In order to incorporate the strain-softening and shear dilatation behavior of geomaterials in the analysis

a strain-softening stress-strain model with stress-dropping and a simplified model of ?v-?1 and ?1-?3 are adopted. Based on the extended spatial mobilization plane (SMP) theory

the governing equations of axisymmetric problem in the plane strain condition

the partial differential equations for the boundary-value problem of cavity expansion in cohesive soils are established; and the closed-form solutions of stresses

strains

displacements in the elastic and plastic regions are obtained. Consequently

the maximum radius of plastic region and ultimate cavity pressure are solved for cylindrical cavity expansion. Based on numerical results

the strain-softening rate and the effects of soil dilatancy on expansion of cylindrical cavity are examined. Also a comparative study is made for the present solution and current solution based on Mohr-Coulomb criterion in order to display the effect of intermediate principal stress. The results indicate that soil strain-softening and shear dilatancy as well as the intermediate stress have considerable effect on both ultimate cavity pressure and maximum radius of plastic region in the cylindrical cavity expansion.