Utilization of admixture stabilized native expansive soil as a CNS material for heave control

摘要

Severe distress could be observed in the structures with foundations on expansive soils due to their swelling and shrinkage behavior. Several remedial techniques were proposed, among which the cushion materials, especially the cohesive non-swelling (CNS) cushion, becomes one of the primarily applicable techniques to alleviate the heave. Since the availability of suitable CNS materials becomes a significant limitation, this study offers a solution to this problem by converting the native expansive soil into a suitable CNS material. One of the significant industrial wastes, fly ash, was added to convert the selected expansive soil into a suitable material. Varied proportions of fly ash were added, and the index and engineering properties of the modified material were studied. The microstructural examination was made using the scanning electron microscopy (SEM). The efficacy of the prepared CNS material in reducing the heave was studied by performing the laboratory scale model tank studies in which varied thickness of CNS cushion was provided on the top of the expansive soil, and heave was measured on its top under saturated conditions. Four cycles of wetting and drying process were carried out to understand the efficacy under repeated swell and shrink cycles. A significant reduction in the heave of expansive soil was noticed when the thickness of the CNS layer became 75% of the thickness of the soil. This study offers a novel method of utilizing local expansive soil as an efficient CNS material by local stabilization.