EXECUTION METHOD OF TUNNEL INVERT BY MOVABLE WORK FLOOR AND MOVABLE WORK FLOOR

PROBLEM TO BE SOLVED: To protect an invert concrete placing part when curing placing concrete, to allow excavating work by heavy machinery and the passing of a carrying vehicle of excavated sediment, and to early stabilize an excavating surface of a working face side near part particularly when base rock is weak. SOLUTION: After excavating an advancing side invert, an outer floor 28 of a movable work floor for fitting and inserting the outer floor 28 in a freely liftable inner floor 24 is arranged on a tunnel bottom surface 18 already placed with invert concrete, and the invert concrete placing part is protected when curing the placed invert concrete by moving the inner floor 24 to the outer floor 28, and the excavating work by the heavy machinery and the passing of the carrying vehicle of the excavated sediment can be allowed.