STUDY ON ONE-DIMENSIONAL CONSOLIDATION THEORY OF UNSATURATED SOIL WITH GENERAL BOUNDARY CONDITIONS

The boundary conditions of unsaturated soil consolidation have an important effect on the consolidation theory, which reflects the exhaust and drainage state of soil boundary during the consolidation process. For the complexity and diversity of boundary conditions in practical engineering, the general boundary conditions of single-layer unsaturated soil are introduced in this paper, and a calculation model for one-dimensional consolidation with general boundary condition at the top and completely impermeable boundary condition at the bottom is established under instantaneous loading. Based on the Fredlund's one-dimensional consolidation theory, the solutions of excess pore presures are derived by applying the Laplace transform, and then the corresponding solutions in the time domain are obtained through inverse Laplace transform. An example is studied with reasonable boundary parameters, and the semi-analytical solutions are degenerated into several kinds of solutions in conventional conditions. The solutions are compared with the results from previous literature in order to verify the accuracy of the solutions, and the consolidation behaviors of unsaturated soil at different conditions are illustrated. The results show that the semi-analytical solutions under general boundary conditions are equivalent to a general solution with broad applicability. By changing the value of the relevant boundary parameters, the change process from completely impermeable boundary to fully permeable boundary can be simulated. During the consolidation, dissipation process of excess pore air pressure and excess pore water pressure is affected by boundary conditions. The semi-analytical solutions in this paper can be used for practical engineering under different boundary conditions.