Contaminant Migration in Construction and Demolition Waste Roadbeds Under Rainfall

Roadbeds made of construction and demolition waste are a sustainable civil engineering solution aimed at reducing the accumulation of construction and demolition and converting it into a helpful resource. In this paper, we simulated and predicted the extent and trend of heavy metal migration in soil within the roadbed made of construction and demolition waste and evaluated the simulation results of heavy metal infiltration to soil and groundwater after 10 years by using the finite element numerical simulation software. The results showed that the maximum concentration of Hg infiltration was 5.5 × 10–4 mol/m3, and the maximum concentration of Cd infiltration was 6 × 10–4 mol/m3. The migration rate was positively correlated with the infiltration concentration, and the migration rate did not change significantly with the rainfall. This is because the transport of heavy metals is still mainly due to higher concentrations of heavy metals in the roadbed, and heavy metal ions will gradually diffuse to the surrounding environment with water flow, thus leading to an increase in metal concentrations at the monitoring sites. The study of solute transport of heavy metals can help to assess the degree of contamination in soils, rocks, and water bodies and determine whether the heavy metal content in the environment exceeds the safety standards, which is of great practical significance.