SCR is defined as the quotient: Rock-quality designation (RQD) is a rough measure of the degree of jointing or fracture in a rock mass, measured as a percentage of the drill core in lengths of 10 cm or more.
In this respect pieces of core that are not hard and sound should not be counted though they are 100 mm in length.
RQD has considerable value in estimating support of rock tunnels.
RQD forms a basic element in some of the most used rock mass classification systems: Rock Mass Rating system (RMR) and Q-system.
RQD is defined as the quotient: Many rock mass classification systems use core recovery parameters as input parameter, such as Rock Mass Rating and Q-system.