| 摘要 |
PROBLEM TO BE SOLVED: To provide an external cone undercut system exhibiting high supporting ability even applying a dynamic load or even against cracked concrete. SOLUTION: In order to form a plastic hinge part 5 by extending an enlarged piece 4 from the plastic hinge part 5 to the front loose end of a base body 6, the outside diameter (a) of a base body 2 is reduced from the hinge part 5 to an annular shoulder part 6 located adjacently to the rear and opposed to a driving direction S, diameter is enlarged again from the hinge part 5 to the direction of the front loose end of the base body 2, the circumference of the enlarged piece 4 located adjacently to the plastic hinge part 5 is surrounded by an enlarged sleeve 8, the front area of at least the driving direction S of the enlarged sleeve 8 is enlarged in a radial direction, and the maximum outside diameter (h) of the enlarged sleeve 8 is set smaller than or equal to the maximum outside diameter (a) of the base body 2.
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