One Dimensional Shear Wave Propagation in Improved Soils Subjected to Sinusoidal Vibration and El Centro Ground Motion

National and international codes specify design basis ground motion, at free field, in terms of spectral time period/frequency versus acceleration/velocity/displacement. These specifications are broadly enveloping different types of founding media and are conservative, in general. Local site effects are not considered in these codes. For one of the mega power project in alluvial soils, liquefaction potential is assessed from lower SPT values, and corroborated by other geotechnical investigations. To overcome these deficiencies, founding strata is improved by means of soil cement stabilization. An attempt has been made to assess response due to one dimensional shear wave propagation through such local improvement of soil by about 10 meters. Its effect on the design basis ground motion at founding level is investigated. Initially, vibratory motions as sine wave of 0.2g are applied to understand natural dynamic characteristics of the medium. Further, El-centro time history is applied, for two cases, viz., natural and improved conditions. Response, in terms of acceleration spectra, and dynamic amplification factors is studied. From the results, it is concluded that, for alluvial medium, improving the medium with soil–cement mix will reduce peak spectral acceleration, and, seismic demand on the design of superstructure.