Waste Rock Behavior at High Pressures: Dimensioning High Waste Rock Dumps - Multiscale Geomechanics: From Soil to Engineering Projects - page 103

management at a later stage. Indeed, the design criteria have to avoid the creation of
unnecessarily restrictive requirements at the closure stage.
Considering the mechanical behavior of the waste rock at high pressures,
subjected to overburden stresses well beyond any precedent, the front slope of a
dump should be designed with a smooth global angle, much flatter than 37°, with the
objective of generating a smaller loaded zone destined to constitute a high-strength
and high-permeability buttress. The decrease in stresses in the waste rock forming
the buttress will contribute to reduce degradation effects on the materials due to both
mechanical and leaching (natural or forced) actions [VAL 07].
Slopes with a low overall angle can be built on the waste rock dump by
constructing layers of limited thickness, instead of dumping the waste rock
regardless of height restrictions. The different layers, each with a local slope of
about 37°, should include intermediate berms to control any local instabilities
(affecting one layer). To control potential instabilities affecting more than one layer,
it is recommended that a large berm is included at a certain number of lifts, in
accordance with the overall stability.
An example of the application of these recommendations is presented in
Figure 4.17, showing the final geometry of a HWRD located in a narrow
mountainous valley in a highly seismic area. Figure 4.18 shows an example of a
stability analysis using the limit equilibrium method (LEM). These analyses were
complemented with a dynamic analysis and three-dimensional stability analysis
based on LEM.
Figure 4.17. Final layout of a high waste rock dump located in a
mountainous environment with high seismicity [ARC 06-07]