An Alternative Method to Estimate Fundamental Period of Layered Soil Deposit

Abstract

There are several approximate methods available for the estimation of fundamental period of layered soil deposits. Approximate methods based on weighted average of shear wave velocities of the layered soil profile are most widely employed in practice. On the other hand, methods which are more accurate are tedious and iterative in procedure; hence they are unpopular for quick estimation of fundamental period of soil deposits. A new method for computing the fundamental period of multilayered soil deposit is proposed in the present study. In this method, layered shear wave velocity profile is replaced with an equivalent linearly varying profile. Subsequently, based on analytical solution for fundamental period of the deposit with linearly varying shear wave velocity profile, an equation to estimate the fundamental period of the actual layered soil deposit is proposed. The efficiency of the proposed method and other available methods is relatively verified by comparing their results with values computed from recorded earthquake accelerograms of instrumented geotechnical downhole arrays. This comparative study, establishes accuracy and consistency of the proposed method vis-à-vis exact methods. © 2014, Indian Geotechnical Society.