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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 sand water content changes will cause the dielectric properties change, affecting the soil electromagnetic wave propagation speed. After measuring the electromagnetic wave velocity by the GPR reflection wave method, the water content can be obtained based on the correct soil dielectric constant model, which has the characteristics of rapid, continuous and non-destructive. In order to achieve the target, three typical sand samples with different grain sizes were taken as samples, the dielectric constant was measured by GPR reflection wave method, the key factor affecting the dielectric constant of soil sample and the model of dielectric constant were discussed. Calculating Soil Water Content Based on Dielectric Theory. The results show that the variation of particle size gradation does not cause a large change of the dielectric constant of sand; the water content is the key factor to determine the dielectric constant, and the relationship between the two can be expressed by the fitted Topp or Alharathi formula; The constants follow the Looyenga mixed dielectric constant model. The research results have been effectively applied in continuous testing of soil moisture content of earthwork.