Estimating Atterberg Limits of Fine‐Grained Soils by Visible–Near‐Infrared Spectroscopy

Abstract

Two methods each to measure each Atterberg limit (SL, PL, and LL) were evaluated. A Vis‐NIRS technique successfully estimated Atterberg limits for fine‐grained soils. The Atterberg limits correlated with typical clay signatures in the Vis‐NIR spectrum Vis‐NIRS model performance was independent of the method used to generate the reference data. The Atterberg limits (shrinkage limit [SL], plastic limit [PL], and liquid limit [LL]) describe the physico‐mechanical behavior of soils and thus are crucial for civil and agricultural applications. Conventional laboratory methods for measurement of these limits are tedious and costly for a large number of samples. Our objective was to develop visible–near‐infrared spectroscopy (Vis‐NIRS, from 400–2500 nm) based reliable models to estimate the Atterberg limits. Two conventional methods for each Atterberg limit were used to generate the reference data: paraffin wax and Hg methods for SL; rolling and motorized devices for PL; and Casagrande cup and drop‐cone penetrometer methods for LL. Calibration models were built on 80% of the data using partial least squares regression and validated with the remaining 20% of the dataset. The Vis‐NIRS independent validation of LL showed very good estimation with standardized RMSE (SRMSE = RMSE/Range) of 0.16 and 0.15, respectively, for LLdrop‐cone and LLCasagrande methods. Similarly for PL, the Vis‐NIRS estimation accuracy was quite good with SRMSE values of 0.18 and 0.22, respectively, for PLmotorized and PLrolling. Reasonably good estimation was obtained for the SLparaffin and SLHg with SRMSE of 0.25 for both methods. The results suggest that the Vis‐NIRS calibration models and the accuracy following validation were similar for the pair of methods used for the SL, PL, and LL. Finally, analyses of the model regression coefficients revealed that the important wavelengths to estimate the SL, PL, and LL in the Vis‐NIR regions were present across the entire Vis‐NIR spectrum and were strongly related to clay type and content.

Characterization of lateritic soil based on literature and lab testing

“…Besides the mentioned conventional methods, some researchers tried to find new methods for determining these values. For example, Rehman et al [40] studied visible-near infrared spectroscopy(Vis-NIRS) for identifying these indices. In the current study, the fall cone method and threading by hand have been utilised to determine the liquid limit and plastic limit, respectively.…”

Review of Recent Developments and Understanding of Atterberg Limits Determinations

“…On the basis that for large sample quantities the conventional laboratory measurement methods are tedious and costly, some researchers have proposed new microstructural and mineralogical based testing methods for consistency limits determinations. For instance, Rehman et al [83] developed visible-near-infrared (vis-NIR) spectroscopy based models, correlating the Atterberg limits with typical clay signatures in the vis-NIR spectrum (from 400 to 2500 nm), reportedly obtaining very good and quite good estimation accuracies for LL and PL determinations, respectively, attributable to a strong correlation between them and spectrally active components related to soil clay mineralogy (mainly O-H bonds and Fe oxides). From field spectroscopy investigations of forest soils in Iran, Mousavi et al [84] reported that partial least-square regression modeling for the parameters of LL and I P in the raw spectra and the first derivative of the spectrum is very suitable, but is weak and not acceptable for PL determination.…”

Determining Liquid Limit and Plastic Limit of Clay Soils by Electrical Surface Conduction and Diffuse Double Layer Thickness

“…Therefore, there is a need to identify a scientific approach to determine the liquid limit and plastic limit of clays through a direct measurement without depending on the operator's judgement within a comparatively shorter timescale. Some recent developments have been made to find an alternative to the Atterberg limit estimation by the utilisation of spectroscopy [23,24], data-driven prediction models developed by artificial intelligence [25,26], and hygroscopic water content [27], to name a few. However, the consideration of spectroscopy may not seem an ideal solution in the geotechnical industry if there is a lack of understanding of electromagnetic radiation, wavelengths, and associated functional ability.…”