Slope stability rating (SSR) classification system

SSR considers five additional parameters whose relative effects on the stability of fractured rock slopes were precisely examined based on data retrieved from different rock slope sites. An overall rating for the rock mass is obtained from the summation of the individual ratings of each parameter. In this method data was collected from different mine sites to get the information of Dry unit weight, GSI, Intact rock properties (Young’s modulus, UCS and Reduced mass ???……………) and final designed geometry (Disturbance factor, slope height and slope angle).

 

Among the number of parameters that may influence the stability of jointed rock masses besides the discontinuities condition (reflected by the GSI value), the following five parameters have been retained:

1.    Uni-axial Compressive Strength (UCS) of intact rock

2.    Rock type (Lithology)

3.    Slope excavation method

4.    Saturation of slope

5.    Horizontal earthquake acceleration

 

The final SSR value of a given rock mass is obtained on the basis of rating values of all the parameters, as illustrated in Table 2.7.

 

 

Table 2.7 SSR (Slope Stability Rating) rock mass classification system for preliminary evaluation of slope stability

Parameters

1

UCS (In Mpa)

0-10

10-25

25-50

50-100

100-150

 

0

7

18

28

37

 

2

Rock type

Group1

Group 2

Group 3

Group 4

Group 5

Group6

0

4

9

17

20

25

3

Slope excavation method

Waste damp

Poor blasting

Normal blasting

Smooth blasting

presplitting

Natural slope

-11

-4

0

6

10

24

4

Ground water rating

Dry

0-20%

20-40%

40-60%

60-80%

80-100%

0

-1

-3

-6

-14

-18

5

Earthquake force rating

0

0.15g

0.20g

0.25g

0.30g

0.35g

0

-11

-15

-19

-22

-26

 

The SSR value is obtained by summation of the individual rating of each parameter, whose relative weight was calibrated based on a number of case studies. The system was additionally reviewed and subsequently modified on those case studies.