Site classification and soil liquefaction evaluation based on shear wave velocity via HoliSurface approach

Abstract

This study employs the HoliSurface technique, a geophysical method, to classify sites and evaluate liquefaction susceptibility in the southwestern Greater Accra Region of Ghana. Shear wave velocity (Vs) profiles to a depth of 13 m were acquired from 26 surveyed sites. A reliable extrapolation method was then used to estimate the Vs₃₀ (Vs₃₀₍₁₃₎) of each site, allowing classification based on the Eurocode 8 system. Most sites (20) were classified as Site Class C (Vs₃₀: 180–360 m/s), indicating moderately dense soils with improved geomechanical properties at depth. Five sites exhibited high stiffness and resistance to liquefaction (Site Class B). The site at Tetegu East (Vs₃₀: 110 m/s, FoS: 0.525) was, however, found to be extremely weak (Site Class D), hence prone to seismic failure. Airport City (Vs₃₀: 190 m/s, FoS: 0.647), despite a Site Class C classification, exhibited a low FoS value, indicating liquefaction susceptibility. A key limitation of this study was the inability to acquire Vs data to a depth of 30 m due to spatial constraints at most sites, necessitating the use of extrapolated Vs₃₀ values, which may introduce uncertainties. Additionally, joint inversion of group velocity dispersion with HVSR or RMP curves, which could enhance reliability, was not employed due to the preliminary nature of this study. Despite these limitations, the findings align with established standards and provide critical insights for urban planning, highlighting the need for interventions in high-risk zones to mitigate potential disasters.