Effect of soil particle mineralogy on embankment dams

The 1971 San Fernando earthquake led to the failure and large displacement of the Lower San Fernando dam, which was constructed by the hydraulic filling method. Hydraulic filling has been condemned as producing liquefiable sand deposits, and in situ relative densities as large as 60% have been reported in the Lower San Fernando dam. On the other hand, laboratory element tests on loosest specimens of primarily quartz sands, pluviated through air or water (resembling the soil fabric produced by hydraulic filling) have been dilative, which brings into question the failure mechanism of the Lower San Fernando dam. In this paper, the behaviour of the dam during the 1971 earthquake is studied using the results of an improved sliding-block deformation analysis, which incorporates the shearing behaviour from ring shear tests of two sands with different mineralogies: quartz sand, and albite sand with some carbonates. The results indicate that sand particle composition and compressibility may have caused the failure and large displacement of the Lower San Fernando dam, even in a dense state (relative density ∼60%).