The discharge channel of the Setúbal Thermoelectric Power Plant showed signs of settlement in the reinforced concrete lining panels on the left bank. Horizontal cracks, with a maximum width of approximately 10 mm, were visible along the first five panels.

An underwater inspection confirmed the suspected undermining of the foundations, revealing excavation and erosion of the canal bed sand on the left bank to a depth of at least 1 meter. The entire foundation lintel was exposed, with an under-excavation of around 10 cm. The objective was to stabilize the settlement and prevent the rupture of the channel lining.

Applied Technique

To stabilize the settlement and prevent the failure of the channel lining, the following works were carried out (on one panel as a pilot test):

• Stabilization of the pilot panel through the injection of cement-based grout to consolidate and fill the voids in the foundation soil beneath the panel;
• Repair of damage to the panel above and below the waterline (cracks and fissures);
• Placement of a riprap layer to stabilize the canal bed and prevent scouring at the foundation area of the panel;
• Repair of the stormwater drainage network in the road adjacent to the canal, which was damaged and clogged (in the area of the pilot panel), and installation of drainage systems.

The stabilization of the pilot panel was carried out by injecting cement-based grout. The repairs were performed using underwater techniques.

Results

Using underwater techniques, it was possible to effectively rehabilitate the power plant's discharge channel lining without the costly need to halt operations or install cofferdam systems.

Additional information

The work was initially carried out on one panel as a pilot test.