GB496581A - An improved method of driving tunnels under water or in water-bearing strata - Google Patents

Abstract

496,581. Tunnelling ; cofferdams. HALLINGER, G. June 3, 1937, No. 15436. [Classes 68 (i), 68 (ii), and 85] In driving tunnels under water or in waterbearing strata with the aid of a tunnelling shield, timbering or other sheathing, the site is first enclosed by piling either at the sides and ends of sections or throughout at the sides, the piling extending from above water level to an impervious stratum, or at least to below the bottom of the tunnel, and the shield &c. being driven through the enclosed site. In waterbearing strata, sheet piling w, Fig. 3, is driven throughout the length of the tunnel or of the water-bearing strata, or in sections shut off by sheet piling w<1>, the piling extending into an impervious layer or below the floor of the proposed tunnel. If two or more tunnels are to be driven, intermediate walls w<2>, Fig. 6, may also be driven. When working below water, the spaces between the pilings may be filled with earth d, and dams e of earth may also be formed externally, the transverse walls w<1> being then extended laterally, preferably at an angle, to prevent the dams being washed away. A cover f, which may be curved, may be placed on the earth between the walls w. In Fig. 7, the walls w are connected by hinged ties h tightened by turnbuckles i, and conerete j is then placed on to the water bed and round the ties h by means of hoppers k ; earth may be placed on the concrete and dams e formed as in Fig. 6. After construction of the tunnel, the piles may be removed or cut off at the level of the concrete j; the cut-off sections may be welded together for further use. In Fig. 8, the piling w forms part of the casing in which the tunnel lining is formed, with or without a separating layer n. If the upper part of the tunnel is formed in advance of the lower part, brackets m are provided on the piling to support the upper part of the lining. Weak concrete o may be filled in between the concrete j and lining. In Fig. 10, the upper part s<1> of the lining is preformed and lowered in sections on to the river bed or into a trench y formed therein; alternatively, iron framework t, protected as by sprayed cement and provided with a sheet-metal facing u, is lowered, sections of the framework being connected as by Z- members p, Fig. 11, and packings q, and fixed to the piles, the framework being then filled with concrete through hoppers v. Water is then pumped out to permit the lower part of the tunnel to be excavated and lined.