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| Effects of salt cation types on the propagation and closure law of desiccation cracks in red soil |
| WANG Hui*, CHEN Xiaoyue, WANG Wei |
| College of Water Resources and Civil Engineering, Hunan Agricultural University, Changsha, Hunan 410128, China |
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Abstract In order to investigate the influences of salt ion concentration and its type in irrigation water on the process of soil crack change and to provide data theoretical support for the safety of irrigation water in south China, the south subtropical typical red soil was soaked by using four solutions of NaCl, KCl, CaCl2 and MgCl2 with the solute concentration of 15 g/L, 10 g/L, 5 g/L and 2.5 g/L, respectively. The dry and wet processes were simulated by using isothermal evaporation and water spraying, respectively. In order to analyze the process of red soil fracture development affected by salt cation type, the geometric parameters of soil crack were extracted by using digital image technology. The results showed that the cracks in the drying process of red soil increased most rapidly with the moisture content decreased from 30% to 10%, and reached the maximum value when the soil mass moisture content was lower than 10%,and then remained stable afterwards. The crack area density of red soil was significantly positively correlated with the concentration of four salt cation. The crack length density was significantly negatively correlated with K+ and Mg2+, and significantly negatively correlated with Ca2+. The order of the positive effect of four ions on the cracking area of red soil was Na+>K+>Ca2+>Mg2+. Compared with distilled water treatment, the larger promotion effects were found in the 10 g/L of NaCl, and 15 g/L of KCl, CaCl2 and MgCl2 solutions, which increased by 155.0%, 160.1%, 109.4% and 39.2%, respectively. The cracked water content was lower than the closed water content. Moreover, the cracked and closed water contents of red soil increased after soaking with four kinds of salt cation solutions.
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Received: 31 March 2020
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