Authors: Fakeye, A.M., Ige, O.O. and Oluwafemi, O.
Abstract
Mid-infrared (MIR) spectroscopy has emerged as a rapid and cost effective complementary to conventional laboratory methods utilized for assessing soil properties. The study intends to evaluate the potential of MIR spectroscopy for non-destructive estimation of some engineering soil properties along Ilorin – Kabba expressway.
Fifty georeferenced soil samples from different Basement Complex rock of Southwestern Nigeria were subjected to Fourier-Transform-Infrared-Spectrometric (FTIR) analysis within the spectral region ranging from 4000 – 400 cm-1 of electromagnetic radiation. Four preprocessed filtering methods such as moving average, normalization, multiplicative scatter correction, Savitzky-Golay (SG) first derivative algorithm were applied in the pre-treatment of spectral information. Partial Least Squares Regression (PLSR) was employed to develop calibration models for soil properties, with model performance assessed using the coefficient of determination (R2), root mean square error (RMSE) and ratio of performance to deviation (RPD). The results showed that MIR spectroscopy effectively
estimated the properties including sand and clay content, liquid limit, plasticity index, optimum moisture content, maximum dry density, and soaked California Bearing Ratio, achieving an average R2 of 0.6, RMSE of 1.32, and RPD of 2.1. This study demonstrates the capability of MIR spectroscopy as a rapid and efficient tool for simultaneous estimation of multiple soil properties relevant for engineering purposes. Further research is recommended using diverse non-parametric data mining techniques to enhance soil predictive accuracy.