Rock Mass Rating (RMR) & Q‑system Calculator – Bieniawski & Barton for Tunnel Support

Rock Mass Rating (RMR) & Q‑system Calculator

Bieniawski RMR • Barton Q‑system • UCS • RQD • Joint rating • Tunnel support • Rock classification

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📐 1. RMR (Bieniawski) & Q‑system (Barton) – Rock Mass Classification

Two widely used empirical systems for rock mass quality and tunnel support design:

• RMR (Rock Mass Rating): Sum of ratings for UCS, RQD, joint spacing, joint condition, groundwater, and joint orientation.
• Q‑system (NGI): Q = (RQD/J_n) × (J_r/J_a) × (J_w/SRF). Support is based on equivalent dimension.

RMR classes: I (100–81) very good, II (80–61) good, III (60–41) fair, IV (40–21) poor, V (<20) very poor.
Q value: >40 excellent, 10–40 good, 4–10 fair, 1–4 poor, <1 very poor.

🚀 2. Rock Mass Classification Calculator

RMR Parameters

Uniaxial compressive strength UCS (MPa)

Rock Quality Designation RQD (%)

Joint spacing (m)

Joint condition (scale 0–20, typical: 20 = very rough, fresh; 10 = slightly rough, slightly weathered)

Groundwater condition (litres/min per 10m tunnel)Dry (0 L/min) → +15Damp (1–5 L/min) → +10Wet (5–25 L/min) → +7Dripping (25–125) → +4Flowing (>125) → 0

Joint orientation adjustment (–12 to –5)

Q‑system Parameters

RQD (%) – same as above

Joint set number J_n (1–20)

Joint roughness number J_r (1–4)

Joint alteration number J_a (0.75–20)

Joint water reduction factor J_w (0.5–1.0)

Stress reduction factor SRF (0.5–20)

📊 3. Rock Mass Quality Visualization

📈 4. RMR & Q History

📘 5. How to Use the Calculator

1. Enter UCS, RQD, joint spacing, joint condition, groundwater, and orientation for RMR.
2. Enter RQD, Jn, Jr, Ja, Jw, SRF for Q‑system.
3. Click "Compute RMR & Q" – both ratings and classes are displayed.
4. 2D schematic shows relative rock mass quality (bar chart).
5. Batch CSV: upload multiple designs for comparison.
6. PDF report includes all parameters, RMR, Q, and support recommendations.

❓ Frequently Asked Questions

❓ What is typical RQD for good rock?

RQD > 75% is excellent, 50–75% fair, 25–50% poor, <25% very poor.

❓ How to choose Jn, Jr, Ja?

Jn: 1–2 for few joints, 4–6 for two sets, 9–12 for three sets. Jr: 4 for rough, 2 for smooth, 1 for slickensided. Ja: 0.75–1 for healed, 2–4 for altered, up to 20 for clay-filled.

❓ What support does Q-system recommend?

For Q < 0.1: heavy shotcrete + steel ribs. Q 0.1–1: shotcrete + rock bolts. Q 1–4: systematic bolting. Q > 4: occasional bolts or unsupported.

🌐 References

Bieniawski (1989) – Engineering Rock Mass Classifications | Barton, Lien, Lunde (1974) – Q-system | NGI Q-support chart

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© ERH RMR & Q‑system Calculator – For preliminary rock classification. Final design requires site‑specific geotechnical investigation.