As part of a study undertaken to assess the impact of high-pH fluid circulation on the shear strength behaviour of a compacted soil with different additives and due to the complexity of the existing constitutive theories, a new approach was used, based on an evolutionary polynomial regression, for modelling the processes. EPR is an evolutionary-based data mining technique with the capability of generating transparent and structured representation of behaviour of materials and systems from measured data without any need for the data to be processed. EPR model developed and assessed using data from a set of triaxial tests. The outcome from developed model was compared to the experimental results expressing good consistency.