Abstract: According to bending theory , the authors set up the casing mechanical model under nonuniform collapse ,which is solved by using canonical equation and the distribution of bending moment,shear force,axial force,stress and deformation on the circumference of casing under nonuniform collapse.Calculation shows that the casing collapse resistance decreases greatly under nonuniform loads.Model not only shows good casing collapse mechanism,but also can improve casing collapse resistance design.

Key words: deep well, casing nonuniform collapse, collapse resistance collapse mechanism