The 'rock quality designation' (RQD) is defined as:
Choose the correct answer
Ratio of recovered core to total drilled length (regardless of size)
Percentage of core pieces ≥ 100 mm length to total core run — indicates rock fracture intensity
Rock compressive strength
Permeability of rock
Correct Answer
B. Percentage of core pieces ≥ 100 mm length to total core run — indicates rock fracture intensity
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RQD = (total length of pieces ≥ 100 mm in core run) / (total core run length) × 100%. Deere (1963). RQD 0–25%: very poor; 25–50%: poor; 50–75%: fair; 75–90%: good; 90–100%: excellent. Used for: rock mass classification, foundation design, support design in tunnels. Obtained from diamond core drilling (NX core, 54.7 mm dia).
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