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Rehabilitation of the Tailrace of the Setúbal Thermal Power Station
The Setúbal Thermal Power Station tailrace showed signs of settlement in its left bank reinforced concrete covering panels. Horizontal gaps with a maximum width of 10 mm could be seen in the first 5 panels (photo 2).
An underwater inspection confirmed the suspected lack of support for the foundation, with excavation and dragging of the sand at the bottom of the channel on the left bank to a depth of at least 1 metre, exposing the entire foundation lintel with an excavation of approximately 10 cm (photo 4).
In order to stabilize the settlement and avoid the rupture of the channel covering, the following work was performed (on one panel, as a test):
- Sstabilisation of the test panel with a cement grout injection to consolidate and fill the existing gaps in the soil beneath the panel,
- Repair of damage to the panel above and below the water line (gaps and cracks),
- Application of a gravel layer to stabilize the bottom of the channel and avoid removing sand in the panel foundation area,
- Repair of the rainwater drainage system of the roads next to the channel that was cracked and blocked (in the test panel area) and installation of drains.
The use of underwater working techniques allowed us to effectively rehabilitate the Station's tailrace covering without the need for costly stoppages or the creation of drying systems.
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View of the downstream channel.
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Horizontal gap in the left bank covering panels.
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Underwater work.
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Removal of the foundation lintel with 10 cm excavation.
