ABSTRACT
The Hongrin hydroelectric pumped storage scheme is located in Switzerland (Canton of Vaud); it was constructed at the end of the 1960s and presents two concrete arch dams 123 m high (northern dam) and 90 m high (southern dam). Both arch dams are connected by means of an artificial gravity abutment located on the central hill dividing both valleys.
The scheme is now more than 50 years old and over the decades, damages have materialized on the central artificial gravity abutment; namely, marked concrete cracking appeared along some horizontal construction joints, probably caused by insufficient concrete curing at the time of the construction (thermal cracking due to heat hydration). Over the years, such cracking pattern caused slow irreversible downstream displacements of the artificial gravity abutment in the range of 8 to 10 mm, which tend to increase over time.
The paper presents and discusses how the case was handled, starting for the monitored behaviour of both dams, the observation of damages in the artificial gravity abutment especially after the 2015 heatwave, the engineering studies considering a 3D model of both dams and the simulation of 15 years of operation, leading to the strengthening project consisting in the implementation of a total of approx. 50ʹ000 kN vertical prestressed anchors in the artificial gravity abutment. The rehabilitation works took place in 2018. As a result, favorable results in terms of structural behavior are being observed.
