Bridge Umbeluzi - Mozambique

Structure protection for the long run

On the Goba Line, which links the port of Maputo in Mozambique with the landlocked Swaziland, an old bridge over the Umbeluzi river was showing serious signs of decay and had to be replaced by a new bridge. The new 362 metre long bridge, made of steel and concrete, meets the increased carrying capacity needs of both nations and supports a load of 27 tonnes per axle. Trains of over 100 wagons can pass along the new bridge. It will be intensively used over the years, so durability and low-maintenance were a priority. Mozambican President Filipe Nyusi stated during the inauguration of the new bridge: “Traffic must flow over this bridge to be commercially aggressive in mobilising traffic, otherwise the bridge will not have a speedy return on the investment.”

Challenge

The bridge is equipped with a ballasted track system. To ensure the durability the bridge had to be protected against micro-cracks caused by ballast hitting the concrete structure on the sides. This problem was addressed from the beginning in view of experiences over the world with problems caused by deterioration of concrete bridges through lack of protective measures.

The vibration caused by passing trains might in the future cause problems with the condition of the concrete and it also evokes a so-called mirror-effect. The vibration in the track superstructure is mirrored back to the passing train, which in the long run may affect the rolling stock.

The dynamic loads of passing trains result in ballast attrition. This causes a greater deflection of the track and an extra need for maintenance.

Rockdelta solution

Rockdelta resilient mats installed between the ballast and the concrete are an effective solution for minimizing problems at the transition zones and to assure full structural protection.At the same time the vibration attenuation that is one of the core properties of Rockdelta mats prevented the mirror-effect from occurring.