Environmental Engineering Reference
In-Depth Information
Figure 19.15.
Rotating screw device for breaking up the salt layer on top of alumina red mud tailings.
(Photograph courtesy of Geographe Earthmoving).
Table 19.7.
Typical values of effective friction angle
of tailings (adapted from Vick,
1983).
Effective stress range (kPa
(1)
)
Material
(degrees)
Copper
Sands
34
750
33-37
625
Slimes
33-37
625
Taconite
Sands
34.5-36.5
-
Slimes
33.5-35
-
Lead-zinc-silver
Sands
33.5-35
-
Slimes
30-36
-
Gold slimes
28-40.5
900
Fine coal refuse
22-39
270
22-35
1100
Bauxite slimes
42
175
Gypsum tailings
32 (c
22 kPa)
450
Note:
(1)
From zero to these maximum values.
in pore pressures at the collapse surface, and is a lower strength envelope than the drained
shear strength (see Figure 6.9).
19.4.6.2
Undrained shear strength
The undrained shear strength of the “slimes” or clay-silt sized part of the tailings can be
important both from the view of overall slope stability in upstream construction and the
strength of the surface of the tailings for rehabilitation.
The strength can be determined by appropriate triaxial testing, e.g. using the SHANSEP
method (Ladd and Foott, 1974), but must be related to the field situation by a knowledge
