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Step 1 — Select UCS Range (R1)
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Choose the Uniaxial Compressive Strength range that best describes your intact rock material. Options range from extremely weak rock under 1 MPa to very strong rock above 250 MPa. This parameter contributes up to 15 points.
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Step 2 — Select RQD Range (R2)
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Choose the Rock Quality Designation percentage obtained from drill core recovery. Options range from very poor under 25% to excellent between 90% and 100%. This parameter contributes up to 20 points.
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Step 3 — Select Spacing of Discontinuities (R3)
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Choose the average spacing between joints, bedding planes, or other discontinuities in the rock mass. Options range from very close spacing under 60mm to very wide spacing over 2 meters. This parameter contributes up to 20 points.
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Step 4 — Select Condition of Discontinuities (R4)
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Choose the condition that best describes the joint surfaces including roughness, weathering, infilling material, and separation. This is the most heavily weighted parameter and contributes up to 30 points.
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Step 5 — Select Groundwater Condition (R5)
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Choose the groundwater condition observed in the rock mass, ranging from completely dry to freely flowing water with inflow greater than 25 liters per minute. This parameter contributes up to 15 points.
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Step 6 — Select Orientation Adjustment (R6)
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Choose the correction factor for the orientation of discontinuities relative to the excavation direction. This is a penalty parameter ranging from 0 for very favorable orientation to minus 12 for very unfavorable orientation.
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Step 7 — Click Calculate RMR Score
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Once all six parameters are selected, click the Calculate RMR Score button to instantly see your results.
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Step 8 — View Your Results
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The calculator displays your total RMR Score out of 100 along with the Rock Mass Classification, animated parameter breakdown bars, a highlighted score scale, and detailed engineering recommendations for each class:
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Class I — 81 to 100 → Very Good Rock — minimal support required
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Class II — 61 to 80 → Good Rock — local bolting at crown
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Class III — 41 to 60 → Fair Rock — systematic bolting and wire mesh
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Class IV — 21 to 40 → Poor Rock — shotcrete and steel support required
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Class V — 0 to 20 → Very Poor Rock — heavy support and multiple drifts