| 摘要 |
PROBLEM TO BE SOLVED: To enable installation of a precedent underground displacement gage without making a widened tunnel section.SOLUTION: The following processes are carried out: an outer tube installation process in which an outer tube 5 is installed from a tunnel face 2 toward a starting point 3 of displacement measurement in a natural ground 1 above the scheduled construction position of a tunnel; an inner tube insertion process in which an inner tube 6 is inserted into the outer tube 5 and a solidification material 8 is filled in an inner space 7 of the outer tube that is outside of the inner tube; a displacement gage installation process in which a bendable displacement gage 14 is inserted into the inner tube 6 that opened on a tunnel drilling surface 13 near the starting point 3 of displacement measurement when the outer tube 5 and inner tube 6 were broken off in a tunnel drilling process; and a bent tube installation process in which an end 10 of a bent tube 9 is connected to the outer tube 5 that opened on the tunnel drilling surface 13 near the starting point 3 of displacement measurement along with the inner tube 6, and the other end 11 of the bent tube 9 is placed facing toward a tunnel pit 21 at a location rearward of the tunnel drilling direction than a support 12 installed near the starting point 3 of displacement measurement. |
