Abstract:

Based on the equal-strain hypothesis and Fredlund's consolidation theory of unsaturated soil mechanics, a semi-analytical solution to consolidation of unsaturated soil with vertical drains considering drain resistance and the smear effect is proposed. Firstly, the governing equations are transformed into easy-to-solve equivalent linear partial differential equations by introducing new variables and the Laplace transform, with both drain resistance and smear effect conditions in the solution derivation taken into account. By utilizing Crump's method, the inverse Laplace transform is then used to obtain the average excess pore-air and pore-water pressures and the average consolidation degree in the time domain. Moreover, the validity of the solution is verified by degenerating and comparing with the existing solution to the foundation with ideal boundary conditions of unsaturated soil based on the free-strain assumption. The results show that an increase in the drain resistance factor, smear coefficient, or smear zone radius ratio will extend the consolidation time. Drain resistance and the smear effect are considered useful for more reasonably predicting the consolidation degree of unsaturated soil with vertical drains.

Key words: unsaturated soil, equal strain, drain resistance, smear effect, semi-analytical solution