Drill bit for breaking waste pipe pile, and method for breaking waste pipe pile and pouring new pile

The invention discloses a drill bit for breaking a waste pipe pile, and a method for breaking the waste pipe pile and pouring a new pile. The drill bit comprises a core shaft, spiral blades are arranged at the external circumference of the core shaft, and a connecting part in butt joint with a drill pipe of a drill jig is arranged at the top of the core shaft. A plurality of cutting teeth are formed at least below the middle of the spiral blades, a vertical steel bar bundle formed by a plurality of short steel bars in a welded mode is arranged at the bottom of the core shaft, the steel bar bundle is coaxial with the core shaft, and the outer diameter of the steel bar bundle is less than or equal to the inner diameter of the to-be-crushed waste pipe pile. The key of the method is that the two steps of waste pile crushing and new pile hole forming are integrated and conducted synchronously. According to the drill bit and the method, the waste pipe pile with the depth exceeding 20 meterscan be effectively broken