# Cracks in Arch Dams: An Overview of Documented Instances
## 2 Observational Data/Material: Summary of Case Studies
### Double Curvature Dams
As a result, small cracks were detected on the upstream and downstream surfaces, while the bedrock of the dam abutment remained stable. _Kariba_ dam (1959): From the beginning of its exploitation, the structure showed some swelling. In 1963, localized cracks appeared to be forming. The right abutment was found to be insufficient to resist the load of the structure, so a large concrete block was added to the downstream face anchored by tendons, making the last four arch monolithts part of the original thrust block. In addition, the abutment was upgraded with grouting and underground buttresses. Since 2012 and due to the appearance of cracks on the right foundation, the dam has been at risk of collapse. Therefore, in 2018, work was started to repair the cracks. _Karun IV_ dam (2010). In 2011, cracks emerged in blocks 7 and 9 on the left bank, which led to the entry of water into a control gallery. In 2014, extensive analysis work was carried out, involving the processing of detected cracks with specific resins. This inspection exercise led to the detection of other cracks in the heel of the dam. These cracks are oriented downstream, while they are sub-horizontal on the upstream face of the dam. Additionally, these cracks lean toward the foundations near the mid-thickness of the dam. _Kolnbein_ dam (1977): Cracks developed in the upstream heel of the dam at the first impounding in both the foundations and the concrete of the dam, which enabled water to reach the central third of the base of the dam. Various interventions were adopted: reinforcement of the grout curtain with cement grout to reduce the uplift in 1979; injection of polyurethane resin, freezing of the central part of the bottom of the dam during the imposition in 1980-81; placement of a concrete blanket covered by plastic sheets at the bottom of the valley in 1981-83; repair and extension of the plastic sheets and grouting of the grout curtain in 1984-85. _La Tiajera_ dam (1994): A crack was identified along the connection between the vault and the base before starting to apply the load; that crack reached the core of the perimeter gallery. Various interventions were carried out between 1999 and 2002: solidification of the galleries, crack anchoring, injection of cracks, installation of irrigation in the walls and placement of reinforced concrete strips at the crest. _Matka_ dam (1938): In 2012, visual evidence was found of two cracks parallel to the slope at the top of the dam, but after considering the accumulation of limescale and moss, it was concluded that the cracks must have been older. In 2016, the cracks were repaired by grouting. _Nuraghe Arrubiu_ dam (1957): It was necessary to gradually inject the contraction joints during the pouring of the concrete (before the heat of hydration could dissipate and the concrete had cooled down). As a result, immediately after the end of the construction phase, numerous horizontal cracks appeared in the upper part of the upstream face, mainly in the horizontal construction joints. New cracks continued to develop until 1971, at which point a certain equilibrium seems to have been reached. In total, 176 cracks were identified. In 1995, epoxy resin injections were used to restore the continuity of the structure. _Pacoima_ dam (1928): As a consequence of the 1971 San Fernando earthquake, some instances of contraction joint opened near the thrust block. During the 1994 Northridgeearthquake, the contraction joint between the dam and the thrust block at the left abutment opened at the crest level. This opening was tied to a crack that ran diagonally across the bottom of the thrust block until it reached the abutment rock. The diagonal crack in the lower part of the thrust block corresponded to the enlargement of a slip plane below the rock masses. As a result, the left abutment was strengthened with 35 post-tensioned anchors. _Punt dal Gall_ dam (1969): Several cracks formed along the length of the dam, especially in the upper control gallery.