Engineering Rock Mechanics

240 Rock mechanics interactions and rock engineering systems

line, with W being the furthest having the highest C + E value. The
dominant factors, C > E, plot to the right of the C = E line, as is the case
for F and C.
The overall conclusion is that we have a moderately interactive system
structure in which Water Flow has the strongest interaction. Fractures
and Construction slightly dominate the system (being slightly to the
right of the C = E line) and Rock Stress and Water Flow are slightly
dominated by the system (being slightly to the left of the C = E line).
These conclusions depend, of course, on the values assigned to the
interactions.

414.9 In developing a rock mass classification system for estimating

the relative instability of natural rock slopes in the Italian Alps

(Mazzoccola and Hudson, 19965), the following parameters were

chosen.

P1. Geology P2. Folds P3. Faults P4. Rainfall

P5. Freeze P6. Previous P7. Intact rock P8. Weathering

and thaw instability strength

P9. Number P10. Orientation P1 1. Aperture P12. Persistence

of sets

P13. Spacing P14. Mechanical P15. Rock mass P16. Hydraulic

properties strength conditions

P17. Slope P18. Slope P19. In situ P20. Potential

orientation dimensions stress instability

The 20th parameter, 'Potential instability', was added in a similar

way to the Construction term in Q14.4 in order to consider the effects

of the parameters on potential instability.

An interaction matrix was generated using these 20 parameters

as the leading diagonal terms. The interactions in the off-diagonal

terms were then assigned a value according to the same scheme as

in Q14.8:

0 - no interaction; 1 -weak interaction; 2 - medium interaction;

3 - strong interaction; 4 - critical interaction.

This gave (C,€) co-ordinates and values of C + E and C - E as follows.

pi p2 P3 P4 P5 P6 P7 P8 P9 P10

C 24 34 52 17 21 22 15 9 24 28

E (^5 4 3 4 17 42 8 27 13 12)
C+E 29 38 55 21 38 64 23 36 37 40
C-P 19 30 49 13 4 -20 7 -18 11 16
P11 P12 P13 P14 P15 P16 P17 P18 P19 P20
C 27 26 18 9 9 21 21 8 18 0
E (^22 19 20 26 40 29 17 19 16 60)
C+E (^49 45 38 35 49 50 38 27 44 60)
C-E 5 7 -2 -17 -31 -8 4 -11 2 -60
5Mazzoccola D. E and Hudson J. A. (1996) A comprehensive method of rock mass
characterization for indicating natural slope instability. Q. 1. Eng. Geol., 29,37-56.