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Version: 3.4.8 (unreleased)

Geomechanics

The geomechanics tools take you from a digital outcrop to the numbers an engineering geologist works with. You can sort the discontinuities into sets and describe each one. You can give the sets a shear strength and classify the rock mass. You can then test the slope, mapped over every point of the real surface rather than one idealised face.

Each command is on the right-click menu of the object it works on: a mesh or point cloud in the Data tree, orientations in the Interpretations tree, or a branch of the Collections tree. The ribbon is kept for actions in the 3D view, so there is no Geomechanics tab.

Screening, not design

Every map here is a screening tool. Each result is drawn from your measurements, your choices of set and strength, and the shape of the model. Check where the numbers come from before you rely on them, and take a slope that matters into the analysis you sign off with.

How the pieces connect​

 Orientation measurements ──► Sets (Collections > Sets)
          │                     │   set statistics, Terzaghi correction
          │                     │   joint strength per set
          ▼                     ▼
 Stereonet and Mohr diagram   Slope Stability on a mesh or point cloud
   (one face)                   kinematics → factors of safety
          │                     │
 Stress tensors ──────────────► slip potential, Mohr circles
          │
 P21 / P32 maps ──► Block Size (Jv, RQD, block volume) ──► Geotechnical domains
                                                      Rock materials ──┘
                                              RMR89, Q, GSI, Hoek-Brown
StepWhat you doWhere
SetsTag each measured plane with the discontinuity set it belongs to: by hand with its Set property, or with Auto-cluster — k-means, a Fisher mixture that can choose the number of sets by BIC and leave stray measurements in a noise class, Vollmer's P-maximisation, fuzzy k-means or density clustering (DBSCAN), with D max, the silhouette and P-bar to help choose the number of sets — which tags the clusters J1, J2 and so on. Folders still work as sets too.Sets, Orientation
Describe the setsTurn on Set Statistics on the stereonet for each set's mean plane, Fisher K, α95 and cones, with Terzaghi Correction for the bias of sampling planes from one direction.Stereonet
Joint strengthGive a set a Mohr-Coulomb or Barton-Bandis strength of its own. Kinematics uses its friction angle, the factors of safety use its strength, and the Mohr diagram draws its envelope.Sets
StressKeep one or more stress tensors, choose the active one, invert fault-slip data for a new one, and plot planes against it on the Mohr diagram or map slip potential on a mesh.Stress Tensors, Stress Inversion, Mohr Diagram
RoughnessGrow planar patches on a mesh; each patch gets a JRC from profiles down its dip, and the Hurst exponent and spectral pre-factor of its roughness down-dip and along strike. Map the same spectra in windows over a whole mesh.Grow Planar Patches, Roughness Spectra, Roughness Map
Block sizeMap the volumetric joint count Jv, RQD derived from it, and block volume from a fracture intensity layer.Block Size
Rock massDescribe the intact rock as a rock material and the rock mass as a geotechnical domain; read RMR89, Q, GSI, the Hoek-Brown parameters, Erm and the equivalent Mohr-Coulomb strength, each over a GSI range.Rock Mass Classification
SlopesMap kinematic failure modes and, if you ask, limit-equilibrium factors of safety and the probability of failure against design targets over a mesh or point cloud at one or more scales, or for one face on the stereonet.Slope Stability, method
BenchesMeasure an open-pit wall's benches from the scan — heights, face angles, berm widths — against the modified Ritchie width and a design surface.Bench As-built
BoreholesImport RQD, core recovery and fracture counts as log curves, and televiewer or oriented-core picks (alpha, beta) as plane measurements placed along the hole with their Terzaghi weights.Geotechnical Borehole Data
Key blocksMap the governing removable block that every three sets cut from the real surface at each point, or cut a DFN's fractures behind a mesh into real blocks (block theory), with factor of safety, volume and mode, the movable blocks as a mesh and the in-situ block size distribution; overhangs and roofs included.Key Blocks
RockfallCluster the significant M3C2 change between two epochs of a slope into rockfall events with their volumes, fit their magnitude-frequency, give rates and back-analyse which sets released them; run lumped-mass trajectories down the slope from the source areas, with maps of reach, energy and bounce height.Rockfall Inventory, Rockfall Trajectories
TunnelsCompare a tunnel scan with its design profile along a centreline — overbreak and underbreak chainage by chainage — with a spalling screen (Kirsch, Martin et al. 1999), each set's orientation to the drive (Bieniawski 1989) and Q support guidance; make the design surface.Tunnel As-built
RecordsEvery Slope Stability, Block Size, Key Blocks, Bench As-built, Tunnel As-built and rockfall run is recorded with what it read and its seed, and flagged as stale when a set it read changes.Analysis Runs
Report and exportExport the per-set table and the domains' classification as CSV, import a field sheet of domain inputs, export a DFN's fractures to 3DEC as an Itasca geometry file, add a geotechnical data sheet, the bench table or the probability of failure figure to a report, and ask Athos about the sets, the rock mass, a block's factor of safety or a slope's hazard.Sets, Geotechnical Domains

One selection everywhere​

What you select in one place is selected in all of them. Selecting a plane anywhere — on a stereonet, on the Mohr diagram, in the Interpretation tree or in the 3D view — marks it in every other view, so you can find a pole on the net, see it on the outcrop, and check where it falls against the failure envelope:

  • Stereonet: click a pole to select its measurement, Ctrl+click to add, or use the rubber-band tools on the Stereonet tab. Double-click flies the 3D view to the pole.
  • Mohr diagram: click a point, or drag a box round several; Ctrl adds.
  • Tree: selecting an orientation folder selects every measurement in it, so a set's folder shows the set.
  • 3D view: a selected orientation is drawn larger, opaque and outlined.

The right-click menus of the stereonet window, the Charts-pane stereonet and the Mohr diagram all start with Go To in 3D View, or Go To Selected in 3D View when the whole selection is to go.

Licence​

The Mohr diagram, the probability of failure figure, stress inversion, more than one stress tensor and choosing the active tensor need the Geomechanics module on your licence. The other tools on this page work without it. Without the module, a message explains what is missing; your stress tensor still works and every stress analysis still uses it.

See also​