Abstract:

Land degradation due to wind erosion is a global problem， and the impact of saltation particles on the ground surface is the key soil wind erosion process. At present， the fragmentation process and mechanism of soil agglomerates in saltation movement have not been fully revealed. This paper explores the critical fragmentation velocity and fragment size distribution of dry dense soil agglomerates in collision with the ground through indoor simulation experiments， and obtains the following preliminary conclusions： （1） Under low-velocity impact， the collision process between soil agglomerates and the ground is mainly in the damage state， and the cracks generated by the collision form penetration cracks along the meridional plane； under higher velocity， cones appear in the collision contact area leading to agglomerate fragmentation. （2） The particle size， density， compressive strength， and Young's modulus jointly determine the threshold velocity. Specific functional relationships and empirical constants are given by the dimensional analysis and experimental data. （3） During the collision， the dust release of loam varies significantly with the velocity， and the dust release of clay， sandy soil， sandy clay， and loamy clay is mostly less than 1% of the aggregate mass. （4） The number and size of fragments after the collision can be described by the two-parameter Weibull distribution function. The collision of soil agglomerate fragments differs from that of conventional brittle materials such as glass and ceramics due to the presence of internal defects.

Key words: soil aggregate, threshold velocity, fragment size distribution, Weibull distribution