Influence of initial and boundary conditions on one-dimensional consolidation of unsaturated soil

Unsaturated soil is common in practical geotechnical engineering and is defined by more characteristics than saturated soil. Based on the Fredlund and Rahardjo’s one-dimensional (1-D) consolidation theories of unsaturated soil, the behaviors of unsaturated soil under different initial and boundary conditions are investigated. The differential quadrature method (DQM) is employed to obtain the solutions that consider different boundary conditions and various initial pore water and air distributions. DQM is an efficient numerical technique for initial and/or boundary problems, and it can obtain sufficient accuracy with a small number of discretized points. It can avoid cumbersome computations in solving eigen-equations encountered with the analytical solution. A special case for which the analytical solution is available in the literature is employed to compare with and verify the accuracy of the DQM solution. Good agreements are found in the comparisons. Then the average degree of consolidation is studied for the different boundary conditions. Finally, the characteristics of the 1-D consolidation of unsaturated soil are investigated under various initial pore pressure distributions. It is found that the initial and boundary conditions have a significant influence on the consolidation of unsaturated soil.