Goldfield Mill Deck Project Kambalda WA

Design & Services, Structural Design

NRM Consultants as structural consultants to Goldfields undertook an initial structural review of the existing mill deck slab for corrosion and concrete performance. The investigation subsequently found that the mill deck, composite construction of Hollowcore plank and topping, were structurally delaminated and compromised. This posed a risk to the use of Franna and other mine maintenance vehicles on the deck and possibility hampered the maintenance during shutdown due to imposed safety limits on the deck. Consequently, structural remediations were requested that allowed for the remediation of the mill deck in a phased operation, which was to be conducted during periods of limited shutdown.

The structure had to be temporarily braced for the loss of diaphragm action with the removal of the planks. Temporary bracing and support had to be installed before the removal of the deck structure. These were inspected during site visits.

Once the bracing was installed, planks were removed and replaced in a total of three phased operations. NRM Consultants were present during the construction operation to ensure that the engineers’ details were installed as instructed.

Gold Fields has nine operating mines in Australia, Peru, South Africa and West Africa (including the Asanko JV) and one project in Chile. St Ives has four underground mine areas and seven open pits contributing to the Mineral Reserve. There are seven underground mines and 16 open pits contributing to the Mineral Resource. Current ore stockpiles contribute 6.1% of the Mineral Reserve at the reporting date. There is a centralised administrative office and engineering workshop complex.

Challenge

The challenge for this project was to phase the project within the framework of the establishment mine shutdown periods. It was also a task to maintain the structural robustness of the gravity tower which was supported by the main mill deck structure. The challenge was to not damage the steel structure below the deck which relied upon the diaphragm action of the planks. In our structural detailing, we increased the structural diaphragm action and improved the composite performance of the steel supports to enhance the Franna load that could be accommodated on the deck.

Solution

NRM Consultants provided structural documentation in accordance with best structural practice utilizing our vast experience in the hollow-core precast plank product and knowledge of composite design.  The solution was a phased project that reinstated the slab construction with increased loading performance and greater resilience for durability.  We produced extensive structural documentation, health and safety risk assessment, on-site management and review services.  We overcome site obstacles noted during the works and in post concrete report issues of reduced strength.  We were able to validate the design with reduced compressive strength although additional durability coating had to be added on top of the concrete for protection.