FAQ¶
Quick answers to the most common questions about Rock Mechanics NX: which classification to choose, how to estimate missing parameters and how to produce the report.
Which classification should I choose?¶
It depends on the problem. For a general characterisation or for underground works, start from Barton's Q-index (Barton) or from Singh & Goel's N-index (Singh & Goel). For slope stability use Romana's SMR (Romana); if the slope is in soft rock (RMR < 40) turn to Robertson's SRMR (Robertson). For carbonate rock masses, Jašarević's n-index is calibrated (Jašarević). There is nothing stopping you from computing more than one on the same survey and comparing the classes.
What is the difference between the Q-index and RMR?¶
They are two different systems. Bieniawski's RMR is a sum of ratings on a 0–100 scale (see RMR); Barton's Q-index (Barton) is a product/ratio of six joint parameters and varies on a logarithmic scale, typically from \(0{,}001\) to \(1000\). They measure the same quality with different quantities and are linked by empirical correlations; the most widely used is \(RMR = 9 \ln Q + 44\).
How do I estimate RQD if I have no borehole cores?¶
From the discontinuity survey. With the Palmström relation you derive it from the volumetric joint count: \(RQD = 115 - 3{,}3\,J_v\). Alternatively, with the Priest and Hudson formula, from the average number of joints per linear metre \(\lambda\). Both are described in RQD.
Can I import the survey from GMS or eGeo Compass?¶
Yes. Rock Mechanics NX reads geostructural survey data coming from GMS and from eGeo Compass, so you do not have to re-enter the attitudes by hand. Supported formats and import procedures are described in File formats.
What is the difference between planar and wedge sliding?¶
Planar sliding is the movement of a block along a single discontinuity that daylights on the slope face: it is a 2D limit-equilibrium check (see Planar sliding). Wedge sliding, on the other hand, concerns a tetrahedral wedge bounded by two intersecting discontinuities, and is analysed in 3D along their line of intersection (see Sliding 3D).
When do I use Rock Mechanics and when RockPlane?¶
Use Rock Mechanics for the geomechanical classification of the rock mass, the derivation of the characteristic parameters and the basic checks of the kinematics (planar and wedge sliding). Switch to RockPlane when you need to design the remedial measures (bolts, anchors, meshes) on a planar failure with a tension crack and two joints, with verification according to NTC/Eurocodes.
How do I obtain cohesion, friction angle and modulus of the rock mass?¶
These are the characteristic parameters that the app derives automatically from the classifications. Once the quality index (RMR, Q or GSI) has been computed, Rock Mechanics applies the known correlations to return the cohesion \(c\), friction angle \(\varphi\) and deformation modulus \(E\) of the rock mass, ready to be entered into the stability checks.
How do I export the report?¶
From the export function: the app generates the calculation report with the survey data, the indices, the classes and the characteristic parameters, together with the graphical outputs. The procedure, formats and customisations are described in Export and report.
Where do I find the figures and the CAD drawing cited in the manual?¶
On the Resources page: you can download the kinematics figures in PDF, the planar-sliding drawing in DWG and the historical manual of the desktop version.
How do I report an error or a bug?¶
Write to info@geostru.ai describing the problem and, if possible, attaching a screenshot and the project file that reproduces it.
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