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.

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Study of Slope Stability of Tailings Dam Height Expansion from Elevation (RL)2000m to RL 2035 at Hidden Valley Mine, Papua New Guinea

 This video was recorded live during Cooperative International Network for Seth Science and Technology (CINEST) in 2021. Hope you learn something here.

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Study of Slope Stability of Tailings Dam Height Expansion from Elevation (RL) 2000m to RL 2035m at Hidden Valley Mine, Papua New Guinea

 ABSTRACT

The tailings dam height expansion from the initial RL of 2000 m to 2035 m at Hamata Tailings (Dam) Storage Facility (TSF) at Hidden Valley Mine in Papua New Guinea pose some risks in terms of slope stability conditions. In this study it is proposed to analyse the TSF at four stages. i.e.RL 2000, RL 2015, RL 2025 and RL 2035. Based on the design parameters and material properties, this study utilizes Phase 2 software to analyse the slope stability conditions of the TSF. The embankment construction methodology in stage 1 is downstream whereas the other stages (2-4) are upstream method of construction. Numerical Simulation (Modeling) of the TSF is done in four stages (1-4) with three parameters, (1) Simulation without Reinforcement; (2) Simulation with Reinforcement (s); and (3) Simulation with Seismicity. Simulation result(s) that give Critical Shear Strength Reduction Factor (SRF) of 1.3 or above is/are ideal for consideration in this study. The findings in this study is somewhat useful for the mining company for future height expansion plans for the TSF and also it is helpful to government for assessment purposes for future TSF height expansion proposals. Future Researchers may analyse other safety aspects not covered in this study.

 Keywords: Tailings dam, slope stability analysis, Dam Height expansion, embankment, Shear Strength Reduction Factor(SRF), RL-Reduced Level(m), downstream construction method, Upstream Construction Method. Phase 2 Numerical Simulation, Reinforcement, Seismicity.

 

Google image of Hidden Valley TSF

Note: Full paper for this abstract  is ready and can be accessed upon request via contact form in this website.

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Slope Stability Analysis of Hamata Tailings Dam, Hidden Valley Mine, Papua New Guinea

 ABSTRACT

Construction and management of Tailing dams in Papua New Guinea (PNG) is faced with many challenges such as high altitude with high rainfall (2000-5000 mm/yr), high seismicity and structurally controlled zones which pose threat to the slope stability of tailings dams. Therefore, slope stability analysis is necessary to give confidence to some extent to the stakeholders. The location for this study is at Hamata Tailings (dam) Storage Facility (TSF) at Hidden Valley Mine in PNG which has two rock/earth filled embankments, the main dam and the saddle dam with downstream construction method. Currently the TSF owner is planning to raise the dam height from RL 2000 to RL 2015 with extra 15 Mt storage capacity as the pond water approaching its designed capacity at RL 2000. The objective of this study is to analyse the slope stability of Hamata TSF using phase 2 based on the design basics for the crest expansion from RL 2000 to RL 2015 and beyond and recommend an ideal slope stability under various conditions in terms of shear strength reduction factor ((SSRF). The results obtained in this study is useful for PNG Mining Regulators in comparing company results in the appraisals for tailings dam development proposals and, it will be useful to future researchers in PNG and other similar tropical regions.

 Keywords: Tailings dam, slope stability analysis, Hamata TSF crest expansion, embankment, Shear Strength Reduction Factor, RL-Reduced Level(m).

 

Google image of Hidden Valley TSF

Cross Section 2

Note: Full paper for this abstract  is ready and can be accessed upon request via contact form in this website.

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Tailings Dam Construction in Papua New Guinea a Challenge

Tailings dam constructions in Papua New Guinea (PNG) are faced with natural factors such as  high altitude with high rainfall (2000-5000mm), active seismic zone and other geotechnical structural factors which pose threat to the stability of tailings dam and potential failure.  As such, the PNG government has allowed mining companies to discharge tailings into the river systems over the last 30 to 40 years which pollutes the riverine and ecology within the vicinity of the mine impacted communities downstream.  However, the PNG Government intend to discourage riverine tailings disposal and encourage tailings dam construction in PNG.

The current tailings dams in PNG include Hidden Valley Tailings Storage Facility(TSF) and K92 Mine Tailings Dam.

The Porgera Gold Mine discharges its tailings into the Strickland River in the Enga Province. The Ok Tedi Copper and Gold Mine at the Mt.Fubilan, Tabubil in the Western Province discharges its tailings into the Ok Tedi River System.

The Lihir Gold Mine in the Luise Caldera of New Ireland Province places its tailings onto the deep sea floor (DSTP).

The Ramu Nickel and Cobalt Mine at Kurumbukari in the Madang Province also practice the deep sea tailings placement (DSTP).

The Wafi Golpu project is an advanced project with the Special Mining Lease Application lodged with the Mineral Resources Authority and is under technical appraisal by government at its engaged  independent consultants. This project proposed for a DSTP.

The Frider River Project proposed for an Integrated Storage Facility which will contain waste rock and tailings at the same time. The dam will also but used as hydro-dam to generate electricity.

The government of Papua New Guinea will never or might not allow riverine tailings discharge for all future mines in the country. It would be either by practice of building of Tailings Storage Facilities of place them one deep seafloor.

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