Effects of pre-dynamic loading on hydraulic properties and microstructure of undisturbed loess

The frequent earthquakes in the loess area and the geological disasters induced by them have caused huge threats to the safety and property of the local residents, and most disasters are highly dependent on moisture in the soils. In this study, the effects of pre-dynamic loading on the hydraulic properties of loess are investigated through the variation of soil water characteristic curves, which control the interaction between soil and moisture. The results are analyzed based on the combination of mercury intrusion porosimetry (MIP) and scanning electron micro-scope (SEM) tests, which reveal the influence of pre-dynamic loads on microstructure, for a more comprehensive understanding. It is found that both the initial water content of soil samples and the magnitude of applied pre -dynamic loads have impacts on soil water characteristic curve (SWCC). When initial moisture content is low, the dynamic load causes the loess structure to form a seismic damage zone, resulting in downward movement of SWCC and a reduction in the air entry value. When the moisture content is high, the soil structure gets denser after vibration, leading to reversed influence. For both cases, the effect increases as the PGA amplitude increases. The outcomes of different experiments have achieved good agreement.