What is Rock-quality designation (RQD)?

What is Rock-quality designation (RQD)?

• A. 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.
• B. Is a measure of porosity
• C. Is a test to determine shear strength
• D. Is used to identify rock type

Answer: (A)

RQD measures how continuous and intact a rock mass is by looking at the drill core. It is calculated as the percentage of the recovered core that consists of pieces at least 10 cm long, summed over the interval of interest and divided by the total core length examined. A higher RQD means fewer joints and fractures in the rock mass, indicating better quality for engineering purposes, while a lower RQD indicates more fracturing and weaker rock mass. This concept helps engineers estimate rock mass quality for design decisions such as support, stability, and excavation planning. It does not measure porosity, neither tests shear strength nor identifies rock type, though it complements those assessments by signaling how jointing affects the rock mass.

RQD measures how continuous and intact a rock mass is by looking at the drill core. It is calculated as the percentage of the recovered core that consists of pieces at least 10 cm long, summed over the interval of interest and divided by the total core length examined. A higher RQD means fewer joints and fractures in the rock mass, indicating better quality for engineering purposes, while a lower RQD indicates more fracturing and weaker rock mass. This concept helps engineers estimate rock mass quality for design decisions such as support, stability, and excavation planning. It does not measure porosity, neither tests shear strength nor identifies rock type, though it complements those assessments by signaling how jointing affects the rock mass.