ABSTRACT
Earthquakes induce an additional load on embankment dams. Under certain conditions, the seismic effect represents a major risk for large dams. It imposes a need during the analysis – in order to obtain a realistic solution – in addition to the static conditions existing before the earthquake, to also take into consideration the state of additional load during an earthquake. Earthquake load is of short duration, cyclic and involves motion in both horizontal and vertical directions. Earthquakes can affect embankment dams by causing any of the following consequences:
• Sliding, or the instability of both the upstream and downstream slopes. As a final consequence, sliding can lead to total failure of a dam;
• Deformations, i.e. vertical and horizontal displacements of the embankment, followed by developed cracks, especially exhibited in the zone of the dam’s crest;
• Reduction of freeboard as a result of considerable crest settlement caused by additional compaction of the embankment due to ground motion, which may, in a worst case scenario, result in overtopping of the dam;
• Differential movement in the contacts of the dam’s body, abutments and embankments – the concrete parts – which would increase the hazard of contact seepage and the formation of privileged seepage paths along contact surfaces;
• Liquefaction, or loss of shear strength in zones of the embankment or its foundation, due to increase in pore pressures which, in a worst case, may lead to failure of a dam (De Alba et al., 1988; Seid-Karbasi & Byrne, 2004);
• Differential movement in a possible fault passing through a dam’s foundation below its body;
• Overtopping of the dam by flood waves due to earthquake-induced landslides into the reservoir from the valley sides;
• Damage to appurtenant hydraulic structures, both general and specific, as well as to the equipment, including damage caused by landslides and rockfalls in very steep valleys (as happened in 2008, during the Wenchuan earthquake in China).
