Discussion to the article Undrained shear strength prediction of clays using liquidity index, by Q. Wang, S. Qiu, H. Zheng, R. Zhang

Abstract This communication presents a critical discussion of the article “Undrained shear strength prediction of clays using liquidity index”, authored by Q. Wang, S. Qiu, H. Zheng, R. Zhang, and recently published in Acta Geotechnica ( https://doi.org/10.1007/s11440-023-02107-9 ). Various inaccurate claims and flaws regarding the Authors’ newly developed three-parameter strength–liquidity index ( S u – I L ) models/correlations are highlighted and discussed herein. In particular, comparing existing two-parameter and their newly developed three-parameter S u – I L models, contrary to the Authors’ claims, no improvement in prediction accuracy is achieved over the two-parameter model by introducing a third model parameter. Rather, it is shown herein that the existing two-parameter and the Authors’ three-parameter S u – I L models are mathematically identical. Furthermore, two of the Authors’ newly developed S u – I L correlations, i.e., relating the triaxial-compression and shearbox derived strengths to the liquidity index, are shown to be inaccurate, forecasting gross under- and over-predictions of the measured strengths, respectively. This highlights the need for a reassessment of the proposed correlations, and emphasizes the importance of accurate and reliable correlations in geotechnical engineering.