Construction World December 2023

YUSUFELI DAM Y usufeli Dam is a 275 m high concrete arch dam on the Coruh River in the Artvin Province of Turkey. The dam has a developed crest length of 540 m and a section thickness of 8 m at the crest and 90 m at the base on the central portion of the arch. Yusufeli Dam is the highest dam in Turkey, the fifth highest double curvature arch dam in the world and ninth highest dam in the world. The dam was constructed with conventionally vibrated mass concrete and the structure contains 4 million cubic metres of concrete. The average concrete placement rate of the order of 140 000 m 3 per month achieved at Yusufeli Dam represents a world record for conventional mass concrete. The Yusufeli hydropower project includes an underground power station located beneath the right abutment immediately downstream of the dam, with an installed generation capacity of 558 MW and an average annual energy production of 1,8 billion kWh. It is predicted that the dam will contribute an annual amount of 1,65 billion Turkish Lira to the Turkish gross domestic product. As the central component of the Çoruh River hydropower development, Yusufeli Dam and HEPP is a landmark achievement for Turkey and a significant contributor in the country’s progress towards carbon neutrality. The dam was constructed with conventionally vibrated mass concrete and the structure contains 4 million cubic metres of concrete, impounding 2,1 billion m 3 of water at full supply level. Excavation for Yusufeli Dam commenced in 2014 and the final concrete lift in the dam body was placed in 2021. Impoundment was initiated at the beginning of 2023 and the water depth had reached 256 m by early September. With an underground power station located beneath the right abutment, the project has a hydropower generation capacity of 558 MW and annual energy production is anticipated at 1,8 billion kWh. The dam has a controlled crest spillway, with three gates, which is supplemented by two controlled spillway tunnels on the right flank discharging into the river approximately 1 km downstream of the dam. The dam has a system of four mid-level outlets, which discharge into the spillway plunge pool immediately downstream. The key innovations for Yusufeli Dam were:

placement. • The foundation modelling using Leapfrog allowed a very detailed

understanding of the foundation rock mass, which could then be modelled accurately thanks to modern Finite Element analysis software. • Developments in the understanding of mass concrete that came through Roller Compacted Concrete technology were put to good use at Yusufeli Dam to allow a concrete mix with lower total cementitious materials content. • Secondary issues were discovered in the generic relationships between tensile and compressive strength in concrete when applying the aggregate requirements that allowed a reduction in cementitious materials content. • A comprehensive system of foundation improvement and verification of the improvement achieved was applied. • A comprehensive monitoring and behaviour verification through analysis was implemented to assure safe impoundment. • The analysis stages and processes were more comprehensive than usual, reflecting the size and importance of the dam. • A very comprehensive process of design evolution with foundation excavation was followed. • All aspects of the construction were fairly exceptional and the record-breaking concrete placement rates were achieved thanks to a very well-organised construction team and the incorporation of two additional concrete plants, feeding concrete to the placement location by conveyor, enhancing the delivery capacity of the three cable cranes, particularly for the lower sections of the dam. 

PROJECT INFORMATION

• Company entering: ARQ Dams • Client: Limak Construction SA for DSi (Turkish State Hydraulic Works) • Main Contractor: Limak Construction SA • Consulting engineer: ARQ

• The use of “cushion concrete” as a stiffness transition between the high strength and high elastic modulus concrete of the arch and the lower strength, lower elastic modulus foundation rock mass. • The stress-relaxation creep of the fly ash rich CVC was lower than would normally be the case, allowing more rapid cooling without cracking. • Low stress-relaxation creep and proactive modelling of the concrete post-cooling and joint grouting process in conjunction with instrument monitoring allowed

more rapid concrete cooling and consequently more rapid concrete

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22 nd Best Projects Awards 2023