Construction method for staged upward pulling of self-propelled steel casing in complex stratum

The invention belongs to a construction method for staged upward pulling of a self-propelled steel casing in a complex stratum, which comprises the following steps of: integrally pulling out the traditional self-propelled steel casing at one time by using the power of a rotary drilling rig after integrally completing pile foundation concrete pouring; a method which may cause failure in a complex stratum is changed into a method which adopts staged pouring on pile foundation concrete in the complex stratum and staged partial pulling-out of the steel casing, and a rotary drilling rig synchronously completes pulling-out of the steel casing in the complex stratum by means of an auxiliary lifting chassis and a jack when necessary. The problem that the self-propelled steel casing cannot be pulled out due to insufficient power of a drilling machine in pile foundation construction in a complex stratum is solved. The method is simple in process, easy to operate, time-saving, labor-saving and high in construction effic