A general semi-analytical solution for predicting axisymmetric consolidation behavior of multi-layered unsaturated soil

In geotechnical engineering, one common application of geosynthetics is to prefabricate vertical drains for accelerating the consolidation of soft soils. The consolidation phenomenon of the soil around a vertical drain is generally modeled as an axisymmetric consolidation system. Considering the unsaturated and layered properties of natural soil, this paper attempts to constitute a reliable model for predicting the axisymmetric consolidation behavior of multi-layered unsaturated soil. On the basis of the common eigenfunction expansion and Laplace transform methods, a general semi-analytical solution is derived to assess the excess pore-air and pore-water pressures as well as the soil settlement. The correctness and accuracy of the derived solution are verified against the available analytical solution for a homogenous case and against the finite difference solution for two multi-layered cases. A typical worked example incorporating an asymptotic load is provided to demonstrate the axisymmetric consolidation behavior of a three-layered unsaturated soil, and the influences from the coefficients of air and water permeability are illustrated and discussed. © 2021, Saudi Society for Geosciences.