The most common classification method of drill cores is the Rock Quality Designation
(RQD) value, which indicates the percentage of rock cores longer than 10 cm in a given
core section. This core logging procedure is the basic parameter in the most useful
rock mass classification methods like Rock Mass Rate (RMR) and Rock Mass Quality (Q).
It is also used to determine the Geological Strength Index (GSI), which has become
widely used in the last 20 years. One of the basic problems of the RQD value is that
it does not distinguish different rock cores longer than 10 cm (100% is obtained for
one piece of 1 m length and 10 pieces of 10 cm length) and a uniform result is obtained
for shorter units. In this paper, the so-called Integrated RQD (Int_RQD) factor is
introduced to eliminate these problems and to provide a better description of fracture
density in the core logging procedure. As it uses the original core logging procedure,
historical RQD data can also be reevaluated. Considering that RQD is an input parameter
for most rock engineering classifications, these systems such as GSI can be reviewed
based on the new RQD definition proposed herein.
