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Tunnel & Rock Parameters
The Tunnel and Rock Input Data dialog is used to input:
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Tunnel Radius
In-Situ Stress
rock mass Elastic Properties
rock mass Strength Properties
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RocSupport uses these parameters to compute the Ground Reaction
Curve for your tunnel. The rock mass strength properties can be entered
as either Mohr-Coulomb or Hoek-Brown parameters. This will depend
on the Solution Method
selected in the Project Settings dialog.
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Tunnel & Rock Parameters:
Mohr-Coulomb Properties
If the Solution Method = Duncan Fama, then Mohr-Coulomb parameters
are entered because the Duncan Fama solution method for the Ground
Reaction Curve is formulated in terms of the Mohr-Coulomb failure
criterion. The Tunnel and Rock Input Data dialog will appear as follows.
Input Data (Mohr-Coulomb Strength Properties).
If you select the “Calculate From Hoek-Brown” button in
the lower left corner of the dialog, another dialog will appear. This
allows you to compute the Mohr-Coulomb friction angle and other properties,
based on Hoek-Brown parameters such as Geological Strength Index (GSI),
intact rock constant mi and intact rock UCS. The calculations are
based on the latest updates to the Hoek-Brown failure criterion (2002).
Dialog to compute Mohr-Coulomb parameters from Hoek-Brown
parameters.
Finally, notice the “Pick” buttons in the above dialog.
These lead to handy charts and tables which allow you to readily obtain
estimates of GSI, mi, UCS and D, based on rock type, surface conditions
etc. See the Estimation
of Rock Parameters topic for more information.
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Tunnel & Rock Parameters:
Hoek-Brown Strength Properties
If the Solution Method (in the Project Settings dialog) = Carranza-Torres,
then Hoek-Brown parameters are entered in the Tunnel and Rock Input
Data dialog, as shown below. The Carranza-Torres solution method for
the Ground Reaction Curve is formulated in terms of the Hoek-Brown
failure criterion.
Input Data (Hoek-Brown Strength Properties).
Notice the “Pick” buttons, which allow you to readily
obtain estimates of GSI, mi, UCS and D, using handy built-in charts
and tables. See the Estimation
of Rock Parameters topic for more information.
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Tunnel & Rock Parameters:
Estimation of In-Situ Stress
If in-situ stress conditions are not known, then you can obtain an
estimate by selecting the Calculator button beside the In-Situ Stress
option in the Tunnel and Rock Input Data dialog. This will display
the following dialog. The estimated in-situ stress is simply equal
to the depth of the tunnel from the ground surface, multiplied by
the rock unit weight.
Dialog for estimation of in-situ stress.
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