Comparison of Geophysical and Geotechnical Investigations of a Deep Soil Site in Indo Gangetic Plains-Paper

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The study compares geophysical and geotechnical methods for characterizing deep soils in Roorkee, Uttarakhand, an alluvial city in seismic Zone IV near major Himalayan fault systems. Six sites across Roorkee East, Roorkee West, and the Solani River area were investigated.<br /><br />Shear-wave velocity (Vs) profiles were estimated using Multichannel Analysis of Surface Waves (MASW) and microtremor Horizontal-to-Vertical Spectral Ratio (HVSR) measurements. MASW constrained shallow soil velocities, while HVSR helped estimate deeper structure; the curves were jointly inverted to derive the profiles. Results were compared with borehole and Standard Penetration Test (SPT) data, using published empirical relationships to convert penetration resistance to Vs.<br /><br />The geophysical results showed generally increasing velocities with depth. Reported Vs30 values were 357 m/s for Roorkee East, 273 m/s for Roorkee West, and 274 m/s for the Solani River area. Bedrock depth estimates varied from 132 m in Roorkee East to 285 m near the Solani River. SPT-based estimates were generally lower than the geophysical estimates, but the two approaches showed overall agreement.<br /><br />The authors conclude that MASW and microtremor methods provide relatively rapid, non-invasive, and less costly tools for site characterization. They complement conventional geotechnical investigations, and results from either approach can help guide the other.

Keywords

Roorkee

Uttarakhand

alluvial soils

seismic Zone IV

MASW

HVSR

shear-wave velocity

Vs30

borehole data

Standard Penetration Test