CAISSON METHOD

PROBLEM TO BE SOLVED: To provide a caisson method in which a pore water pressure in the vicinity of an excavated ground surface is lowered partially and the atmospheric pressure of an airtight workroom is brought near to an atmospheric pressure and a working can be conducted. SOLUTION: In the caisson method, the airtight workroom S is formed under a workroom slab 32 and a ground is excavated. Groundwater pushed down at the atmospheric pressure of the workroom S is made to flow into the pipe 51 at the low atmospheric pressure from the inside of the pipe 40 and can be pumped up by repeating a process, in which a casing pipe 40 is buried previously to the ground 10, a collecting pipe 51 having a collecting port 52 in a lower section is inserted into the pipe 40 and the ground 10 is excavated under the state, in which water in the pipe 51 is pumped up, sucking air in the pipe 51, every time the pipe 51 is lowered along the inside of the pipe 51. Since the atmospheric pressure in the pipe 51 is lowered, the pore water pressure in the vicinity of the excavated ground surface 20 is lowered partially and the ground can be excavated under the state in which the atmospheric pressure of the workroom S is brought close to the atmospheric pressure. COPYRIGHT: (C)2005,JPO&NCIPI