# Cracks in Arch Dams: An Overview of Documented Instances
## 2 Observational Data/Material: Summary of Case Studies
### Single-Curvature Gravity-Arch Dams  
Baishan dam (1984): The base concrete was poured over the summer, resulting in a large difference between the maximum temperature rise and the stabilized concrete temperature, which exceeded 40 \({}^{\circ}\)C. Despite this, no relevant cracking was observed in the dam concrete, even when it was subsequently subjected to severe cold temperatures. The main and solely feasible reason for cracking was that the MgO content in the cement used was large (up to 4.5%), and the combustion temperature of the cement was relatively low, resulting in a compensatory shrinkage effect of the MgO-containing concrete.  
Chencun dam (1971): After detecting cracks in 1972, the reservoir level experienced an obvious increase in the decade of the 1980s, and the crack mouth opening displacement (CMOD) decreased from the rapid growth. In contrast, in 1987, the CMOD records rose rapidly as a result of epoxy grouting. The reason for this was that the grout limited the free crack closure in high-temperature situations and impacted the minimum CMOD, so the minimum CMOD readings of most of the segments climbed.  
Dam D (1992): Along this dam, 135 cracks were identified, mostly in Section 9 of the dam. In order to properly monitor the cracks, a total of 134 joint meters were installed in the dam, 74 of them located in Section 9 of the dam.  
Dam E (2012): In 2010, the first four cracks were detected on the surface. The expanding state of the cracks worsened when water was allowed to pass over the surface. The cracks became deeper and wider, and two of them even extended from the surface upstream to the surface downstream.  
Isola dam (1960): The dam began to deform upstream after about 5 years. Initially, the central area of the crest moved an average of 0.3 mm/year, a rate that increased from 1985 to about 1 mm/year. One crack was clearly detected in the early 1980s, although it was presumed to have originated during construction. This crack was monitored and its width was growing at a rate of 0.15 mm/year.  
Sayano-Shushenskaya dam (1978): Between 1988 and 1989, a horizontal construction joint or crack opened close to the upstream face at 87.5 m above the dam base. In 1990, horizontal block joints and cracks were found to have opened in an area 50 m from soil contact. In 1991, the opening of block joints and cracks was detected at 192 m above the base of the dam. Furthermore, it was found that radial section joints on the downstream face penetrated to a depth of up to 3 m with an opening of 1.6-3.8 mm.  
_Spitallamm_ dam (1932): After pressure grouting, a crack developed which caused a disconnection between the face concrete and an intermediate tanking concrete zone. The geometrical structure of this crack consisted of a nearly horizontal progression from downstream to upstream along the construction joints; a lateral extension across eight blocks; a vertical detachment at the interface between the face concrete and the tanking concrete located over an elevation of 101.86 m to 31.86 m above the dam base. As a result of the above, the substitution of the original dam with a new dam was initiated in 2019.