The phreatic level as spectral response modificator of acceleration, velocity and displacement

Danna Molina

Abstract


The spectral response of acceleration, velocity and displacement of soil deposits is studied using finite element procedures in a hyperbolic model of plane deformations under undrained conditions. The elastic and dynamic properties of 63 profiles are incorporated in the analyses, selected to be compatible with soils in dry state, with phreatic level to a depth of 2 meters and at half of the profile height. Ten (10) base rock motions having different amplitude and frequency characteristics are considered from near, intermediate and distant sources, for a total of 1890 analysis. It is shown that the frequency contents, magnitude and position of the peak response developed at the surface of a soil deposit is influenced by the combined effect of the soil properties, the characteristics of the base rock motions and the phreatic level position. It is observed that the presence of water affects the spectral response of velocity and displacement significantly, which are related directly with the structural damages. The spectral response according to the epicentral distance and soils types S1, S2, S3 y S4 are analyzed, by means of formats spectral combined of acceleration-displacement, acceleration-velocity and velocity-displacement.


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References


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