The Rock Quality Designation index (RQD) was developed by Deere (Deere et al 1967) to provide a quantitative estimate of rock mass quality from drill core logs.

RQD was proposed by Deere (1964) as a measure of the quality of borehole core. The RQD is defined as the ratio (in percentage) of the total length of sound core pieces that is 0.1 m (4 inch) or longer to the length of the core run.

Rock quality designation (RQD) has several definitions. The most widely used definition was developed in 1964 by D. U. Deere. It is the borehole core recovery percentage incorporating only pieces of solid core that are longer than 100 mm in length measured along …

ROCK QUALITY DESIGNATION (RQD) Developed by Don U. Deere in 1964 Significantly expanded by Deere , et al in 1967 A useful index for determining rock quality from core recovery RQD= Length of “sound” core > 10 cm (4 in) X 100 Total Core Run Length

Calderón, M. Deere 1988 - The Rock Quality Designation (RQD) in Practice.

The RQD is an index of rock quality in which a modified core recovery per centage is obtained by counting only pieces of sound core 4-in. (100 mm) or greater in length of NX size or larger core diameters.

Jan 16, 2017 · RQD was devised in 1964 as an index for classifying the relative quality of rock core obtained from small diameter core drilling (about 50 mm) (Deere and Deere 1989). Since such a humble beginning, RQD has been adopted as …

Rock quality designation (RQD) has several definitions. The most widely used definition was developed in 1967 by D. U. Deere to provide a quantitative estimate of rock mass quality from drill core logs.

The Rock Quality Designation (RQD) has been utilized for twenty years to assess rock quality in various engineering applications, particularly in tunneling and shaft construction.

The Rock Quality Designation (RQD) index was developed over 20 years ago to qualitatively describe rock quality and tunneling conditions. It measures the percentage of intact core pieces longer than 10cm in borehole cores.