Stability investigation of embankments of a tailings pond for its dry closure: an Indian case study.

The demand for mineral products has increased substantially in recent years due to the rise in economic development. This results in the production of a significant volume of tailings waste. Due to this reason, the height (H) of existing tailings pond (TP) is frequently raised to accommodate the excess tailings released. This article presents a case study in which the stability of a TP, which was raised in phases to increase its storage capacity, is examined to understand its suitability for closure. While raising the heights in phases, geosynthetic reinforcements were introduced across the height of embankments to enhance the overall stability of TP. Furthermore, the height was increased by utilizing both downstream (D/S) as well as upstream (U/S) construction techniques. While examining the suitability of TP for closure, elaborate two-dimensional numerical simulations are performed to assess the overall stability of reinforced embankments of TP using finite-element-based software RS2. Initially, the stability analyses are carried out for the embankments at the end of final construction (i.e. after raising the height of TP) by utilizing the shear strength reduction technique. Subsequently, the stability of embankments is examined by incorporating the effect of seepage using partially coupled stress-seepage analyses. Results obtained from both analyses are expressed in terms of the critical strength reduction factor (SRF). Moreover, an attempt has been made to study the effect of beach width in determining the location of the phreatic line (which plays a vital role in assessing the overall stability of TP) within the TP. A decreasing trend in the SRF is observed when the beach widths behind the TP embankments are reduced from 5H to zero. Furthermore, the point of exit of phreatic line at the D/S slope of TP embankments is significantly lowered (for both D/S and U/S case) when the beach widths are increased from 0 to 5H. In addition, the critical SRF is observed to increase by 28.71% and 15.60% for D/S and U/S case respectively, when the geosynthetic reinforcements are used within the TP embankments. Overall, the TP in its current state is found to be stable, and with no further scope for raising, dry closure is recommended. [ABSTRACT FROM AUTHOR]