Small-strain shear stiffness (G0) is an essential parameter to predict deformation characteristics and dynamic properties of granular materials. It is empirically known that G0 increases with decreasing a void ratio (e0) and increasing isotropic stress level (p0 '). Recently, the effect of particle shape on G0 has been studied; however, the mechanism underlying the evolution of G0 is not fully understood. Using the discrete element method (DEM), this contribution quantifies the G0 of granular materials by performing small-strain probing where multi-sphere clumped particles are used to vary particle shape and surface topology systematically. The Hertzian contact theory is applied for each sphere-element contact to capture the stress-dependent contact stiffness. The results reveal that G0 is well correlated with e0 or mean coordination number for a given particle shape; however, G0 is measurably reduced when finer sphere-elements dominate inter-particle contact responses. The present study proposes two contact-scale expressions of G0 for non-spherical particles based on contact area (CA) and micromechanical effective medium theory (EMT) by extending the EMT expression for spherical particles; both can capture the effects of particle shape and p0 ' on G0 under given conditions where particle breakage does not occur.

Particle size distribution (PSD) of coral sand is a critical factor that influences the mechanical properties at the coral sand-geogrid (CS-GG) interface, which is affected by both particle breakage and various temperatures. However, relevant researches are scarce currently. This study conducts a series of large-scale interface shear tests on coral sand with three PSD ranges (0.25 similar to 1mm, 1 similar to 2mm, and 2 similar to 4mm) at varying temperatures (5 degrees C similar to 80 degrees C). Experimental results demonstrate that the IB value at the CS-GG interface ascends and then descends with the increase of PSD from 20 degrees C to 40 degrees C. The IB value at the interface descends and then ascends with the increase of PSD from 60 degrees C to 80 degrees C; The PSD curves at the interface indicate that the particle breakage degree of coral sand increases with rising temperature (5 degrees C similar to 40 degrees C); The larger PSD of coral sand, the smaller fractal dimensions (D) of the interface; A mathematical formulation of the relationship between the relative breakage rate (Br) and the D value at interfaces is presented, which considers temperature effects; The relationship between the total input energy (E) and the Br value has been expressed by empirical formulations with different PSD ranges, where the fitting curve for 2 similar to 4 mm coral sand exhibits a hyperbolic pattern.

This paper proposes a new, computationally efficient, approach to modelling the anisotropy of surface charge on kaolinite particles in particle-scale simulations. We represent each kaolinite particle as a flat ellipsoid and calculate the total interaction energy/force between two ellipsoids as a weighted sum of face-to-face, edge-toedge, face-to-edge, and edge-to-face interactions. The weightings of these interactions are smooth functions of the relative orientations of the particles. This model was employed in coarse-grained molecular dynamics simulations of virtual samples under isotropic compression to investigate the influence of the pore water pH on microfabric formation and the mechanical behaviour of kaolinite. The simulations effectively captured the influence of pore water pH on microfabric formation and compressive behaviour, as previously reported in experimental research. The virtual sample with a pore water pH of 4 (acidic pore water) formed an aggregated and flocculated microfabric and exhibited higher compressibility during isotropic compression. In contrast, the virtual sample with a pore water pH of 8 (alkaline pore water) formed a dispersed and deflocculated microfabric and showed lower compressibility. The efficacy of the model is demonstrated here through coarse-grained molecular dynamics simulations, but it could also be implemented in a discrete element method code.