The Hazelmere Dam in South Africa during capacity expansion.
The Hazelmere Dam in South Africa, located about 30 kilometres north of Durban, plays a central role in supplying drinking water and irrigation to the coastal region of KwaZulu-Natal. Originally built in 1977, it had a capacity of just under 24 million cubic metres. In 2017, the dam was raised by seven metres – a major infrastructure project with international participation. Paul Maschinenfabrik from Dürmentingen played an exciting role in this: With its many years of experience and in-depth expertise in the field of prestressed concrete technology, it made a significant contribution to the success of the construction project. For over 100 years, Paul has been synonymous worldwide with precision, reliability and technological leadership in mechanical engineering ‘made in Germany’.
By raising the dam from 86 to 93 metres, the capacity nearly doubled to around 44 million cubic metres of water. The surface area of the reservoir now covers approximately 1.9 km². An enormous additional load acting on the dam and an equally great challenge to its stability. The Australian ground anchor specialist SRG was commissioned with this demanding task. For this project, SRG relied on leading-edge technology from Upper Swabia: Two high-performance stressing jacks were ordered from Paul Maschinenfabrik – with a stressing force of 15,000 kN and 22,000 kN, each with a stroke of one metre. The stressing operation was to be carried out in a single stroke – a special technical feature. A total of 40 ground anchors were stressed using the smaller of the two stressing jacks – each with up to 61 strands.
At the time of delivery, the 22,000 kN stressing jack from Paul was the most powerful stressing jack in the world. For comparison: 22,000 kN corresponds to a tensile force of approximately 2,200 tons. This would be enough to lift 55 fully loaded lorries. Using this technical colossus, the SRG team installed a further 43 ground anchors, each with 91 strands – these were also considered to be the most powerful permanent ground anchors in the world at the time. SRG proposed the idea of a more efficient anchor solution as early as the tendering phase: Instead of the original anchor design from 1977, larger and more powerful anchors were used. This reduced the number of ground anchors required from the original 243 to just 83 – an optimisation that was convincing both technically and economically. In order to precisely control the prestressing force of these 83 anchors, Paul developed a special lifting device in 2018, which was also delivered to SRG. Due to financial delays, the last ten ground anchors were not stressed until October 2022 – a late completion of a technically and logistically extraordinary project.
In addition to delivering these two stressing jacks, affectionately called ‘Big Ladies’ by the customer SRG, Paul also carried out the calibration of these stressing jacks prior to delivery in collaboration with partner institutes in Germany and Switzerland. Both stressing jacks, weighing seven and ten tons respectively, were transported to South Africa by air freight, which also posed challenges for Lufthansa. Unloading in Durban required the use of a mobile crane.
In March 2024, the South African Government News Agency reported on the successful completion of the Hazelmere Dam. With an 83 per cent increase in capacity, the structure is expected to make an important contribution to the reliable water supply in the region in future. With its technology and expertise, Paul Maschinenfabrik has made a decisive contribution to this international infrastructure project – once again demonstrating its competence in prestressed concrete technology.
