Document Type: Research Paper
This study extends the theory of three-dimensional consolidation to unsaturated soils
and formulates the theory for finite element analysis by treating the pore water and pore air as a
mixed pore fluid. This formulation considers variations in the permeability and compressibility of
the mixed pore fluid with changes in the void ratio and degree of saturation. The compressibility of
the mixed pore fluid is derived using Boyle’s Law. An example of the settlement of a vertical
drain is investigated and discussed; this example demonstrates that the numerical analysis theory is
applicable and reliable. The results indicate that the rate of consolidation of unsaturated soils is
clearly slower than that of saturated soils, the rate of dissipation of the pore fluid pressure is
considerably slower, and the permeability of the mixed pore fluid decrease during consolidation.
This theory is applicable to unsaturated soils with high degrees of saturation and can be used to
obtain more reliable predictions of unsaturated soil consolidation.