RQD (Rock Quality Designation)
Compute the RQD (Rock Quality Designation), R = (sum of core pieces ≥ 10 cm / total drilled length)·100%, an index of rock-mass quality obtained from drill-core logging. It measures the degree of fracturing: an RQD above 90% indicates excellent, intact rock; below 25%, heavily fractured, poor-quality rock. It underlies geomechanical classification (RMR, Q) in tunnels and slopes. Enter the sum of pieces ≥ 10 cm and the total length.
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RQD (Rock Quality Designation)
When a borehole is drilled for site investigation, the rock comes up as cylinders — the drill core. RQD (Rock Quality Designation), created by Deere in 1964, turns the condition of that core into a single number: R = (sum of the pieces ≥ 10 cm / total drilled length)·100%. Long, intact pieces indicate sound rock; a lot of short fragments betray a fractured rock mass. The rating scale: RQD 90–100% is excellent rock; 75–90% good; 50–75% fair; 25–50% poor; below 25%, very poor. RQD is an input to the RMR and Q geomechanical classifications, which guide tunnel support, slope stability and foundation design. Enter the sum of the pieces ≥ 10 cm and the total drilled length.
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