| 摘要 |
PROBLEM TO BE SOLVED: To solve problems of a conventional barrier method using a sheet stuck to a grid and a bellows method using ring type ribs arranged in several parts in the vertical direction of a cylindrical sheet for preventing mud, cement milk and the like adhering to a rod and a screw from scattering around when the screw is pulled out from the ground during excavation work carried out while injecting a hardening material such as the cement milk, wherein a rod length is redundant in the barrier method allowing no vertical extension/ shrinkage, and damage is caused in the bellows method by the shrunk bellows protruding inward and touching the screw and a wire rope. SOLUTION: In a dispersion preventing body, a lower ring 2 protruded outward is arranged in the lower end of a sleeve 1, and an upper ring 3 protruded inward is arranged in the upper end of the sleeve 1. Several dispersion prevention bodies with different dimensions are stacked while mutually overlapping in their circumferences on the outside and the inside for allowing expansion and shrinkage. COPYRIGHT: (C)2003,JPO
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