Application of Geotextile on Slope Stability for Establishment of Tailings Dam in Gold Mines – The Case of Hidden Valley Mine, Papua New Guinea

1. Introduction

The Hidden Valley (HV) tailings dam/storage facility (TSF – Fig.1) is constructed with downstream method of embankment. The initial dam crest elevation was designed for RL 2,000 with a storage capacity of 40Mt of tailings with a mill throughput of 4.2Mtpa, (Rynhoud et al., 2017). The TSF has reached its designed capacity at RL 2,000 and the mining company plans to raise the dam height to RL 2,015 to increase the volume. In this study, it proposes for further 20m dam height expansion in two stages (RL 2,025 & RL 2,035) with the application of geotextile reinforcements for slope stabilization.

Fig.1 Hidden Valley (HV) tailings dam

2.Numerical Simulation

Analysis of the TSF is carried out in 2 cross sections (Fig.2) with 4 stages (stg): RL 2,000(stg.1), RL 2,015(stg.2), RL 2,025(stg.3), RL 2,035(stg.4). Phase2 software is used for numerical simulations with: (1) no reinforcement; (2) geotextile reinforcement. Desired critical shear strength reduction factor (SRF) is 1.3 and above.

Fig.2 Model view of section AA' and BB' at RL 2,000

3. Results, Discussion and Conclusion

Fig.3 Stability of dam at different RL with no support

Fig.4 Stability of dam with reinforcements at different RL in X2

Fig.5 Effectiveness of reinforcements at RL 2,000 (X1)

It is unstable at initial stage with no support in X1(Fig.3). Geogrid and Geocomposites are unstable in X1, whereas structural interface is stable in X1(Fig.5). In X2, it is stable at initial stage, but unstable as the dam height increases (Fig.3). Geogrid and Geocomposites are stable at initial stage but, unstable as dam height increases (Fig.4). Structural interface is consistent and stable (Fig.4).

RL 2,035 is possible to achieve with the application of geotextile reinforcement in structural interface for stability in both X1 and X2.