Por: F.A. Flores e I. Zarate, Ingenieros Geotecnistas Mexicanos, O. Flores y V.L. Hernández, Instituto de Ingeniería, México, y V.L. Hernández, WSP, México.

Abstrac

LIn the mining industry, large earthfill structures known as waste rock dumps (also referred to as tepetateras or terreros in Spanish) are constructed to contain solid mining waste. They consist primarily of large volumes of end-dumped material placed in multiple sections extending for several kilometers, with heights ranging from 150 to 500 m. Consequently, slope design is a critical aspect of their construction.

This paper presents the design of a waste rock dump intended for construction in four stages. Considering the construction stages, slope stability is evaluated for each stage under both static and pseudostatic conditions. In addition, stress-deformation analyses and a transient seepage analysis are performed. 

To carry out this evaluation, previous site exploration campaigns conducted in the foundation area and in an adjacent waste rock dump were considered. The assignment of mechanical parameters considered the variation in stress throughout all stages of construction. A total of 312 stability analyses were performed using limit equilibrium methods under different parametric conditions. 

A sensitivity analysis was conducted by plotting slope height against the corresponding factors of safety obtained for Stages 1 through 3. The results of the sensitivity analysis indicate that, under both static and seismic loading conditions, the minimum required factor of safety is satisfied in most cases, provided that a maximum slope height is not exceeded. Finite difference analyses were also performed, incorporating variations in the friction angle for each layer comprising the waste rock dump, as well as localized variations in the mechanical properties of individual elements within the embankment body. 

In addition, transient seepage analyses were performed to evaluate the infiltration of rainfall into the waste rock dump. The analyses were carried out using the finite element method, considering an initial steady-state seepage condition followed by an extreme rainfall event resulting in water infiltration into the embankment. These analyses evaluated the pore water pressures generated within the embankment slopes, as well as the seepage forces that could give rise to localized instability.