Effect of adding sand on clayey soil shear strength

Abstract

The effect of adding sand on clayey soil shear strength is investigated in this study. Five different percentage of clay-sand mixtures are used; 100% clay with 0% sand termed 100C, 60% clay with 40% sand termed 60C-40S, 30% clay with 70% sand termed 30C-70S, 15% clay with 85% sand termed 15C-85S, and as well as 100% sand termed 100S. The used clay was obtained from Baghdad city in Iraq and classified as CH soil, while the used sand was taken from Al-Khider area from Iraq and classified as SW soil. The initial dry unit weight for all mixtures is 16 kN/m3. The results show that the variations of the soil shear strength properties with soil components content changes almost as polynomial function. The results show that the soil cohesion (C) decrease as the sand percentage increases, while the angle of internal friction (f) increases as the sand percentage increases. The cohesion (C) decreases with 68%, 99%, 97% and 100% as the sand percentage increases with 40%, 70%, 85% and 100% respectively from pure clay soil 100C. While, the angle of internal friction (f) increases with 148%, 410%, 471% and 676% as the sand percentage increases with 40%, 70%, 85% and 100% respectively from pure clay soil 100C. Finally, a predicted (fitting) equations are achieved for the variation of the clayey soil shear strength properties with sand content with good agreement.