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Reliable sealing procedure with WEBAC
The Merowe Dam is a large hydropower project in Sudan. It dams up the river Nile about 375 km north of Khartoum. In 2000, the construction of the gigantic structure started which has a crest length of 9,280 m and a crest height of 67 m.
96% of the dam consist of main dams, rockfill dams and earth-core rockfill dams on each river bank. The smallest but most important dam section in the middle houses the water inlet power station (length = 370 m) and the spillway (length = 154 m). Since 2010, ten water turbines have generated about 80% of Sudan’s power requirement.
During the concrete work for the power station, maximum temperatures amounted to 40° - 50°C, and despite especially developed cooling systems cavities and water inclusions in the concrete structure were the result. Nor was a proper installation of the planned sealings in the horizontal construction joints and the vertical casting joints possible under these circumstances. The concrete had lost its “waterproofing” properties.
After damming the Nile not only water but also Nile mud penetrated the dam. Maintenance and service passages within the dam could no longer be walked on, and a safe operation was no longer possible. It was therefore urgently necessary to carry out a post-construction sealing measure on the structure.
Core drillings with a length up to 13 m were made from the galleries, the maintenance passages within the dam, into the water-bearing construction joints in a targeted manner. In so doing, slanting drill holes had to be made into the casting joints. In order to penetrate deep enough into the structural component, a special WEBAC® packer technology used in mining and tunneling was applied. Using this technology, the packers can be fixed in the structural component at any desired depth. In this way it was possible to inject all open joints with WEBAC® injection resins section by section and selectively seal them against the pressing water with up to 5 bar.
In the first step, the PU injection foam resin WEBAC® 150 was used to quickly and temporarily stop water from penetrating and to fill the cavities. In the next step, the PU injection resin WEBAC® 1403 was used to durably seal the structure with great success.
Given the exceptionally high temperatures and the very high air humidity the injection technique also had to be adapted to the special conditions on site. Thanks to the simple mixing ratio of 1 : 1 the two WEBAC PU injection resins which have both been tried and tested in classic structural sealing operations for many years are also ideally suited for reliable application by means of the 2-comp. pump WEBAC® IP 2K-F2. The separate delivery of the components to the mixing head prevents any premature reaction of the components and ensures fast reaction times regardless of the material’s workable life.
This is how the damage to the Merowe Dam has been repaired from 2011 with the help of pragmatic and smart sealing solutions from WEBAC, going beyond data sheets and sets of rules. The Merowe Dam can now continue to serve its purpose of power generation and irrigation.