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Table 3 Summary of Laboratory Results (Parameters for Stability Analysis) 3.3 Re-Design Options

Table 3 Summary of Laboratory Results (Parameters for Stability Analysis) 3.3 Re-Design Options

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Fig. 1 Configuration of the Stage 6 TSF (Source: Knight Piésold, 2016) Table 1 Current Beach Conditions of Main North and South Embankments (June 2018) maintained above the minimum 1.5 as per the LI 2182. The various Stage 6 embankments include:
Fig. 1 Configuration of the Stage 6 TSF (Source: Knight Piésold, 2016) Table 1 Current Beach Conditions of Main North and South Embankments (June 2018) maintained above the minimum 1.5 as per the LI 2182. The various Stage 6 embankments include:
Fig. 3 Allowable Bearing Capacity (kPa) for North Embankment Beaches
Fig. 3 Allowable Bearing Capacity (kPa) for North Embankment Beaches
fig. 2 Allowable Bearing Capacity (kPa) for South Embankment Beaches
fig. 2 Allowable Bearing Capacity (kPa) for South Embankment Beaches
Table 2 Summary of Laboratory Test Results (Construction Specification)
Table 2 Summary of Laboratory Test Results (Construction Specification)
Fig. 4 Average Bearing Capacity (kPa) for Embankments
Fig. 4 Average Bearing Capacity (kPa) for Embankments
Fig. 5 Schematic Section of the Regular Downstream Raise at Stage 7 Raise 1:1.25 (V: H) slope that extends about 6 m on to the tailings beach. The downstream arm of the raise will be placed entirely over the Stage 6 face to maintain the same slope at the rear side with a reduced expanse of land take at the natural ground level compared to the downstream method. of a 5.5 m lift from elevation 1044.5 mRL to the regulated 1050 mRL above the Stage 6 raise with a section of the upstream toe sitting upon the tailings beach as platform. Fig. 7 shows a Schematic Section of the Centreline Raise at Stage 7. The geometry shows regular 10 m crest with an upstream face at
Fig. 5 Schematic Section of the Regular Downstream Raise at Stage 7 Raise 1:1.25 (V: H) slope that extends about 6 m on to the tailings beach. The downstream arm of the raise will be placed entirely over the Stage 6 face to maintain the same slope at the rear side with a reduced expanse of land take at the natural ground level compared to the downstream method. of a 5.5 m lift from elevation 1044.5 mRL to the regulated 1050 mRL above the Stage 6 raise with a section of the upstream toe sitting upon the tailings beach as platform. Fig. 7 shows a Schematic Section of the Centreline Raise at Stage 7. The geometry shows regular 10 m crest with an upstream face at
Fig. 6 Schematic of a Modified Upstream Raise at Stage 7 Raise
Fig. 6 Schematic of a Modified Upstream Raise at Stage 7 Raise
Fig. 7 Schematic of the Proposed Centreline Raise at Stage 7 Raise
Fig. 7 Schematic of the Proposed Centreline Raise at Stage 7 Raise
Table 4 Summary of Key Model Outcomes Modelled outputs showing upstream and downstream analysis’ critical slip surface locations and FoS for the centreline design (South Embankment) are presented for review. Fig. 8 shows a Model of Slip Surface locations and FoS for the centreline option.
Table 4 Summary of Key Model Outcomes Modelled outputs showing upstream and downstream analysis’ critical slip surface locations and FoS for the centreline design (South Embankment) are presented for review. Fig. 8 shows a Model of Slip Surface locations and FoS for the centreline option.
Table 5 Summary of Stability Analysis Results
Table 5 Summary of Stability Analysis Results
Fig. 8 Model of the Slip Surface Locations and FoS for the Centreline Option The analysis was based on the assumption that the Stage 6 capacity was filled up and the Stage 7 raise construction was just completed and available for operations. Upstream and downstream analysis of the critical slip surfaces for the three methods revealed that upstream analysis yielded sufficiently high FoS values (minimum 2.8) for all walls whereas the downstream analysis yielded FoS values ranging from 2.8 to a minimum of 1.6. These values are consistent with the minimum FoS value of 1.5 required under Regulation 264 (b) and (k) of LI 2182. The upstream FoS values for the northern embankments were higher than those of the southern embankments whilst the downstream values were lower than the latter respectively. The recent use of cycloning at the northern beaches and the rockfill zone within the southern walls may possibly explain the observed patterns in FoS data.
Fig. 8 Model of the Slip Surface Locations and FoS for the Centreline Option The analysis was based on the assumption that the Stage 6 capacity was filled up and the Stage 7 raise construction was just completed and available for operations. Upstream and downstream analysis of the critical slip surfaces for the three methods revealed that upstream analysis yielded sufficiently high FoS values (minimum 2.8) for all walls whereas the downstream analysis yielded FoS values ranging from 2.8 to a minimum of 1.6. These values are consistent with the minimum FoS value of 1.5 required under Regulation 264 (b) and (k) of LI 2182. The upstream FoS values for the northern embankments were higher than those of the southern embankments whilst the downstream values were lower than the latter respectively. The recent use of cycloning at the northern beaches and the rockfill zone within the southern walls may possibly explain the observed patterns in FoS data.
Table 6 Summary of Sustainability Analysis It is evident from Table 6 that the aggregate rankings for technical, economic and regulatory elements for upstream design was 91. However, the centreline option ranked 14 points higher at 105 and therefore considered a more suitable approach and thus recommended for adoption by ARL as short term strategy in developing future raises. Overall, the centreline method would present lower environmental and socio-economic risks to local area resources resulting from any accidental dam failure.
Table 6 Summary of Sustainability Analysis It is evident from Table 6 that the aggregate rankings for technical, economic and regulatory elements for upstream design was 91. However, the centreline option ranked 14 points higher at 105 and therefore considered a more suitable approach and thus recommended for adoption by ARL as short term strategy in developing future raises. Overall, the centreline method would present lower environmental and socio-economic risks to local area resources resulting from any accidental dam failure.
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