The contact Angle plays an important role in matrix suction of unsaturated soils, but few studies consider the effect of contact Angle hysteresis on matrix suction. In this paper, taking sandy soil as an example, the influence of contact angle hysteresis on the suction of unsaturated soil matrix is studied by soil particle model calculation and experimental method. When the contact angle is less than 90°, the unsaturated soil will also produce water repellency, which is different from the capillary law that the contact angle is less than 90°, which has hydrophilic properties. When the water content is the same, the suction of the matrix decreases continuously with the increase of the contact angle; this model can lay a foundation for the study of water repellency of unsaturated soil. With the increase of water content, the matrix suction is not affected by the soil contact angle; it is proved that the contact angle in unsaturated soil is not a constant, but varieswith the change of external environment. In the process of dehumidification, the apparent contact angle of sand at the same moisture content < receding contact angle; there is a difference in the matrix suction between the continuous measurement method and the intermittent measurement method, and the matrix suction of the continuous measurement method > the matrix suction of the intermittent measurement method. This study provides a theoretical basis for the study of unsaturated soil matrix suction.
 

Unsaturated soil· matrix suction· Soil-water characteristic curve(SWCC) ·Contact angle Hysteresis· Sand soil