LUIS VALENZUELA P, RAMON VERDUGO A, JOSE CAMPANA Z & CARMEN G OPAZO A


and downstream compacted gravel shoulders with upstream and downstream intermediate filters of granular materials founded on fluvial deposits of gravels, and sands with a total maximum thickness of 55m beneath the central part of the dam. A typical section of the dam is presented in Figure 20.


Figure 20. Cross-section design of the Convento Viejo dam[18]


Construction of the project began in 1973, but work was halted in 1975 due to financial constraints. Construction resumed in 1978-1979, but once again was detained. The cofferdam and slurry wall allowed for the formation of a smaller reservoir that was in operation until the dam was fully completed in 2008. The construction of the earth dam under a new design, but incorporating the works realized until 1979, and an adjacent concrete dam for the spillway, were initiated in 2006 and finalized in 2008[18].


The Maule earthquake of 2010 (M = 8.8) was somewhat greater than the MCE considered in the design (MCE of M = 8.5). The results of the register for the Maule earthquake of three tri-axial accelerographs installed in the dam – and in an adjacent tunnel – are indicated in Table 2.


Superficial cracks were detected at the dam crest. It was not possible to identify, during repeated inspections of the earth dam, any seepage flow or filtrations in the downstream slope of the dam. One of the piezometers located at the crest of the dam presented a sudden rise in water pressure – interpreted as a possible crack in the clay core – but no increase in seepage or infiltrations confirmed this hypothesis. The maximum vertical deformations recorded at the crest, after the main earthquake, were lower than 35cm[18] A study through numerical analysis, which was carried after the earthquake, suggested that the earthquake modified the fundamental period of the wall; analysis which should be confirmed with the registration of new strong earthquake[19].


204 DAM ENGINEERING


Vol XXXI Issue 3


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