METHOD FOR ASSEMBLING INNER FORM

PROBLEM TO BE SOLVED: To provide a method for assembling an inner form excellent in constructibility.SOLUTION: In a method for assembling an inner form, the ring-shaped inner form is formed by making a plurality of arc-shaped form pieces installed along an inner peripheral surface of a tunnel cavity section in such a manner as to go around the inner peripheral surface, in the case of assembly of the inner form for forming the lining section between an inner peripheral surface of the tunnel cavity section and the inner form by being installed along the inner peripheral surface of the tunnel cavity section formed of an excavated hole formed by excavating natural ground; and the tubular inner form extended in an excavation advance direction is assembled by sequentially providing the ring-shaped inner forms in the excavation advance direction. The inner forms, in which both end surfaces 6 and 6 of a ring formed of a plane crossing the central axis of the ring are not parallel to each other, are used as the plurality of ring-shaped inner forms 2. The end surfaces of the ring-shaped inner forms are joined together in the state of butting against each other. Thus, the tubular inner form 1A having a central axis 7 of a tube extended linearly is assembled, or the tubular inner form 1B having the central axis of the tube extended in a curved shape is assembled.