Assessment of empirical equations for the compression index of fine-grained soils in Missouri

The use of correlations and empirical relationships in geotechnical engineering provides a fast, cost-effective means of predicting the value of a parameter based on the values of certain other, possibly more easily determined, parameters. The correlation between two or more soil properties has been found to be dependent in varying degrees on soil type, the testing method used to obtain the numerical value of the parameter itself and the homogeneity of the soil. Many empirical correlations among soil properties have been published. These correlations, based on widely sourced data, may not be appropriate for local situations. Hence, there is a need for correlations that are based on local data. This paper evaluated the validity of published empirical equations for the index of fine-grained soils in Missouri, USA. Four indices were used in the assessment including the root mean square error, the ratio of the estimated to laboratory-determined compression index, the ranking index and the ranking distance. Results reveal the overall best correlations for the Southeast Region and "Other Regions" of Missouri are given by Azzouz et al. (Soils Found 16:19-29, 1976).