Solid waste material reuse analysis: filling the road subgrade with riverway silt and sediment

This study proposes to explore solid waste material (SWM) reuse of the riverway silt and sediment, and examines the impacts of chemical composition on road construction through sensitivity analysis. Considering the characteristics of silt mixture, it is necessary to investigate the modified materials to improve the mechanical feasibility for subgrade filling. In this study, the water content of riverway silt and sediments was found to be important to determine the selection and content of modified materials. Specifically, the riverway silt and sediment with low water content could be improved effectively with 6 to 8% lime. Compared to the original sludge, the improved mixture had better particle size and permeability, and the carrying capacity also grew 2 to 3 times. On the other hand, the reuse of riverway silt and sediment with high water content over 40% was provided with multiple schemes. Among them, the modification scheme of construction waste or garbage slag showed well mechanical properties and environmental benefits in the sensitivity analysis, especially for the high water content sludge modified by the mixture of garbage slag and lime. The California bearing ratio (CBR_2.5) was 2 to 5 times higher than the original silt, which would promote the reuse of multiple solid wastes in road construction. Finally, this study puts forward engineering measures to prevent heavy metals from polluting the water and soil environment by silt-improved soil roadbeds, and the improved riverway silt and sediment roadbeds were proved to be safe and reliable for the environment during service.