Preservation hole manner, part casing and preservation hole device null for preservation hole

摘要

PROBLEM TO BE SOLVED: To provide a hole keeping method which can easily eliminate the fear of collapse at a weak part without reducing the diameter of a dug hole, and to provide a hole-keeping partial casing for use in the hole keeping method, and a hole keeping device for inserting and fixing the partial casing into the bole.;SOLUTION: This hole keeping method forms an enlarged hole part 7 by partially enlarging a weak part 2 of collapsible nature in a hole 1 dug, then inserts a cylindrical hole-keeping partial casing 8 whose diameter can be increased into the hole while its diameter is reduced, and increases the diameter of the partial casing 8 in the enlarged hole part 7 to fix the partial casing 8 to the hole wall of the enlarged hole part 7. The hole-keeping partial casing 8 for use in the method comprises a plurality of casing pads each being long-sized and having an arcuate cross section and vertically arranged into a cylindrical shape, a plurality of collapsible link mechanisms which interconnect the adjacent casing pads in such a manner that the interval between the adjacent casing pads can be increased or reduced, and a locking mechanism for fixing the movements of the link mechanisms while the adjacent casing pads are held apart.;COPYRIGHT: (C)2001,JPO