Region-Specific Correlations Between VS 30 and Time-Averaged VS and SPT-N Values at Different Depths for the Indo-Gangetic Basin

Anbazhagan, P and Bajaj, K (2020) Region-Specific Correlations Between VS 30 and Time-Averaged VS and SPT-N Values at Different Depths for the Indo-Gangetic Basin. In: Indian Geotechnical Journal, 50 (3). pp. 454-472.

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Abstract

Time-average shear wave velocity at top 30 m depth (VS 30) is extensively used for site characterization and amplification parameters estimation. However, due to various reasons, the shear velocity profile (VS) does not reach to 30 m depth. In this study, using the multichannel analysis of surface waves, VS profiles at 275 locations have been determined in the Indo-Gangetic Basin (IGB). Further using VS profiles, new correlations between VS 30 and VS Z (where z is the average depth) have been developed for z< 30 and z> 30 m. For z< 30 , second degree polynomial equation has been used for deriving VS 30 and VS Z correlation for z ranging from 5 to 29 m in 1 m increment. Whereas for z> 30 , both linear and second-order polynomial equations have been used. Based on the variation of residual with VS 30, it has been observed that second-order polynomial equation derived using orthogonal regression is performing better in both cases. Additionally, new correlations between VS 30 and SPT-NZ, with z equals to 5, 10, 20, 30, 40 and 50 m, have been derived. This correlation is further used in deriving the N30 map of the IGB as per BIS:1893 useful for Indian scenario. Further, the depth corresponding to one-quarter of wavelength for various periods has been studied. The velocities known up to 30 m depth are relevant for site amplification at period up to 0.5 s. This is the first time such extensive study has been carried out in the IGB for correlation of VS 30 and VS Z, for both deep and shallow depths. © 2019, Indian Geotechnical Society.

Item Type:	Journal Article
Publication:	Indian Geotechnical Journal
Publisher:	Springer
Additional Information:	The copyright for this article belongs to Springer.
Keywords:	Amplification; Polynomials; Shear waves; Surface waves; Wave propagation, MASW; Multi-channel analysis of surface waves; Orthogonal regression; Parameters estimation; Second degree polynomials; Second-order polynomial; Second-order polynomial equations; Site amplification, Shear flow, correlation; parameter estimation; regression analysis; S-wave; surface wave; wave velocity, Gangetic Plain
Department/Centre:	Division of Mechanical Sciences > Civil Engineering
Date Deposited:	06 Feb 2023 07:24
Last Modified:	06 Feb 2023 07:24
URI:	https://eprints.iisc.ac.in/id/eprint/79888

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