If you are working on rock mechanics, you are likely to have encountered, or used, the Hoek and Brown rock strength criterion. The Hoek and Brown Strength criterion is used to derive strength estimates of rock masses that are not dominated by a single discontinuity (known as structurally controlled behavior). This typically involves rock masses that have few no discontinuities, rock masses with discontinuities that are oriented in a way that they do not dominate the engineering response, or highly broken up masses.
A nice online widget to calculate the Hoek and Brown Rock Mass Strength is ORMAS, which stands for Online Rock Mass Strength. It has been developed by Dr. Rouzbeh Geraili Mikola.
The widget is very easy to use: You just select the units and then plug in the appropriate values in the input parameters. Every time you update a value, the charts of σ1 vs σ3 and shear stress vs. normal stress are automatically updated, which allows you to see the impact of the change in a parameter value.
The input parameters required are the uniaxial compressive strength of intact rock σci, Geological Strength Index GSI, the intact rock material parameter mi, and the disturbance factor D. If you are not sure about what to use, just click on the button with the “+” symbol to get more guidance, which is the guidance provided by the authors of the paper. The input parameters are used to develop the strength envelope, which is non-linear. By selecting also the maximum σ3, one can linearize the nonlinear envelope and calculate equivalent c and φ.
You can also plug in and intact Rock Elastic Modulus Ei and calculate the rock mass modulus Erm
You can also export all results as figures or an excel file.
In all, ORMAS is a great tool to quickly, even in the field calculate Hoek and Brown rock mass and it is completely free to use!
Check out the quick video review at the video gallery below.
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ORMAS is a free software for determining rock mass strength parameters, based on the Generalized Hoek-Brown failure criterion. The first version of th...
