A Rock Mass Rating value above 60 indicates which condition of the rock mass?

• A. The quality of the rock mass is good or very good
• B. The rock mass is poor
• C. The rock mass is marginal
• D. The rock mass is very poor

Answer: (A)

Rock Mass Rating measures how good or bad a rock mass behaves as a structural material for engineering purposes. A higher score means better rock mass quality, with fewer and less problematic discontinuities, stronger intact rock, and less adverse groundwater influence. When the rating is above 60, it indicates good to very good rock mass quality. This suggests the rock is relatively intact and stable, making excavation or support requirements more modest. Lower values correspond to poorer quality rock masses with more discontinuities, weaker blocks, and greater groundwater issues, requiring more extensive support.