How to Calculate and Solve for Rock Density Designation | Rock Mechanics The image above represents rock quality designation.

To compute for rock quality designation, two essential parameters are needed and these parameters are Sum of the Length of Core Pieces > 10cm (S) and Total Length Drilled or Core Recovery (L).

The formula for calculating the rock quality designation:

RQD = 100(S / L)

Where:

RQD = Rock Quality Designation
S = Sum of the Length of Core Pieces > 10cm
L = Total Length Drilled or Core Recovery

Let’s solve an example;
Calculate the rock quality designation? Given that the sum of the length of core pieces > 10cm is 20 and the total length drilled or core recovery is 14.

This implies that;

S = Sum of the Length of Core Pieces > 10cm = 20
L = Total Length Drilled or Core Recovery = 14

RQD = 100(S / L)
RQD = 100(20 / 14)
RQD = 100(1.428)
RQD = 142.85

Therefore, the rock quality designation is 142.85.

Calculating the Sum of the Length of Core Pieces > 10cm when the Rock Quality Designation and the Total Length Drilled or Core Recovery is Given.

S = RQD x L

Where:

S = Sum of the Length of Core Pieces > 10cm
RQD = Rock Quality Designation
L = Total Length Drilled or Core Recovery

Let’s solve an example;
Calculate the sum of the length of core pieces > 10cm? Given that the rock quality designation is 32 and the total length drilled or core recovery is 11.

This implies that;

RQD = Rock Quality Designation = 32
L = Total Length Drilled or Core Recovery = 11

S = RQD x L
S = 32 x 11
S = 352

Therefore, the sum of the length of core pieces > 10cm is 352.