Shear Wave Velocity Profiling & Rock Mass Characterization at Pavagadh Hill Using the Multichannel Analysis of Surface Waves (MASW)

Abstract

Multichannel Analysis of Surface Waves (MASW) is a geophysical method used for subsurface characterization by measuring the variation of shear-wave velocity (Vs) with depth and evaluating the stiffness properties of near-surface materials. The prime focus of this study is MASW testing was carried out at multiple locations situated at different elevations of Pavagadh Hill to characterize subsurface rock mass conditions and to understand the variation of engineering parameters along the hill slope. Conventional borehole-based seismic testing methods such as cross-hole and downhole testing are expensive, intrusive and spatially limited in heterogeneous geological conditions. Surface wave based geophysical techniques have therefore emerged as efficient and non-destructive alternatives for continuous subsurface characterization. Among these techniques, the Multichannel Analysis of Surface Waves (MASW) method has become one of the most accepted approaches for estimating shear-wave velocity profiles using the dispersive characteristics of Rayleigh waves propagating through layered media. The obtained Vs profiles were used to evaluate variation in subsurface stiffness and rock mass conditions with depth at different elevations. Further, Vs₃₀ values were calculated for selected locations and the sites were classified according to NEHRP site classification criteria. Based on the estimated shear wave velocity important engineering parameters such as shear modulus (G), rock mass deformation modulus (Em), Geological Strength Index (GSI), Uniaxial Compressive Strength (UCS) and bearing capacity were evaluated. The results obtained from this study provide valuable input for safe foundation design, slope stability assessment and infrastructure development at Pavagadh Hill.