| 摘要 |
PROBLEM TO BE SOLVED: To provide a decompression construction method of a pneumatic caisson for enabling work by a worker in a workroom even in construction of a great depth.SOLUTION: A water cutoff part 7 is formed in an outer peripheral surface of a caisson 1 above a blade port part 4 of the caisson 1 under a condition that a ground upper part is a water permeable layer 11 and its lower part is a water impermeable layer 12. Spring-out of underground water is almost none in the uniform water impermeable layer 12, and underground water of the upper water permeable layer 11 flows in. However, at the time when requiring an entrance of at least the worker in sinking construction, since atmospheric pressure in a workroom 2 can be reduced by applying water cutoff means (the water cutoff part 7) for blocking up a clearance 6 with the water impermeable layer 12 above a friction cut part 5, even in the construction of the pneumatic caisson of the great depth, internal atmospheric pressure in the workroom 2 is set to 0.7 MPa or less, and ideally, to 0.4 MPa or less, to thereby enable going in and out to the workroom 2 of the worker. |
