Under the General tab in the Project Settings dialog, if you select the Advanced button, the following analysis settings can be configured.
Stress used in settlement calculation
Two options are available for the stress used in the settlement calculations:
Use vertical stress only
Use mean 3D stress
By default, settlement is calculated using only the vertical stress. A more accurate analysis can be performed by using the three-dimensional mean stress in the calculations. The mean stress at any point is the average of the volumetric stress components. NOTE:
Mean stress is only used in the calculation of Immediate Settlement. The mean stress is not used in the calculation of Consolidation Settlement and Secondary Settlement because the relationship between strain and mean stress is not clearly defined for non-linear materials.
Mean stress is also applicable for calculations of excess pore pressure.
For more information, see sections 3.1 and 4.2 in the Settle3D Theory document.
Secondary consolidation parameters
If you are carrying out a time dependent consolidation analysis, and you are considering secondary consolidation (i.e. creep), then the following parameters can be specified for the secondary consolidation analysis.
Start of secondary consolidation (% of primary)
Minimum stress for secondary consolidation (% of initial)
The start of secondary consolidation is specified with respect to the percent completion of primary consolidation. The default value is 95 percent.
In order to prevent the creep settlement calculation from being initiated at unduly low levels of stress, a minimum loading stress value is also specified, with respect to the initial stress. The default value is 1 percent.
Buoyancy Effect
As settlement occurs, material tends to sink further below the water table elevation. This will increase pore pressure, decrease effective stress, and decrease the amount of settlement at a given point, and is referred to as the buoyancy effect. By default, we ignore this effect in the settlement calculations, as it is usually quite small.
In some cases, the buoyancy effect could be significant. If you wish to include the buoyancy effect in the settlement calculations, then select the Include buoyancy effect checkbox in the Advanced Settings dialog. For further information, see section 5 in the Settle3D Theory document.
Vertical Stress Reduction
As settlement occurs, the height of the soil column above a given point decreases. Assuming that the material density does not change, this will decrease the vertical stress at the point. By default, we ignore this effect in the settlement calculations, as it is usually quite small and difficult to quantify precisely.
In some cases, this effect may be significant (e.g. for models with large settlement). If you wish to include this effect in the settlement calculations, then select the Include vertical stress reduction checkbox in the Advanced Settings dialog. For further information, see section 6 in the Settle3D Theory document.
Settlement Cutoff
This option allows you to specify the minimum amount of loading stress required to induce settlement, as a fraction of the in-situ effective stress at any point. If the loading stress at depth drops below the specified fraction of the in-situ effective stress, then no settlement will occur below this point.
To use this option, select the Use settlement cutoff checkbox and enter the ratio of loading stress/in-situ stress to be used as the cutoff value. By default this option is OFF, which means that settlement can occur at any loading stress.