Study On The Engineering Properties And Microstructure Of Flax-fiber Reinforced Silty Clay Contaminated By Zinc-ion Solution

With the rapid development of industry,urban pollution is increasingly serious,especially heavy metal pollution,which is very serious to the environment.At present,the research on engineering properties of polluted soil is not perfect,and these problems will threaten the safety of the project.In order to solve these problems,combining heavy metal contaminated soil with reinforcement technology can effectively improve the mechanical properties of heavy metal contaminated soil and the utilization rate of the project,reduce its permeability,leaching performance and repair cost.This paper chooses zinc-ion solution and flax-fiber reinforced soil as the research objects.Its mechanical properties were studied by direct shear test,consolidation test and triaxial test,and its permeability and leaching properties were studied by permeability test and leaching test.In the above experiments,the reasons for the changes in mechanical properties,permeability and leaching properties of zinc-ion brown hemp fiber reinforced soil were analyzed and explained from the microscopic perspective by means of optical microscope and chemical reaction,and the conclusions were as follows:(1)At the same zinc-ion concentration,the shear strength of contaminated reinforced soil increases with the increase of confining pressure.Under the same confining pressure,the shear strength of contaminated reinforced soil increases first and then decreases with the increase of zinc-ion concentration.When the pressure is low,the compression modulus increases and the compression coefficient decreases with the increase of zinc-ion concentration.At higher pressure,the compression modulus decreases and the compression coefficient increases with the increase of zinc-ion concentration.With the increase of zinc-ion concentration,the pore ratio of contaminated reinforced soil decreased first and then increased,the angle of internal friction increased,and the cohesion decreased.(2)When the concentration is about 1?10 mg L^-1,with the increase of zinc-ion concentration,the permeability coefficient of polluted flax-fiber reinforced soil decreases significantly.When the concentration is about 100 mg L^-1,the permeability coefficient of polluted flax-fiber reinforced soil has little change with the increase of zinc-ion concentration.When the flax-fiber reinforced soil is not polluted,the permeability coefficient increases with the increase of confining pressure.When the zinc-ion concentration was 1 mg L^-1,10 mg L^-1and 100 mg L^-1,with the increase of confining pressure,the permeability coefficient first decreased and then tended to be stable.With the increase of confining pressure,the porosity of flax-fiber reinforced soil decreased.With the increase of zinc-ion concentration,the porosity of flax-fiber reinforced soil increased at first and then decreased.(3)In the leaching process,zinc-ion has a slight influence on the acid and alkaline of the flax-fiber reinforced soil,so that the p H value of both the analytical solution and the leached solution is slightly affected in the test process,and rises slowly in the range of 2?3.Analytical sample,it is found that when using distilled water to immerse zinc ions pollution flax-fibers reinforced parsing,zinc-ion in the soil is resolved to make distilled water into zinc-ion in distilled water pollution liquid,zinc-ion concentration increases with increasing of the number of days with the experiment,in the first 6.5days of zinc-ion concentration slightly decreased after the peak.In the adsorption test,0.1 g L^-1,1 g L^-1and 10 g L^-1solution of Zn(NO₃)₂was used to leach the flax-fiber reinforced soil.The zinc-ion concentration of the leached solution of the three soil columns increased gradually with the testing time,and the concentration of the three was close to 11.3 g L^-1at the 6th to 8th day.Engineering properties of zinc-contaminated flax-fiber reinforced soil were studied,which laid a certain test foundation for reducing the safety hidden danger in practical engineering.