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


#### **Table 11.**

*Joint water reduction factor (Jw) values [13].*


High professionalism is required for estimation of the values of parameter used in this system. The poor professional users may face trouble while approximating the score of the parameters and may approximate the lesser value for Q-System,

**3 Jr values Jr**

**4 Ja values φ<sup>T</sup>**

C A little altered joint-walls with Non-softening mineral coatings; sandy particles/ clay free fractured rock, etc.

G Strongly over-consolidated, non-softening, clay mineral fillings (less than 5 mm Continuous thickness).

H Medium or low over-consolidation, softening, clay mineral fillings (less than 5 mm continuous thickness).

L Zones of clay, disintegrated rock. Joint alteration depends on the percentage of swelling clay-size particles.

N Thick continuous zones of clay. Joint alteration depends on the percentage of welling clay-size particles.

O Thick and continuous clay zones. Joint alteration depends on the percentage of swelling clay-size particles.

I Swilling clay fillings, i.e., montmorillonite (less than 5 mm continuous thickness).

b. Rock-wall contact before 10 cm shear with a slim mineral filling

c. No rock-wall contact due to thick mineral filling even after shear

A Hard impermeable filling firmly healed hard such as epidolite/quartz 0.75 B Only surface staining with unaffected joint walls. 25–35° 1

D Silty/sandy clay coatings. Small clay fraction. 20–25° 3 E Mineral coatings with clay of low friction, such as Mica/Kaolinite etc. 8–16° 4

F Clay-free fragmented rock, sandy particles 25–30° 4

J Zones or bands of crushed rock. Medium or low over-consolidation. 16–24° 6 K Zones of clay, disintegrated rock Medium or low over-consolidation. 12–16° 8

M Thick continuous zones of clay or band of clay. Strongly over consolidated 12–16° 10

iii. Jr. = 0.5 can be used for planar, slickensides joints having lineation, provided that the lineation

**approx.**

25–30° 2

16–24° 6

12–16° 8

6–12° 8–12

6–12° 8–12

12–16° 13

6–12° 13–20

**Ja**

Note: ii. 1. Add 1.0 if the mean spacing of the relevant joint set is greater than 3 m.

are oriented for minimum strength.

a. Rock-wall contact (no filling, just coatings)

*Joint roughness number (*Jr*) values [13].*

**Table 9.**

*Slope Engineering*

**Table 10.**

**62**

*Joint alteration (Ja) values [13].*

The width and altitude of the underground excavations mainly depend on the class of rock mass and considered as significant elements in design of underground excavations. The facet of width or altitude directly disturbs the stability when amplified or declined. To highlight the safety obligation, Bortan et al. (1974) further

which is considered the weakness of this classification system [14].


**Table 12.**

*Stress reduction factor (SRF) values [13].*


**Table 13.**

*Rock mass classification based on Q-system [13].*

carry the addition of a fresh parameter to Q-System named as excavation support ratio (ESR). The lower value of ESR symbolizes the necessity of great level firmness and vice versa. The ESR is used for the estimation of support system that can be set up to sustain the stability and also associated to the anticipated use of excavation. Incorporating various conditions, different values of ESR are summarized in **Table 14**. Based on the width and altitude of underground excavation, ESR shows the Equivalent dimension that is achieved by means of the Eq. (4) [13].

$$De = \frac{\text{width or altitude in meter}}{\text{ESR}} \tag{4}$$

wide-ranging framework established on the empirical data that what kind of support system is recommended in case of rock bolt's center to center spacing and the thickness sprayed concrete, and also give the energy absorption of fiber strength-

This classification system established and improved by Hoek and other researchers including the block size and its shear strength in order to estimate value of GSI quantitatively. The GSI index value for any rock mass is depend on the estimation techniques, expertise and reliability of these two input parameters. Sonmez and Ulusay developed the arithmetical basis for GSI value calculation and present quantitatively GSI chart as given in **Figure 5** [16]. Further research were carried out for quantification of GSI value by (Cai, et al.,2004), they present the assessment method for block size, joint and joints wall condition for GSI value

GSI system should not be considered as the replacement for other classification systems like RMR and Q-System, as this system cannot recommend any support system for stability of rock mass. This system can only be used in estimation of rock mass properties and input parameters for numerical modeling [15]. The comprehensive practice for estimation of input parameters for numerical analysis of stress condition and the remedial measures is presented in **Figure 5** (Hoek, 2013). The GSI index may be estimated by subsequent various methods used for

*Method A:* Using this method the GSI is estimated by skilled geologist or mining engineers from the data collected (observational data) at site and then the value of

ened sprayed concrete.

**Figure 4.**

quantification.

**65**

assessment of rock mass.

GSI is evaluated from chart [17].

**4.2 Geological strength index (GSI)**

*Permanent support system recommendation chart for Q-system [13].*

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

The support chart proposed by Bortan et al. (1974) as shown in **Figure 4**, is based on the Q-system ratings and equivalent dimension for the endorsement of permanent support system for underground excavations. This chart provides a


**Table 14.** *Excavation support ratio (ESR) [13].*

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

**Figure 4.** *Permanent support system recommendation chart for Q-system [13].*

wide-ranging framework established on the empirical data that what kind of support system is recommended in case of rock bolt's center to center spacing and the thickness sprayed concrete, and also give the energy absorption of fiber strengthened sprayed concrete.
