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Calcimator

Rock Mass Rating (RMR) Calculator

Calculate Bieniawski RMR classification from UCS, RQD, joint spacing, condition, and groundwater ratings.

Inputs

Results

RMR Score

55

Rock ClassIII
DescriptionFair Rock
Stand-Up Time1 wk for 5 m span
Cohesion Range200-300 kPa
Friction Angle25-35°
How to Use This Calculator
  1. Enter the UCS Rating (0–15) based on uniaxial compressive strength of intact rock.
  2. Set the RQD Rating (3–20) from drill core Rock Quality Designation measurements.
  3. Enter Joint Spacing Rating (5–20) and Joint Condition Rating (0–30) from field mapping.
  4. Set the Groundwater Rating (0–15) based on observed inflow or pore pressure.
  5. Review RMR Score, Rock Class (I–V), and Stand-Up Time to design support and excavation sequences.

How the result changes with Joint Condition Rating

Joint Condition RatingRMR Score
343
1151
2060
2767

What each input means

UCS Rating
Uniaxial compressive strength rating (0-15)
RQD Rating
Rock Quality Designation rating (0-20)
Joint Spacing Rating
Discontinuity spacing rating (0-20)
Joint Condition Rating
Condition of discontinuities rating (0-30)
Groundwater Rating
Groundwater condition rating (0-15)

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    UCS Rating = 7, RQD Rating = 13, Joint Spacing Rating = 10, Joint Condition Rating = 15 = 5 input(s) provided
  2. Calculate RMR Score
    RMR Score
    55 = 55
  3. Calculate Rock Class
    Rock Class
    III = III
  4. Calculate Description
    Description
    Fair Rock = Fair Rock

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