PURPOSE: To increase friction resistance force by feeding fluid under pressure into a tube in a space formed by ringlike inner form taper plates to press the taper plates and pressing a form against a lining by component force. CONSTITUTION: A taper plate 3 part narrowing and squeezing a plate member 2 of a form toward an inner side and vertical plate 4 part for joint are provided alternately or by placing a plate 3 at the center to form an inner form 1. Furthermore, after inserting a flexible and tough tube 7 capable of inflating and deflating into a ridge-shaped box 6 of adjacent plates 3, concrete is placed into a space 14 surrounded by a shield tail 10, the from 1, and a press ring 13 so that a shield machine 13 advances and digs by a shield jack 12 while pressurizing the concrete by a press jack 11. After producing the concrete, fluid is fed into the tube 7 to press the plate 3 by inflated inflation pressure, and the form 1 is uniformly pressed against a lining 15 by component force to increase friction resistance force. Consequently, tensile stress of the lining 15 becomes uniform, and it is possible to prevent a crack due to the concentration of local tensile force.
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