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Support: Predefined Support Types
RocSupport allows you to simulate the application of rockbolts,
steelsets or shotcrete around the circumference of the tunnel. Within
each support category, you may select from one of several predefined
support types (e.g. 34 mm rockbolts, 203 mm flange I section rib steelsets,
or 50 mm thick shotcrete).
Each specific support type has an associated maximum support pressure
and maximum average strain. These support characteristics have been
estimated by Hoek (1999) using
simplifying assumptions. The support properties are used to determine
the support reaction curve.
You may combine more than one support type in the same model (e.g.
rockbolts and shotcrete) by selecting the checkboxes in the dialog.
The properties of the combined support system will be used to determine
the overall support reaction curve.
Support Parameters – Rockbolts.
The Steelsets option includes the following pre-defined support types
– Wide Flange Rib, I Section Rib, TH Section Rib, 3 bar lattice
girder and 4 bar lattice girder. The out-of-plane spacing can be user-defined.
Support Parameters – Steelsets
(Wide Flange Rib).
The Shotcrete option allows you to simulate the application of different
thicknesses of shotcrete, at different curing stages.
Support Parameters – Shotcrete.
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Support: Custom
If none of the predefined support types is suitable for the project,
it is possible to define your own custom support type. This allows
you to specify any combination of Maximum Support Pressure and Maximum
Average Strain, which will define the support reaction curve.
The list of custom support types created by the user is automatically
saved with the project. It can also be made a default list for all
new projects.
Support Parameters – Custom.
To create a new custom support type, select the Insert New button
and enter the properties in the following dialog. Select OK to add
the new custom support type to the list in the Support Parameters
dialog.
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Support: Installation
The final parameter, which is required by RocSupport to fully
define the interaction between the ground reaction curve and the support
reaction curve, is the point at which the support is installed, relative
to the advancing tunnel face. This determines the origin of the support
reaction curve on the rock-support interaction plot.
Support installation options.
There are three methods of specifying the point at which the support
is installed:
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Distance from the tunnel face
At a specified tunnel convergence
At a specified
tunnel displacement
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If you are using option 1 (distance from tunnel face), you must enter
the distance at which the support is installed from the advancing
tunnel face. This value of distance is used in conjunction with a
semi-empirical deformation profile curve to determine a value of tunnel
convergence that corresponds to the specified distance. The following
tunnel deformation profile is used by default in RocSupport.
Default longitudinal deformation profile.
If necessary, the user can create their own customized deformation
profile by selecting the Advanced button in the Support Parameters
dialog. This will allow you to define a customized deformation profile,
using the dialog shown below.
Dialog for creating a user-defined deformation profile.
If you are using options 2 or 3, then you simply enter a value
of tunnel convergence or tunnel wall displacement directly in the
Support Parameters dialog. In this case the tunnel deformation profile
is not used.
Support installation at a specified tunnel convergence.
Whichever option you use for defining the point of support installation,
the value of tunnel convergence which is calculated (option 1) or
entered directly (options 2 or 3) determines the origin of the support
reaction curve on the rock-support interaction plot (i.e. it determines
the position of the support reaction curve with respect to the ground
reaction curve).
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Support: References
Hoek, E., (1999) Support for very weak rock associated with faults
and shear zones. Proc. International Symposium on Rock Support and
Reinforcement Practice in Mining, Kalgoorlie, Australia, 14-19 March,
1999.
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