Abstract: Described herein is a tubular apparatus for making rigid tubular structures, comprising a flexible cylindrical wall (11, 11?) defining inside it a hollow passage (19), and suited for being wound, in particular on a spool, and continuously laid for use. According to the invention, said cylindrical wall (11, 11?) comprises a fabric (12, 13, 15, 12?, 13?, 15?) comprising inside it at least one gap (14;14?), which develops in the axial direction of said cylindrical wall (11, 11?), said fabric (12, 13, 15; 12?, 13?, 15?) comprising means suitable for operating under traction (15, 15?) when present within said at least one gap (14; 14?) is a fluid (20), injected under pressure for stiffening the tubular apparatus (10; 10?).