GEOTECHNICAL PROPERTIES OF DIFFERENT SOILS USING SPECTROSCOPY TECHNIQUE

Abstract

Different soils with low, medium and high plasticity undergo changes in volume upon wetting and drying which has serious implications on planning, design and construction and overall performance of engineering infrastructure. The traditional method of assessing soil plasticity is time consuming, labour intensive and the continuous sampling of site may also not be feasible. Interpolation of limited number of samples to get the desired results may lead to overlooking of any problematic soil. Remote sensing technique was an excellent alternate option in such a situation. For the study, 24 samples of soil were collected from various parts of India. Soil engineering parameters – Atterberg Limits – Liquid Limit (LL), Plastic Limit (PL), Shrinkage Limit (SL), Plasticity Index (PI) and Shrinkage Index (SI) were measured in Soil Mechanics Laboratory. Reflectance spectra of each soil were acquired using ASD Fieldspec spectroradiometer to develop a relationship between the geotechnical properties and reflectance spectra. Laboratory analysis revealed variation in their swelling and shrinkage potential. On the basis of Indian Standard Soil Classification System (ISSCS), fine grain classification can be given on the basis of Plasticity Index and Liquid Limit. Multivariate prediction models like partial least square regression (PLSR) and multiple linear stepwise regressions (MLR) analysis are used to construct empirical prediction model for the estimation of engineering parameters from their reflectance spectra. Correlation coefficients obtained showed that a large portion of variation in the engineering parameters can be accounted for by the spectral parameters. The high value of prediction model (r = 0.989, 0.979 and 0.990 for LL, PL and SL respectively) indicates the spectroscopy potential in estimating geotechnical properties of soil from their reflectance spectra. Therefore, remote sensing has potential applicability in the geotechnical investigations of soils.