| 摘要 |
PROBLEM TO BE SOLVED: To provide an underwater filling method in which underground water pollution caused by the separation of a filler in water can be effectively prevented and an arbitrary section in an underground cave 2 can be limitedly backfilled. SOLUTION: A first filler 4 is injected to both ends of a backfill section E of an underground cave 2 through an injection pipe 3. An appropriate quantity of underwater inseparate admixture effectively preventing separation of materials in water is added in the first filler 4, and its specific gravity is adjusted to be slightly larger than 1, 1.05 for instance by mixing fine air bubbles. Hence, it settles owing to its own weight and it is prevented from horizontally spreading to form a state where the underground cave is closed. Subsequently, a second filler 6 is injected into the closed space through injection pipes 5. The mixing ratio of the underwater inseparate admixture in the second filler 6 is lower compared with the first filler and its specific gravity is larger than that. The second filler is securely filled in the limitted section because it is limitted to horizontally spread by the first filler 4.
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