Patent GB-1049745-A (GB)
Title: A submarine channel dredging system for the laying of flexible pipes or cables
IPC: E02F5/10
Filed: 1963-07-18
Abstract: 1,049,745. Laying pipes. R. HARMSTORF. July 18, 1963 [Aug. 22, 1962], No. 28393/63. Heading F2P. [Also in Divisions E1 and H2] A submarine channel dredging equipment for simultaneously cutting a channel in the bed 20 of a river or other water course and laying one or more continuous flexible pipes or cables in the channel, comprises a vertically extending dredging box 3 carried by a water craft 1 and having at the leading side thereof hydraulic means including a channel for water under pressure leading downwardly to a number of nozzles situated below the surface of the bed when in operation, and having at the trailing side thereof a shoot for guiding the pipes or cables into the dredged channel. The dredging box has suspension means capable of applying a downward thrust thereto, a towing hawser extending forwardly from the leading side, and means for steering the box comprising a pair of control hawsers 5 anchored thereto and extending at an angle on opposite sides of the direction of the channel to take-up gear for winching the hawsers. Two barges are lashed together and two derricks 10 and 98 are supported on the mast 102 of one of the barges and from them are suspended, respectively, the dredging box 3 and flexible pipe or cable carriers 30. The box 3, with nozzles arranged along its edge, is suspended by a rope 64 on one side of barge 1 and held by the cables 5, which are guided to winches on the other barge whereby, by differences in the amounts of winding and/or unwinding, the box 3 may be steered. In addition, cables are attached to the top of the box 3 and are operated by winches 18. The box, Fig. 6 (not shown), is in two parts, a conduit channel and a water channel. By means of a series of doors 54 the conduit channel 31 can be opened to allow the insertion of lengths of piping or cables. Three are laid alongside one another in separate grooves defined by ridges 55. The pipes or cables are wound on drums, on one of the barges, and enter the conduit channel 31 through an inlet member which is packed with grease to assist their passage through the grooves. To prevent the pipes from floating as they emerge from the rear of the box 3, a tube passes liquid concrete or gravel on to the pipes or the pipes are filled with water. High pressure water produced by a pump is led to the head of the box through a hose. The water channel has three compartments 34, 38 and 43. Water under pressure passes direct from the head into the middle compartment 38 whence it leaves through nozzles 39, 40, 41, 42. The inlets from the head to the compartment 34 are controlled by valves which can be opened or closed to supply additional water as required to upper nozzles 35, 36, 37 and lower nozzles 44, 45, 46, 47 to scour away the earth in front of the box. A suction tube 49, passes upwards through the compartment 43 and carries suction nozzles 50. A vacuum is created in the suction tube 49 by the action of the water jets leaving the nozzles and thus a mixture of water and soil is carried up the suction tube, whence it may be transferred to the flexible pipe already laid. Nozzles 53 with rearward extensions 103 cause water jets to loosen the soil at the place where the pipes leave the rear of the shoot 31. A vibrator is arranged on the head member and reduces friction between the box and the earth. The frequency of vibration is varied to suit the geological formation of the soil. The barge is insulated from vibration by a roller. The whole apparatus is advanced across the river bed by the pull of the tow line, either from a winch on the far bank, or from a winch 22 on one of the barges from which the line passes round a pulley on the bank. As the dredging box 3 goes deeper, distance members are fitted between it and the head 14. The operation may be observed by an echo recording apparatus. The piping may be kept under pressure during the operation. In hard soil and rock a pre-blasting operation is used. To facilitate cable laying, a pull-through wire is placed in the cable-enclosing pipe and the latter may be filled with oil or water in order to decrease the cable weight by the buoyancy volume thereof.