WINZE DIGGING PLUG WITH DIAMETER-EXPANDABLE AND ANNULAR RUBBER MEMBER FORMED FROM DECOMPOSABLE RUBBER MATERIAL

摘要

PROBLEM TO BE SOLVED: To provide a winze digging plug capable of reducing cost of winze digging or shortening a process by surely performing winze hole filling and winze processing under severe development drilling conditions and facilitating removal or channel securing.SOLUTION: The winze digging plug includes: a mandrel; at least one diameter-expandable and annular rubber member placed on an outer peripheral surface of the mandrel; and at least one slip. The winze drilling plug is characterized in that (i) the mandrel is formed from a decomposable material, (ii) the at least one diameter-expandable and annular rubber member is formed from a decomposable rubber material in which a reduction rate of 50% distortion compression stress after 24-hours immersion in water at 150°C with respect to the compression stress before the immersion is 5% or more and/or a decrease rate of a mass after 72-hours immersion in water at 150°C with respect to a mass before the immersion is from 5 to 100%. The winze digging method includes using the winze digging plug to perform filler processing of the winze hole and then partially or entirely disassembling the plug.