| 摘要 |
PROBLEM TO BE SOLVED: To reduce looseness of a natural ground to the extent possible and eliminate a risk of omission of a washer when a measurement unit is removed from a lock bolt.SOLUTION: The natural ground change state detection structure includes: a washer 11 which is extrapolated in a projection of a lock bolt 10 from a natural ground 3; a nut screwed into a male screw part 10a of the projection so as not to come in contact with the washer 11; a housing 13 which is provided to come in contact with the washer 11, has the nut loosely inserted in its hollow part and has a communication part provided on its lateral side; a lock bolt axial force measuring unit which is extrapolated in the male screw part 10a so as to come in contact with the housing 13; and a nut for measuring 16 which is screwed into the male screw part 10a and supports contact of the lock bolt axial force measuring unit with the housing 13, and contact of the housing 13 with the washer 11. The nut is screwed by a screwing operation via the communication part to come in contact with the washer 11 and, in that state, the nut for measuring 16 is loosened so that the nut for measuring 16, the lock bolt axial force measuring unit and the housing 13 can be detached. |
