Effects of layering on the mechanical properties of cemented tailings backfill under unconfined compression
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Authors
Chiloane, Nhleko Monique
Issue Date
2022-12
Type
Thesis
Language
en
Keywords
Cemented tailings backfill , Backfilled stope stability , Layered backfill , UCS
Alternative Title
Abstract
This study investigated the mechanical behaviour of layered cemented tailings
backfill. Indeed, paste backfill in low stopes can be poured completely at once.
However, this strategy is difficult in large stopes since it exerts excessive pressure
on the barricade leading to the failure of the barricade. As result, layer-by-layer
backfilling poured within a 24-hour interval is adopted. This practice leads to the
stratification of the backfill structure which then results in a layered backfill body.
Several studies on backfill bodies have neglected the effect of layering on the
mechanical strength of the backfill structures. This study attempted to close this
gap by incorporating the shear force between the layers in the estimation of the
safety factor of the backfill structure.
In order to study the mechanical behaviour of layered cemented backfill, laboratory
tests, numerical simulations and mathematical modelling were conducted. Uniaxial
compressive strength tests were performed using an unconfined compression
machine. The OPTUM G3 software package, on the other hand, was utilised for
numerical analysis. The limit equilibrium wedge solution was used to evaluate the
stability of layered cemented backfill while results from the laboratory tests were
used to develop a deformation model of layered cemented backfill.
It was concluded from the deformation model that the strength of cemented backfill
decreases with increasing layers of backfill at early age (14 days). Nonetheless,
the strength of layered cemented backfill gradually increases when more layers
are added. The limit equilibrium solution was also improved by incorporating the
shear forces acting along the backfill-backfill interfaces and the sliding plane. The
limit equilibrium solution also demonstrated a decreasing safety factor when the
shear force along the backfill interfaces is included. In contrast, the safety factor
decreased with increasing stope height. It is however recommended in future that
advanced numerical analysis is explored to develop stability graphs that would
predict the waiting period for the backfill body to set till the next blast. This would
pave the way for improved safety and productivity of mines.