Class No.

v

iv

iii

ii

i

SMR value

0 - 20

21 - 40

41 - 60

61 - 80

81 - 100

Rock mass description

Very bad

Bad

Normal

Good

Very good

Stability

Completely unstable

Unstable

Partially stable

Stable

Completely stable

Failures

Big planar or soil like circular

Planar or big wedges

Planar along some joint and many wedges

Some block failure

No failure

Probability of failure

0.9

0.6

0.4

0.2

0