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Analysis Options
The main analysis options in Settle3D are configured in the Project Settings dialog, and include:
A summary of the analysis options is given below. For detailed information see the Settle3D Theory Manual.
Project Settings dialog
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Analysis Options: Stress Computation Method
The Stress Computation Method determines how the 3-dimensional stress distribution due to loading is calculated. Two options are available:
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Boussinesq
2:1
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The Boussinesq method uses the theory of elasticity to calculate the vertical stress under a point load in a homogeneous, semi-infinite half space. The solution is given by the following equation. To compute the stresses under a distributed load, the Boussinesq solution is integrated over the area of the footing.
Boussinesq method parameters
The 2:1 method assumes that the zone of influence for an applied rectangular load has a slope of 2:1 as shown in the following figure.
2:1 method parameters
The vertical loading stress at some depth is then calculated from:
For a non-rectangular footing, the stress is calculated by computing the area of the load at the surface. With increasing depth, the area over which the load is applied increases at a 2:1 ratio and the magnitude of the loading stress decreases correspondingly.
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Analysis Options: Time Dependent Consolidation
To perform a time dependent consolidation analysis, you must select the Time Dependent Consolidation Analysis checkbox in Project Settings, and choose the Time Units (seconds, minutes, days, months, years).
When the Time-dependent Consolidation Analysis checkbox has been selected you will be able to define:
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Time-dependent material properties
Time-dependent loading conditions
Times at which results are to be computed
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If the Time-dependent Consolidation Analysis checkbox is NOT selected, then you can carry out a settlement analysis which calculates immediate settlement, and long-term consolidation (at "infinite" time).
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Analysis Options: Units
In the Project Settings dialog you can choose the Units that you wish to use for Stress, Settlement and Time.
The Stress Unit options are Metric (MPa, kPa, tonnes/m2) and Imperial (ksf, tons/ft2). The selected Stress Unit determines the units of stress, length, force used in the analysis, as summarized in the table below.
The Settlement Units determine the units used for the output of settlement/consolidation results. The Settlement Unit options are Metric (meters, centimeters, millimeters) and Imperial (feet, inches). The available Settlement Units will vary according to the selection of Stress Unit (metric or imperial).
If you are performing a time dependent consolidation analysis (see above) then you must specify the time units for the analysis (seconds, minutes, days, months, years). The time units will be used for applicable input parameters and analysis results.
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Analysis Options: Staging
A Settle3D analysis can be performed in any number of stages. Staging represents the sequence in which you would like to define and analyze your model. The number of stages is entered in the Project Settings dialog.
Four stages defined in Project Settings
Staging can be used in a variety of ways, for example:
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Loads can be applied at different stages, in any sequence.
Load magnitudes can be applied in user-defined increments at different
stages.
Load or excavation depth can be changed at different stages.
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For time-dependent modeling:
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Stages can represent different times of load application
Stages can represent different times at which you would like to compute
analysis results
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Analysis results for each stage are viewed by selecting the corresponding stage tab at the bottom of the screen.
Stage tabs
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Analysis Options: Groundwater
Groundwater pore pressure can be defined by selecting the Groundwater checkbox in Project Settings, and entering the depth of the groundwater table.
For a multi-stage model, the depth of the water table can be changed at different stages.
For a time dependent consolidation analysis, groundwater must be defined, it is not optional.
When groundwater has been defined, drainage conditions can also be specified, see the Groundwater page for more information.
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