EFFECT OF SOIL GELS ON HYSTERESIS PHENOMENA IN SOILS

Based on the analysis of the exist mechanisms of the hysteresis of soil water retention curve (WRC), as well as ideas about the nanostructural organization of soils, it is concluded that hysteresis can be caused either by stable (non-colloidal particles) or labile (gels) parts of the solid phase of soils. Due to the fact that until now the main attention has been paid to the study of the effect of stable solid phase of soils on the hysteresis of WRC, it was proposed to investigate the effect of soil gels on hysteresis. For this purpose, the effect of moisture content of soil samples prepared by drying and moistening on the initial viscosity of soil pastes was studied. It has been established that well-pronounced hysteresis is observed for samples of all studied soil types. To explain the hysteresis, two mechanisms based on changes in soil gels in the humidification-drying processes are proposed. One of them is based on the slowness of swelling and shrinkage of soil gels when they absorb and release water. The second is on the greater hydrophobicity of the surface of gels containing less water, and water slipping on hydrophobic areas of the surface with a decrease in the viscosity of pastes. Thus, the conducted studies have shown that hysteresis phenomena in soils are caused by soil gels and their changes during drying and moistening of soils.