On the border between Zambia and Zimbabwe stands the Kariba hydroelectric dam, one of the world’s largest. It was weakened by a crack that opened up in the plunge basin due to pressure from flood waters and now requires major remodelling work including blasting, excavation, and concrete injection reinforcement of the plunge basin. In order to carry out the work at the foot of the dam completely safely and isolate the work zone, Razel-Bec’s engineering and innovation teams designed an innovative coffer dam which is currently under construction: the process to construct the piles out of the water, then float them into place, guarantees the quality of the structure.
In January 2020, the first of the total of seven piles forming the coffer dam was built on a semi-immersed lift before being lowered into the water to its floating level (4.5m). It was then moved to its final location by a barge, filled with concrete and raised using climbing formwork to reach its definitive height of 12 metres.
In early 2021, the piles will be linked together with waterproof metal doors, sealing the coffer dam. 2,000,000m3 of water will have to be pumped in successive stages to make the plunge basin accessible and begin the remodelling and reinforcement work. Once this has been completed, the coffer dam will have to be disassembled before the valves can be reopened.
Faced with numerous lateritic road rehabilitation sites damaged by overloaded HGV traffic, Razel-Bec’s teams have developed a cold recycling reinforcement technique called emulsion-based recycling & improvement in partnership with Bomag. This technique is used to treat damaged lateritic roads in place, by adding bitumen emulsion. The road surface and base courses are ground up using a pulvimixer. A Bomag MPH 600 recycler then mixes in bitumen emulsion and water. The mixture is then levelled and compacted to form the new base course.
This technique was trialled for the first time in the Ivory Coast in 2017-2018 on the project to rehabilitate the road linking the towns of Bongouanou, Kotobi, and Akoupé. It is currently in use in Mali, on a site to rehabilitate a 6.5km section of the RN6 highway in Bamako.
Finally, its use is being considered for sites in Cameroon and Burkina Faso. With its low consumption of both materials and energy, plus its efficiency and durability, emulsion-based recycling and improvement could prove a hit with plenty of project owners on the African continent.
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