双相混合物等效介电常数探地雷达数值研究

Study on effective permittivity of two-phase mixture based on GPR numerical simulation

等效介电常数是混合物微观结构的宏观表征,与介质的属性参数密切相关.在传统随机介质建模理论的基础上,通过增加量化约束限定条件,精准控制双相混合物各组成物质的体积占比,建立了22个体积占比相同、孔隙粒径尺度不等和20个孔隙粒径尺度相等、体积占比不同的双相混合物介质模型,进行探地雷达数值模拟,研究超宽频带条件下双相混合物各组成物质体积占比和孔隙粒径大小对其等效介电常数及探地雷达波场特征的影响.结果表明:对于各组成物质体积占比相同、孔隙粒径尺度不等的双相混合物,其等效介电常数基本相同,说明混合物等效介电常数主要取决于其各组成物质的体积占比及其介电常数,但由于混合物内部孔隙粒径尺度不等,其电磁散射强度和能量衰减损失存在明显差异;对于孔隙粒径尺度相等、体积占比不同的双相混合物,其空气体积占比越小,等效介电常数越大,与Rayleigh模型、CRIM模型等混合物等效介电常数经验公式计算结果差值越小、吻合越好,同时,其散射波振幅强度和波形杂乱程度越弱,研究结果可为解译双相混合物介质属性参数提供参考和指导.

Effective dielectric constant is the macroscopic characterization of the microstructure of the mixture,and it is closely correlated with the property parameters of the medium.Based on the theory of traditional random medium model,and by adding quantitative constraint conditions,the volume proportion of various components of the two-phase mixture was precisely controlled,and then 22 two-phase mixture medium with the same volume proportion and different pore size as well as 20 with equal pore size but different volume proportion were established for numerical simulation of Ground Penetrating Radar(GPR).Then the influence of the volume proportion and pore size of various components of the two-phase mixture under the condition of ultra wide band on its effective dielectric constant and the wave-field characteristics of GPR were studied.The results indicated that,for the two-phase mixture with equal volume proportion and different pore sizes of various components,its effective dielectric constant was basically the same,showing that the effective dielectric constant of the mixture mainly depended on the volume proportion and its dielectric constant of various components.However,as the internal pore size of the mixture was different,there were significant difference between the electromagnetic scattering intensity and energy attenuation loss;For the two-phase mixture with equal pore size and different volume proportion,the smaller its air volume ratio was,the greater the effective dielectric constant would be.Meanwhile,the smaller the difference with the calculation result obtained by the empirical formula of the effective dielectric constant of the Rayleigh model and CRIM model was,the better the matching would be,and at the same time,the weaker the scattered wave amplitude intensity and waveform clutter degree would be.Therefore,the research results can provide some guidance for interpreting the attribute parameters of the two-phase mixture medium.