Defensive design of concrete gravity dams

Failure of a concrete gravity dam during an earthquake could occur as a sliding instability along an earthquake-induced crack, possibly assisted by uplift pressures from water flowing into the crack. Reliable assessment of the likelihood of such an event is thought to be difficult, and this suggests a need for designs which are less prone to cracking and uncertain behavior than are typical existing designs. Several schemes for reducing the potential for cracking during earthquake loading are investigated by finite element simulations: use of a sliding plane at the base of the dam, modification of the cross-sectional shape, use of a joint in the upper part of the clam, prestressing, and hydrodynamic isolation. The sliding plane, modified cross-section, and upper joint may only be applicable to new construction, while prestressing and hydrodynamic isolation could also be used to upgrade existing dams. While all of the schemes show potential, modification of the cross-sectional shape is probably the most practical considering acceptability, cost and effectiveness