DESCRIBING SOIL HYDRAULIC-PROPERTIES WITH SUMS OF SIMPLE FUNCTIONS
DESCRIBING SOIL HYDRAULIC-PROPERTIES WITH SUMS OF SIMPLE FUNCTIONS
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DOI：
10.2136/sssaj1993.03615995005700010006x
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发表时间：
1993-01-01
影响因子：
2.9
通讯作者：
SMETTEM, KRJ
中科院分区：
文献类型：
--
作者：
ROSS, PJ;SMETTEM, KRJ
简单的功能不足以描述许多领域的土壤，特别是那些大量的大孔隙度的水力特性。考虑与有效饱和度S（psi）= SIGMA（i=1）N phi（i）S（i）（psi）相对应的土壤孔隙尺寸分布f（psi）= SIGMA（i=1）N phi（i）F（i）（psi），其中psi为基质压头，phi（i）为有效孔隙度分数，S（i）（psi）为常用的简单持水函数，f（i）（psi）= S（i）′（psi），根据Mualem模型，我们发现相对水力传导系数为K（r）（psi）= S（p）[SIGMA（i=1）N phi（i）g（i）（psi）/SIGMA（i=1）N phi（i）g（i）（0）2，其中g（i）（psi）= integral-psi/-xpsi-1f（i）（psi）dpsi，p是孔隙相互作用指数。如果分布的孔隙不相互作用，则适当的关系为K（psi）= SIGMA（i=1）N K（si）K（ri）（psi），其中K（si）是分布i的饱和电导率，并且K（ri）= S（p）[g（i）（psi）/g（i）（0）]2。我们注意到，当m = 1 - 1/n时，货车范希滕函数S（psi）= [1 +（-ψ）n]-m导致在psi = 0处的斜率K '（psi）为无穷大，除非n大于或等于2，如果考虑大范围的基质压头，这对于野外土壤是不现实的。饱和附近的渗透系数通常表示为K（psi）= K（s）exp（apsi）。我们引入函数S（psi）=（1 -ε apsi）exp（ε apsi），根据Mualem的模型，它给出了电导率K（psi）= K（s）（1 -ε apsi）p exp[（p + 2）ε apsi]，如果a = 2alpha，则接近饱和，如果p = 0，则完全相等。作为一个例子，一个函数使用此模型的一个孔径分布和货车van Eschchten模型的另一个进行了比较，一个函数使用两个货车Eschchten分布。后者给了一个稍微改进的适合聚合土壤的含水量和电导率数据。
Simple functions do not adequately describe the hydraulic properties of many field soils, particularly those with substantial macroporosity. By considering the soil pore-size distribution f(psi) = SIGMA(i=1)N phi(i) F(i)(psi) corresponding to the effective saturation S(psi) = SIGMA(i=1)N phi(i) S(i)(psi), where psi is matric pressure head, the phi(i) are fractions of effective porosity, the S(i)(psi) are simple water retention functions in common use, and f(i)(psi) = S(i)'(psi), we show that the relative hydraulic conductivity according to the Mualem model is K(r)(psi) = S(p)[SIGMA(i=1)N phi(i) g(i)(psi)/SIGMA(i=1)N phi(i) g(i)(0)2, where g(i)(psi) = integral-psi/-x psi-1 f(i)(psi) dpsi and p is a pore interaction index. If the pores of the distributions do not interact, the appropriate relation is K(psi) = SIGMA(i=1)N K(si)K(ri)(psi), where K(si) is the saturated conductivity of distribution i and K(ri) = S(p)[g(i)(psi)/g(i)(0)]2. We note that the van Genuchten function S(psi) = [1 + (-alphapsi)n]-m with the restriction m = 1 - 1/n leads to an infinite slope K'(psi) at psi = 0 unless n greater-than-or-equal-to 2, which is unrealistic for field soils if a wide range of matric pressure heads is considered. Hydraulic conductivity near saturation is often expressed as K(psi) = K(s) exp(apsi). We introduce the function S(psi) = (1 - alphapsi) exp(alphapsi), which gives, according to Mualem's model, a conductivity K(psi) = K(s)(1 - alphapsi)p exp[(p + 2)alphaphi] that approximates K(s) exp(apsi) near saturation if a = 2alpha and is exactly equal if p = 0. As an example, a function using this model for one pore-size distribution and the van Genuchten model for the other was compared with a function using two van Genuchten distributions. The latter gave a slightly improved fit to water content and conductivity data for an aggregated soil.