Core recovery parameters#Rock quality designation

The RQD value or RQD number is in geotechnical engineering and engineering geology a value to classify core samples ( cores ) of a rock rock and means "Rock Quality Designation index ". The rock or mountain classification after the RQD value goes back to Deere (1963).

Definition

RQD is defined as the ratio:

For the total length include lost fragments. - The RQD value should be determined as soon as possible after drilling.

Classification table

Application

With the help of the RQD value, one can conclude with experience formulas on the compressive strength of the rock ( rock strength ), for example using the RMR value.

Disadvantage

A core sample of 1 m length, divided into eleven fragments to 9 cm in length is, according to this criterion judged very bad. But it breaks down into nine fragments to 11 cm in length, it has an excellent RQD value, although both cores are actually almost the same.