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Bolts
Phase2 offers state-of-the-art bolt modeling capabilities for both rock and soil applications. The following bolt types can be modeled:
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End Anchored (e.g. rock bolts)
Fully Bonded (e.g. soil nails)
Plain Strand Cable
Swellex / Split Set
Tieback
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Bolts: Adding Bolts
Bolts can easily be added to a model with the Add Bolt Pattern option, which allows you to quickly apply a bolt pattern to a boundary.
Bolt pattern around horseshoe tunnel
Bolt patterns can be applied:
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normal to boundaries
in a radial pattern (i.e. from a fixed drilling point)
at a given angle.
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The bolt length and in-plane spacing are specified in the Add Bolt Pattern dialog. Out-of-plane bolt spacing is entered in the Define Bolt Properties dialog.
Add Bolt Pattern dialog
Bolt pattern applied at 15 degree angle from horizontal
Bolts can also be added individually (rather than using the pattern bolting option), and can easily be edited (e.g. change length or orientation) after they have been added to the model. Any number of different bolt types can be used in a single model; there are no restrictions on the number of bolts or bolt types that can be used simultaneously.
Two bolt types applied in two overlapping patterns
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Bolts: Properties
Bolt properties (e.g. strength and stiffness) are entered in the Define Bolt Properties dialog.
Bolt Properties dialog
There are 5 different bolt models available in Phase2: End Anchored, Fully Bonded, Plain Strand Cable, Swellex/Split Set or Tieback. Bolts can have peak and residual (i.e. post-peak) strength, and pre-tensioning can be applied. For more information on these bolt models see the Define Bolt Properties topic in the Phase2 Help system.
Plain Strand Cable bolt properties
For the Plain Strand Cable bolt type, you can define the location of bulges along the cable by selecting the Add Bulges checkbox (optional). In the Define Bulges dialog you can select the bulge type (25 mm Garford Bulb or 21 mm Nut-Case), and define the number of bulges and locations along the bolt.
Define Bulges dialog for Plain Strand Cable bolts
Swellex / Split Set bolt properties
Swellex/Split Set bolts are assumed to have a 100% bond length with the surrounding rock mass. Tieback bolts can have a user-defined bond length.
Tieback bolt properties
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Bolts: Staging
For multi-stage models, the bolt installation sequence can be specified with the Assign Properties dialog. Bolt staging can also be specified when bolts are initially added, or with the right-click menu after they are added. A removal stage can also be specified, although bolts are automatically removed if the material around them has been excavated.
Three stage model of power cavern with staged support installation
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Bolts: Analysis Results
After the Phase2 analysis has been computed, you can examine the stresses and displacements within the bolts, which allows you to optimize the required support system. The bolt data can be:
The Show Values option allows you to display bolt results directly on the model, in the form of a histogram or line graph, superimposed directly on the bolts. The numerical values can also be displayed, and the display can be customized.
Axial force plotted as a histogram along each bolt with Show Values
The available data will depend on the bolt type. For example, for End Anchored or Fully Bonded bolts, you can view the Axial Force or Stress in the bolts. For other bolt types you can view Axial Force, Axial Stress, Bolt Displacement, Rock Displacement and Shear Force.
Graph of Axial Force in Fully Bonded Bolt
The Show Yield option highlights yielding (failure) in bolt elements.
Bolt yielding (tensile failure) highlighted in yellow
If bolts have a non-zero residual strength, then failed bolt elements can still carry load after yielding.
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