Slopes - Geotechnical Investigation and Design Tables - page 183

Table 14.24 Sensitivity of rock slopes to various factors (after
Richards et al., 1978).

Slope height

Rank

10 m 100 m 1000 m

1
2

< -------------------- Joint inclination -------------------- >
< --------- Friction angle --------- >

Cohesion

3 Unit weight Cohesion Water pressure

4 Friction angle Water pressure Cohesion

5 Water pressure <---------- Unit weight ---------->

Figure 14.4 Rockfalls.

14.25 Rock falls
•

The rock fall motion governs rock trajectory, and design of rock traps (fences and
ditches)

Table 14.25 Rockfall motions and effect on slope heights up to 40 m (Ritchie, 1963).

Slopes Rock fall motion Effect on trap depth Effect on trap width

>

75 ◦ Falling 1.0 m to 1.5 m 1.0 m (Low H) to 5.5 m (High H)

45 to 75 ◦ Bouncing Largest depth at a given height 1.0 m (Low H) to 5.5 m (High H)

1.0 m to 2.5 m

45 ◦ Rolling 1.0 m to 1.5 m 1.0 m (Low H) to 2.5 m (High H) < <