Repair of the air slope of the Iskar dam
"National Electricity Company" EAD
Iskar Dam
Repair of compromised stone joints with different geometries – 457,10 м;
Restoring areas with missing stones– 32,32 м²;
Restoration of areas with both missing and detached stones– 60 м²;
Restoration of areas with detached stones – 43 м²;
Запълване и възстановяване на каверна в тялото на бързотока с размери 600 × 200 × 50 – 0,60 м³;
Cleaning, restoration and treatment of longitudinal joints between the fast flow and wing walls, as well as joint 10/11– 210 м;
Hydroblasting of areas to be repaired– 1920 м²;
Collection and transportation of construction waste to a landfill at a distance of up to 50 km – 10 м³.
The project includes the implementation of construction and installation works to restore the stone cladding of the air slope of the Iskar dam, as well as the rehabilitation of the joints between the wing walls and the rapid flow of the facility.
The dam is a massive gravity structure, built of conventional concrete, with a height of 74.65 m and a crown length of 204 m. The air slope is lined with local red sandstone, which gives the characteristic architectural appearance of the facility.
Condition before repair
As a result of many years of operation and the impact of atmospheric factors – temperature amplitudes, intense rainfall and snow accumulation – a number of defects have occurred in the cladding and structure:
erosion and destruction of the joints between the stone elements
partial detachment and fall of cladding blocks
compromised concrete joints
damage to the wing walls and areas around the high-voltage line
All problem areas have been previously examined, described and mapped in a technical report, which served as the basis for the implementation of the repair activities.
Implementation via rope access
Due to the specifics of the site and the impossibility of effectively using scaffolding or lifting equipment, all construction and installation works were carried out using the alpine method, via rope access.
The activities were carried out by qualified industrial mountaineering technicians, certified for work at height, while complying with all safety and control requirements.
Before the restoration works began, the surfaces were thoroughly cleaned by water jetting with a hydroblaster under pressure up to 250 bar.
The restoration of the stone cladding was carried out with materials corresponding in type, structure and color to the original red sandstone, in order to preserve the authentic architectural appearance of the dam wall.
The main activities include the restoration and rearrangement of compromised stone elements, the rehabilitation of joints between the cladding stones using specialized repair systems, the restoration of compromised concrete joints and the repair of sections between the wing walls and the bottom of the rapid flow with UV-resistant polyurethane and microporous rope
All activities were carried out with materials intended for the repair of concrete structures and hydrotechnical facilities, ensuring durability and stability during operation.
About the site
The Iskar Dam is located in the upper reaches of the Iskar River, near the city of Sofia, and is the main source of water supply for the capital.
The dam wall is part of the Iskar cascade and, according to current legislation, is classified as a facility with the first high degree of potential danger, which requires the implementation of all repair activities under extremely high quality and safety requirements.
