Engineering Rock Mechanics

198 Rock mass classification

Table 12.2 (cont)

Q-vstem of ReD J,

Rock Mass Classification e 7 - SRF J.

s

2

m: ~~con(inuourumaorhodrofclay(rccp:,h.j: fa

description of clay coadition)

I

..

k'

b

Dry ucavations a minor inflow. e.g. 5 ymin locally

Medium inflow or pressure, oeeasiond outwash of

joint fiUingl

(I) We~ssronuin&rseclingacava&~whkhmaycau~

loosenin8 of mk IMU when auvul & Ucowed

MUltipk OeCUmnar OfWC&US rOmr COllUiriillg ShJ

or chcmidly disintegrated mck, very lmre rumwndirq

rod: (MY depth)

Single w&ur lol~~ smuininp clay or chcmiullj

disintcgnlcd rock (excavation depth dl m)

disintegnlcd rock (uclvatica dcptb >M m)

a:

b

C: siagk W&U3 ZmCI COllIdw Clay OI ehunidJ

d MultipkrbcvroDesincomp~trock(clay-froc).loo~

e: Single shm zone$ in Eompnent rock (clay-free) (dcptl

of ucavmion 60 m)

f: Single shcv zcmu in Eompcml mck (clay- frcc) (dcptl

of excavation >SO m)

g: Loose open jointa. hcavily jointcd 01 'rugas cub'. CIC

(MY depth)

CunOunding rock (My depth)

(ii) Compeunr rock rock SITUS problem

h Lowrtrtrs,ncarswfaa

j: Mcdiumsmsr

k High-SllUS. VUy dghl IIIUClUIO (USUdy f8VOUnbk It

stability. may b unfavourble for wall stability)

L: Mild rock bunt (murive rock)

m: Hcdvy rock bunt (massive rock)

(Ill) Squeezln8 rock: pbrricpow of hmpelenr rock de

n: Mild squcuing rock pmsun

p: Heavy squeezing rock pressure

(lv) Swellin8 mk: chemkd nvelllng activiry depending 01

q: Mild swelling mck prruwc

I: Heavy swelling rock PIUSUR

rlu iqRuence of high rod pressures

presence ofwanr

c: Large inflow or high prruvls in wmpetcnr mck with

unfilled joints

d Large inflow or high pwurc, considuable outwash o

joint Illlings

blasting, decaying with time

Exceptionally high inflow or W~ICI p-un Eontinuin,

without noticeable decay

e: Exceptionally high inflow (x warn prarun at

E

6.0.8.0 a

8.0-12.0

5.0

0.0.13.0 a

13.0-m.0

SRF

10.0

5.0

2.5

1.3

5.0

2.3

5.0

2.3

1 .O

0.5-20

5-10

10-m

5-10

10-m

5-10

10-15

J. I .o

0.66

0.5

0.33

0.2-0.1

0.1-0.05

.Ibc(ulor.!

d*dW

~tmsLlsdE

rrddmdude

ofttaban ItbcIISbiUQ,

luhvmmblo

I

rcowtion

.5-10.0

12.3 Applications of rock mass classification

systems

Using either of the classification systems described in the previous two

sections, the engineering quality of a rock mass can be assessed. The RMR

system gives a number between 0 and 100, and the Q-system gives a

number between 0.001 and 1000. By these approaches, we are able to

produce a description of the rock mass based on classes defined by the