The variability in particle morphology significantly impacts the mechanical properties of rockfill materials. To enhance the understanding of this influence, this study collected basalt rockfill particles from 6 different site sources, with their morphology captured by 3D scanning technology, and then the morphological characteristics categorized through cluster analysis. True triaxial tests for these 6 particle groups were simulated using discrete element method (DEM), and the effects of elongation, flatness, convexity, and intermediate principal stress coefficient on the stress-strain relationship and peak strength were qualitatively assessed through principal component analysis (PCA). Further, by controlling the elongation, flatness, and convexity, 3D reconstructed particle models were created by spherical harmonics (SH) analysis, and the true triaxial tests on these models were simulated to quantitatively clarify the influence of morphological parameters on the macroscopic stress- strain relationship, peak strength, microscopic contact, anisotropic evolution, and other characteristics. Considering the size effect in rockfill materials, multi-scale models incorporating particle morphology were further evaluated across four sample scales. The results indicate that, on the macro scale, the three morphological parameters and the middle principal stress coefficient each have substantial effects on peak strength independently, while the interaction among these parameters does not have a notable influence on the strength. With increasing convexity, the peak strength of samples gradually decreases, while an increase in elongation and flatness leads to a trend of initially increasing and then decreasing strength. On the micro scale, the increase in both elongation and flatness results in a more uniform fabric in the main and lateral directions, while the coordination number shows a trend of initially increasing and then decreasing before stabilizing gradually. The influence of elongation on the main direction fabric is slightly smaller than that of flatness, while convexity has minimal effect on these microscopic features. Additionally, the morphological parameters not only impact the deformation capacity of samples but also demonstrate heightened sensitivity to the strength-size relationship of the sample due to interlocking and boundary constraints between particles. This underscores the pivotal role of morphological parameters in governing the mechanical motion of particles during the sample size scaling process, consequently influencing the strength of the material.

Municipal solid waste incineration bottom ash (MSWIBA) emerges as a potential alternative to natural aggregates due to its similar mineral composition and engineering properties as embanking fillings. However, the instability and environmental pollution risks of MSWIBA limit its large-scale application. This study proposes to employ Enzyme Induced Carbonate Precipitation (EICP) technology to enhance the mechanical properties of MSWIBA and reduce its environmental impact. Initial analyses focused on the basic physicochemical properties and morphological changes of MSWIBA before and after modification. Then the modified MSWIBA exhibited improvements in shear resistance, resilient modulus, and permanent deformation behavior. It was also found that existing resilient modulus and permanent deformation predicting models for soils are applicable to EICPmodified MSWIBA. The column leaching tests were conducted on samples subjected and not subjected to freeze-thaw and dry-wet cycles. The results revealed the modified MSWIBA released reduced heavy metal concentrations in both water and acid leaches. These findings establish a solid theoretical foundation for employing EICP-modified MSWIBA as an embankment fill material, highlighting the potential for wider adoption of this eco-friendly alternative in road constructions.

Particle morphology has well-known effects on the mechanical properties of granular materials as it influences particle contact and packing density. Although thermal conduction of sands also depended on such two behaviors, the effects of particle morphology on thermal conductivity are not fully understood. Several series of laboratory experiments were conducted to determine particle roundness, sphericity, and thermal conductivity of five river sands prepared with the same gradation and mineral composition but different porosities. A new predictive model was proposed within the framework of the classical Cote and Konrad's model that could capture the experimental data well. The results showed that the statistical distributions of roundness and sphericity follow the normal distribution pattern, and the expected value can be used as an evaluating index to depict the particle morphology of sand samples. Thermal conductivity of dry natural sands decreased with increasing porosity that exhibited a linear decreasing trend in a semi-logarithmic scale. The decreasing rate was found to depend on the overall morphology factor, defined as the average expected value of particle roundness and sphericity. For a given porosity, thermal conductivity increased with increasing overall morphology factor. Interestingly, thermal conductivity was less affected by the particle morphology with increasing porosity. The new model incorporating the particle morphology and mineral composition with satisfactory accuracy was far superior to the Cote and Konrad's model. Additional research is recommended to assess the effects of threedimensional particle morphology, applied stress, and particle stiffness on thermal conduction of natural sands.

This paper investigates the effects of particle morphology (PM) and particle size distribution (PSD) on the micro-macro mechanical behaviours of granular soils through a novel X-ray micro-computed tomography (mu CT)-based discrete element method (DEM) technique. This technique contains the grain-scale property extraction by the X-ray mu CT, DEM parameter calibration by the one-to-one mapping technique, and the massive derivative DEM simulations. In total, 25 DEM samples were generated with a consideration of six PSDs and four PMs. The effects of PSD and PM on the micro-macro mechanical behaviours were carefully investigated, and the coupled effects were highlighted. It is found that (a) PM plays a significant role in the micro-macro mechanical responses of granular soils under triaxial shear; (b) the PSD uniformity can enhance the particle morphology effect in dictating the peak deviatoric stress, maximum volumetric strain, contact-based coordination number, fabric evolution, and shear band formation, while showing limited influences in the maximum dilation angle and particle-based coordination number; (c) with the same PSD uniformity and PM degree, the mean particle volume shows minimal effects on the macro-micro mechanical behaviours of granular soils as well as the particle morphology effects.

Particle morphology is an important factor affecting the mechanical properties of granular materials. However, it is difficult to quantify the morphology characteristics of the complex concave particle. Fortunately, complex particle can be segmented by convex decomposition, so a new shape index named convex decomposition coefficient (CDC) related to the number of segmentations is proposed. First, the pocket concavity was introduced to simplify the morphology hierarchically. Second, the cut weight linked to concavity was defined and convex decomposition was linearly optimised by maximizing the total cut weights. Third, the CDC was defined as the minimum block number where the block area ratio cumulatively exceeded 0.9 in descending order. Finally, the proposed index was used to quantify the particle morphology of coral sand. The results demonstrate that the CDC of coral sands mainly ranges from 2 to 6, with a positively skewed distribution. Furthermore, CDC correlates well with three shape indices: sphericity, particle size, and convexity. Larger CDC is associated with smaller sphericity, larger particle size, and smaller convexity. The index has certain scientific research value and practical significance.

The diverse and complex morphology of loess particles creates various contact patterns, impacting the mechanical properties of loess, and directly influencing the stability and safety of engineering structures in loess regions. In order to explore the effects of realistic loess particle morphology on mechanical behaviors, the discrete element method (DEM) and image processing techniques were employed to investigate both macro and micro mechanical properties, such as cohesion, internal friction angle, mechanical coordination number, and distribution of contact force. The results demonstrate that particle morphology greatly impacts the mechanical properties of loess samples. Samples with realistic particles exhibit higher peak stress, shear modulus, cohesion, internal friction angle and mechanical coordination number compared to those with spherical particles. Particle morphology has a significant effect on particle rotations and fabric anisotropy, while exerting only a minor influence on particle displacement. A comprehensive understanding of the relationship between the particle morphology and mechanical properties of loess samples contributes to enhancing the stability of engineering structures in loess areas.

Particle morphology plays a crucial role in determining the mechanical behavior of granular materials. This paper focused on investigating the effects of boundary conditions on the triaxial mechanical properties of soil samples, with particular consideration given to the influence of particle shape. To achieve this, a numerical model was proposed, which couples the finite difference method (FDM) and the discrete element method (DEM) to simulate the behavior of a rubber membrane and soil particles, respectively. The particle morphology was accurately reconstructed using spherical harmonics (SH) analysis, and the shell cells in the FDM were utilized to construct the boundary modeling. Through a series of simulations, the macroscopic and microscopic mechanical responses of soil particles, both within and outside the shear band, were investigated. The obtained simulation results were then compared with those derived from the DEM simulation using a particle-based membrane. The research findings pertaining to the influence of boundary conditions and particle shape provide significant contributions to our understanding of granular material behavior. These findings offer valuable insights that can be applied in the design and analysis of geotechnical structures.

Black carbon (BC) aerosol is one of the most important factor in global warming. BC radiative forcing remains unconstrained, mainly because of the uncertain parameterizations of its absorption and scattering properties in the atmosphere. The single sphere model is widely used in current climate assessment of BC aerosols due to its computational convenience, however, their complex morphologies in particle level are excessively simplified which leads to computed inaccuracy. In this study, we present a dynamic model for optical calculations of BC aerosol ensembles considering their complex fractal aggregate morphologies with the constraint of max monomer numbers (N s, max) and radius (a max). We show that the simulation accuracy of the dynamic model with suitable values of N s, max and a max may achieve similar to 95% while the computation time may reduce to similar to 6%. We find that optical properties of BC aerosol ensembles can be simulated for higher accuracy or faster calculation by performing different selections of monomer numbers and radius in their size distributions. This method enables extensive and accurate optical calculations of BC particles with complex morphologies, which would be useful for the remote sensing inversion and the assessment of climate.

This contribution investigates the characteristics of elastic wave velocities (Vp and Vs) during triaxial shearing tests under dry and drained conditions. Samples of tested materials with different particle morphologies (i.e., particle shape and surface roughness) were prepared under three strategies, namely, similar initial void ratios (e0), relative densities (Dr0), and side tapping numbers (Nt). Regarding the elastic wave velocities as functions of e0 and confinement r at very small strain ranges, i.e., V = a(B - e0)(r 1kPa)b, a was seen to increase for more angular materials or smoother surfaces, while b and B were seen to decrease as the particles became more angular or the surfaces became smoother. During triaxial shearing, Vp increased initially and then tended to decrease more gently, whereas Vs increased initially and then showed a marked decrease before convergence upon shearing regardless of the e0 for the given material. The influence of particle morphology on the absolute values for Vp and Vs was found to be complex during shearing, whereas the wave ratio (Vp/Vs) was consistently greater under rougher conditions for the same shape. Importantly, the wave ratio (Vp/Vs) was found to correlate well with the particle morphology: more angular materials and rougher surfaces exhibited a greater Vp/Vs ratio normalized by the stress and density conditions for each material, which further indicates a higher degree of fabric anisotropy with reference to the microscopic evidence in the literature. (c) 2024 Production and hosting by Elsevier B.V. on behalf of The Japanese Geotechnical Society. This is an open access article under the CC BYNC -ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).