Preliminary Study On Resistivity Characteristics And Influencing Factors Of Artificial Contaminated Soil

In recent years,in situ testing technology has been rapidly developed in the monitori ng and evaluation of polluted sites.In situ testing technology is to monitor and evaluate t he scope and extent of soil pollution through electrical or other geotechnical testing meth ods.Among them,resistivity detection has the advantages of economy,high efficiency,n o damage to the soil,and wide detection range,which can effectively reflect the contami nation distribution information and site management effect of the contaminated site.How ever,the soil resistivity characteristic is easy to be affected by a variety of factors,such a s moisture content,porosity,pollutants and curing agents used to control polluted sites.I n order to clarify the influence of different factors on the test results,this thesis conducte d an indoor experimental study on the influencing factors of soil resistivity characteristic s using artificially prepared contaminated soil(the source soil is a campus surface layer o f pulverized clay)and standard sand,which will provide a theoretical basis for the later a pplication of the resistivity method to the monitoring and evaluation of the solidified rem ediation of contaminated sites.The main research results are as follows.(1)Indoor experiments with the system have shown that when the test frequency is1-10 k Hz,the resistivity decreases slowly as the test frequency increases;when the test frequency reaches 100 k Hz,the decrease in resistivity increases.Therefore,it is advisable to use a low frequency(1-10 k Hz)to measure resistivity.In addition,soil resistivity decreases with increasing water content,porosity,and heavy metal concentration until it plateaus.The soil resistivity decreases sharply when the water content of the soil sample is between 5 and 15% and decreases at a lower rate when the water content reaches 20-30% and remains stable when the water content reaches 30%and above.Soil resistivity decreases as a function of the increase in porosity.The resistivity of soil samples decreases sharply when the heavy metal(Cu,Cr,Cd)ion doping is below 1000 mg/kg,decreases slowly from 1000 to 3000 mg/kg,and remains stable beyond 3000 mg/kg.At the same heavy metal mixing amount,the resistivity of different types of heavy metal contaminated soils showed: Cu>Cd>Cr.(2)The resistivity of the cured remediation soil increased with the increase of the cement admixture and curing age at the admixture of 5-15% cement curing agent.The resistivity of the cured remediation soils decreased when the concentration of heavy metal ions increased to 3000 mg/kg～5000 mg/kg at a certain amount of curing agent and maintenance age,indicating that the high concentration of heavy metal ions inhibited the electrical conductivity of the cured soils,which confirmed the feasibility of the resistivity method for evaluating heavy metal contaminated soils.Scanning electron microscopy was used to analyze the microstructure of the different cured remediated contaminated soils and to identify the mechanism of the effect of excess contaminants on electrical conductivity.(3)Based on the results of the indoor experimental tests and the existing research base,the factors affecting the resistivity of soil samples were identified and a soil resistivity model was given regarding the different influencing factors,which provides a reference for the evaluation of the curing effect of contaminated soils using the resistivity method.