Waste Rock Behavior at High Pressures: Dimensioning High Waste Rock Dumps - Multiscale Geomechanics: From Soil to Engineering Projects - page 87

4.4.2. Triaxial tests

Waste rock tested on compressional triaxial paths, with initial confining
pressures of up to 2.5 MPa, are indicated on Table 4.1. The samples were
completely saturated before each of the tests.

The effective mean stress [p'] and vertical stress [σ v '], reached at the end of the
different tests, performed are equivalent to overburden heights of about 300 m to
560 m, as indicated in Figure 4.3 .

Grain size distribution
(GSD) tested

Material Initial confining pressure, σ ' 3 (MPa)

ROM waste
rock

Homothetic MGS
20 cm (8”)

CID: 0.1; 0.2; 0.5; 1.0; 2.0

Homothetic MGS
20 cm (8”)

CID: 0.2; 1.0; 1.5; 2.5

Leached waste
rock

CID: 1.2 (initially consolidated at 2.0); 2.0.
CIU: 1.7; 2.5

Cut < 20 cm (8”)

Crushed waste
rock

MGS 20 cm (8”) CID: 1.0; 1.6; 2.5

MGS: maximum grain size; CID: compressional triaxial drained; CIU: compressional
triaxial undrained

Table 4.1. Detail of triaxial tests performed

Waste Rock Dump

Maximum
Height ~ 990 m

~ 560 m

~ 400 m

Leached WR
(oedometric test)

~ 300 m

Leached and Crushed WR
(triaxial & oedometer)

ROM (triaxial &
oedometer)

Figure 4.3. General layout of a high waste rock dump. Equivalent overburden loads
to the final mean stresses reached in tests