Environmental Engineering Reference
In-Depth Information
FIGURE 2.78
Core recovery of 100% in hard, sound limestone: very poor recovery in shaley, clayey, and heavily fractured zones.
RQD is obtained by summing the total length of core recovered, but counting only those
pieces of hard, sound core which are 10 cm (4 in.) in length or longer, and taking that total
length as a percentage of the total length cored. If the core is broken by handling or
drilling, as evidenced by fresh breaks in the core (often perpendicular to the core), the
