Mohr - Coulomb Parameters
If possible the strength parameters should be determined in-situ measurements. The results of in-situ and laboratory experiments show that the angle of internal friction is found for the majority of discontinuities in the rock mass in the range of 27° to 47°. Approximate values of the angle of internal friction φ and cohesion c for rocks based on the RMR classification are stored in the following table:
Rock class | I | II | III | IV | V |
RMR | 100 - 81 | 80 - 61 | 60 - 41 | 40 - 21 | < 20 |
Angle of internal friction φ [°] | > 45 | 35 - 45 | 25 - 45 | 15 - 25 | < 15 |
Cohesion c [kPa] | > 400 | 300- 400 | 200 - 300 | 100 - 200 | < 100 |