ABSTRACT

The processes of soil cracking with water loss in saline soils are still not well understood. It is of great significances to further understand the mechanism of desiccation cracking in saline-alkali soil and provide guidance for engineering practice in saline-alkali area. Silt loam and sand samples were saturated with NaCl solutions (5, 50, and 100 g/L) and undergone the evaporation tests, during which the water loss and surface cracking parameters were obtained. Results showed that evaporation and crack development influenced each other. The evaporation rate for both sand and silt loam samples saturated by NaCl solution was lower than the reference samples, and decreased as the concentration of NaCl solution increased. In addition, the water content for both two types of samples first rapidly decreased and then entered a stable state during evaporation; however, silt loam soil moisture experienced a “second decline” when surface crack developed rapidly. Compared to the reference sample, NaCl solution inhibited crack development in silt loam, which in turn impeded water evaporation; however, no surface cracks were observed in sand samples. Furthermore, crack area and crack length decreased as the concentration of NaCl solution increased, and higher NaCl concentration resulted in an earlier abrupt increase in crack number followed by a stable state. The present findings reveal that the interaction between water evaporation and surface cracking is shown by soluble NaCl, including the chemical effects on soil particles from free Na⁺ and the physical effects on soil pores from precipitated NaCl crystals during water loss.

摘要

盐渍土中土壤开裂和失水的过程仍然没有得到很好的理解。对进一步了解盐碱土干燥开裂机理，为盐碱地区工程实践提供指导意义重大。粉砂壤土和沙子样品用 NaCl 溶液（5、50 和 100 g/L）饱和并进行蒸发测试，在此期间获得失水量和表面开裂参数。结果表明，蒸发和裂纹发展相互影响。NaCl溶液饱和的砂壤土和粉砂壤土样品的蒸发速率均低于参考样品，并且随着NaCl溶液浓度的增加而降低。此外，两种样品的含水量在蒸发过程中均先快速下降，然后进入稳定状态；然而，当地表裂缝迅速发展时，粉砂壤土的水分经历了“二次下降”。与参考样品相比，NaCl 溶液抑制了粉砂壤土的裂缝发展，进而阻碍了水的蒸发；然而，在沙样中没有观察到表面裂纹。此外，随着 NaCl 溶液浓度的增加，裂纹面积和裂纹长度减小，较高的 NaCl 浓度导致裂纹数量较早突然增加，随后达到稳定状态。目前的研究结果表明，可溶性 NaCl 显示了水分蒸发和表面开裂之间的相互作用，包括游离 Na 对土壤颗粒的化学作用。当表层裂缝迅速发展时，粉砂壤土水分经历了“二次下降”。与参考样品相比，NaCl 溶液抑制了粉砂壤土的裂缝发展，进而阻碍了水的蒸发；然而，在沙样中没有观察到表面裂纹。此外，随着 NaCl 溶液浓度的增加，裂纹面积和裂纹长度减小，较高的 NaCl 浓度导致裂纹数量较早突然增加，随后达到稳定状态。目前的研究结果表明，可溶性 NaCl 显示了水分蒸发和表面开裂之间的相互作用，包括游离 Na 对土壤颗粒的化学作用。当表层裂缝迅速发展时，粉砂壤土水分经历了“二次下降”。与参考样品相比，NaCl 溶液抑制了粉砂壤土的裂缝发展，进而阻碍了水的蒸发；然而，在沙样中没有观察到表面裂纹。此外，随着 NaCl 溶液浓度的增加，裂纹面积和裂纹长度减小，较高的 NaCl 浓度导致裂纹数量较早突然增加，随后达到稳定状态。目前的研究结果表明，可溶性 NaCl 显示了水分蒸发和表面开裂之间的相互作用，包括游离 Na 对土壤颗粒的化学作用。这反过来又阻碍了水的蒸发；然而，在沙样中没有观察到表面裂纹。此外，随着 NaCl 溶液浓度的增加，裂纹面积和裂纹长度减小，较高的 NaCl 浓度导致裂纹数量较早突然增加，随后达到稳定状态。目前的研究结果表明，可溶性 NaCl 显示了水分蒸发和表面开裂之间的相互作用，包括游离 Na 对土壤颗粒的化学作用。这反过来又阻碍了水的蒸发；然而，在沙样中没有观察到表面裂纹。此外，随着 NaCl 溶液浓度的增加，裂纹面积和裂纹长度减小，较高的 NaCl 浓度导致裂纹数量较早突然增加，随后达到稳定状态。目前的研究结果表明，可溶性 NaCl 显示了水分蒸发和表面开裂之间的相互作用，包括游离 Na 对土壤颗粒的化学作用。⁺以及失水过程中沉淀的 NaCl 晶体对土壤孔隙的物理影响。