Rock Materials
The Rock Materials branch holds the project's intact rock materials: the strength and stiffness of the rock between the discontinuities. A geotechnical domain is made of one of them, and takes its UCS, mi, modulus and unit weight from it. See Rock Mass Classification.
Context menu
Right-click the Rock Materials branch header or a material.
- New from Rock Type — A submenu of rock types; choose one to add a material with its typical values (below).
- New Custom Material — Add a material with the default values, named Rock Material. (
ID_ROCKMATERIAL_NEW) - Duplicate — (a material) Add a copy. (
ID_ROCKMATERIAL_DUPLICATE) - Rename — (a material) Domains that use it follow the new name. (
ID_ITEM_RENAME) - Delete — (a material) Domains that used it keep its name and report it as missing. (
ID_POPUP_ITEM_DELETE)
Properties
Rock Material
| Property | Description |
|---|---|
| Name | Name of this intact rock material. |
| Rock Type | Choosing a rock type loads its typical values: mi (Marinos & Hoek 2000), the modulus ratio MR (Hoek & Diederichs 2006), a mid-range UCS and unit weight. Replace them with test values when you have them. |
| Source | Where the values come from: Typical (preset), Laboratory test, Field estimate or DEM calibration. A preset's values are typical of the rock type, not of this rock. |
Intact Rock
| Property | Default | Description |
|---|---|---|
| UCS (MPa) | 50 | Uniaxial compressive strength of the intact rock, σci. |
| mi | 10 | Hoek-Brown constant of the intact rock. |
| Ei (MPa) | 0 | Young's modulus of the intact rock. 0: estimated as MR × UCS. |
| Modulus Ratio MR | 400 | Ei / UCS, used for Ei when it is 0 (Hoek & Diederichs 2006). |
| Unit Weight (kN/m3) | 26 | Sets the stress range of the equivalent Mohr-Coulomb fit. |
| Tensile Strength (MPa) | 0 | From a Brazilian or direct tension test; 0 when not tested. |
| Poisson's Ratio | 0.25 | Of the intact rock. |
| Ei Used (MPa) | Read-only: Ei as given, or MR × UCS when Ei is 0. |
A material needs a UCS, an mi and a unit weight above zero; until it has them, domains made of it cannot be evaluated, and the messages panel warns you.
Rock type presets
Choosing a rock type sets mi, UCS, MR and unit weight, sets Ei to 0 (so Ei Used is MR × UCS) and sets Source to Typical (preset). It keeps the tensile strength and Poisson's ratio.
| Rock type | mi | UCS (MPa) | MR | Unit weight (kN/m³) |
|---|---|---|---|---|
| Granite | 32 | 150 | 425 | 26.5 |
| Granodiorite | 29 | 140 | 425 | 26.5 |
| Diorite | 25 | 150 | 325 | 27.5 |
| Gabbro | 27 | 200 | 450 | 29 |
| Dolerite | 16 | 200 | 400 | 29 |
| Rhyolite | 25 | 120 | 400 | 25 |
| Andesite | 25 | 150 | 400 | 26 |
| Basalt | 25 | 180 | 350 | 28 |
| Tuff | 13 | 30 | 300 | 22 |
| Conglomerate | 21 | 80 | 400 | 25 |
| Sandstone | 17 | 70 | 275 | 24 |
| Siltstone | 7 | 50 | 375 | 25 |
| Mudstone | 4 | 20 | 250 | 24 |
| Claystone | 4 | 10 | 250 | 23 |
| Shale | 6 | 40 | 250 | 25 |
| Limestone (micritic) | 9 | 90 | 900 | 26 |
| Limestone (sparitic) | 10 | 90 | 700 | 26 |
| Dolomite | 9 | 100 | 425 | 27 |
| Chalk | 7 | 10 | 1000 | 20 |
| Gypsum | 8 | 25 | 350 | 23 |
| Anhydrite | 12 | 80 | 350 | 29 |
| Marble | 9 | 100 | 850 | 27 |
| Hornfels | 19 | 200 | 550 | 27 |
| Quartzite | 20 | 200 | 375 | 26.5 |
| Gneiss | 28 | 120 | 525 | 27 |
| Schist | 12 | 60 | 675 | 27 |
| Phyllite | 7 | 40 | 550 | 26 |
| Slate | 7 | 80 | 500 | 27 |
The UCS of a preset is a mid-range value for the rock type. Real values for a rock type vary widely, so test values are always better.