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Estimating Input Parameters
RocData provides convenient built-in charts and tables for estimating typical strength parameters for various rock and soil types. These charts and tables are accessed by selecting the Pick button  located beside input parameter edit boxes in the sidebar.
Selecting Pick button for GSI estimation
When you select a Pick button, a table or chart will appear, allowing you to determine a suitable value for the desired parameter, based on rock or soil type, physical characteristics, in-situ conditions etc. Parameter estimation is available for the following strength criteria in RocData:
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Estimating Parameters: Generalized Hoek-Brown
Each of the parameters used as input for the Generalized Hoek-Brown criterion - sigci, mi, GSI and D - can be estimated using charts and tables built into RocData.
For example, if you select the GSI button, you will see the following chart.
GSI chart (Rock Type = General)
Once you have determined a value of GSI, select OK in the Pick dialog. The value will be automatically loaded into the sidebar, and the RocData calculation will automatically be carried out (i.e. output parameters and failure envelopes will be re-calculated using the selected input data).
There are TWO distinct GSI charts in RocData:
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One for general rock mass types, and
A second for weak, heterogeneous rock mass types such as flysch, which
extends the useful range of GSI down to values as low as 5.
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GSI chart (Rock Type = Flysch)
Dialog for estimation of mi value
Dialog for estimation of Disturbance Factor
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Estimating Parameters: Mohr-Coulomb
The parameters of the Mohr-Coulomb criterion - cohesion and friction angle (c and phi) - can be estimated for a variety of rock and soil types, by selecting the appropriate Pick button in the sidebar.
Selecting Pick button for cohesion estimation
The tables for c and phi are shown below. Using the Search option in the dialogs, you can quickly locate the parameters for a material of interest.
Cohesion values for a variety of rock and soil types
Friction angle (phi) values for various rock and soil types
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Estimating Parameters: Barton-Bandis
The parameters of the Barton-Bandis criterion - phir, JRC, and JCS - can be estimated by selecting the appropriate Pick button in the sidebar.
Selecting Pick button for JRC estimation
When you select a Pick button, a table or chart will appear, allowing you to determine a suitable parameter value. The dialogs for estimating phir and JRC are shown below.
Phi (residual) dialog
The residual friction angle phir can be calculated with respect to the basic friction angle phib, using the equation shown in the dialog. See the Barton-Bandis strength criterion topic for more information.
JRC dialog
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