| 摘要 |
PROBLEM TO BE SOLVED: To provide an invert as a convenient tool capable of efficiently forming a manhole. SOLUTION: A deformable cylindrical body 20 formed to a semi-circular arc-shaped semi-cylindrical body for the cross section in conformity with an invert cross sectional shape and a shape-keeping portion 30 which bends and supports the cylindrical body portion 20 to an arbitrary curve shape are arranged at predetermined intervals in the longitudinal direction of the cylindrical body portion 20. The shape-keeping portion 30 comprises two diaphragms 32a, 32b overlapped as a pair formed to a ring shape with the same center as cylindrical body portion's at the inner surface side of the cylindrical body portion 20, an outer peripheral edge portion of the lower half side is embedded in the cylindrical body portion 20, and adjusting means such as bolt 38 or the like is provided permitting to adjust the mutual interval of the diaphragms 32a, 32b at the arbitrary position in the peripheral direction.
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