Extrusion and expansion branch disc screw pile, construction method thereof and pile forming device used in construction

The invention discloses an extrusion-expansion branch plate screw pile, a construction method thereof and a pile forming device used in construction, the screw pile comprises a straight rod section, an expansion force bearing plate, a threaded section and an expansion bottom head which are fixedly connected in sequence, and a plurality of branch force bearing frames are uniformly distributed on a pile body. A screw pile is built, a drill rod descends by one screw pitch and clockwise rotates by more than two circles, and a straight rod section is drilled; after reaching a pile end bearing layer, a pile end expanded head is formed; the drill rod ascends by a screw pitch and anticlockwise rotates by a circle, and grouting is conducted; and constructing a support force frame and an expansion force bearing disc, grouting in the lifting process of the drill rod, placing a reinforcement cage, and solidifying, so as to complete the construction of the extrusion and expansion branch disc screw pile. The pile forming d