未饱和砂土含水量GPR反射波法检测研究

Nondestructive and Quick In-Situ Testing of Unsaturated Sandy Soil Water Content Using Ground Penetrating Radar Reflection Method

未饱和砂土含水量变化会引起介电性质改变,影响土体中电磁波传播速度。利用GPR反射波法测得土体电磁波速后,基于正确的土体介电常数模型可求得含水量,这一过程具有快速、连续、无损特点。为实现目标,以不同粒径组成的3组典型砂土为样品,利用探地雷达反射波法测定其介电常数,研究影响土样介电常数的关键因素和遵循的介电常数模型,讨论基于介电理论的土体含水量求取方法。研究表明粒径级配差异不会引起砂土介电常数较大变化;含水量是决定其介电常数的关键因素,两者关系可采用拟合的Topp或Alharathi型公式表示;砂土介电常数遵循Looyenga混合介电常数模型。研究成果在土方路基含水量连续检测中得到有效应用。

Unsaturated soil moistures content variation will change its dielectric constant,affect electromagnetic wave propagating speed in it.So if electromagnetic wave propagating speed had been measured nondestructively and quickly with GPR method,the water content of soil could be calculated with good dielectric constant model.In order to achieve this object,dielectric constant of over 30sandy soil samples were measured by using GPR reflection method in laboratory,the relation between moisture content and electric constant,the fitting dielectric constant model of sandy soil were studied with those data.Research results showed that dielectric constant of sandy soil accorded to mixed volume model,which may be obtained from Looyenga Formula.Although particle grade of soil samples were different,but their dielectric constants increased with moisture constant according the same formula as Topp-type or Alharathi-type Formula.These new viewpoints were made true with a case study of soil roadbed inspecting.