GB865567A - Improvements in or relating to the construction of tunnels - Google Patents

Abstract

865,567. Tunnels. BERTLIN, D. P. Feb. 13, 1959 [Jan. 28, 1958], No. 2843/58. Class 85. A tunnel is built on a sea or river bed from a multiplicity of interfitting lengths 2, each length initially having a removable bulkhead 31, 32 near each end, by sinking a second tunnel length and guiding it so that one end thereof mates with the end of a first tunnel length already on the sea bed and from which water has been removed up to bulkhead 31 near the end to be mated; sealing the tunnel lengths together; opening the bulkhead 31 in the first tunnel length manually from within the said length so as to remove water from the neighbourhood of the joint between the lengths; and then removing water from the second tunnel length by removing or opening the second bulkhead 32. The lengths 2 are handled by means on mobile platforms 4 and supporting legs 5 of the kind used for off-shore oil-well drilling, and are provided, at one end, with feet 10 which rest upon platforms 7 which are formed by depositing screed from a retractible and revoluble pipe having a blade at the lower end to form the level surface. The ends 9 of the length are socketed and the other ends are spigotted and each length is guided during lowering to the length last laid by connecting links 24 which are formed to embrace and slide down the cables 13 of the last laid length, so that, finally, because the stub axles 21 are much below the axis of the descending length, the links 24 pivot about the axles 14 and swing the spigot into the socket. The tunnel length is first floated to the platform 4, the cables 13 are placed in recesses in the faces of the links and retained therein by complementarily recessed cover plates which are bolted to the links, the length is flooded sufficiently to sink it, and the mating ends are joined. A packing 29 is compressed as the external pressure forces the last laid length into the previous one, and the joint is finished with lead caulking 35. Settlement in the tunnel may be countered when it occurs by injecting cement grout 36 through radial channels 37. The stub axles 14, 21 are on metal plates secured to the lengths by bolts with internal nuts, and when the length is laid, the plates and stub axles may be released by removing the nuts. The bulkheads are built-in sections 11 secured to a frame 12 extending across the tunnel section, and include a pressure gauge 33 and a valve 34 for releasing water from a length being laid, to the main length of the tunnel. The laid tunnel is flanked by banks of rubble and is covered by sand retained between the rubble banks. The tunnel is divided by a horizontal floor, the upper section being for road traffic and the lower for rail traffic. A ventilation shaft 42 has pipes 43 projecting upwardly' to above the sand covering, foul air being forced out of these pipes. A casing 44 guides a shut-off plate and also a slide carrying two non-return valves, which are used in alternation, to permit repair of either valve. A warning beacon is positioned where the tunnel emerges from the water.