Total core recovery (TCR) is the borehole core recovery percentage.

TCR is defined as the quotient:

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http://upload.wikimedia.org/wikipedia/en/math/c/8/7/c871ff1f29e75ffc44ae1e387071af05.pngRecovery and Rock Quality Designation)" /> = Sum of length of core pieces

http://upload.wikimedia.org/wikipedia/en/math/1/d/e/1de1c5ee106557e996ed76d3ea5aa144.pngRecovery and Rock Quality Designation)" /> = Total length of core run

Solid core recovery (SCR) is the borehole core recovery percentage of solid, cylindrical, pieces of rock core.

SCR is defined as the quotient:

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http://upload.wikimedia.org/wikipedia/en/math/8/c/d/8cd36cd7c26883dd99e1e68f08e98bc4.pngRecovery and Rock Quality Designation)" /> = Sum of length of solid, cylindrical, core pieces

http://upload.wikimedia.org/wikipedia/en/math/7/1/b/71bacf0d592985053ad8b2476bc65ed3.pngRecovery and Rock Quality Designation)" /> = Total length of core run

RQD is defined as the quotient:

http://upload.wikimedia.org/wikipedia/en/math/c/0/0/c00836f990040864033aede114fa5faa.pngRecovery and Rock Quality Designation)" /> %

http://upload.wikimedia.org/wikipedia/en/math/c/c/3/cc39c17aa596099016b86bf7931eb332.pngRecovery and Rock Quality Designation)" /> = Sum of length of core sticks longer than 100 mm measured along the center line of the core

http://upload.wikimedia.org/wikipedia/en/math/7/1/b/71bacf0d592985053ad8b2476bc65ed3.pngRecovery and Rock Quality Designation)" /> = Total length of core run

Classification table

From the RQD index the rock mass can be classified as follows:

RQD	Rock mass quality
<25%	very poor
25-50%	poor
50-75%	fair
75-90%	good
90-100%	excellent

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