GB835804A - Improvements relating to methods of forming foundations - Google Patents

Abstract

835,804. Foundations. PRE-STRESSED CONCRETE CO. Ltd. June 30, 1958 [July 18, 1957; Oct. 1, 1957; Nov. 25, 1957], Nos. 22820/57, 30702/57 and 36703/57. Class 20(2) [Also in Group XXI] A method of founding a permanent structure in soil, wherein a foundation block is dropped and the kinetic energy acquired in falling causes it to penetrate the ground to such a depth as to develop the required load bearing capacity. Two methods of achieving the necessary kinetic energy are described. In the first the block is raised by a helicopter and in the second the block is raised by a gantry only a short distance and is accelerated by rockets. The weight of the block may be increased at the time of dropping by a detachable weight which is subsequently recovered and re-used. The use of such a weight will usually bring the centre of gravity of the block sufficiently near to the bottom to ensure aerodynamic stability, but fins or a drag parachute may be used. Dimensional examples of blocks are given, showing the penetration achieved. The height from which the blocks must be dropped can be determined by dropping small diameter graduated cylinders. Foundation blocks of various shapes are described e.g. flat-ended, pointed, shouldered and with a helical finthe last two intended to have increased resistance to extraction. In cases where a group of foundations are formed with separate foundation blocks 45 and 50 (Fig. 27) to carry a single structure, such as a pylon, the blocks are preferably dropped or projected connected together by chains or ropes 47. As they fall all the blocks are given a rotary movement which causes the blocks 50 to fly out. Rotation is produced by tangentially arranged rockets or inclined fins. A foundation block designed to resist an upward pull is shown at Fig. 30. Two fins 64 lie initially within the chamber 59 with their ends in the slots 60. The block is dropped with parts in the position shown in full lines but after it has penetrated the ground a pull on the cable 62 moves the cone 61 and causes the fins 64 to project from the block. An alternative design, Fig. 33 comprises four similar segments 76 connected by a hinge 77. In the space enclosed by the segments is a plug 79 which can be pulled by the cable 81 to expand the segments. Fig. 36 shows a concrete cylinder 92 which has pivoted fins 94 which rotate to project from the cylinder when it is pulled upward and which are locked in the extended position by grout injected through a duct 98. In a modification the fins are moved outward by a cable operated cam.