CONCRETE CORE FALL PREVENTION FIXTURE AND FLOOR SLAB THROUGH HOLE FORMATION METHOD

To provide a concrete core fall prevention fixture which can prevent the fall of a concrete core generated upon forming a through hole when the through hole is blocked to a floor slab of an existing structure with an efficient measure, and a floor slab through hole formation method.SOLUTION: There is provided a concrete core fall prevention fixture 10 for supporting from below and recovering a concrete core CO generated when a floor slab S1 forming a concrete existing structure C is drilled so as to penetrate with a drilling rod R2 to form a through hole H1, and comprises: a bar stock 11; and a diameter expansion material 15 which is rotatably fitted to the bar stock 11 and changes a posture between a diameter reduction posture and a diameter expansion posture. When the fall prevention fixture 10 is inserted into a relatively small-diameter preceding introduction hole Ha which is formed at the floor slab S1 prior to the formation of the through hole H1, the diameter expansion material 15 lies in the diameter reduction posture, and when the diameter expansion material 15 bulges below the floor slab S1, the posture is changed to the diameter expansion posture, and the formed concrete core CO is supported with the diameter expansion material 15 in the diameter expansion posture.SELECTED DRAWING: Figure 6 【課題】既設構造物の床版に貫通孔を閉塞するに当たり、貫通孔の形成の際に生じるコンクリートコアの落下を効率的な措置にて防止することのできる、コンクリートコアの落下防止治具と、床版の貫通孔の形成方法を提供する。【解決手段】コンクリート製の既設構造物Ｃを形成する床版Ｓ１を、削孔ロッドＲ２にて削孔貫通して貫通孔Ｈ１を形成した際に生じるコンクリートコアＣＯを、下方から支持して回収する、コンクリートコアの落下防止治具１０であり、棒材１１と、棒材１１に回動自在に取り付けられ、縮径姿勢と拡径姿勢との間で姿勢変更する、拡径材１５とを有し、貫通孔Ｈ１の形成に先行して床版Ｓ１に形成されている、相対的に小径の先行導孔Ｈａに落下防止治具１０が挿通される際は、拡径材１５は縮径姿勢であり、床版Ｓ１の下方に拡径材１５が張り出した際に拡径姿勢へ姿勢変更し、形成されたコンクリートコアＣＯを、拡径姿勢の拡径材１５が支持する。【選択図】図６