In-pipe concrete down-filling and up-jacking technology for concrete-filled steel tube arch bridge

The invention discloses an in-pipe concrete down-filling and up-jacking technology for a concrete-filled steel tube arch bridge. The technology comprises the steps as follows: a slurry outlet pipe is arranged at the arch crown of an arch pipe; (1) two pairs of filling openings of the arch pipe are symmetrical about the slurry outlet pipe as the center line, each pair of filling openings comprises an upper filling opening and a lower filling opening employing the specific cross section of the arch pipe as a middle interface, each upper filling opening is lower than the corresponding lower filling opening, the linear distance between the highest points of the cross sections is L/2, and L is the span of the arch pipe; (2) an exhaust pipe is arranged at the arch foot; and (3) the arch pipe from the cross section to the arch foot is simultaneously filled with concrete through two lower filling openings, after the filled concrete exceeds each upper filling opening, pump pipes are transferred to the upper filling op