Appendix C: Rock mass classification tables - RMR and Q 499
Joint Alteration Number (J,)
(i) Rock wall contact
0.75
1.0
2.0
(a) Tightly healed, hard, non-softening,
impermeable filling, i.e. quartz or epidote
(b) Unaltered joint walls, surface staining only
(e) Slightly altered joint walls. Non-softening
mineral coatings, sandy particles, clay-free
disintegrated rock, etc.
fraction (non-softening)
coatings, i.e. kaolinite, mica. Also chlorite,
talc, gypsum, and graphite, etc., and small
quantities of swelling clays (discontinuous
coatings, 1-2 mm or less in thickness)
3.0
4.0
(d) Silty or sandy clay coatings, small clay
(e) Softening or low-friction clay mineral
(ii) Rock wall contact b@re 10 cm shear
4.0 (f) Sandy particles, clay-free disintegrated rock,
6.0 (g) Strongly over-consolidated, non-softening
etc.
clay mineral fillings (continuous, t5 mm in
thickness)
softening, clay mineral fillings (continuous,
<5 mm in thickness)
(continuous, <5 mm in thickness). Value of .I,
depends on percentage of swelling clay-sized
particles, and access to water, etc.
8.0 (h) Medium or low over-consolidation,
8.0-12.0 (j) Swelling clay fillings, i.e. montmorillonite
(iii) No rock wall contact when sheared
6.0, 8.0
or 8.0-12.0
(k) Zones or bands of disintegrated or rock and
clay - see (g), (h), (j) for description of clay
condition
fraction (non-softening)
see (g), (h), (j) for description of clay
condition
5.0 (1) Zones or bands of silty clay, small clay
10.0,13.0
or 13.0-20.0
(m) Thick, continuous zones or bands of clay -
25-35"
25-30"
20-25"
8-16'
25-30"
16-24'
12-16'
6-12"
6-24"
*Values of @r are intended as an approximate guide to the
properties of the alteration products, if present.
mineralogical