METHOD FOR FORMING OPENING IN PLAIN CONCRETE BODY

PROBLEM TO BE SOLVED: To economically form an opening. SOLUTION: In forming an opening, right and left longitudinal sections at a part for making the opening are cut by a wire saw to form a longitudinal sectional line. A core boring hole 20 is formed in the part of making the opening partitioned by the longitudinal sectional line. The core boring hole 20 comprises a horizontal core boring hole 20a and a perpendicular core boring hole 20b. A cylinder head 24 is inserted in each horizontal core boring hole 20a on the first stage, and the cylinder heads are simultaneously expanded to form a horizontal breaking line B1 by the breakage. Next, the cylinder head 24 is inserted in each perpendicular core boring hole 20b opened in a part above the horizontal boring holes 20a on the first stage, and the cylinder heads are expanded to form a longitudinal cutting line C1. When the longitudinal cutting line C1 is formed, a part above the horizontal boring hole 20a on the first stage is completely separated by the part of the longitudinal cutting line C1 and divided into blocks 34. The divided blocks 34 are successively removed.