| 摘要 |
PROBLEM TO BE SOLVED: To allow efficient execution. SOLUTION: A double pipe comprising an inner pipe 5 and an outer 2 bendable respectively is used, and the inner pipe 5 is advanced into the ground from the ground surface around an existing structure CS. An insertion hole H reaching at least the lower section of the existing structure from the ground surface around the existing structure CS is formed by the inner pipe 5, and the outer pipe 2 is inserted into the insertion hole formed in sequence. When the outer tube 2 is inserted to reach at least the lower section of the existing structure CS, the inner pipe 5 is recovered, with the outer pipe 2 left, then improvement countermeasures are applied to the lower ground of the existing structure CS by using the outer tube 2 as a casing pipe or the like for inserting a chemical injection pipe, for example.
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