Semi-analytical solution for undrained cylindrical cavity expansion in variably saturated soils

The effect of different initial degrees of saturation on the behaviour of variably saturated soils around an expanding cavity has not been adequately studied thus far. Therefore, this study aimed to fill this gap. Moreover, it sought to theoretically explain the cylindrical cavity expansion response in unsaturated three-phase media, particularly focusing on its effect on the cavity wall during the transition from an unsaturated to a saturated state. To this end, a semi-analytical solution based on a hydro-mechanically coupled Sheng–Fredlund–Gens model was proposed for the undrained cavity expansion problem in variably saturated soils in which unsaturated and fully saturated regions coexisted around the cavity. The cylindrical cavity expansion and expansion pressure response in initially unsaturated soils (considering different initial degrees of saturation) and initially fully saturated soils were explored. The proposed solution further extends the cavity expansion theory to unsaturated soils. Furthermore, this work could serve as a theoretical framework for modelling of the cavity expansion problem in the variably saturated soils considering the effect of hydraulic state transition.