Multivariate interrelatedness of geotechnical and petrophysical properties towards developing near-surface lithology clusters in a sedimentary terrain

Abstract

The study reports the approach of interrelating geotechnical and petrophysical parameters to develop near-surface lithology clusters in a sedimentary terrain. Field-based and laboratory-based geophysical, geotechnical, and petrophysical measurements were carried out with a view to finding correlations among related parameters, grouping the parameters into depth clusters, and determining trend correlations between field-acquired and laboratory-obtained parameters. Four agglomerate hierarchical cluster signatures were identified at depth 0–30 cm, three at 30–60 cm, and five at 0–90 cm. Principal component 1 retained 74% of data variation and differentiated the petrophysical parameters according to Poisson’s ratio (v) and velocity ratio (Vp/Vs). Principal component 2 explained another 14% of variability in the original responses and separated parameters based on elastic modulus (E) and clay fraction (C). Degree of correlation of Vp/Vs with porosity (Φ), sand fraction (S), C, unconfined compressive strength (U), and California bearing ratio (R) followed order Φ > S > C, and U > R. Trend correlation of shear velocity at 1 m showed good agreement (R2 = 0.992) between field and laboratory data with an amplification factor of 4.13 separating the corresponding values. Lithology determined from soil analysis agreed with that inferred from measured electrical resistivity while geotechnical, petrophysical, and geophysical spatial analysis supported site lithology configuration patterns. Thus, multivariate association of geotechnical and petrophysical parameters exhibited potentials for rapid and exploratory near-surface lithology mapping even at a regional scale.