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Gold mine stockpile cover

News International-French

29 Jan 2016

Advantic engineers delivered a remedial structural system that enabled the safe and cost effective operation of a gold mine in Kalgoorlie, Western Australia by combining multi-material structural analysis, high tolerance manufacturing of structural polymer materials, focused “design for constructibility” expertise, and construction installation support.

Kalgoorlie Consolidated Gold Mines Pty Ltd (KCGM), a joint venture between Barrick Gold Corporation and Newmont Mining Corporation, had determined that a 258 foot (78.5 meter) suspended conical roof structure (stockpile cover) required structural remediation works to critical steel members in order meet business objectives of safe and sustainable production until the end of the life of the gold mine, currently projected for 2029. Site conditions included aggressive chemical attack coupled with damaging impacts by heavy earthmoving equipment.

The result was substantially reduced load carrying capacity of 80 foot (24 meter) long primary structural steel members undergoing compression and bending. Prior to Advantic’s involvement, KCGM engineers undertook substantial engineering investigation and analysis of the structure to understand critical loads, member forces and the subsequent risks to the business, via the assistance of traditional external engineering consultants. A number of conventional material solutions incorporating steel, concrete, and grout had been proposed with costs ranging from $8 million to $13 million AUD, each requiring an extensive shutdown period to complete the remedial construction effort, which would dramatically impact the operation of the plant and its ability to meet its yearly production targets. The large capital expense, coupled with the impact to production and operations amid volatile mineral prices, required the client to re-think the path forward. KCGM looked to Advantic for an alternative solution.

Conventional Material Solution: $8 to $13 million AUD
Advantic Structural Jacket Installation: $3 million AUD
Cost Savings: $5 million AUD 63% less than the conventional

Recognizing that little guidance exists in the successful design and integration of advanced composite material solutions in infrastructure applications, Advantic provided a staged engineering approach as an integral activity within the project delivery program.

Corroded and Damaged Steel

Engineering Design
After reviewing all existing documentation and studies on the structure, Advantic formulated conceptual solution approaches including analytical design methodologies, preliminary first principle analyses, and basic material selection and characterization. Preliminary design, however, does not end at the drafting table. A site visit enabled the Advantic team to meet with KCGM project management team as well as potential installation contractors. A concise agenda enabled the rapid extraction of information concerning critical construction opportunities and limitations as well as to build relationships with key personnel. Finite element analyses were performed on each critical structural member to investigate the optimized design geometries necessary to achieve minimum material performance requirements. Each member was modeled independently, including an accounting of all field-surveyed damage and cross section reduction due to corrosion. Leveraging strong  relationships with global adhesives manufacturers, Advantic performed a further experimental program to identify and characterize performance for the design geometries and load paths. The final design solution involved a system-level approach incorporating multiple material interactions: stainless steel, thin bond line structural adhesive, Advantic polymer composites, and field-installed thick bond line structural adhesive. The solution took the form of hundreds of Advantic ‘jackets’ installed to provide continuous reinforcement of the existing structural members. Due to the criticality of the work and nature of the design solution, being a world first, KCGM requested third party engineering peer review of the design effort and outcomes, which was undertaken by two independent design firms.

Advanced Manufacturing Given that this was a first production run of a new product, Advantic rapidly developed the constituent material supply chain, manufacturing methods of multi-material assembly, and quality control program necessary for such a critical structural work. KCGM engaged a third party to oversee manu-facturing quality control throughout the effort by reviewing the production processes and records by Advantic, as well as Advantic’s suppliers.

An aggressive delivery schedule was required for the project, which Advantic accommodated by internally expediting manufacturing though use of additional specialist tooling and drawing on flexibility in human resources to ramp up production. A total of 648 Advantic jackets were manufactured in less than eight weeks, comprising a stainless steel outer skin bonded over an inner, precast polymer structural sleeve made with Advantic’s trademarked Fortis cast epoxy polymer, which contains glass microspheres, making it one-fifth the weight of conventional concrete solutions.

System Integration KCGM desired to install the remedial jackets during a planned maintenance shutdown of the facility. Construction delays would result in production loss to the operation which would consequently add to the overall ‘total’ project cost, and as such the methods and speed of installation were critical to project success.

The jackets were designed to be structurally bonded to the prepared surface of the existing steel members with an advanced structural adhesive.

Complicating efforts, the environmental conditions were anticipated to be extremely hot, dry, and dusty, requiring substantial forethought on adhesive application due to potential for shortened cure time and surface contamination detrimental to bond strength. Further to this, the client required the installation solution to be as simple as possible to enable traditional construction resources to undertake the works, without any specialist knowledge or training in adhesives and polymers.

Advantic Jacket Schematic

Advantic sought to overcome these challenges via the development of an extensive installation Work Methodology document complete with step-by-step instructions with three-dimensional CAD renderings and photographs for each step. As part of the Work Method preparation, Advantic fabricated a full scale model section of the existing structure on their manufacturing floor and prototyped the installation method.

The Work Method document became part of the tender package for the works, and was a source of constant reference during installation and facilitated in briefing of the contractor’s staff.