SAFETY PERFORMANCE OF DAMS IN CHILE’S HIGHLY SEISMIC ENVIRONMENT
represented by the following: Santa Juana dam, built in 1995, which will be commented on in more detail later, and Puclaro, Corrales and El Bato dams which are briefly described as follows:
Puclaro dam is 83m high and was built in 1999. As with the other CFGD dams it is formed by a compacted gravel embankment with an upstream concrete face connected to a plinth and a diaphragm wall of plastic concrete (58m) built through the fluvial foundation consisting mainly of sandy gravel that has an estimated maximum depth of 100m. The crest width is 8m, upstream slope is 1.5:1 (H:V) and downstream 1.6:1 (H:V). Corrales dam, constructed between 2000 and 2004, is 69m high and also a CFGD-type dam with compacted gravel and a similar geometry to Puclaro and El Bato dams. It was not necessary to include a diaphragm wall.
El Bato dam is 55m high and was built in 2011 with similar geometric characteristics as Puclaro and Corrales, and a diaphragm wall 40m deep.
These three CFGD-type dams, the locations of which are shown in Figure 24, were inspected by the MOP[15] a few days after the Illapel earthquake of 16th September 2015 (M = 8.4) along with other dams also located in the III and IV Regions of Chile. Puclaro dam is 167km from the earthquake’s epicentre, Corrales 98.4km, and El Bato only 94.3km from the epicentre. None of these dams presented any significant damage, showing only typically local surficial rip-rap slides, movement in some auxiliary structures such as ladders and lighting poles, and surficial cracks at the crest. At the Corrales and El Bato dams, which are closer to the earthquake’s epicentre, there were also observed openings of the vertical joints of the concrete faces which required sealing maintenance and also cracks at some points of the union between the concrete faces and the concrete parapet.
The CFRD Santa Juana dam is located approximately 17km east of Vallenar City, in northern Chile. It was completed in 1995, and has a capacity of 166Mm3. The maximum height of the dam is 113.4m, with a crest length of 390m. It was constructed with rock particles with a maximum size of 1m and 0.65m in the upstream and downstream supporting shoulders, respectively.
All the material was adequately compacted. A cross-section showing the distribution of these two materials is presented in Figure 32. It can be seen that the upstream and downstream slopes are 1.5:1 (H:V) and 1.6:1 (H:V), respectively. The concrete face has a variable thickness, from 45cm at the base to 30cm at the top, where it has been transformed into a parapet wall.[17] The shape of the gorge of the narrow valley eroded by the Huasco River is shown in Figure 31. The profile is rather regular, probably due to the homogeneity of the rock properties at both sides of the river. A cut-off wall made from plastic concrete, 30m in depth, was built in the fluvial material located on the riverbed.
Vol XXXI Issue 3
DAM ENGINEERING
213
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