Coupled consolidation via vertical drains in unsaturated soils induced by time-varying loading based on continuous permeable boundary

Abstract

Considering continuous permeable boundary and coupled radial-vertical flow in this paper, a generalized semi-analytical solution for the consolidation enhanced by vertical drains (VDs) in unsaturated soils under time-varying loading is proposed. Firstly, the continuous permeable boundary is introduced into the axisymmetric consolidation model. Afterwards, the coupled controlling governing equations of excess pore pressures (EPPs) are solved by mathematical methods such as the decoupling technology, the Laplace transformation and inversion. Then, the validity of the current solution is verified by special cases with double-permeable boundary conditions (BCs) and instantaneous loading. The case analyses eventually were carried out, and the results show that the smear effects slow down the consolidation process but that is not obvious when the smear parameter is great than five. The effect of vertical flow on consolidation becomes insignificant when the ratio of radial to vertical permeability coefficient is greater than five; conversely, when its value is less than five, the above effect increases with the enhancement of the permeability properties at the top (or bottom) boundary. Moreover, the new solution can be applied to time-varying loadings, and different distributions of top and bottom boundary permeability.