Transverse Cracking on Embankment Dams Due to Earthquakes

In recent years several major earthquakes have occurred in California causing significant damage. Many earth dams of various sizes have been affected by these events. Cracking is a common result of these events with the severity determined by the magnitude of and distance from the energy release, the condition of the dam, and special geometries or factors associated with the individual dam structures. Cracking transverse to the dam axis is a particular concern since there may be a possibility of releasing reservoir water through those cracks which could further enlarge with erosion and compromise the dam. While no such event has occurred, engineers are aware of this potential mechanism.

The Loma Prieta Earthquake of 1989, the Landers Earthquake of 1992, and the most recent Northridge Earthquake of 1994 have affected many of the more than 1200 dams in the state. The authors briefly describe the damage to several dams influenced by these quakes and summarize the transverse embankment cracking found on 20 of them after those events. The authors provide a simple correlation between transverse cracking depth and settlements of the structures due to ground shaking. This correlation may be useful in helping to establish freeboard requirements for other dams located in a seismic environment.

Cases cited; Almaden, Elmer J. Chesbro, Guadalupe, Vasona Percol., Lexington, Upper San Fernando, Los Angeles, Los Angeles North Dike, Lower Franklin, Santa Felicia, Wide Canyon, Sycamore Canyon, Cogswell, Porter Estates, Las Llajas, Brand DB, Rubio.