To investigate the suction effect on the stress and strain of soil around cylindrical cavity, the analytical solution of effective stress in unsaturated soils was derived. In the elastic and plastic regions, the Hooke’s law and the modified Cam-Clay model were respectively employed. Taking suction as a hardening parameter, the governing equations about stress-strain around the cylindrical cavity were established. By introducing the auxiliary variable, the equilibrium differential equation in Eulerian system was transformed into Lagrangian system. The cylindrical cavity expansion in unsaturated soils was analyzed by solving the first-order ordinary differential equations where the elastic-plastic boundary was the initial conditions. Taking the values of stress and specific volume at the elastic-plastic boundary as initial values, the effects of suction and initial specific volume on the distributions of stress and strain were calculated and analyzed. The results showed that the soil around the cylindrical cavity changed from elastic state to plastic state due to the cavity expansion, and the suction had a significant effect on the stress state of plastic region. With the suction increase, three stress components, as well as the ultimate cavity pressures increased. For loose soils with larger void ratio, the ranges of plastic region reduced with the suction increasing. The specific volume decreased monotonously along the radial direction, which tended to be obvious as the suction increasing. However, for dense soils with smaller void ratio, the effect of suction on the ranges of plastic region was so small that could be ignored. The specific volume near the elastic-plastic boundary increased due to the dilatancy occurring. The larger the suction were, the more obvious of the dilatancy appeared. Finally, the reliability of the proposed method was verified by comparing with the data from lateral pressure test and calculation by the finite element method.
