Monotonic and cyclic mechanical characteristics of reconstituted soil with high liquid limit reinforced by steel slag

Soil with high liquid limit is often encountered in southern China, which is unsuitable for direct use as embankment fill. Current soil reinforcement methods entail high carbon emissions, necessitating mitigation for a low-carbon future. In this study, a reconstituted soil is reconstituted to simulate the soil with high liquid limit from the site of the reconstruction and expansion project for the Zhangshu-Ji'an Highway in Jiangxi, China. This reconstituted soil was reinforced using steel slag, varying in grain sizes and employing two mixing methods. The mechanical characteristics of the pure and reinforced soil were examined by a series of monotonic and cyclic triaxial tests. The results indicate that decreasing the grain size of steel slag increases the monotonic shear strength and leads to a decrease in the permanent strain under cyclic loading, regardless of the mixing methods. The reduction in grain size of steel slag increases the total frictional surface area, thereby enhancing soil strength and resistance to deformation. Compared to the samples by uniform mixing with the steel slag, the samples by layered mixing results in a greater shear strength and a more significant permanent strain, because the concentrated steel slag grains and reconstituted soil particles produce greater friction and more significant compressibility, respectively. Overall, smaller grains of the steel slag by uniform mixing are more effective for reinforcing weak soil with high liquid limit, as it provides a higher monotonic strength and a lower permanent deformation, and reduces rapid energy dissipation under cyclic loading, compared to layered mixing.