The Maguga Dam Project
Komati Basin Water Authority (KOBWA)
The Komati River Bridge
The existing bridge on the MR1 between Piggs Peak and Mbabane has to be replaced with a new bridge as the existing bridge will be overtopped with at least 8m of water when the Maguga Dam is built and fully inundated. The consulting engineers responsible for the design and construction supervision of the bridge is the Maguga Dam Joint Venture. This joint venture consists of Consult4 from South Africa and ZMCK Consulting Engineers from Swaziland.
The project to construct the new bridge with associated roadworks was awarded to Grinaker Construction in May 1998 for a contract amount of E21 million and a contract period of 12 months.
The new bridge consists of two abutments, six piers and seven span pre-stressed continuous hollow concrete box deck. All foundations for the abutments and piers were founded on medium to hard rock and anchored with galvanized dowels drilled into the rock. The centre pier is 32 metres tall. The piers are hollow with solid sections at the bottom and top. A total of 1440 m3 of concrete and 150 toms of reinforcement were used to construct the piers.
It was decided to use the incremental launching method to construct the 305 metres bridge deck across the Komati River. The advantage of this construction method is that no temporary support is needed during the construction of the deck.
The 305 metre long deck has a 6% super elevation, a 375 metre radius and a 1.75% uphill grade. The deck was constructed in twenty segments of 15.2 metres each behind the first abutment. A total of 125 m3 of concrete and 23 tons of reinforcement were used to construct one segment. The segments were cast in three stages and were constructed at a rate of one per week. The segments were stressed to each other with pre-stress cables and pushed across the river over the piers with a steel launching
nose. The minimum concrete strength needed for stressing was 30 MPa which was normally reached within 60 hours. The design 28-day strength of the concrete used for the deck was 50 MPa. A total of 70 km of pre-stress cables was used to stress the segments together.
The central four piers were temporarily stayed during the launching operation to withstand the launching forces with a total length of 2.4 km of stressing cables.
The final launch was carried out on Wednesday 18th August 1999 when the 6800 ton deck was pushed into its final position.
Further Details
Further details of the project can be obtained from:
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The Komati Basin Water Authority (KOBWA)
Suite 1010 The Pinnacle
1 Parkin Street
PO Box 5085
Nelspruit 1200
Republic of South Africa
Tel +27 1311 23 191
Fax +27 1311 24 704
Email kobwanpt@cis.co.za
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The Swaziland Komati Project Enterprise (SKPE)
4th Floor Dhlan'ubeka House
Cnr. Tin & Walker Streets
Mbabane
Swaziland
Tel +268 404 7950
Fax +268 404 7954
Email: komatpcu@realnet.co.sz Website: www.ecs.co.sz/komati/ |
The information provided above does NOT in any way represent the OFFICIAL opinion or views of KOBWA or the Swaziland Government about the Maguga Dam Project
This page was last updated on 05 November 2001
Social and Environmental Responsibility
The Components of the Development
The Komati River Bridge
The Piggs Peak Bulk Water Supply