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体积含水率-介电常数关系是时域反射法(TDR)测量土体体积含水率的理论基础。通过对重塑的南宁膨胀土进行试验,选择经验公式法、边界法及理论模型法模拟其体积含水率-等效介电常数的变化规律。研究发现,南宁膨胀土的实测值落在Hashin-Shtrikman边界和Wiener边界以内,但Hashin-Shtrikman边界具有更小的范围;由于膨胀土的黏性较大,结合水存在显著的影响,Topp公式计算值偏高,但采用考虑三相组分含量的Looyenga公式可反映结合水的影响,从而得到更好的结果;理论模型法的Maxwell-Garnett模型和差分有效介质模型(DEM)需要考虑三相的构成,单独采用气相连续或水相连续的模拟结果均不理想,但如考虑土中水、气分布形态,采用饱和度作为权重函数对单相计算结果进行加权平均后可取得较好的效果。
The relationship between volumetric water content and dielectric constant is the theoretical basis of time domain reflectometry (TDR) to measure the volumetric water content of soil. Through the experiment of the remolded Nanning expansive soil, the empirical formula method, boundary method and theoretical model method were used to simulate the variation of volumetric water content - equivalent dielectric constant. The results show that the measured value of Nanning expansive soil falls within the Hashin-Shtrikman boundary and the Wiener boundary, but the Hashin-Shtrikman boundary has a smaller range. Due to the viscous nature of expansive soil and the combined effect of water, Topp formula However, the Looyenga formula which considers the content of three-phase components can reflect the effect of bound water to obtain better results. The Maxwell-Garnett model and the DEM of the theoretical model method need to consider three-phase However, the results of continuous or discontinuous gas-phase simulation are not ideal. However, considering the distribution of water and gas in the soil, using the saturation as the weight function, the single-phase calculation results can achieve better results.