高钙粉煤灰固化重金属污染土的工程性质试验研究

高钙粉煤灰是燃煤电厂排出的固体废物，其堆放不仅需占用大量土地，而且对周围环境存在严重威胁。通过系统的室内试验，着重研究了高钙粉煤灰固化铅与锌污染土的工程性质，揭示了其作用机制，探讨了利用高钙粉煤灰固化重金属污染土的可行性。试验结果表明，土体受到重金属离子污染后其无侧限抗压强度降低，掺入高钙粉煤灰可提高土体强度，并能抑制重金属离子的滤出；污染物浓度较低时，固化污染土中的Pb2+和Zn2+均能得到有效固化，污染物浓度较高时，Zn2+的固化效果优于Pb2+。干湿循环试验结果表明，高钙粉煤灰固化污染土的强度随干湿循环次数的增加，先增大后减小；固化土体中重金属离子浓度较低时，滤出液中金属离子浓度随干湿循环次数增加而增大；重金属离子浓度较高时，滤出液中金属离子浓度基本保持不变。

Engineering properties of heavy metal contaminated soil solidified/stabilized with high calcium fly ash

High-calcium fly ash is an industrial by-product generated during the combustion of coal for energy production, which is characterized by higher concentrations of calcium, carbon and hydraulic minerals. Previous studies have proved that high-calcium fly ash can enhance the strength of heavy metal contaminated soils and lower the mobility of heavy metal ions. In this paper, laboratory experiments and theoretical analysis are used to investigate the properties of strength, leaching, drying and wetting cycle of Pb and Zn contaminated soils solidified/stabilized by high calcium fly ash. The results show that the unconfined compressive strength of soil decreases due to the presence of heavy metal ions. Adding high-calcium fly ash to the contaminated soils can significantly improve the strength and reduce the amount of heavy metal ions that filter out. The strength of Zn contaminated soils solidified with fly ash is superior to the Pb contaminated soils. Both Pb2+ and Zn2+ can be effectively immobilized at low concentration; while Zn2+ is more effectively immobilized at high concentration. With the times of wetting and drying cycle increases, the unconfined compressive strength increases first, and then decreases. The heavy metal concentration of leachate increases as the times of wetting and drying cycle increases when the content of heavy metal in the soil is low. Times of wetting and drying cycle have little effect on the leaching properties of heavy metal when it is at a high level in the soil.