Abstract
A key parameter necessary to properly evaluate dynamic response of soil is shear modulus. The shear modulus is usually estimated by using shear wave velocity (Vs) of soil measured through in situ geophysical tests. Since the shear modulus is the key parameter for geotechnical earthquake engineering problems both quantitatively and qualitatively, its measurement shall be done precisely. However, in many cases, shear wave velocity is estimated through field test like SPT N-value of soil whenever the precise measurement of Vs is not available. There are many empirical equations exist worldwide which correlate soil type and SPT N-value with expected shear wave velocity. However, all these equations are developed based on some field measurements limited to selected sites and geology. In the present paper, actual shear wave velocity measurements for five different project sites are compared with that estimated using 22 soil specific correlations including correlations recommended for Indian soil sites. The selected five project sites represent different parts of India i.e. Gujarat, Punjab, Andhra Pradesh, Uttar Pradesh, consist of different geologic origins. Present study review available correlations and highlights that shear wave velocity estimated through available correlations differ largely with actual measured data. Since, the measurement of SPT N-value depends upon many factors, the direct measurement of shear wave velocity using correlations may not converge for actual engineering applications for many sites. The actual measured data along with SPT N-value measurement data are presented in the paper.
