The main objective of this research is the evaluation of mechanical behavior of over consolidated clay-sand mixtures. For this purpose, behavior of clayey soil mixed with different percentage of sand (20%, 40% and 60%) was studied by carrying out triaxial tests. The specimens were consolidated at a given effective stress and then over consolidated. The results indicate that, irrespective of some exception, the values of shear strengths increase by increasing of sand content from 0% to 60%. Secant deformation modulus of specimens increases when added sand content is 20% and 40%, while it decreases with an increase in sand content from 40% to 60%.