...................... is an index of the ratio between the sum of the lengths of core fragments longer than 10 cm and the total length of the core run.
MH SET - 2021, SET Exam - 2021,
Answer: D
The index is the Rock quality designation (RQD).
Deere's RQD is the sum of the lengths of intact core pieces 10 cm or longer, expressed as a percentage of the total length of the core run. It is a simple measure of how jointed the rock mass is and is used in rock mass classifications such as RMR and Q.
The other three are laboratory strength tests, not indices from core length. The uniaxial compressive test crushes a cylinder axially; the Brazilian test splits a disc to give indirect tensile strength; the point load test breaks a piece between two cones to give a strength index.
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