Hydraulic And Containment Performance Of Shmp-amended Soil-bentonite Vertical Cutoff Wall Backfills Against Heavy Metals

Soil-bentonite vertical cutoff wall is an efficient way to control the migration of contaminants in groundwater.With the financial supports of National Natural Science Foundation of China under Grant No.41330641 and No.50878052,this dissertation presents a systematic study of the permeability,chemico-osmotic efficientcy and sorption properties of SHMP-amended soil-bentonite vertical cutoff wall.The main conclusions are shown as follows:?1?The engineering properties of SHMP-amended bentonite slurry and backfill are investigated.With the increase of SHMP or bentonite dosage,the workability of slurry is obviously improved.The water content of backfill that meets the requirements of the slump decreases with the increase of SHMP dosage.The dosage of SHMP should not below 0.5%,while that of bentonite in slurry is 8%.?2?Flexible wall permeability test and modified fluid loss test are conducted to investigate the chemical compatibility of backfills amended by SHMP.The results shows that the SHMP-amended backfill has an evident superiority in chemical compatibility.The backfill with 2%SHMP maintains a low hydraulic conductivity(10^-9 m/s)when permeated with lead solutions.The hydraulic conductivities tested via modified fluid test are higher than those tested through flexible wall permeability test.?3?The adsorption properties are investigated via batch adsorption test while diffusion of Pb and Zn through amended backfill is studied by chemical soil column test.The results indicates that the maximum Pb?II?and Zn?II?adsorption capacities increased by 29%and 28%respectively after the backfill is amended by 2%SHMP.SHMP-amended backfill presents better adsorption capacity in single-metal aqueous solutions than in Pb-Zn combined solution.There is not much change in the effective diffusion coefficients of lead and zinc between the amended backfill and backfill,while the chemico-osmotic efficiency coefficient of amended bakfill increased by 2³ times.?4?The impact of contaminated ground water and sea water on bentonite slurry workability and the hydraulic conductivity of amended-backfill is researched.The results suggests that the quality of mix water has a strong effect on the workability of bentonite slurries,which could be improved by the addition of SHMP to some extent.For a bentonite slurry containing 8%bentonite with 2⁴%SHMP,the ionic strength and relative abundance of monovalent and divalent cations of mix water is supposed to be lower than 15 mmol/L and 10?mmol/L?^1/2respectively.The hydraulic conductivity of amended backfill with 2%SHMP is below the typical regularoty limit(10^-9 m/s)when permeated with contaminated ground water and sea water.