Cast-in-place pile lengthened pile casing for bad foundation

The utility model discloses a cast-in-place pile lengthened casing for bad foundation, which comprises a bottom cylinder, the upper surface of the bottom cylinder is provided with a first clamping groove, the inner wall of the first clamping groove is in lap joint with a first connecting ring, the upper surface of the first connecting ring is fixedly connected with a connecting cylinder, and the upper surface of the connecting cylinder is provided with a second clamping groove. A second connecting ring is in lap joint with the inner wall of the second clamping groove, a connecting plate is fixedly connected to the upper surface of the second connecting ring, an I-shaped clamping plate is fixedly connected to the side face of the connecting plate, a threaded hole is formed in the upper surface of the connecting plate, and a lead screw is in threaded connection with the inner wall of the threaded hole. According to the cast-in-place pile lengthened pile casing for the bad foundation, the lead screw rotates to d