Abstract:The problem of cylindrical cavity expansion in soil was analyzed with the unified strength yield criterion, strain compatibility equations in cylindrical coordinates and the associative flow rule. The theoretical relationship among the initial radius a0，expansion radius a and expansion pressure p of the cylindrical bore was derived by employing the basic displacement formula of plastic zone and the displacement changes of soil around the cylindrical bore. Then, the radius of plastic zone rpwas obtained by this theoretical relationship and the relative formulas about the radius of plastic zone rp. In addition, the closed form solutions of stresses, strains, displacements in the elastic and plastic regions were obtained in concrete problems of cavity expansion. Furthermore, the parameters of the unified strength theory and the soil were analyzed. Finally, an illustrative example was taken to analyze the change rules of stress and displacement fields, the radius of plastic zone a0 and expansion pressure p.
