Willard Dam - Behavior of a Compressible Foundation

Willard Dam, a 14.5-mile-long, 36-ft-high embankment was constructed on an arm of the Great Salt Lake. The foundation consists of an interfingering of the deltaic deposits from the Weber-Ogden river system and Bear river with lakebed sediments several hundred feet thick. This foundation material is highly compressible, low strength, and variably impermeable. The silt or clay has a borderline classification between organic and inorganic and low and high compressibilty. The paper describes the highlights of 14 yr of investigation, testing, design and construction that went into creation of a structure that by normal soil mechanics practices could not be built. Its behavior during construction and since completion, based on a extensive installation of behavior measuring apparatus has disclosed performance that has not previously been observed. This should be taken into consideration where construction for similar foundation conditions is contemplated.