Engineering geology aspects for design and classification - Tunnel Engineering: Basics and Additional Services for Design and Construction - page 42

Thanks to theoretical advances in rock mechanics, quantitative parameters came to be intro-
duced ever more for classification purposes. Particularly worth mentioning are the works of
Wickham [256], Barton [14], Bieniawski [22] as well as John and Baudendistel [99]. Since
the end of the 1960s, the tendency has moved away from generally applicable rock mass
classifications to project-related classification. Further details are dealt with in [142].

Table 2-8 Comparison of basic classification systems.

K. Terzaghi 11 rock mass classes (1 to 11) from “competent rock” to “loosely consolidated sand“

G.E. Wickham No fixed classes but RSR (Rock Structure Rating) values from 25 to 100, which

denote improving rock mass quality with increasing values

J. Stini 5 rock mass classes (1 to 5) from “rock more or less brittle” to “mild rock mass,

very squeezing“

H. Lauffer 7 rock mass classes (A to G) from “stable” to “very squeezing“

G. Seeber 3 rock mass classes (1 to 3) from “stable” to “squeezing“

F. Pacher,
L. v. Rabcewicz

6 (5) rock mass classes (I to Vb) from “stable” to “loose” (Tauern Tunnel)

W. Berger 7 support classes (0 to 6) from “without structural support” to “special measures“

Z.T. Bieniawski 5 rock mass classes (I to V) from “very good rock” to “very poor rock” with

ratings from 100 to 1

N. Barton No fixed classes but Q (Quality) values from 0.001 to 1000 for “exceptionally poor

soil” to “exceptionally good rock“

K.W. John and
M. Baudendistel

7 Tunnelling Procedure Classes, (TPC-1 to TPC-7) from “very favourable” to “very
unfavourable” with evaluation from 100 to 0 %

2.4.2.3 Q System (Quality System)
The Q System of rock mass classification was developed in 1974 by Barton, Lien and
Lunde in Norway [14, 22]. The system is based on an analysis of more than 200 tunnel
projects in Scandinavia. Thanks to this analysis, it can be described as a quantitative sys-
tem. It is intended as a system for engineers to simplify the design of tunnel support.
The Q System is based on the numerical estimation of the following six parameters:
1. Determination of the rock mass quality ( RQD = Rock Quality Designation)
2. Number of joint sets as the joint set number ( J n )
3. Roughness of the least favourable joint as the joint roughness number ( J r )
4. Degree of alteration or filling of the weakest joint as the joint alteration number ( Ja )
5. Water ingress as the joint water parameter ( J w )
6. Stress conditions ( SRF = Stress Reduction Factor)
These six parameters are collected into three quotients, which give a weighted mathemati-
cal value for the rock quality Q calculated as follows:

RQD
J

J
J

J
SRF

r
a

w

Q = · ·

n