Evaluation of the accuracy of commonly used empirical correlations in predicting the compression index of Iraqi fine-grained soils

Several empirical correlations were proposed in the literature to predict the compression index of fine-grained soils using either of the soil properties such as the liquid limit, plasticity index, initial void ratio and natural moisture content. However, the accuracy of these correlations to predict the compression index of Iraqi fine-grained soils has not been investigated before. Hence, this research has been carried out to evaluate the effectiveness of the available correlations in predicting the compression index of fine-grained soils collected from different regions in Iraq. A methodology, based on statistical analysis, has been employed to analyse the differences between predicted and measured compression index values. In addition, a database of properties of fine-grained soils has been collected from the literature to enable the statistical assessment. The results showed a significant scatter in the prediction among the examined correlations, where most of the correlations performed poorly in the predictions. However, it has been shown that the correlations proposed by Rendon-Herrero (J Geotech Eng 109(5):755–761, 1983) and Al-Khafaji and Andersland (J Geotech Eng 118(1):148–153, 1992) provided a good estimate of the compression index compared with other empirical correlations.