基于地质雷达法的非饱和黄土介电特性及界面反射机理研究

Research on Dielectric Property and Interface Reflection Mechanism of Unsaturated Loess by Ground Penetrating Radar

基于地质雷达方法研究非饱和黄土的介电性能,以及地质雷达波在空气-黄土界面中的反射机理及规律,利用地质雷达等对非饱和黄土相对介电常数与电导率进行系统试验研究,分析了黄土混合相对介电常数与其固、气、液各相的相对介电常数的内在关系;提出不同压实度与含水率与黄土相对介电常数的数理关系,以及不同地质雷达天线频率对黄土含水率-相对介电常数物理关系的影响规律。分析结果表明:非饱和黄土相对介电常数与黄土含水率和压实度呈正相关的数理关系;相同的黄土试样测试的相对介电常数与地质雷达天线主频的大小正相关;不同含水率的非饱和黄土界面反射数值模型表明,含水率越大,地质雷达回波强度越大。以上结论对非饱和黄土工程的地质雷达法探测工作具有指导作用。

The dielectric property of loess and the reflection mechanism and law of ground penetrating radar( GPR) wave are studied in this article. Through tests on the relative permittivity and conductivity of unsaturated loess,the inner relation between relative permittivity and three phases( gas,liquid,and solid) is analyzed. Moreover,the mathematical-physical relations of relative permittivity versus compaction degree and moisture content are obtained. The influence of GPR antenna frequency on the moisture content-permittivity relation is also analyzed. Results suggest that relative permittivity of unsaturated loess is positively related with moisture content and compaction degree; given the same loess sample,relative permittivity is positively related with antenna frequency. In addition,the interface reflection numerical model of relative permittivity versus moisture content is built,indicating that echo intensity of GPR grows with the increase of moisture content. The above conclusions are of guiding significance for GPR detection of unsaturated loess engineering.