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 strengh, and variably impermeable. The silt or clay has a borderline classification between organic and inorganic and low and high compressibility. The paper describes the hightlights of 14 yr of investigation, testing, design and construction that went into the creation of a structure that by normal soil mechanics practices could not be built. Its behavior during construction and since completion, based on an extensive installation of behavior measuring apparatus has disclosed performace that has not previously been observed. This should be taken into consideration where construction for similar foundation conditions is contemplated.