Undrained Yielding of Black Cotton Soil Treated with Calcium Carbide Residue

Abstract

This study focuses on the use of calcium carbide residue (CCR) together with black cotton soil (BCS) to produce a stabilised material. Undrained shear strength of the CCR-treated soil was measured in this work. Optimum CCR dosage was obtained from Atterberg limits, pH and unconfined compressive strength tests. Triaxial tests were then conducted on the treated samples to study the effect of confining pressure on the pore pressure response. The results showed that the treated samples started to destructure only upon reaching their primary yield stress. The primary yield stress was shown to increase with the increase in CCR content. The variation of the predicted and observed yield surface was then determined by directly fitting an intuitively acceptable curve to the effective stress paths with the help of a destructuring parameter. This parameter was shown to depend upon the CCR content and confining pressures. The gradient of the ultimate state increased with the increase in CCR content. All stress paths appeared to cross the state boundary surface of the original untreated clay to reach a new peak. These results are attributed to the development of additional shear resistance of the CCR-treated soil because of the cementation and the effect of fabric anisotropy.