The RQD index (Rock Quality Designation), developed by Deere between 1963 and 1967, is defined as the percentage of recovery of cores of more than 10 cm in length (on their axis) without taking into account fresh breaks from the drilling process with respect to the total length of the borehole.

Contenido

Para determinar el RQD (Rock Quality Designation) en el campo o zona de estudio de una operación minera, existen tres procedimientos de cálculo.

First procedure

It is calculated by measuring and adding the length of all pieces of core greater than 10 cm in the core interval of 1.5 m from the cores obtained in the exploration.

Core discs caused by mechanical rock failure should be included as part of the RQD.

where.

Second procedure

It includes the calculation of the RQD based on the number of cracks per meter, determined when carrying out the lithological-structural survey (Detail line) in the predetermined area or zone of the mining or geotechnical operation, in a longitudinal section of exposed wall. (Priest and Hudson, 1976).

where.

Third procedure

It includes the calculation of the RQD based on the number of cracks per cubic meter (Joint Volumetric number), determined when carrying out the lithological-structural survey (Detail line) of the walls of the predetermined area or zone of the geotechnical operation: where.

It is calculated by adding the number of cracks per meter that independently cut each of the 3 axes of an imaginary cube in the rock body under analysis. A crack should not be counted in more than one axis, for example, if a crack cuts both the axis and the axis, we will count it either in the axis or in the axis but not in both. For greater precision, we will measure an appropriate length on each axis and then find the number of cracks in a single meter, making a simple rule of 3:.