Lu Ma

The micro-stiffness ratio plays a significant role in the dynamic response characteristics of rock materials when analyzed using particle flow code. In this study, a macro–micro parameter model is developed to relate the micro-stiffness ratio to the macro-Poisson's ratio, revealing the relationships between multi-scale parameters. Large-scale split Hopkinson pressure bar numerical simulations are conducted to investigate the sensitivity of the dynamic mechanical characteristics of limestone to variations in the micro-stiffness ratio. The results indicate that, under impact loading, the force chain gradually concentrates toward the center of the specimen, forming a symmetrical saddle-shaped boundary. As the micro-stiffness ratio increases, both the normal peak stress and elastic modulus decrease, while the normal strain rate and strain acceleration increase. Axial and radial stresses exhibit similar sensitivity to the micro-stiffness ratio. The proportion of axial dissipated energy increases with the micro-stiffness ratio, whereas the proportion of radial dissipated energy decreases. The initiation time of damage evolution is significantly correlated with the micro-stiffness ratio: higher ratios lead to earlier initiation of damage evolution but slower damage accumulation. Consequently, the failure mode transitions from sudden brittle failure to slow and gradual failure.

Seepage erosion around sheet pile walls represents a critical failure mechanism in geotechnical engineering, yet the underlying mechanisms governing the onset of erosion remain poorly understood. This study presents a comprehensive multi-scale investigation employing a coupled computational fluid dynamics (CFD)-discrete element method (DEM) to elucidate the onset mechanisms of seepage erosion in gap-graded soils with varying the fines content under different hydraulic gradients. The results demonstrate that increasing the fines content enhances the overall erosion resistance, as evidenced by reduced particle mobilization and eroded mass ratio. Particle tracking analysis reveals that the fines content fundamentally influences the spatial distribution of the erosion. Specimens with low fines content exhibit distributed erosion throughout the domain, while specimens with higher fines content show concentrated erosion around the sheet pile wall and downstream regions. Micromechanical analysis of local contact fabric and contact forces indicates that this spatial heterogeneity stems from the mechanical coordination number and mechanical redundancy, characterized by the reduced magnitudes of these parameters for the region with lower erosion resistance. These findings establish that the fines content governs both global erosion resistance and spatial erosion patterns, providing essential insights for optimizing soil gradation design and advancing fundamental understanding of seepage erosion mechanisms.

Liquid surface tension is produced at interfaces between liquid and air, due to the different molecular attractions on both sides. If the adhesion between a liquid and a solid wall is greater than the cohesion of the liquid itself, the liquid surface rises in a concave form due to the action of the surface tension, and the liquid near the surface produces a suction head. Conversely, if the liquid-solid adhesion is less than the cohesion of the liquid, the surface drops down in a convex form and the liquid has a pressure head. This paper systematically investigates the surface shape and tension distributions of static liquids near solid walls. The scenarios investigated the walls of double vertical plates. For the plane-based problems, an analytical method is used to extract exact solutions. For a double plates, fitting formulae are presented. All of the quantities required for these results can be easily measured in different gravity environments.