Device and method for evaluating integrity of full-size cement sheath under underground working condition

The invention discloses a device and a method for evaluating the integrity of a full-size cement sheath under an underground working condition, and mainly aims to provide an experimental device for simulating the underground working condition in a full-size and full-process manner, and the experimental device is matched with a corresponding experimental method so as to solve the defects existing in the existing indoor cement sheath integrity research. The device is characterized in that the upper end cover and the lower end cover are used for sequentially installing the full-size casing pipe and the simulation stratum pipe and sealing the full-size casing pipe and the simulation stratum pipe through pressure generated by the double-thread screw, then annular pressurization is conducted on the inner portion of the full-size casing pipe so as to simulate the situation of changes of the inner pressure of the casing pipe under different working conditions during production, and cement paste is injected into the a