Abstract
Structural characteristics of local saline-alkali soil in the Yellow River Delta were studied by microscopic test methods of liquid nitrogen vacuum freeze-drying machine, fully automatic mercury intrusion porosimetry, X-ray diffractometer, and high- and low-vacuum scanning electron microscope. Permeability of the saline-alkali soil belongs to two grades of micropermeable water and extremely micropermeable water. Average volume ratio of pores with diameters no more than 2 μm is 86.25%; therefore, the saline-alkali soil may mainly consist of micropores and ultramicropores. Most void ratios of the soil are not beyond 0.5, and its dry densities are all greater than 1.6 g/cm3. Because average proportion of the clay minerals is only 12.24%, they are obviously not the main reason for poor permeability of the local saline-alkali soil. Based on the structural characteristics of compact structure and slightly developed fracture, mechanisms of surface runoff, and water-salt migration of the local saline-alkali soil, a salt-discharging engineering model mainly with surface runoff was established considering auxiliary infiltration and without interflow. Salt content distribution of the local saline-alkali soil is studied experimentally, by which relationship between salt content and conductivity has been fitted as y = 2.74x. The relationships between depth and salt content in the saline-alkali soil region present that the depth of salt-discharging engineering as open ditch should be beyond 60 cm. From the relationships between precipitation and salt content, the effectiveness of engineering measure shown in the salt-discharging model has been verified immediately or indirectly, and the engineering salt-discharging model may be suitable for managing saline-alkali soil in the Yellow River Delta.
Highlights
Agricultural development in the world has been seriously limited by the saline-alkali soils
In China, area with salinealkali degrees are increasing every year, especially in the Yellow River Delta region, where irrigation farming is mainly dependent on water from the Yellow River; severe saline-alkali soil may be due to these reasons, including lower and even land, poor drainage, side infiltration of the Yellow River water, and ascending seawater or its infiltration. e key measures to manage saline-alkali soil are to exclude soluble salt in soil and stop salt from rising
Relationships between microstructure and physical or mechanical parameters of clay soil, in Zhanjiang city, were studied by scanning electron microscope, mercury intrusion porosimetry, and gas adsorption test [8]. e results provide an important reference for the study of the relationship between the microstructure of soil and its physical and mechanical properties. ese references are mainly about clay soil, soft soil, and loess, while the research on the microstructure of saline-alkali soil is less
Summary
Agricultural development in the world has been seriously limited by the saline-alkali soils. To manage saline-alkali soil fundamentally, microstructure of the soil should be studied for revealing its engineering features and physical characteristics. Analyzing microstructures from consolidation test results of clay soils by X-ray diffractometer and scanning electron microscope, their deformation features of expansion, compressibility, and permeability are studied by different minerals and microstructures when ameliorating the soil with limes [6]. Microstructures and minerals of soft clay soil were identified by scanning electron microscope and X-ray. Relationships between microstructure and physical or mechanical parameters of clay soil, in Zhanjiang city, were studied by scanning electron microscope, mercury intrusion porosimetry, and gas adsorption test [8]. E results provide an important reference for the study of the relationship between the microstructure of soil and its physical and mechanical properties. Relationships between microstructure and physical or mechanical parameters of clay soil, in Zhanjiang city, were studied by scanning electron microscope, mercury intrusion porosimetry, and gas adsorption test [8]. e results provide an important reference for the study of the relationship between the microstructure of soil and its physical and mechanical properties. ese references are mainly about clay soil, soft soil, and loess, while the research on the microstructure of saline-alkali soil is less
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