Drilling bit and rotary drilling rig

The invention discloses a drilling bit and a rotary drilling rig, and relates to the field of building machines, which can use a piston door to push soil downward from the top of the drilling bit so as to pour soil, and can improve the construction efficiency of the rotary drilling rig in a cohesive soil layer. The technical scheme of the invention is that the drilling bit includes a piston door having a connection rod and a circular plate; convex keys are arranged on the outer side of circular plate; the piston door is arranged in a barrel; the barrel includes a connection zone, a first guide rail zone, a horizontal guide rail zone and a second guide rail zone which are successively connected; groove guide rails matching the convex keys of the piston door are arranged on the barrel; a circular top door is connected to an inner wall of the connection zone; a bottom door is arranged on the bottom of the barrel; during drilling, soil can enter the barrel via the bottom door; and while the soil is poured, the ba