Scaling of Physical Properties of Soils by Using Non-Similar Media Concept

土壤的容重随着田间的自然和人工过程而变化。土壤容重RHO_b越大，进气吸力h_e越大，导水系数K_s越小。尽管基于泊肃叶定律的 Kozeny-Carman 方程和基于 Miller 和 Miller (1956) 的类似介质概念 (SMC) 的坎贝尔方法都能够从理论上预测水力传导率的体积密度依赖性，但它们的适用性和局限性一直很模糊。本研究提出了一种非相似介质概念（NSMC）模型，由固相特征长度S、孔隙相特征长度d和固相形状因子tau组成，用于预测给定土壤的he和Ks值作为其rho_b的函数。通过将NSMC模型与Campbell法和Kozeny-Carman方程进行比较，实验表明NSMC模型在he(rho_b)和Ks(rho_b)的预测中不仅适用于团聚土，也适用于分散土。NSMC模型对沙土的适用性足够高。该模型对聚合羊毛的适用性取决于适当的形状因子 tau^<**> 的发现。 tau^<**> 值接近但稍大于 rho_b/rho_s 可能会给出粗略估计，但强烈建议测量 h_e-rho_b 关系，通过该关系确定可靠的 tau^<**> 值。 NSMC 模型是一个新的且不断发展的模型。结果表明，NSMC模型对机械压实粘土的K_s作为rho_b函数的预测能力较差。这种压实土壤的 NSMC 模型可以通过将形状因子定义为堆积密度或压实能量的函数来改进。

The bulk density of a soil changes with natural and artificial processes in a field. The larger the bulk density RHO_b of the soil, the larger the air entry suction h_e and the smaller the hydraulic conductivity K_s. Although both the Kozeny-Carman equation, based on Poiseuille's law, and Campbell's method, based on a similar media concept (SMC) by Miller and Miller (1956), are able to predict bulk density dependencies of hydraulic conductivities theoretically, the applicabilities and limitations of them have been vague. This study proposed a non-similar media concept (NSMC) model, composed of a characteristic length for the solid phase S,that for the pore phase d and a shape factor tau of the solid phase, to predict he and Ks values of a given soil as functions of its rho_b. By comparing the NSMC model with the Campbell method and the Kozeny-Carman equation, it was clarified experimentally that the NSMC model is applicable to aggregated soils in the predictions of he (rho_b) and Ks (rho_b) as well as to dispersed soils.The applicability of NSMC model to sandy soil was sufficiently high. The applicability of this model to an aggregated woil depended upon the findings of an adequate shape factor tau^<**>. The tau^<**> value close to but a little larger tha rho_b/rho_s may give a rough estimation, but it is strongly recommended to measure the h_e-rho_b relation by which a reliable tau^<**> value is determined.The NSMC model is a new and growing model. It was shown that the predictability of K_s as functions of rho_b of mechanically compacted clayy soils by the NSMC model were relatively poor. The NSMC model for such compacted soils may be improved by defining the shape factor as a function of the bulk density or compaction energy.