CSIR_NET_JUNE_2019
82)
From a drill length of 200 cm individual cores of 30cm, 20cm, 40cm,
and 12 cm lengths were obtained from a rock mass. What is the Rock
Quality Designation (RQD) of a rock mass.
A)
55%
B) 65%
C) 25%
D) 51%
(Thanks to Chandrasekhar, ANU)
Solution:
Rock
Quality Designation:
It
is a rough measure of the degree of joining (or) fracture in a rock
mass, measured as a percentage of the drill core in lengths of 10 cm
(or) more.
High
quality Rock mass has RQD >75%
Low
quality Rock mass has RQD <50%
Therefore
RQD = $(\frac{l_{sum of the length of the core peices }}{l_{total
sum of the core}})\times100 %$
Given
that $l_{total}= 200cm$
$l_{sum
of total of the core pieces}= 30+20+40+12=102 cm$
$RQD
= \frac{102}{200}\times100$
RQD=
51%
Reference: https://en.wikipedia.org/wiki/Core_recovery_parameters
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