Research On Remediation And Long-Term Stability Of Solidified/Stabilized Heavy Metal Contaminated Soil

The research on remediation and long-term stability of solidified/stabilized heavy metalcontaminated soil is a hot issue of the domestic and international environmentalgeotechnical profession.To carry out the research on solidified/stabilized technology andmechanism of heavy metal contaminated soil is beneficial to environment protection,therestoration of engineering site and sustainable development.Based on this background,with the financial support of the National Natural ScienceFoundation of China under Grant （40802079，41172273）, the remediation and long-termstability of cement/PFA solidified/stabilized heavy metal contaminated soil has beenstudied.With the help of routine soil test,leaching experiments as well as wet and drycycling test,the author aims at exploring the variation law of strength and leachingcharacteristics of cement/PFA solidified/stabilized Pb/Zn contaminated soils as well as thevariation law of strength and leaching characteristics and micro-structure form under wetand dry cycling test. The following findings were drawn from these tests:(1)Summarize the current situation of domestic and foreign disposal of contaminated soilremediation technology.The state-of-the-arts of the study and practices of soil remediationtechnologies especially S/S method are introduced.(2)The contrast of UCS,shear strength and compression characteristics of cement/PFAsolidified/stabilized Pb/Zn contaminated soils are discussed. Explore the impact of thedifferent reaction mechanism exist in the repair of the curing agent and the different heavymetal ions on the strength characteristics of solidified soil.And propose the controllingfactors in development of the stabilized soil strength. Pointed out that the heavy metal ionsaffect the hydration and pozzolanic reaction in the curing agent to influence the strengthdevelopment of soils. At the same time the overall evaluation from the perspective of thestrength characteristics of the remediation effect are discussed.(3) The contrast of the heavy metal ion concentration in filtrate from leaching experimentsof cement/PFA solidified/stabilized Pb/Zn contaminated soils are discussed. Explore theimpact of the different reaction mechanism exist in the repair of the curing agent and thedifferent heavy metal ions on the Leaching characteristics of solidified soil. And proposethe controlling factors in changes of the leaching characteristics in stabilized soils. Pointedout that hydration gel surface adsorption and the formation of metal hydroxide precipitation is the main reason affecting the leaching characteristics of soils. At the same time theoverall evaluation from the perspective of the leaching characteristics of the remediationeffect are discussed.(4) The variation law of strength and leaching characteristics of solidified/stabilized soilunder wet and dry cycle effect are discussed.And the reaction mechanism that impact thethe variation trends are analyzed. Pointed out that the balanced state between the promotioneffect of hydration products and the damage effect of wet and dry cycle of the strength andleaching characteristics is the main factors to control the remediation effect of contaminatedsoils.(5) Using scanning electron microscopy to analyze the morphology of samples under wetand dry cycle effect,The result is consistent with the macro indicators of the strength andleaching characteristics under wet and dry cycle effects.