Effect of fly ash layer addition on bearing capacity of expansive soil

Abstract

The long-term structural performance of roads is mainly governed by the characteristics of subgrade soil. Subgrades with high compressive clays are one of the challenging aspects worldwide. Expansive soils swell and shrink due to moisture variations. Such variations cause serious structural failures, commercial losses, and fatalities worldwide. One of the most effective and economical methods to improve the engineering behaviour of expansive soil is addition of stabilizing agents such as lime or fly ash to expansive soil. In this study, a high plastic black cotton soil (BCS) is stabilized using fly ash (FA). Laboratory experiments and model tests were performed to determine the geo-engineering properties and to study the strength behaviour of virgin clay soil and treated clay soil with fly ash. The experimental investigations indicated the decrease in plasticity index and free swell index of BCS-FA mixes with an increase in FA content. Moreover, the increase in CBR of BCS-FA mix and layered BCS-FA composite was observed. Further, bearing capacity tests were performed on subgrades prepared with BCS-FA layers and BCS-FA mix with up to 40% FA content. The detailed methodology adopted for theoretical and experimental investigations are presented and the obtained results are critically evaluated.