| 摘要 |
PROBLEM TO BE SOLVED: To provide natural ground prelining construction for a tunnel whereby a uniform improver can be constructed for the natural ground around a steel pipe to provide a stable prelining effect. SOLUTION: A steel pipe 1 fitted with a sleeve 11 is inserted into the natural ground, after which an injection pipe having packers 22, 22 in front of and behind an injection hole is inserted into the steel pipe. With the injection hole 21 facing an injection hole 10 and with the front and rear packers 22, 22 working on the inner surface of the steel pipe 1, sealing grout SG is forcibly fed through the injection pipe and discharged from the injection hole 21 through the injection hole 10 while deforming the sleeve 11. This first process is effected for each injection hole 10,10... to pack the sealing grout SG around the steel pipe 1. Thereafter a second process, in which grout for penetrative injection is forcibly fed through the injection pipe and discharged from the injection hole 21 through the injection hole 10 while deforming the sleeve 11, is effected for each injection hole 10,10... to cause the grout for penetrative injection to penetrate the natural ground around the steel pipe 1 while breaking the sealing grout SG, so as to improve the natural ground.
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