LUIS VALENZUELA P, RAMON VERDUGO A, JOSE CAMPANA Z & CARMEN G OPAZO A
There are two concrete gravity dams that were built around 1950: Marga Marga dam (21m high) built privately in 1949 in the Valparaiso region for irrigation purposes, and Arroyo Salado dam (34m) built in 1951 by a mining industry for water supply purposes. La Ventana dam (25m high) is another concrete gravity dam built by the mining industry in 1975 in the Central Region for water supply purposes. No damages caused by earthquakes have been reported at the last two dams. No information on the current situation of Marga Marga dam has been found.
Hydroelectric company Endesa built two concrete gravity dams: Calabocillo dam (20m high), built in 1975, and Polcura (26m high), built in 1980. Both dams, located in the Central Southern VIII region of Chile, were not affected by the Maule earthquake of 2010 even though they are located quite near to the fault trace and initial epicentre of the earthquake.
5.2 Concrete arch dams
Two arch dams have been built in Chile: one in 1910 (El Sauce dam) and the other almost 60 years later (Rapel dam), both of which remain in operation.
El Sauce dam (26m high) was built in the Valparaiso region by private investors as part of a hydroelectric project that operated up until 20 years ago. Nowadays the reservoir is used for water supply purposes[25]. No damage to this dam has been reported, even though it is situated in a zone of high seismic activity and not far from the epicentre of the Valparaiso earthquake of 1985.
Rapel dam (112m high) is a concrete gravity arch with double curvature. It was built in 1968 by Endesa and was an important milestone in the development of Chilean engineering of dams because of the extensive and intensive studies carried out in terms of rock mechanics, concrete technology, stress-strain and seismic analysis[20]. Numerical analyses were incipient in dam design in the 1960s; nevertheless a complex physical model was developed under the supervision of Prof. Lombardi from Switzerland.
This dam has been subjected to two major earthquakes: the Valparaíso earthquake of 1985 and the Maule earthquake of 2010. The Valparaíso earthquake (M = 8.0) affected mainly the region of San Antonio port and the town of Melipilla, precisely the region where Rapel dam is situated, which is only 100km from the earthquake’s epicentre. The accelerograph installed in a tunnel in the left abutment of the dam registered the following PGA: 0.31g (E-W) and 0.14g (N-S) in horizontal direction and 0.11g in vertical. An inspection carried out after the earthquake concluded that globally the seismic performance of the dam was satisfactory. Even though it suffered damage in several places they were not considered significant from a safety and operational point-of-view. The arch dam did not suffer any significant damage, but the appurtenant structures did. The spillway walls were cracked, and there was leakage at the wall of the right spillway. The upper part of one intake tower also cracked and separated from the dam.
In one report it is mentioned that “the satisfactory performance of the dam was consistent with the excellent seismic capacity exhibited by many concrete arch dams (to that date)”. It is
216 DAM ENGINEERING Vol XXXI Issue 3
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