| 摘要 |
PROBLEM TO BE SOLVED: To provide a long-size prelining construction method not requiring the inner surface of a tunnel to increase in width and capable of preventing decrease in strength of a roof. SOLUTION: This long-size prelining construction includes inserting, prior to excavation of a tunnel 10, a number of pipes 11 diagonally into portions around the upper half of the cross section of the tunnel 10 to be excavated, then injecting a ground improver 14 via the pipes 11 into the portions around the upper half of the cross section to be excavated to improve the natural ground, and excavating the tunnel 10 thereafter. In this AGF construction, the pipes 11 are curved and inserted into the upper half of the cross section in such a way as to project in the radially outer direction of the tunnel 10.
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