*Design Techniques in Rock and Soil Engineering DOI: http://dx.doi.org/10.5772/intechopen.90195*

application in different rock engineering fields such as mining, hydro power projects, tunneling and hill slope stability (Kumar S. S., 2012). The geo-mechanics classification incorporates the following 6 parameters that are computable in the

While using this classification system, the rock masses are divided into a number of structural regions. Each region is classified independently [12]. These six parameters are being given different rating based on different geological and geotechnical

Based on the overall rating of RMR calculated form above mentioned parameters support systems are being recommended for the project site. Support recommen-

This system of rock mass classification was devised by Barton et al., (1979) in

Norwegian Geotechnical Institute (NGI), explicitly for the design of tunnel established on 212 case histories. The rock mass classification system is generally used for tunnel design throughout the world and has been used in approximately 1260 various projects and considered as one of the best classification systems for design of tunnels (Kumar N., 2002). The extreme ratings of Q-System shows good quality of rock mass and the lowest ratings designate poor quality of rock mass. The minimum and maximum of Q-index ranges from 0.001 to 10000 on logarithmic scale. According to this classification system Q is the function of six independent

Q

<sup>¼</sup> *RQD Jn*

� *Jr Ja*

*RQD* Rock Quality designation index, *Jn* shows joint set number, *Jr* shows number of joint roughness estimated for the set of joint that is most terrible and dangerous to alignment of tunnel, *Ja* show joint alteration number estimated for the most dangerous and unfavorable set of joint along the alignment of tunnel, *Jw* is joint water condition which shows the water reduction factor, Stress Reduction Factor, SRF is comprised to consider the consequence of in-situ stress condition on the whole quality of Rock. The following comments are offered by Barton et al. (1974) for explaining the meaning of the parameters used to decide the value of Q.

� *Jw*

demonstrating the organization of the rock mass, is a

*SRF* (3)

.

dation based on RMR value is given in **Table 6**.

site and from cores [6]:

*Slope Engineering*

1.Uniaxial compressive strength

2.Rock quality designation (RQD)

3. Spacing of discontinuities

4.Condition of discontinuities

6.Orientation of discontinuities

5.Ground water condition

condition as shown in **Table 5**

parameters as defined by Eq. (3).

The first quotient *RQD*

rough measure of the block size.

*Jn* 

*4.1.6 Q-system*

Where,

**56**

**57**


Infilling (gouge)

**59**

Rating Weathering

Ratings **F. EFFECT OF**  Drive with dip - Dip 45–90°

Very favorable

Drive against dip - Dip 45–90°

Fair *\*Some conditions are mutually exclusive. For example, if infilling is present, the roughness of the surface will be* 

*\*\*Modified after Wickham et al. (1972).*

**Table 5.** *Rock mass rating system [5].*

**DISCONTINUITY**

Strike

perpendicular

 to tunnel axis Drive with dip - Dip 20–45°

Favorable Drive against dip - Dip 20–45°

Unfavorable *overshadowed*

 *by the influence of the gouge. In such cases use A.4 directly.*

 **STRIKE AND DIP** 

None

 Hard filling <

Hard filling

Soft filling <5 mm

Soft filling >5 mm

> >5 mm

> 5 mm

> > 6

Unweathered

6 **ORIENTATION**

 **IN** 

**TUNNELING**

**\*\***

5

3

1 Strike parallel to tunnel axis

> Dip 45–90°

Very unfavorable

Dip 0–20 - Irrespective

 of strike°

Fair

Dip 20–45°

Fair

 Slightly

Moderately

Highly weathered

weathered

weathered

4

2

2

0

Decomposed

0

*Design Techniques in Rock and Soil Engineering DOI: http://dx.doi.org/10.5772/intechopen.90195*

#### *Slope Engineering*


#### **Table 5.**

*Rock mass rating system [5].*
