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Rock quality designation (RQD) is a widely used index in geotechnical engineering and rock mechanics for characterizing the quality of rock masses. RQD is an essential parameter for rock mass classification, which is necessary for the design and construction of various engineering structures such as tunnels, dams, mines, and slopes. The RQD values are used to classify rock masses into different categories, based on the degree of fragmentation and the quality of the rock mass. The categories of rock masses based on RQD are: Very Poor Rock Mass: RQD values less than 25% indicate a very poor rock mass, which is highly fragmented and has low strength and stiffness. Poor Rock Mass: RQD values between 25% and 50% indicate a poor rock mass, which is moderately fragmented and has moderate strength and stiffness. Fair Rock Mass: RQD values between 50% and 75% indicate a fair rock mass, which is less fragmented and has high strength and stiffness. Good Rock Mass: RQD values between 75% and 90% indicate a good rock mass, which is almost intact and has very high strength and stiffness. Excellent Rock Mass: RQD values greater than 90% indicate an excellent rock mass, which is completely intact and has extremely high strength and stiffness. RQD % Quality <25 Very poor 25–50 Poor 50–75 Fair 75–90 Good 90–100 Very good #rock #geology #engineering #civilengineering #corecutting #corebox #soiltest #sbc #soil
