The Seismic Rehabilitation of the Mormon Island Auxiliary Dam Key-Block

摘要

Mormon Island Auxiliary Dam (MIAD) near Folsom, Calif., is a zoned earthfill embankment dam that was completed in 1953 as part of federal Central Valley Project water management scheme. Studies by the Bureau of Reclamation indicate that MIAD has a high seismic risk associated with foundation liquefaction leading to embankment failure. Upgrades were performed using in-situ soil improvement techniques over 10 years ago, however more recent studies concluded that the seismic risk remained at an unacceptable level. In response, the Bureau of Reclamation designed a downstream key-block with fill overlay. The key-block consists of a mass of lean concrete founded on moderately weathered bedrock and overlain by structural backfill built at the toe of the dam.