Study On Soil Mechanics And Durability Of Cadmium Contaminated Soil By Inorganic Hardened Materials

In recent years,soil cadmium pollution has brought many problems,the use of cement and other solid remediation of heavy metal contaminated soil continued to be concerned about,through the cement and other curing can make waste contaminated soil reuse in engineering practice.In this experiment,cement,fly ash and lime were used as curing materials to cure cadmium contaminated soil.The mechanical properties and leaching leaching risk of the contaminated soil were measured by indoor macroscopic test.The durability characteristics of the frozen soil under freezing and thawing conditions were also analyzed.The internal pore structure and distribution of the contaminated soil under certain curing age were measured by indoor microscopic experiment,and the characteristics of the cured structure were studied.For the reuse of cadmium contaminated soil for useful exploration,to provide practical engineering reference,based on the above research,the following conclusions:(1)Using the orthogonal test scheme and the results of unconfined compressive strength,the influence of the curing material on the curing degree was obtained by the analysis of the difference between the four factors and the three levels of the orthogonal test.The influence degree was from large to small cement>lime>fly ash.The contribution rate of cement to its curing strength reached 59.71%on 28 days,and the effect of lime on the unconfined compressive strength was significant during the 7th-28th day of curing.Fly ash had contributed to the enhancement of cadmium-contaminated soil.(2)The leaching test of heavy metal leaching concentration of leaching filtrate decreased with the increase of age,and the decrease was higher in the early stage,and the decline in the later stage was stable.Curing materials such as cement and other hydration products in the early heavy metal bonding and alkali environment,the role of heavy metal precipitation is weak.Leaching solution pH between 11.5-11.6,heavy metal leaching leaching concentration changes greatly.(3)With the increase of the number of freeze-thaw cycles,the unconfined compressive strength of the contaminated soil decreased,and the strength decreased after freezing and thawing cycles more than 15 times.The plastic deformation deformation of the contaminated soil is changed greatly by the freeze-thaw cycle,and the plastic deformation is obviously increased.In the freeze-thaw cycle 0-15 times,the concentration of heavy metal leaching leaching increased rapidly,15-20 times after leaching leaching concentration increased slowly.(4)9 groups of contaminated soil samples by nuclear magnetic resonance test,it found that the pore size is mainly concentrated in the 0.01?m-0.1?m between.And with the cement,fly ash and other curing materials increased the content of pore size in the range of 0.01?m-0.1?m pore volume has increased.For the pore size of more than 10?m pores accounted for more pollution of the solidified soil strength is relatively low,while its heavy metal leaching leaching concentration is also high.It is found that such pores with pore size greater than 10?m are harmful pores for curing contaminated soil.