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The discrete element method (DEM) has demonstrated significant advantages in simulating soil-tool interaction and an appropriate contact model notable affected the simulation accuracy. The accuracy of numerical simulation is compromised due to the variations in soil properties when tillage implements are employed in clay-moist soil conditions. This study aims to establish a discrete element model of clay-moist soil based on the Edinburgh Elasto-Plastic Adhesion (EEPA) contact model. Calibration tests using a combination of direct shear tests and cone penetration tests were conducted to identify sensitive parameters that need to be calibrated in the model and analyze the effects of each parameter. The results indicated that contact plasticity ratio and surface energy had significant influence on representing the mechanical properties of clay-moist soil. Then, by utilizing scanning technology to acquire furrow shape data, soil bin test was conducted to validate the reliability of the calibration parameters. Using sensitive parameters as variables, the actual value of clay-moist soil with a moisture content of 33 % as the target value obtained from experimental tests. The optimal combination was: the coefficient of static friction of 0.45, the coefficient of rolling friction of 0.18, and the surface energy of 27.95 J.m-2, the contact plasticity ratio of 0.59. The relative error between the simulated draft force value and the actual measured value was 7.98 %, and the relative errors in the furrow type parameters did not exceed 5 %. The accuracy of the calibration results was verified through comparative analysis of simulation and empirical results. This study provides a scientific approach for employing DEM in modeling clay-moist soil-tool interaction.

期刊论文 2025-10-01 DOI: 10.1016/j.compag.2025.110518 ISSN: 0168-1699

Contact Lens (CLs) are often disposed of via toilet or sinks, ending up in the wastewater treatment plants(WWTPs). Millions of CLs enter WWTPs worldwide each year in macro and micro sizes. Despite WWTPs'ability to remove solids, CLs can persist and potentially contaminate watercourses and soils. This study evaluates whether different CLs degrade in WWTP aeration tanks. Six daily CLs (Nelfilcon A,Delefilcon A, Nesofilcon A, Stenfilcon A, Narafilcon A, Somofilcon A) and four monthly CLs (Lotrafilcon B,Comfilcon A, Senofilcon A, and Samfilcon A) were immersed in aeration tanks for twelve weeks. Theirphysical and chemical properties, including water content (WC), refractive index (RI), chemical prop-erties (Fourier Transform Infrared Spectroscopy), and mechanical properties were assessed. Results show that all CLs maintained their physical appearance after 12 weeks. Neither Nelfilcon A norNarafilcon A exhibited significant changes in WC and RI, (p>0.05, Tukey test), while other daily lensesshowed variations in at least one parameter. Among monthly CLs, only Senofilcon A showed significant differences in both WC (p0.05 Tukey test). However, Somofilcon A displayed significant changes in stress at break (p<0.0001,Tukey test), and Elongation at Break (p<0.05, Tukey test). No changes were found in the chemicalstructure of any CLs suggesting that twelve weeks in WWTP aeration tanks is insufficient for CLsdegradation. Thesefindings highlight CLs as a potential emerging pollutant, emphasizing their persis-tence in sludge or migration into watercourses and soils (c) 2025 The Authors. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. Thisis an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

期刊论文 2025-09-01 DOI: 10.1016/j.emcon.2025.100505 ISSN: 2405-6650

This paper presents an experimental investigation into the interaction mechanism between aqueous foam and unsaturated granite residual soil during conditioning. Contact filter paper tests and undrained shear tests were used to analyze foam's effects on soil water retention and shear behavior, while surface tension tests, capillary rise tests, and microscopic observations examined the role of soil particles in foam stability. The findings demonstrate that foam-conditioned granite residual soils exhibit three distinct saturation- dependent phases (soil-only, transition, and soil-foam mixture) governed by foam's gas-liquid biphasic nature, with foam injection effectively reducing matric suction in unsaturated conditions. Increasing foam injection ratio reduces shear stress while enhancing pore water pressure, with vertical displacement transitioning from contractive to expansive behavior at low shearing rate. Effective cohesion stress varies with gravimetric water content via a rational function, while other effective cohesion stress and friction angles with respect to foam injection ratio, shearing rate, and gravimetric water content obey exponential relationships. The probability distribution function, cumulative distribution function, and decay pattern of bubbles in foam-only systems and soil-foam mixtures all exhibit exponential relationships with elapsed time. Furthermore, a new water-meniscus interaction model was established to characterize rupture and stabilization mechanisms of foam in unsaturated granite residual soils, with particular emphasis on capillary-dominated behavior. Saturation-dependent particle contact modes were identified for foam-conditioned unsaturated granite residual soils, offering valuable guidance for enhancing soil conditioning protocols in earth pressure balance shield tunneling operations.

期刊论文 2025-06-25 DOI: 10.1016/j.enggeo.2025.108137 ISSN: 0013-7952

Gap-graded soil, characterized by the absence of certain particle sizes, is commonly used in infrastructure projects such as dams and roadbeds. A comprehensive understanding of both the macro- and micro-mechanical behaviors of discontinuously graded soils is essential for their effective use in engineering applications. In this study, drainage triaxial compression tests were conducted on four gap-graded soil samples with different fine-grain contents mainly using the DEM method, whereas the flexible boundary part was performed using the FDM-DEM method. The contacts were classified based on the magnitude of contact forces between coarse and fine particles, considering the coordination number of the particles involved and the normal angular distribution of these contacts. This classification enabled a detailed analysis of how fine particles contribute to stress transmission and structural evolution during shearing. The fabric tensor for these contact types provided further insights into the anisotropy of samples during shearing. On the microscopic scale, the evolution of contact numbers was found to closely align with the observed stress-strain behaviors. Increasing fine particle content significantly altered the role of fine particles in the stress transmission process. With low content of finer particles, initially, fine particles were situated within the voids formed by coarse particles, and the fine particles are gradually embedded into the coarse particles during the loading process. With the increase of fine particle content, fine particles constantly aggregate to block coarse particles and become the main medium of stress transmission.

期刊论文 2025-06-01 DOI: 10.1007/s10706-025-03148-5 ISSN: 0960-3182

Designers often assume a rigid foundation for buildings in seismic zones, believing it ensures safety during earthquakes. However, this assumption may neglect important factors, such as soil-structure interaction (SSI) and the potential for collisions between adjacent buildings. This study investigates the effect of dynamic SSI on the seismic pounding response of adjacent buildings. A nonlinear finite-element analysis was performed on three cases: bare buildings, buildings with linear fluid viscous dampers (LFVDs), and buildings with nonlinear fluid viscous dampers (NFVDs). The dynamic contact technique, in which contact surfaces with both the contactor and target, was employed to mimic the mutual pounding. Key seismic response parameters, including acceleration, displacement, inter-story drift, and pounding forces, were analyzed. The results showed that dynamic SSI significantly affects the seismic performance of adjacent buildings, altering the number, timing, and intensity of collisions. In some cases, SSI increased inter-story drifts beyond code-permissible limits, indicating that relying on a rigid foundation assumption could lead to unsafe structural designs. Additionally, SSI had a notable impact on the forces in NFVDs, highlighting the need for careful design considerations when using these devices. The study further investigates the effect of soil flexibility on the performance of nearby structures under different seismic excitations, focusing on the NFVDs case with a 10 % damping ratio. Incremental Dynamic Analysis (IDA) and fragility analysis were conducted to assess performance under seismic excitations, focusing on three performance levels: Immediate Occupancy (IO), Life Safety (LS), and Collapse Prevention (CP). While SSI had minimal impact on the more flexible buildings, it significantly affected the more rigid building, particularly at LS and CP levels, making it more vulnerable to damage compared to buildings on rigid foundations. These findings underscore the importance of incorporating SSI in seismic design to ensure structural safety.

期刊论文 2025-06-01 DOI: 10.1016/j.istruc.2025.108930 ISSN: 2352-0124

Under cyclic loading, sand will undergo a solid-liquid phase transition during the liquefaction. This study utilizes discrete element method (DEM) to investigate the stage characteristics of sand macroscopic stress-strain response during the solid-liquid phase transition. The microscopic mechanism of sand solid-liquid phase transition is elucidated from the perspective of contact network. The results indicate that based on the sand flowability, the liquefaction process can be divided into solid phase, solid-liquid transition phase, and liquid phase stages. The strong contact network within the sand is the primary contributor to its effective stress, and the degradation of the originally well-connected strong contact network are the reasons for the sand solid-liquid phase transition. A parameter xi c has been proposed to measure the connectivity of the strong contact network. The weak contacts between particles dominates the sliding and rolling between particles, which is the reason for the macroscopic deformation and flow of sand.

期刊论文 2025-05-01 DOI: 10.1016/j.soildyn.2025.109270 ISSN: 0267-7261

A novel theoretical model is proposed to investigate the torsional response of a pile in fractional-order viscoelastic unsaturated transversely isotropic soil with imperfect contact. This model employs Biot's framework for three-phase porous media along with the theory of fractional derivatives. Unlike previous models that assume continuous displacement at the pile-soil interface, this study uses the Kelvin model to simulate relative slippage between pile-soil contact surfaces (imperfect contact). Incorporating fractional-order viscoelastic and transversely isotropic models to describe the stress-strain relationship, comprehensive dynamic governing equations are derived. Using the separation of variables method, inverse Fourier transform, and convolution theory, analytical solutions for the frequency domain response and semi-analytical solutions for the time domain response of the pile head under semi-sine pulse excitation are obtained. Using numerical examples, the effects of model parameters in the fractional-order viscoelastic constitutive model, pile-soil relative slip and continuity model, and soil anisotropy on the torsional complex impedance, twist angle, and torque are presented.

期刊论文 2025-04-01 DOI: 10.1002/nag.3943 ISSN: 0363-9061

This research presents a new mathematical framework for the optimal design of elliptical isolated footings under vertical load and two orthogonal moments. The suggested method considers the spatial variation of contact pressure between the footing and the supporting soil, facilitating an accurate representation of structural requirements. New formulations for bending moment, unidirectional shear, and punching shear are generated using volume integration, accurately representing the complex stress distribution beneath elliptical foundations. Lagrange multipliers are utilized to identify the crucial points of maximum and minimum contact stresses for elliptical and circular footing shapes. A thorough numerical analysis illustrates the benefits of the suggested strategy by contrasting its results with those of a conventional design methodology. The findings demonstrate that the newly created model produces more cost-effective designs while maintaining structural integrity and performance, underscoring its potential as a significant asset in engineering practice. A MATLAB code for design using new formulas is programmed and results obtained to those from literature and were more efficient and economic.

期刊论文 2025-04-01 DOI: 10.12989/acd.2025.10.2.151 ISSN: 2383-8477

In the process of using transportation infrastructure, contact erosion between different particle sizes soil layers can easily occur under complex hydro-mechanical coupling, leading to deformation and damage of structures. To investigate indirect erosion between soil layers under cyclical load effects from a microscopic perspective, a volume of fluid-discrete element method (VOF-DEM) coupled method was adopted in this study. The influence of different water table levels and particle size ratios (PSR) was considered. The study found that: (1) The compressive effect of coarse particles during loading and the stress relaxation effect during unloading can both cause migration of fine particles within one loading-unloading cycle; (2) Immersion of the contact surface between coarse and fine particles is a key factor in inducing particle migration, with the interaction between particles being the most intense at the contact surface; (3) Fully saturated soil experiences the most severe particle erosion and macroscopic deformation; (4) Reducing PSR can effectively improve the integrity of soil structure and suppress erosion of fine particles; (5) Particle migration inevitably leads to axial deformation of the soil, resulting in reduced stiffness and increased energy dissipation during loading-unloading cycles. This study provides new insights into contact erosion under complex hydraulic coupling from a microscopic perspective.

期刊论文 2025-04-01 DOI: 10.1016/j.compgeo.2025.107090 ISSN: 0266-352X

Particle size significantly influences the macroscopic and microscopic responses of granular materials. The main purpose of previous works was to investigate the macroscopic response, but the influence of particle size on the evolution of microstructures is often ignored. The particle size effect becomes more complex under true triaxial stress conditions. Using the discrete-element method, a series of true triaxial numerical tests were carried out in this study to investigate the particle size effect. The mechanism of the particle size effect was elucidated from the perspective of similarity theory first. Then, the evolution of the stress and fabric for the whole, strong, and weak contact network was investigated. Meanwhile, the role played by strong and weak contacts in the particle size effect was discussed. The numerical results demonstrate that the peak stress ratio of the granular materials is enhanced as the particle size increases, which is caused by strong contacts. The peak stress ratio shows a linear relationship with particle size. The particle size effect on the strength is greater under the triaxial compression condition than under the triaxial extension condition. The proportion of sliding contacts within weak contacts gradually increases as the particle size increases. At nonaxisymmetric stress conditions, stress and fabric display noncoaxial behavior on the pi-plane, and an increase in particle size enhances the noncoaxiality, which mainly originates from the weak contacts.

期刊论文 2025-04-01 DOI: 10.1061/IJGNAI.GMENG-9127 ISSN: 1532-3641
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