Internal erosion induces alterations in the initial microstructure of soils, simultaneously affecting physical, hydraulic, and mechanical properties. The initial soil composition plays a crucial role in governing the initiation and progression of seepage-induced suffusion. This study employs the controlled variable method to develop granular soil models with varying particle size ratios, initial fine particle contents, and coarse particle shapes. Seepage suffusion simulations coupled with microstructural analyses are conducted using the CFD-DEM approach. Results demonstrate that particle size ratio, fine particle content, and coarse particle shape exert distinct influences on cumulative erosion mass, fine particle distribution, contact fabric, and mechanical redundancy at both macroscopic and microscopic scales. This numerical investigation advances the fundamental understanding of internal erosion mechanisms and informs the development of micro-mechanical constitutive models. Furthermore, for binary granular media composed of coarse and fine particles, careful control of the particle size ratio and fine content is recommended when utilizing gap-graded soils in embankment and dam construction to improve structural resilience and resistance to internal erosion.

This study proposed a novel hybrid resolved framework coupling computational fluid dynamics (CFD) with discrete element method (DEM) to investigate internal erosion in gap-graded soils. In this framework, a fictitious domain (FD) method for clump was developed to solve the fluid flow around realistic-shaped coarse particles, while a semi-resolved method based on a Gaussian-weighted function was adopted to describe the interactions between fine particles and fluid. Firstly, the accuracy of the proposed CFD-DEM was rigorously validated through simulations of flow past a fixed sphere and single ellipsoid particle settling, compared with experimental results. Subsequently, the samples of gap-graded soil considering realistic shape of coarse particles were established, using spherical harmonic (SH) analysis and clump method. Finally, the hybrid resolved CFD-DEM model was applied to simulate internal erosion in gap-graded soils. Detailed numerical analyses concentrated on macro- -micro mechanics during internal erosion, including the critical hydraulic gradient, structure deformation, as well as particle migration, pore flow, and fabric evolution. The findings from this study provide novel insights into the multi-scale mechanisms underlying the internal erosion in gap-graded soils.

With the rapid development of infrastructure in western China, numerous arch bridges have been constructed as vital transportation hubs spanning river canyons. Understanding the impact of canyon topography on the seismic response of long-span half-through arch bridges crossing canyons is essential. This study first establishes a seismic input method for oblique P-wave and SV-wave incidence, based on the viscous-spring artificial boundary theory, which transforms ground motions into equivalent nodal loads on artificial boundaries. The feasibility of this proposed method is systematically validated. Subsequently, parametric investigations are carried out to explore the effects of seismic wave incidence angle, canyon depth-to-breadth ratio and soil elastic modulus on the ground motion amplification characteristics in V-shaped canyons under oblique P-wave and SV-wave excitations. Finally, dynamic response patterns of the arch ribs and the stress-strain relationships at critical structural components are thoroughly analyzed. Key findings reveal that SV-waves induce significantly different ground motion amplification effects compared to P-waves, with the wave incidence angle and canyon width-to-depth ratio being crucial influencing factors. The connection between the arch footings and the concrete cross braces constitutes the most vulnerable region, frequently exhibiting maximum stresses that exceed the yield strength of C40 concrete under multiple scenarios. Notably, when the depth-to-breadth ratio (D/B) is 0.75, the peak stress at the arch footings reaches 5.18 x 10(7)kPa, surpassing the yield stress threshold of C40 concrete. These findings highlight the need for special seismic fortification measures at these critical connections during bridge design. This research offers valuable insights into the seismic design of long-span arch bridges in complex topographic conditions.

Carrot (Daucus carota) is an important crop grown in Canada and globally. Fresh market carrots have strict cosmetic requirements to command full value at Grade A and are frequently downgraded for irregular shape, size, or pest damage. Organic farming presents challenges for nutrient management, soil health and pest control, which may be mitigated with cover cropping. A 3-year field experiment was conducted on a commercial organic farm to 1) test the effects of six preceding-year cover crop treatments compared to a weedy fallow control on carrot yield and quality, wireworm damage, reasons for downgrading, and populations of plant parasitic nematodes, and 2) characterize within-farm spatiotemperal variability in production to identify strategies to improve and stabilize economic return. Carrot yield (42-55 Mg ha-1), quality (39-92% Grade A) and market value (183-221 $1000 Canadian dollars ha-1) varied drastically across years, and blocks within years (<= 20% differences), but cover crops had no impact on these metrics. The dominant reasons for downgrading were morphological, affecting 7-74% of carrots each year and varying with cover crop only once, where carrots following buckwheat (Fagopyrum esculentum) had fewer shape flaws. Nematodes had no relationship to cover crop or any carrot metric and wireworms damaged only 2% of carrots across all three years. This study found virtually no effect of cover crop species composition on next year's carrots on this farm, and that the farmer-collaborators can optimize their operation by improving crop establishment across space and time, reducing morphological flaws, and seeking higher value for downgraded produce.

In soft soil regions, the construction of irregular-shaped excavations can readily disturb the underlying soft clay, leading to alterations in soil properties that, in turn, cause significant deformations of the excavation support structure. These deformations can compromise both the excavation's stability and the surrounding environment. Based on a large-scale, irregular-shaped excavation project for an underground interchange in a soft soil area, numerical simulations were performed using Midas GTS to analyze the overall foundation pit deformationn. The study explored the effects of groundwater lowering, excavation, and local seepage on the disturbance of surrounding soils and the resulting foundation pit deformationn. The findings reveal that the irregular-shaped excavation exhibits distinctive spatial deformation characteristics, with the arcuate retaining structure's arching effect reducing the diaphragm wall's horizontal displacement. Groundwater lowering exerts a stronger disturbance on shallow soils near the excavation and a weaker disturbance on deeper soils. Excavation-induced stress redistribution notably affects the soils above the excavation surface and those within the embedded region of the support structure. Local seepage primarily disturbs the soils surrounding the leakage point. Additionally, the weakening of soil parameters significantly influences the foundation pit deformationn. Combined disturbance (dewatering + excavation + leakage) induced 32%, 45%, and 58% greater displacements compared to individual factors, confirming the critical role of multi-factor coupling effects.

This study investigates the simultaneous influence of particle shape and initial suction on the hydromechanical behavior of unsaturated sandy soils. Anisotropic loading-unloading tests at constant water content conditions were conducted on three sands with distinct shapes (Firoozkooh-most angular, Babolsar-Subangular, and Mesr-roundest) using a direct shear apparatus. Particle shapes were quantified in terms of sphericity, roundness, and regularity using the results of scanning electron microscopy (SEM) tests. In addition, a coupled hydromechanical model based on elasto-viscoplasticity was developed and validated against the experimental results first. The model was then employed to conduct a parametric study (compressibility, pore water pressure, and permeability) with an emphasis on the role of particle morphology and shape. The findings revealed rounder particles (higher regularity) experienced higher volumetric strain (epsilon v) under lower suction but less epsilon vwith increasing suction compared to angular sands. Moreover, the rate of permeability reduction during loading in Mesr sand was 1.5 times and 2.4 times higher than that of Babolsar and Firoozkooh sands at near-saturation condition. However, this amount decreased with increasing suction. Pore water pressure (PWP) generation was highest in the most angular sand due to its retention characteristics. The relationship between void ratio and PWP was independent of loading cycles and exhibited a linear dependence. Particle shape significantly impacted this relationship, with rounder sands showing a higher rate of void ratio change per unit change in PWP.

The shape of particles significantly influences their mechanical properties, making accurate shape modeling crucial in numerical simulations. This paper proposes a framework for generating particles by applying improved spherical harmonic reconstructions to convex hull surfaces. The framework integrates mesh refinement tech- niques to enhance mesh resolution, enabling the generation of finer surface details than 3D laser scanning. Three parameters are introduced: Delta K1, which controls roundness; Delta K2, which governs roughness; and Rd, which represents the boundary between roundness and roughness in spherical harmonic reconstructions. Introducing these parameters not only allows independent control over the three levels of shape (form, roundness, and roughness) but also enhances the flexibility of the method, enabling the generation of various particle shapes. Granular assemblies with varying roundness and roughness distributions are generated and applied in discrete element method (DEM) simulations of triaxial shear. The results show that roundness is negatively correlated with the peak friction angle, while roughness is positively correlated. The proposed method enhances the ability to generate complex particle shapes, offering a practical tool for modeling and simulating granular materials.

Previous earthquakes reveal that the sedimentary V-shaped canyon (SVC) may result in severe damage of canyon-crossing bridges (CCBs). The seismic response of CCB is affected by various parameters, including sedimentary soil characteristics and fault rupture mechanisms. However, these influential parameters of SVC on the seismic response of CCB have not been sufficiently studied in the existing literature. Thus, this study aims to identify the most influential factor on the seismic response of bridges across SVC using parametric analysis. For this purpose, the spectral element method (SEM) is adopted to simulate the wavefield of SVC considering the fault dynamic rupture. The characteristics of ground motions in the Forward region (FR) and the Middle region (MR) are investigated. The sensitivity of ground motions recorded in SVC to four main influential factors (i.e. shear wave velocity of sedimentary soil Vs, the ratio of sedimentary soil depth to canyon depth d/D, layer sequence O, and fault-to-canyon distance Rrup) is numerically evaluated. Furthermore, the parametric analysis is performed to estimate the impact of these influential parameters on the seismic response of a CCB. The results reveal that the amplitudes of pulse-type ground motions in the illuminated side of SVC increase with the decrease of Vs. As the Vs decreases from 2300 m/s to 400 m/s, the residual deformations of four bearings increase by 293 %, 93 %, 451 %, and 292 %, respectively. When the d/D is 0.3, the velocity pulse ground motions in SVC have the largest PGVs. The base shear of the piers in the case of d/D = 0.3 increases by more than 77.3 % compared to that without considering the sedimentary soil (d/D = 0). The inverted sequence may result in larger seismic responses of bearings and piers compared to normal sequence. Rrup has the most significant effect on the seismic response of CCBs. The higher-order effect and additional plastic hinges are more noticeable when Rrup is less than or equal to 7.5 km.

Particle shape and local breakage significantly affect the deformation characteristics of crushable granular materials. However, in the existing constitutive model research, there is less introduction of particle shape on particle breakage. A quantitative parameter for the three-dimensional particle shape (Average spherical modulus GM\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\overline{G_{M}}$$\end{document}) is proposed in this study. Combined with GM\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\overline{G_{M}}$$\end{document}, the triaxial compression test of granular materials with different particle shapes was carried out, and the particle size distribution before and after the test was determined. The results indicate that the local damage mechanism governs the macroscopic deformation behavior of granular materials, as influenced by the particle gradation of the samples before and after the triaxial compression test. Based on these findings, a binary medium model with a friction element weakening factor is proposed. This model incorporates the effects of particle shape and breakage behavior, significantly enhancing its calculation accuracy. Experimental results demonstrate that the model effectively predicts the deformation of crushable granular materials, accounting for particle shape.

This study investigates the impact of fabric anisotropy on the directional filtration mechanisms in granular filters, which arise from inherent particle shape variations and different preparation methods. Using the discrete element method, diverse filter samples underwent extensive numerical filtration tests in different directions. Subsequently, the pore space of these samples was analysed using an extraction algorithm. The results highlight the significant influence of particle shapes and preparation methods on intensifying anisotropy, which in turn remarkably affects directional filtration properties. Analysis of the pore space reveals variations in pore connectivity across different directions, explaining the observed differences in retention coefficients. This study emphasises the need for a comprehensive approach that accounts for constriction size, number, and connectivity to yield precise results. It contributes valuable insights into the role of anisotropy in granular materials, sheds light on complex directional filtration mechanisms, and advances related applications.