| 摘要 |
PROBLEM TO BE SOLVED: To avoid the retention of sewage in a pit and to reduce the construction period for stage construction for pit portion by replacing the sewage in the retention pit, backfilling with recycled sand, and further placing leveling concrete on the top surface of the pit. SOLUTION: Sewage in a retention pit 4 is removed and the pit is made vacant. Thereafter, recycled sand 10 is poured into the pit 4 for backfilling purpose. At this time, the pit is filled up with recycled sand 10 and the pit 4 is backfilled definitely. Next, leveling concrete is placed to the top surface portion of the pit 4 and a stage 11 is built. In this way, the pit 4 is completely shielded so that no sewage flows to the pit 4 any more and the generation of poisonous gas can be prevented. On the other hand, no disassembling work is performed for this stage 11 even though a repair work in a manhole 1 is completed and the stage remains as it is. By doing this, scaffolding members become unnecessary and the construction materials can be carried in and out more easily thereby permitting a shorter construction period.
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