In response to the environmental challenges posed by oil drilling waste generated from intensified oil production in Algeria, particularly in Saharan regions, this study proposes a valorization approach to mitigate their impacts. Our research aims to transform this waste into a useful resource by incorporating it into road construction mixtures. The study seeks to design an innovative and optimized formulation of gypseous-calcareous soil with oil drilling waste, specifically adapted to road infrastructure. We tested the incorporation of treated oil drilling waste into gypseous-calcareous soil formulations at rates of 5%, 10%, and 15% by weight and with the addition of 4% lime. The study evaluates the evolution of unconfined compressive strength (UCS) in these mixtures, as well as their water sensitivity, influence on California Bearing Ratio (CBR), and direct shear testing. The results reveal significant improvements in the mechanical behavior of the mixture modified with 10% oil drilling waste and 4% lime content, under laboratory curing conditions, achieving a UCS of 2.45 MPa, CBR value of 75% and shear strength parameters with an internal friction angle 35° and the cohesion 45 kPa. The Microstructural analysis further confirmed that the interaction between oil drilling waste and the gypseous-calcareous soil in the presence of lime led to the formation of a more homogeneous and compact matrix, which explains the observed improvement in mechanical properties.
