Research On Engineering Properties And Mechanism Of Solidified/Stabilized Heavy Mental Contaminated Soils

Because of the rapid development of industry, heavy mental contaminated soil becomes a increasingly serious problem. As a result, it is of great significance that launching the research on stabilized/solidified contaminated soil and making use of the study achievements on polluted site.In this paper, cement and fly ash were used as solidifying additive. Systematic tests and theoretical analyses in depth were carried out to investigate the engineering properties, leaching characters, electrical resistivity characters and microstructural changing rules of solidified contaminated soil. The main conclusions are as follows:(l)Curing time, as well as type and content of solidifying additive and heavy mental, was contrastive analyzed to study the influence on unconfined compression strength and compressibility of solidified heavy mental contaminated soils. The results showed that UCS and modulus of compression of cement/fly ash solidified contaminated soil increased with curing time, while coefficient of compressibility on the contrary. UCS and modulus of compression of solidified soil increased with cement content, while coefficient of compressibility on the contrary. Strength and compressibility got worse with the increase of fly ash content. Solidification effect got worse with the increase of heavy mental ion concentration.(2)Triaxial stress and strain characteristics of solidified heavy mental contaminated soils were analyzed. And the deformation of soil sample can be divided into three stage: elastic deformation stage, plastic yielding stage and failure stage. The order of failure stress of 3 kinds of solidified soil was Pb>Cr>Zn, while the order of failure strain was Cr>Zn>Pb. Failure stress decreased with the increase in ion concentration for znic contaminated soil solidified with cement or fly ash, while failure strain on the contrary. Failure stress of znic contaminated soil solidified with cenment was larger than that solidified with cement and fly ash, while failure strain on the contrary.(3)Leaching characters of soil sample with different curing time, type and content of solidifying additive and heavy mental were systematically studied by TCLP test. The results showed that heavy mental ion concentration of percolate of solidified soil decreased with curing time. For solidified lead/znic contaminated soil with cement or cement and fly ash, percolates met the environmental requirements when heavy mental ion concentration was less than 5000mg/kg. For solidified chromium contaminated soil with cement or cement and fly ash, percolates always met the environmental requirements. Fly ash had a poor effect on solidification. The order of parcel adsorption for heavy mental ions in cement and fly ash solidified soil was Cr>Zn>Pb.(4)The changing rules of mean resistivity, pore water resistivity and resistivity structure parameter were investigated. The relationships between resistivity and strength indexs as well as leaching characters were established. It was shown that the order of resistivity for different solidifying additive was cement>cement and fly ash>fly ash. Mean resistivity, pore water resistivity of solidified soil were increased with curing time. Mean structure factor and mean size factor were increased with curing time, while anisotropy coefficient on the contrary. Mean resistivity had a positive correlation with mean resistivity and strength and compressibility, and had a negative correlation with heavy mental ion concentration in percolate.(5)Microstructure characters of soil with different curing time, type and content of solidifying additive and heavy mental were analyzed. The results showed that there were a large amount of hydrated products in cement/fly ash solidified contaminated soil. The void quantity and size of hydrated products decreased with curing. The structure became compact. There were large number of microsphere structure in contaminated soil solidified with cement and fly ash. When concentration of znic ion increased in soil, hydrated products decreased and void quantity increased, while soil became porouser.