Dielectric Parameter Characteristics And Prediction Model Of Diesel Contaminated Silty Clay

Soil environmental recovery and remediation is an important environmental problem in China.Before the formulation of contaminated soil remediation scheme and after the remediation of contaminated sites,the qualitative and quantitative detection of soil pollutants should be carried out.However,there are some problems in the commonly used chemical detection methods,such as limited number of detection points and long detection period and so on.Ground penetrating radar(GPR)is a geophysical method that uses electromagnetic wave to detect the properties and distribution of underground medium.It has the advantages of wide detection range and fast detection speed.Recently,GPR has been widely studied in contaminated soil detection.The dielectric parameter is the link between GPR signal and contaminated soil,who are the core problems to study the dielectric parameter characteristics and establish dielectric model of contaminated soil.Based on an oil contaminated site in Nanning,the GPR reflection and dielectric properties of diesel contaminated soil were studied by laboratory tests and numerical analysis.Finally,the complex permittivity model of diesel contaminated soil with frequency parameters was established.The research results have important guiding significance to realize the quantitative detection of diesel contaminated soil by GPR.The main contents and conclusions of this paper are as follows:(1)Based on the investigation and in-situ sampling of the oil contaminated site in Nanning,Guangxi,the laboratory simulation experiments were designed.Taking the diesel contaminated silty clay as the research object,the single factor analysis method was used to make the contaminated soil sample models with different diesel content,water content and dry density.The GPR and vector network analyzer are respectively used for the soil samples testing,and the corresponding GPR reflection wave and complex permittivity data are obtained.(2)The characteristics of GPR properties of different diesel contaminated soil samples were analyzed,and the relative permittivity characteristics of diesel contaminated soil were obtained.The results show that the radar wave velocity,amplitude and frequency of soil samples decrease with the increase of dry density and diesel oil content of soil sample,but the influence is not obvious when the water content is low;the complex permittivity characteristics and GPR reflection baud performance measured by vector network analyzer.The results show that the values of complex permittivity increase with the increase of soil moisture content,dry density,water content and oil content,and the water content has the most obvious influence on the complex permittivity and radar wave properties of soil samples.(3)In view of the variation of dielectric parameters with frequency in diesel contaminated soil,the quantitative relationship between the complex dielectric constant and the phase medium of soil samples was analyzed from a single medium,and the dielectric model for diesel contaminated silty clay was selected.The model parameters were modified by the measured data,and the frequency parameter was further introduced to establish the volume mixed dielectric model.The average error between the measured data and the calculated results is 7%,which indicates that the frequency domain model of complex permittivity has high accuracy.