Location: Island of Sulawesi
Client: Joint project with Astaldi Thiess
The tropical island of Sulawesi is approximately 1,000km north of Australia and is one of the larger islands in the Indonesian Archipelago, the largest system of island groups to be found anywhere in the world. Located north west of the existing Batubesi Dam at Lake Towuti, the Balambano Dam is being constructed on the Larona River, the island's largest river. It is approximately 30km south west of the nearest population centre at Saroako, which is on the southern shore of Lake Matano.
The Balambano Dam is a gravity rolled and compacted cement [RCC] hydroelectric structure that is being built to supply additional energy to the expanded PT INCO [PT International Nickel Indonesia] major pyrometallurgical nickel processing plant at Saroako, where output is currently set to double to 68,000 tonnes a year. The electric power provided by the dam will reduce the sensitivity of the Saroako mining facility to the fluctuations in the world price for nickel.
The dam is 90 metres high, with a crest length of 350 metres, containing some 546,000 cubic metres of lean concrete, with impermeability guaranteed by a PVC membrane installed on the upstream face of the dam.
A 38 metre wide radial grated spillway is positioned mid way across the dam and around 45,000 cubic metres of conventional concrete was used in the construction of the spillway and power intake structure. Water is conveyed to the powerhouse by two five-metre diameter metal penstocks that are securely anchored to the downstream face of the dam.
To complete the project against the tight deadline, RMD Kwikform utilised a substantial quantity of three of its most versatile and successful systems - Superslim Soldiers, along with Alform Aluminium Beams and the Kwikstage Access and Shoring system.
The project also called for the use of a wide selection of formwork accessories and the design and manufacture of special steel formwork for certain constructional elements. This included the off-site manufacture of 20 tonnes of special curved and shaped sections of formwork that were used to construct the pier and abutment nosings on the upstream face.
Superslim Soldiers were chosen because of their ready availability, their high strength-to-weight ratio, and the system's ability to effortlessly accommodate complex geometric shapes. The Superslim Soldier system was teamed up with Alform Beams, which were used as secondary members spanning between the Soldiers. They were also used to form plywood-decked platforms.
Superslim Soldier and Alform Beam wall forms were craned into position and were restrained using a range of sacrificial cast-in anchors and tiebars welded to the concrete reinforcement bars. Where necessary, special shear brackets were used to space the formwork off completed lower sections of the concrete structure. Superslim Soldiers were also extensively utilised as support brackets and raking shores.
The facing to the Balambano formwork was also supplied by RMD Kwikform as part of its 'total supply' solution. It was mostly either locally sourced plywood or, for certain applications, high strength plywood specially imported for the task from Australia. Steel facing was, however, used for the special pier and abutment nosings.
RMD Kwikform's modular Kwikstage was used extensively for working access to the chute walls and pier abutments. The system was also put to work as temporary falsework on various parts of the project.
Kwikstage was particularly suited to the project, bearing in mind the pressure to return the contract to schedule, as it is highly adaptable, reduces construction times and is renowned as being a particularly cost-effective solution. Indeed, Kwikstage can even be used where projects involve complex multi-curve profiles that are almost impossible to support economically using less sophisticated systems.