CONSTRUCTION OF SHAFT

PURPOSE:To make shaft sinking executable so safely by solving problems on the shortening of a construction period necessary for the high depth shaft, the promotion of cost down, the countermeasure of high hydraulic pressure and so on. CONSTITUTION:A slot 18 is formed up by a large diameter reverse circulation drill 16 equipped with a reamer bit 32. Next, an expanded slot part 34 is formed at a tip part of the slot 18 with the reamer bit 32 of the reverse circulation drill 16. In addition, a cylindrical watertight structure with a cylindrical body in a contracted state, projectable to the side, at a tip part, is installed in this slot 18. In succession, the cylindrical body is expanded in the expanded slot part 34 and, after forming a pit mouth for shield starting use, a hole wall of the slot 18 and each outer circumference of the watertight structure and the cylinderical body are solidified in slurry. The cylindrical body contained in the tip part of the watertight structure has a partition wall partitioning off the slurry side and the cylindrical body inner part, while the cylindrical body inner part is connected to a high hydraulic pressure part, and pressurized water is fed to this high hydraulic pressure part, thereby making it project into the slurry from an opening part formed at the tip part side of the watertight structure.