction of the tunnel is held to be quite feasible from an engineering point of view, and it is believed that it would pass through strata impervious to water, such as chalk marl and grey chalk.
Still, the huge tunnel at Blackwall, which was carried out by Mr. Binnie, Chief Engineer of the London County Council, with Mr. Greathead and Sir Benjamin Baker as Consulting Engineers, is probably one of the most daring and stupendous enterprises of the kind ever undertaken. To hollow out a subway hundreds of feet long under the Thames, only seven feet from the bed of the great river, and through loose gravelly soil, was a great triumph. It was achieved not by uncalculating bravery, but by a wise combination of cool courage, superb skill, and admirable foresight.
To design effectively, to provide for contingencies, to be daunted by no difficulties—these qualities help to produce the Triumphs of Engineers, as well as do great inventive skill, the power of adapting principles to varying circumstances, and high-spirited enterprise in planning and conducting noble and useful works. These works may well rank among the great achievements of man’s effort and the wonders of the world.
THE END.
LORIMER AND GILLIES, PRINTERS, EDINBURGH.
