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Support
For wedges that require support in order to achieve an acceptable
safety factor, three different methods of modeling support are available
in Unwedge: bolts, shotcrete
and pressure.
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Bolts - either pattern
or spot bolts can be applied, and several commonly
used bolt types are explicitly
modeled (e.g. anchored, grouted dowel, cable
bolt etc). Multiple bolt patterns can be
applied on the perimeter.
Shotcrete
- one or more layers of shotcrete can be applied anywhere on
the
excavation
boundary. The shotcrete layers have user defined thickness and
strength.
Pressure
- support can also be modeled as a uniform pressure, applied
anywhere on the boundary. The
pressure option can be used to simulate
the equivalent applied load of
any type of support system.
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Any or all of these support types can be applied to a given model,
in any combination.
Pattern bolts applied to perimeter of cavern.
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Support: 2D Design Views
Support can be applied to the Perimeter of the excavation and / or
to the Ends. To simplify the modeling procedure, the application of
Perimeter Support and End Support is done separately, in two different
views:
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Perimeter support can only be added
in the Perimeter Support Design View.
End support can only be added in the End Support Design
View. |
The support design views are 2-dimensional views that display the
opening cross-section of your excavation and 2-dimensional projections
of the wedges and support. When you select a view, the applicable
options for defining the support will be available from the Sidebar
or the Support menu.
Although support is always initially added in the 2-dimensional views,
it can be viewed and edited in the 3-dimensional views.
Perimeter Support Design View –
only perimeter wedges are visible.
End Support Design View – only
end wedges are visible.
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Support: Pattern Bolting
A regular pattern of bolts can be applied to the excavation with just
a few mouse clicks. Patterns can be applied to the Perimeter or Ends
of the Excavation. The bolt length, pattern spacing, position, and
method of installation (e.g. normal to boundary, radial or at a specified
angle) can all be user defined.
Dialog for specifying pattern bolt parameters (on perimeter).
Radial pattern of bolts applied to roof wedge.
Bolt pattern for roof wedge – Perspective
view.
Normal bolt pattern applied to end wedge.
Bolt pattern for end wedge – Perspective
view.
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Support: Shotcrete
Shotcrete support can be easily added to the excavation. Shotcrete
can be added to the Perimeter or the Ends of the excavation. Multiple
layers can be added and each layer can have different properties (thickness,
shear strength and unit weight).
Dialog for assigning shotcrete property type to shotcrete
layer.
Two layers of shotcrete added to support roof wedge.
Dialog for defining shotcrete properties.
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Support: Pressure
The Pressure option can be used to model the equivalent support pressure
of any type of support system. It could also be used to model any
type of general loading, which could be represented as a pressure
on the excavation boundary.
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The pressure can be applied anywhere on
the excavation boundary, and the
force is always applied normal
to the boundary.
The method of Force Application may be specified as either Active
or
Passive. Passive force application increases the resisting
force in the safety
factor calculation. Active force application
decreases the driving force in the
safety factor calculation. |
Dialog for defining support pressure.
Pressure is represented by the display of green arrows on the excavation
boundary, as shown in the following figure.
Pressure support applied to roof wedge.
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Support: Spot Bolting
Individual bolts can be defined with the Spot Bolting option. A spot
bolt must initially be added to the model using the 2D support design
views. After adding a spot bolt, the position and orientation of the
spot bolt can be edited in the 3-dimensional views. Spot bolts can
be placed at any orientation and do not have to be aligned with the
plane of the opening section.
Editing the position and orientation of a spot bolt in
the Perspective view.
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Support: Editing
Support can easily be edited, if necessary, after it has been added
to the model. Right-click options make this particularly convenient.
For example, if you right-click the mouse on a support element (e.g.
bolts), you will see a popup context menu which presents various editing
and display options.
In the following figure, the right-click option has been used to select
a bolt pattern in the 3D perspective view. The popup menu allows you
to select various options; for example, you could change the bolt
length or the pattern spacing by selecting the Edit Perimeter Bolt
Pattern option.
Editing a bolt pattern.
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Support: Bolt Models
A variety of different bolt types can be modeled in Unwedge,
including:
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Mechanically anchored
Grouted Dowel
Cable bolts
Swellex
Split Sets
User
Defined
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Bolt Properties dialog.
A Bolt Orientation Efficiency Factor can be applied to the tensile
capacity, to account for the fact that a bolt may not be mobilized
in pure tension, but also in shear. In addition, the bolt Shear Strength
can be explicitly accounted for with the Shear Strength option.
Any number of different bolt property types can be created by selecting
the Add button in the Bolt Properties dialog. This allows you to define
and use multiple bolt types with different properties within the same
Unwedge model.
For complete details about the implementation of bolt properties in
Unwedge, see the Theory
section in the Unwedge Help system.
Grouted dowel bolt model.
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Support: Bolt Force Diagrams
A bolt force diagram indicates the potential failure mode of a bolt
at any point along its length and the magnitude of the support force
which is available. The force diagrams are derived from the bolt properties
and are used to compute the support force which a bolt applies to
a wedge.
The bolt force diagrams determined by Unwedge can be displayed
directly on the bolts, as shown in the figure below. Each failure
mode along the bolt length is displayed using a different colour on
the force diagram (for example: pullout = green, tensile = red, stripping
= blue).
Display of support force diagrams on bolts.
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