RQD is expressed as a percentage of drill core segments of at least how long?

RQD is expressed as a percentage of drill core segments of at least how long?

• A. 5 cm
• B. 10 cm
• C. 15 cm
• D. 20 cm

Answer: (B)

RQD measures rock quality by how continuous the recovered core remains. It is defined as the percentage of the total core length that is represented by intact pieces longer than 10 cm. To calculate it, sum the lengths of all core fragments that are at least 10 cm long and not severely broken, divide that sum by the total length of core recovered, and multiply by 100. Fragments shorter than 10 cm are not counted in the numerator, but they still count toward the total core length in the denominator, so they can reduce the RQD. This threshold emphasizes the significance of longer, more continuous segments in indicating rock mass quality. For example, if the total core is 100 cm and the lengths of intact pieces over 10 cm add up to 70 cm, the RQD is 70%.

RQD measures rock quality by how continuous the recovered core remains. It is defined as the percentage of the total core length that is represented by intact pieces longer than 10 cm. To calculate it, sum the lengths of all core fragments that are at least 10 cm long and not severely broken, divide that sum by the total length of core recovered, and multiply by 100. Fragments shorter than 10 cm are not counted in the numerator, but they still count toward the total core length in the denominator, so they can reduce the RQD. This threshold emphasizes the significance of longer, more continuous segments in indicating rock mass quality. For example, if the total core is 100 cm and the lengths of intact pieces over 10 cm add up to 70 cm, the RQD is 70%.