Rock Mass Classification Lab
RMR89, Q, Q-slope and GSI with Hoek–Brown strength and deformation modulus.
Rates a rock mass with the three international classification systems, derives GSI, and converts it into the Hoek–Brown strength envelope, equivalent Mohr–Coulomb cohesion and friction angle, and the rock-mass modulus, for slopes or tunnels.
Overview
RMR89 rates the quality of the mass from intact strength, RQD, spacing, joint condition and water, and gives a class from I to V. The Q-system rates block size (RQD/Jn), inter-block shear strength (Jr/Ja) and active stress (Jw/SRF), and is the basis of tunnel support design. Q-slope adapts Q to rock slopes and gives directly the steepest slope angle that stands without reinforcement.
GSI describes the structure and surface condition of the mass and feeds the generalised Hoek–Brown criterion, which gives the strength of the jointed mass, its equivalent Mohr–Coulomb parameters over the stress range of the design case, and its deformation modulus.
What you enter · What you get
What you enter
- Rock type (mi), intact UCS or Is(50)
- RQD or Jv, mean joint spacing, number of sets
- Jr, Ja and the five RMR condition sub-ratings
- Water (RMR, Jw), stress (SRF), Q-slope factors
- Design case, height or depth, slope angle, disturbance D
What you get
- RMR89, Q, Q-slope angle β and GSI with classes
- Hoek–Brown parameters mb, s, a and rock-mass strengths
- Equivalent c′ and φ′, deformation modulus Erm
- Tunnel equivalent dimension, bolt length and unsupported span
- Five figures and a PDF report
How it works in the field
Method and equations
RMR89 (Bieniawski 1989)
Gives the rock-mass class I–V and approximate mass cohesion and friction.
Q-system (Barton et al. 1974)
Gives the rock-mass quality on a logarithmic scale and, for tunnels, the equivalent dimension, bolt length and maximum unsupported span.
Q-slope (Bar & Barton 2017)
Gives the steepest slope angle that requires no reinforcement.
GSI (Hoek, Carter & Diederichs 2013)
Quantified from the RMR89 joint-condition rating and RQD.
Hoek–Brown criterion (2002 edition)
Strength of the jointed rock mass and its equivalent Mohr–Coulomb parameters over 0 ≤ σ3 ≤ σ3max.
Rock-mass modulus (Hoek & Diederichs 2006)
Simplified relation from GSI and D.
Who uses it
Standards and references
- Bar, N. & Barton, N. (2017). The Q-slope method for rock slope engineering. Rock Mechanics and Rock Engineering, 50, 3307–3322.
- Barton, N., Lien, R. & Lunde, J. (1974). Engineering classification of rock masses for the design of tunnel support. Rock Mechanics, 6, 189–236.
- Bieniawski, Z.T. (1976). Rock mass classification in rock engineering. Proc. Symp. Exploration for Rock Engineering, Johannesburg, 97–106.
- Bieniawski, Z.T. (1989). Engineering Rock Mass Classifications. Wiley, New York.
- Hoek, E., Carranza-Torres, C. & Corkum, B. (2002). Hoek–Brown failure criterion — 2002 edition. Proc. NARMS-TAC, Toronto, 267–273.
- Hoek, E., Carter, T.G. & Diederichs, M.S. (2013). Quantification of the Geological Strength Index chart. 47th US Rock Mechanics / Geomechanics Symposium, ARMA 13-672.
- Hoek, E. & Diederichs, M.S. (2006). Empirical estimation of rock mass modulus. Int. J. Rock Mech. Min. Sci., 43, 203–215.
- Marinos, P. & Hoek, E. (2000). GSI: a geologically friendly tool for rock mass strength estimation. Proc. GeoEng2000, Melbourne, 1422–1446.
- NGI (2015). Using the Q-system: rock mass classification and support design. Norwegian Geotechnical Institute, Oslo.
- Palmström, A. (2005). Measurements of and correlations between block size and rock quality designation (RQD). Tunnelling and Underground Space Technology, 20, 362–377.
At a glance
- Category
- Engineering & geotechnics
- Runs on
- Phone, tablet and desktop browser
- Export
- PDF report, PNG figures
- Access
- Subscribers
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