Sand-Fly Ash-Lime Blends: Mechanical Behavior under Multiaxial Stress Condition

The employment of industrial by-products with pozzolanic properties (e.g., fly ash) is a viable technique for soil stabilization purposes when a more advantageous environmental performance is sought. For routine engineering purposes, compacted soil-binder mixes are considered as isotropic materials, even though a rather cross-anisotropic material structure may be induced during the preparation process. A series of experimental shear tests at constant mean effective stress on laboratory compacted sand-fly ash-lime soil samples has been performed under drained conditions in a true triaxial apparatus. The influence of the intermediate principal stress and the effect of deviatoric linear stress path directions on the mechanical response were particularly investigated. The relative magnitude of the intermediate principal stress ratio, expressed in terms of the $b$-value, $b=({\sigma }_2^{\prime }-{\sigma }_3^{\prime })/({\sigma }_1^{\prime }-{\sigma }_3^{\prime })$, showed significant effects on the stress-strain, volumetric, and strength characteristics of the compacted sand-fly ash-lime soil. The latter decreases as $b$-value increases. However, different deviatoric linear stress-controlled paths conducted at a constant $b$-value revealed a rather isotropic response, which seemed to suggest that the cementation is erasing the inherent material anisotropy. Finally, the tested samples fitted well into the both Willam and Warnke and Kim-Lade failure criteria.