A study of hysteresis of soil and water characteristics of intact loess

There are few studies on hysteresis of soil and water characteristic curve(SWCC) of intact loess, and most of the existing studies focus on remolding soil samples. In order to study the hysteresis characteristics of intact loess in the full suction range, Malan loess (L1) and Lishi loess (L5) in Jingyang were taken as the research objects, their wetting and drying SWCCs were determined by filter paper method and pressure plate instrument. And their pore distribution and mineral composition were measured by mercury intrusion method and X-ray diffraction, respectively. The results show that the SWCCs measured by filter paper method and pressure plate instrument are consistent in the range of pressure plate instrument (0~600 kPa), and the results of two methods are more consistent in the process of drying. Within the total suction range (0~30 000 kPa) measured by filter paper method, the hysteresis of SWCC is characterized by three stages. That is, in the vicinity of natural water content (L1 14.2%, L5 17.3%), SWCC of the two layers of loess has almost no hysteresis; the water content is higher than a certain range of natural water content (L1 is greater than 19.2% and L5 is greater than 18.3%), and there is extremely obvious hysteresis; lower than a certain range of natural water content (L1 is less than 11.2% and L5 is less than 15.4%), there is a weak hysteresis. Repeated drying and wetting cycles under natural conditions result in no hysteresis of SWCC near the natural water content; the potentiation of limited pores on the ink-bottle effect leads to strong hysteresis at high water content; the hydration of clay minerals results in a weak hysteresis at low water content.