Consolidation analysis is an analytical method that calculates the behavior of pore water pressure when it resists external loading, when excess pore water pressure occurs and as the excess pore water pressure reduces with time for an undrained condition.

Pore water pressure in the ground with a small osmotic coefficient instantaneously displays the same behavior as the undrained condition. Hence, it bears most of the compressive load by the created excess pore water pressure, according to the change in load state. However, as time goes by, excess pore water pressure is re-distributed and if there is a drainage boundary, the excess pore water pressure decreases gradually. Because of this, the load previously resisted by the excess pore water pressure is gradually resisted by the soil frame, causing gradual deformation of the soil frame and increasing effective stress within the frame.

The increase in effective stress leads to the deformation of soil structure and this deformation is accumulated in the gravitational direction, eventually displaying settlement behavior in the gravitational direction with time elapse.

This gradual increase in deformation creates settlement at the base of structural foundation and differential settlement at the base foundation greatly affects the stability and safety of the structure.

Characteristics of Consolidation element

In Consolidation analysis, the elements have an additional pore water pressure degree of freedom, as well as displacement degree of freedom, at the nodes. It is assumed that all elements have a degree of freedom for pore water pressure, unless the two boundary conditions (Non-consolidating condition, Drainage condition) are specified, for Consolidation analysis. Hence, for bank materials that do not express consolidated behavior directly, the non-consolidating element conditions need to be defined to apply it as a general structural element. Also, the drainage conditions needs to be defined for drainage boundaries in consolidating elements. If the boundary conditions are properly defined and Consolidation analysis is conducted, the excess pore water pressure is 0 (zero) where the non-consolidation conditions and drainage conditions are applied.

<Consolidation element boundary conditions>