Subsurface investigation of liquefaction, Imperial Valley earthquake, California, October 15, 1979

Abstract

Subsurface investigations were made to study the effects of liquefaction caused by the October 15, 1979 earthquake (M=6.6), at Heber Dunes County Park and at River Park, Imperial Valley, California.Highly detailed profiles were constructed from cone penetration tests, standard penetration tests, large volume disturbed samples, and undisturbed tube samples.Liquefaction effects including sand boils, ground cracks, and lateral spreading occurred at the Heber Road site in a 5-m deep, loose, channel-sand deposit.The deposit occurs in an abandoned channel that is part of an ancient delta.The banks of the channel contain a moderately dense overbank deposit, and a dense point bar deposit.Other than a few sand boils over a buried pipeline, no liquefaction effects occurred in the denser sand deposits outside the channel.Hundreds of sand boils erupted on the flood plain of the New River at River Park.The sand boils at River Park originated from 3-m deep, loose, flood plain sands and silts, and from 6-m deep, medium dense channel sands.A 1.5-m thick, soft, clay layer is sandwiched between the two sand layers that liquefied.The behavior of the sands that did and did not liquefy are in general agreement with behavior predicted by standard engineering analyses.