GGU-CONSOLIDATE: Analytical methods

The governing system boundary conditions are entered using the menu item "Edit/System parameters". If you have chosen to use an analytical method to solve the problem, you will see the following dialog box (example):

You must first enter the layer thickness and the load that initiates the consolidation process.

In order to properly model the temporal development of settlement, the consolidation coefficient C_V is required. This can be calculated from the constrained modulus E_S and the permeability coefficient k or be entered directly, if the value is known from oedometer tests. Enter your data according to the activated check boxes.

Alternatively, the settlements can also be calculated using the compression index C_C. Further information on this can be read by pressing the "Info" button after activating the "Use" compression index C_C check box. In the English-speaking world, in contrast to Germany, the compression index C_C is not defined to base log_e, but to base log₁₀. This can be specified here.

If a secondary settlement is adopted activate the "With secondary settlement" check box and enter the soil parameter C_B(log) (see "Theoretical principles: Secondary settlements").

For the "Classical consolidation (analytical)" you then define the drainage conditions (see lower section of the above dialog box). The number given after "No. of depth subdivisions" defines the number of points at which the program determines the pore water pressure. Because the program performs an integration of the pore water pressures at these points to determine the degree of consolidation, you should ensure that the number of subdivisions is not too small.

For a system utilising "Consolidation (analytical) with vertical drains", drainage is exclusively horizontal, resulting in constant pore water pressures across the layer thickness for all time steps. The "No. of depth subdivisions" in a system with vertical drains can therefore be defined using the minimum value of "3", thereby reducing modelling time. For the same reason, layer thickness does not influence the modelling results. It is only useful for the graphical representation of the pore water pressure distribution.

It is not necessary to define drainage conditions in a system employing vertical drains. Instead of the drainage conditions the "Vertical drainage geometry" group box is shown. Here, you define the drain centres and the drain radius (also see the figure in "Theoretical principles: Analytical solution with vertical drainage").