Elastoplastic solutions for cylindrical cavity expansion in unsaturated soils

Elastoplastic solutions are developed in this paper for cylindrical cavity expansion in unsaturated soils, aiming to provide a theoretical model to analyze the pressuremeter test and pile installation in unsaturated soils. The novelty of the solution lies in the subtle coupling of hydraulic behaviour and mechanical behaviour of the soil in the governing equations. An elastoplastic critical state model for unsaturated soils is used to derive the elastoplastic constitutive matrix for both the undrained (constant gravimetric water contents) and drained (constant suction) expansion of a cylindrical cavity in unsaturated soils, which are finally formulated to a system of first-order differential equations. The governing differential equations are solved as an initial value problem with the initial conditions determined by the yield function of the unsaturated soil model and continuous condition. Parametric studies are performed to investigate the expansion responses of the surrounding soil and particular attention is given to the responses at the cavity wall. The results indicate that suction has significant effects on both the mechanical and hydraulic responses of the surrounding soil.