Consolidation Analysis - FLAC

Authors:
John Small
John Booker

FLAC (Finite Layer Analysis of Consolidation) calculates the time-settlement behaviour of uniform circular, strip or rectangular loadings which are applied to the surface of a horizontally layered soil deposit. The output generated contains the stresses, displacements and pore pressures at user-specified times and points on or within the soil deposit.

Data preparation is carried out using the program's own in-built editor which makes data preparation and checking extremely simple. Once prepared, data may be stored on disk and re-edited or re-used for subsequent runs. An example of the screen display when using the editor to input data is shown below. For large data sets the screen will scroll allowing entry of more data.

The finite layer formulation used in this program (developed and published by the authors) is much more convenient than conventional finite element analyses because of the computational efficiency and the reduced data size. However, the advantages of the finite element method are retained because each soil layer may have different thicknesses and material properties which may be isotropic or anisotropic with respect to both permeability and elastic properties.

The solution is obtained at any time by a forward-marching technique with the solution at a particular time being found from the solution at the previous time step. Initially small time steps need to be used as the dissipation of excess pore water pressures is rapid, however at larger times when dissipation is slower, the time steps may be increased so that the solution process is more efficient.