ISRM grade Flashcards
1
Q
R0
A
Extremely weak
UCS 0.25 - 1.00 MPa
IS50 ***
Indented by thumbnail.
2
Q
R1
A
Very weak
UCS 1-5 MPa
IS50 ***
Material crumbles under firm blows of geological pick, can be shaped with knife.
3
Q
R2
A
Weak
UCS 5-25 MPa
IS50 ***
Knife cuts material with geological but too hard to shape into triaxial specimens.
4
Q
R3
A
Medium strong
UCS 25 - 50 MPa
IS50 1-2
Firm blow with geological pick indented to 5 mm, knife just scrapes surface.
5
Q
R4
A
Strong
UCS 50-100 MPa
IS50 2-4
Handheld specimens broken by a single blow of geological hammer.
6
Q
R5
A
Very strong
UCS 100-250 MPa
IS50 4-10
Require many blows of a geological hammer to break intact rock.
7
Q
R6
A
Extremely strong
Higher > 250 MPa
IS50
> 10
Rock material only chipped under repeated hammer blows, ring when struck.
