Mechanical and hydraulic resistance relations in crust-topped soils
Mechanical and hydraulic resistance relations in crust-topped soils
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DOI：
10.1016/j.catena.2007.05.012
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发表时间：
2008-01-15
期刊：
影响因子：
6.2
通讯作者：
Bedaiwy, M. N. A.
中科院分区：
文献类型：
--
作者：
Bedaiwy, M. N. A.
土壤表面结皮的形成导致机械和水力阻力的增加。在本研究中，研究了模拟喷灌（或降雨）和先喷灌后漫灌条件下两种阻力的变化及其关系。结果表明，在任意动能下，粉壤土的表壳比粘土的表壳厚。粉壤土和粘土的结壳厚度分别为3.9毫米和2.6毫米。机械阻力R-m随KE的增加而增大，其中粉壤土的机械阻力R-m的影响更大，这主要归因于内在阻力和地壳厚度。结壳粘土的稳态入渗速率(i)比结壳粉壤土低得多。R-m和i的变化与地壳厚度的变化密切相关（z(c)）。较厚的结壳比较薄的结壳表现出更强的抗外力能力，这是由于更广泛的颗粒联锁作用。得到的函数表明，厚度对强度的影响在较低的地壳厚度范围内更为显著。两种土壤的z(c)对i的影响均呈负幂函数，粉壤土的i较高。机械阻力，表现出对结壳的高度敏感性，并对增加的严重程度保持响应。粉壤土的R-m变化幅度大于粘土。粉壤土的R-m由0.5 N（无结壳）增加到43 N（最高KE），相对变化（rel(o) R-m）为86。粘土的R-m由0.77 N增加到22 N， rel(o) R-m为28.6。对于粉壤土和粘质土，在最低施用KE （Rel(1) R-m）下，R-m分别增加了6.9倍和4.7倍。水力阻力R-h随处理强度的增加而增大，在粘土中较高。R-m和抗性功R-w均与R-h呈极显著相关。粉壤土在任何给定的R-h下均表现出较大的R-w。虽然R-h在粘土中明显较高，但在粉壤土中变化速率更大。入渗速率对结壳的增加表现出高度敏感，特别是在粘土中。i-R-h关系强烈遵循负幂函数：i = a R-h（-b）。淤泥质壤土和黏性土的i相对于原土的减少因子分别为130倍和180倍，相对于最弱处理的减少因子分别约为23倍和28倍。在功率方程中，Rm的相对变化与rel Rh呈正相关，而rel i呈负相关。传输区吸力psi(u)随R-h的变化符合psi=a R-h(m)函数，其中a和m为土的常数。利用K=a psi（-n）形式的函数，确定了粉质壤土的特征常数a和n分别为0.174和3.01，黏土的特征常数a和n分别为1.367和1.61，得到了特征K-psi函数。(c) 2007 Elsevier B.V.版权所有
The formation of soil surface crusts leads to increased mechanical and hydraulic resistances. In this study, changes and relationships of both resistances under simulated sprinkle irrigation (or rainfall), and sprinkle followed by flooding, were examined. Results indicated that a silt-loam soil developed a thicker surface crust than a clay soil for any given kinetic energy (KE). Crusts as thick as 3.9 and 2.6 mm formed on the silt-loam and clay soils, respectively. Mechanical resistance, R-m, increased with increasing KE, where the effect was greater in the silt-loam and was attributed to intrinsic resistance and crust thickness. Steady-state infiltration rate (i) was much lower in crusted clay than crusted silt-loam soil. Changes of both R-m, and i closely followed changes in crust thickness (z(c)). Thicker crusts showed more resistance against external force than thinner crusts, due to more extended particle interlocking. Obtained functions indicated that the effect of thickness on strength was more significant in the lower range of crust thickness. The effect of z(c), on i strongly followed a negative power function for both soils, with higher i in the silt-loam soil.Mechanical resistance, showed high sensitivity to crusting, and remained responsive to increasing severity. Change of R-m in the silt-loam soil was steeper than that of the clay soil. R-m of the silt-loam soil increased from 0.5 N (non-crusted) to 43 N (highest KE), with a relative change (rel(o) R-m) of 86. For clay, R-m increased from 0.77 N to 22 N, producing a rel(o) R-m of 28.6. Trends were consistent when evaluated relative to the lowest applied KE (Rel(1) R-m), where R-m increased under highest KE about 6.9 and 4.7 times, for the silt-loam and clay soils, respectively.Hydraulic resistance, R-h, increased with increasing treatment intensity, and was higher in the clay soil. Both R-m and the work-of-resistance, R-w, showed highly significant relationships with R-h. The silt-loam soil displayed greater R-w for any given R-h. Although R-h was markedly higher in the clay soil, the rate of change was greater in the silt-loam soil. Infiltration rate appeared highly sensitive to increased crusting, particularly in the clay soil. The i-R-h relationship strongly followed the negative power function: i = a R-h(-b). Relative changes in i under ponding showed reduction factors of > 130 and 180, relative to original soils, and of approximately 23 and 28 times relative to the least intense treatment, for the silt-loam and clay soils, respectively. Relative changes in Rm correlated positively, while rel i correlated negatively, with rel Rh in power equations. The change of transmission zone suction (psi(u)) with R-h fitted the function psi=a R-h(m), where a and m were constants, characteristic of the soil. Using a function of the form K=a psi(-n), the characteristic constants a and n were determined as 0.174 and 3.01 for the silt-loam and 1.367 and 1.61 for the clay soil, and the characteristic K-psi functions were obtained. (c) 2007 Elsevier B.V. All rights reserved.