Enguri Hydropower Plant
Curtain Grouting and Waterproofing of One of the World’s Most Important Hydropower Tunnels
Initial Situation
The Enguri Hydropower Plant is one of the most important infrastructure projects in the Caucasus region and generates approximately 45% of Georgia’s electricity demand. A 15-kilometer-long pressure tunnel with an internal diameter of 9.5 meters connects the dam to the power generation facilities.
Despite several rehabilitation campaigns in previous years, the tunnel was still losing more than 10 m³ of water per second. To reduce these water losses, the tunnel was taken out of service for three months in spring 2021, allowing a comprehensive rehabilitation program to be carried out.
Project Challenge
The rehabilitation works had to be completed within a very limited shutdown period. Of the total 15 km tunnel length, approximately 2.5 km were identified as critical zones requiring intensive treatment.
The geological conditions were extremely challenging. The tunnel passes through karstified limestone formations containing voids, fractures, water-bearing zones, and areas subjected to significant groundwater pressure. Water inflows of up to 200 liters per minute were encountered in some sections.
ARCAN Solution
Extensive curtain grouting operations were carried out to seal water-bearing geological formations surrounding the tunnel. Approximately 420,000 liters of HydroBloc Polygel 530 acrylic gel were injected into water-bearing drill holes.
The highly flexible acrylic gel penetrated deeply into fractures, voids, and permeable rock formations, creating a long-lasting waterproof barrier within the surrounding ground.
HydroBloc 516 water-stop foam was used to control active water ingress and rapidly stop flowing water during the rehabilitation works. The fast-reacting foam allowed difficult water-bearing zones to be stabilized before the permanent grouting operations were performed.
In areas containing larger voids and active water flow, Hybridur 1250 was used. This innovative hybrid material combines the advantages of polyurethane and cement within a single system. The polyurethane component provides immediate water stoppage, while the cement component ensures permanent filling, consolidation, and stabilization of voids and cavities. This intelligent combination proved particularly effective in large water-bearing karst formations where both waterproofing and structural stabilization were required.
To create the grouting curtain, the following works were completed:
- 9,600 drill holes executed
- 54,700 meters of drilling completed
- 420,000 liters of HydroBloc Polygel 530 injected
- 2,370,000 liters of cement grout injected
Result
The rehabilitation works were successfully completed within the planned shutdown period. The extensive curtain grouting and water control measures significantly reduced water losses within the pressure tunnel and improved the long-term operational reliability of the hydropower facility.
The project contributes directly to the protection of one of Georgia’s most important energy infrastructures and supports the long-term security of the country’s electricity supply.
Special Features
At 271.5 meters in height, the Enguri Dam is the highest arch dam in the world. The rehabilitation of the pressure tunnel represents one of the most significant tunnel waterproofing and grouting projects carried out in European hydraulic engineering in recent years.
With 9,600 drill holes, more than 54 kilometers of drilling, and 420,000 liters of injected acrylic gel, the project is an outstanding reference for large-scale curtain grouting using HydroBloc Polygel 530.
Particularly noteworthy was the use of Hybridur 1250 for the treatment of water-bearing karst voids. By combining polyurethane and cement in a single system, the material delivers two critical functions simultaneously: immediate water stoppage through the polyurethane component and permanent filling and stabilization through the cement component. This innovative approach proved highly effective and economical in large underground cavities subjected to active water flow.
The successful execution under extremely challenging geological conditions demonstrates the performance and reliability of modern ARCAN injection technologies in tunnel engineering, dam rehabilitation, and large-scale civil infrastructure projects.
Materials Used on This Project
Project Photos
