Tun′nel-bor′er.
（
Civil Engineering.) A ram, operated by compressed air, for making excavations through rock.
It is said that the battering-ram was used by the ancient
Romans in making tunnels where their aqueducts had to pass through rocky strata.
The present device was invented by
Captain Penrice, an English engineer, and is reported to have been worked with satisfactory results in the quarries of Vaugirard, near
Paris.
a is the ram-head; its face is studded with removable cutters; it is fixed on the piston-rod
b, which is provided with a heavy counterweight
c, and is reciprocated by the admission of air alternately to either side of the piston through valves operated by the hand-lever
d. The air is received through the pipe
e, con nected with a flexible tube leading to the compressed-air engine outside of the tunnel.
The apparatus is mounted on trunnions upon a carriage, and the vertical angle of presentation of the ram is varied by means of the lever
f, which carries a pinion gearing with the toothed sector
g.
h is a handspike, which is inserted in holes in the rims of the truck-wheels for the purpose of maneuvering the carriage.
i shows the cutting devices.
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Tunnel-borer. |
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Dowd's tunneling-machine. |
Fig. 6780 is
Dowd's tunneling-machine for river-beds and treacherous ground.
It has a cylindrical or elliptical shield
a which is pushed against the heading of soil or silt, and iron sections are built up behind it as it advances, forming a tunnel
b; a packing is introduced at the junction of the two.
A scraper in advance of the tube is revolved by gearing and any suitable motor inside.
Water is introduced through a tube in the axis of the scraper-arm.
The mud is withdrawn from the face of the shield and ejected by pipe
i above the tunnel casing.
The tube
w is applied when an obstructing stone or old anchor may be met with, to excavate a hole and sink the obstruction out of the way. One of the lower figures shows the mode of locking the tubes together, and the other the mode of running in a section.
