A 50 m run of core drilled horizontally from an underground drift allowed to recover 42 m of rock core and 38 m of this core was in pieces longer than 100 mm. In the 4 m of recovered rock core with pieces smaller than 100 mm, 2 meters contained fresh and sharp breaks (fractures). (a) Determine the Rock Quality Designation (RQD) value and the corresponding rock quality description. (b) Describe the limitations of using RQD to evaluate rock quality and make suggestions on how you can minimize the sources of error.

Question 10
A 50 m run of core drilled horizontally from an underground drift allowed to recover 42 m of
rock core and 38 m of this core was in pieces longer than 100 mm. In the 4 m of recovered
rock core with pieces smaller than 100 mm, 2 meters contained fresh and sharp breaks
(fractures).
(a) Determine the Rock Quality Designation (RQD) value and the corresponding rock quality
description.
(b) Describe the limitations of using RQD to evaluate rock quality and make suggestions on
how you can minimize the sources of error.