Search Results (267)

Pan-connected interlayers are widely present in oil reservoirs, forming flow channels at different positions. However, conventional profile control agents struggle to plug deep interlayer channels in reservoirs, limiting the swept volume of injected water. Additionally, a clear methodology for physically simulating pan-connected reservoirs with interlayer channels and calculating interchannel flow rates remains lacking. In this study, a physical model of pan-connected interlayer reservoirs was constructed to carry out deformable gel particles (DGPs) plugging experiments on interlayer channels. A mass conservation-based flow rate calculation method for interlayer channels with iterative solution was proposed, revealing the variation law of interlayer channel flow rates during DGP injection and subsequent water flooding. Finally, oil displacement and DGP profile control experiments in pan-connected interlayer reservoirs were conducted. The study shows that during DGP injection, injected water enters the potential layer through interlayer channels in the middle and front of the water-channeling layer and bypasses back to the water-channeling layer through channels near the production well. With the increase in DGP injection volume, the flow rate of each channel increases. During subsequent water flooding, DGP breakage leads to a rapid decline in its along-path plugging capability, so water bypasses back to the water-channeling layer from the potential layer through all interlayer channels. As the DGP injection volume increases, the flow rate of each channel decreases. Large-volume DGPs can regulate interlayer channeling reservoirs in the high water cut stage. Its effectiveness mechanism involves particle migration increasing the interlayer pressure difference, which drives injected water to sweep from the water-channeling layer to the potential layer through interlayer channels, improving oil recovery by 19.74%. The flow characteristics of interlayer channels during DGP injection play a positive role in oil displacement, so the oil recovery degree in this process is greater than that in the subsequent water flooding stage under each injection volume condition. The core objective of this study is to investigate the plugging mechanism of DGPs in pan-connected interlayer channels of high-water-cut reservoirs, establish a method to quantify interlayer flow rates, and reveal how DGPs regulate flow redistribution to enhance oil recovery. Full article

This study investigates the influence of particle morphology on two-dimensional (2D) single rock particle breakage using the combined finite-discrete element method (FDEM) coupled with fractal dimension analysis. Three key shape descriptors (elongation index EI, roundness index Rd, and roughness index Rg) were systematically varied to generate realistic particle geometries using the Fourier transform and inverse Monte Carlo. Numerical uniaxial compression tests revealed distinct morphological influences: EI showed negligible impact on crushing strength or fragmentation, and Rd significantly increased crushing strength and fragmentation due to improved energy absorption and stress distribution. While Rg reduced strength through stress concentration at asperities, suppressing fragmentation and elastic energy storage. Fractal dimension analysis demonstrated an inverse linear correlation with crushing strength, confirming its predictive value for mechanical performance. The validated FDEM framework provides critical insights for optimizing granular materials in engineering applications requiring morphology-controlled fracture behavior. Full article

Buckwheat is a highly nutritious coarse grain crop, yet its industrial processing has long faced two major challenges: the low whole-kernel rate of domestic dehullers and the poor local adaptability of imported equipment. To address these problems, a novel grinding disc-type dehulling machine was developed, featuring upper and lower discs with alternating deep–shallow composite textures to reduce kernel breakage and improve whole kernel rate. A 0–10 mm adjustable gap mechanism was incorporated to suit different buckwheat varieties and particle sizes, enhancing dehulling efficiency. Buckwheat grains were classified into four size ranges: 4.0–4.5 mm, 4.5–5.0 mm, 5.0–5.3 mm, and 5.3–5.7 mm. For all sizes, the optimal rotational speed was 12 r/min, with corresponding optimal gaps of 2.53 mm, 2.80 mm, 3.20 mm, and 3.40 mm, respectively. The whole-kernel rates under these conditions were 32.9%, 37.5%, 45.6%, and 55.1%, respectively, all above 30%, showing substantial improvement. For the 4.5–5.0 mm fraction, orthogonal tests revealed that a small gap (2.859 mm) achieved a dehulling rate of 89.9% and a whole-kernel rate of 38.03%, making it suitable for mass production. A larger gap (3.288 mm) combined with secondary dehulling increased the cumulative whole kernel rate to 50.26%, which is advantageous for producing high value-added products. The novel grinding disc structure balanced frictional and compressive forces on kernels, while the adjustable gap design improved adaptability. Combined with size classification and parameter optimization, this approach provides precise processing schemes for various buckwheat varieties and offers both theoretical and practical value for industrial application. Full article

Hydraulic fracturing is a key stimulation technique for enhancing the productivity of tight sandstone reservoirs, with the conductivity of propped fractures serving as a critical parameter for evaluating stimulation effectiveness. This study investigated the conductivity behavior of propped fractures through laboratory experiments using commonly used oilfield proppants. The effects of proppant size, type, concentration, and proppant combination on fracture conductivity were systematically evaluated. Results show that at low closure stress, conductivity differences among various proppant types are negligible. However, under high closure stress, proppants with lower compressive strength exhibit significantly higher crushing rates, resulting in reduced conductivity compared to high-strength proppants. In mixtures of silica sand and ceramic proppant proppants, increasing the ceramic content lowers the overall crushing rate and mitigates conductivity degradation. Additionally, blending proppants of different sizes under high stress reduces breakage, with finer particles contributing to this effect. Higher proppant concentrations also lead to lower crushing rates and improved fracture conductivity. This work provides valuable insights into optimizing proppant selection and design for reservoir stimulation and oil and gas recovery. Full article

During the machining of unidirectional carbon fiber-reinforced polymers (UD-CFRPs), their anisotropic characteristics and the complex cutting conditions often lead to defects such as delamination, burrs, and surface/subsurface damage. This study systematically investigates the effects of different fiber orientation angles (0°, 45°, 90°, and 135°) on cutting force, chip formation, stress distribution, and damage characteristics using a coupled macro–micro finite element model. The model successfully captures key microscopic failure mechanisms, such as fiber breakage, resin cracking, and fiber–matrix interface debonding, by integrating the anisotropic mechanical properties and heterogeneous microstructure of UD-CFRPs, thereby more realistically replicating the actual machining process. The cutting speed is kept constant at 480 mm/s. Experimental validation using T700S/J-133 laminates (with a 70% fiber volume fraction) shows that, on a macro scale, the cutting force varies non-monotonically with the fiber orientation angle, following the order of 0° < 45° < 135° < 90°. The experimental values are 24.8 N/mm < 35.8 N/mm < 36.4 N/mm < 44.1 N/mm, and the simulation values are 22.9 N/mm < 33.2 N/mm < 32.7 N/mm < 42.6 N/mm. The maximum values occur at 90° (44.1 N/mm, 42.6 N/mm), while the minimum values occur at 0° (24.8 N/mm, 22.9 N/mm). The chip morphology significantly changes with fiber orientation: 0° produces strip-shaped chips, 45° forms block-shaped chips, 90° results in particle-shaped chips, and 135° produces fragmented chips. On a micro scale, the microscopic morphology of the chips and the surface damage characteristics also exhibit gradient variations consistent with the experimental results. The developed model demonstrates high accuracy in predicting damage mechanisms and material removal behavior, providing a theoretical basis for optimizing CFRP machining parameters. Full article

The selection of grinding media significantly impacts the resulting mineral’s liberation degree and grinding quality; this is particularly impactful for granite pegmatite-type quartz. Accordingly, in this study, we investigate the effects of different grinding media on the breakage characteristics of muscovite granite pegmatite-type quartz, focusing also on quartz mineral flotation. An analysis of scanning electron microscope images reveals distinct fracture characteristics among different minerals. Notably, the fractal dimension of mineral fracture roughness in ball-milled products is larger compared to that of rod-milled products, which exhibit a smaller fractal dimension. This fractal dimension serves as a quantitative measure of the microscopic morphology of mineral fractures in the grinding products, establishing a relationship between the roughness of the fractures and the type of grinding medium used. Further analysis of particle size distribution and mineral dissociation indicates that the rod mill produces a higher yield of coarse fractions compared to both ceramic and steel balls, while the fine fraction yield is significantly lower than that of the rod mill and steel balls. Importantly, the rod mill enhances the dissociation degree of quartz, suggesting that it can improve the liberation of mineral monomers and increase the yield of qualified fractions during the grinding process while effectively reducing the phenomenon of overgrinding. Our flotation experiments demonstrate that the recovery rate of quartz using the rod mill is 2.59% and 5.07% higher than that achieved with the ball mill and ceramic mill, respectively. These findings provide theoretical support for the optimization of grinding media and enhancement of mineral flotation recovery. Full article

Calcareous sands are widely distributed across the South China Sea’s continental shelf and coastlines. Understanding their mechanical behavior and microstructural evolution under cementation is critical for coastal engineering applications. While previous studies have investigated cemented calcareous sands, the comparative analyses of particle breakage and microstructural characteristics between cemented and pure sands remain limited. This study combines triaxial compression tests with X-ray CT scanning and Digital Volume Correlation analysis to systematically examine both material types. Pre- and post-loading CT scans enabled the detailed tracking of microstructural transformations. Results demonstrate that cemented specimens exhibit higher strength–stiffness properties with strain-softening behavior compared to pure sand under 200 kPa confining pressures. A quantitative analysis revealed greater particle breakage in cemented sand, while pure sand showed more pronounced increases in particle sphericity and the aspect ratio during deformation, accompanied by reduced porosity variation along specimen height (coefficient of variation decreased from 15.2% to 12.8% for pure sand. Microstructural analysis indicated moderate increases in pore sphericity and reduced anisotropy in both materials. Fractal dimension analysis demonstrated more significant structural reorganization in cemented sands. Both materials exhibited increases in key morphological parameters, including the throat equivalent radius, channel length, pore equivalent radius, and coordination number, with changes being more substantial in cemented sands. Within shear band regions, cemented sands displayed marked reductions in pore and throat quantities. These findings elucidate fundamental relationships between cementation effects and micro–macro mechanical responses, providing theoretical support for geotechnical applications involving calcareous sands. Full article

The application of construction and demolition waste (CDW) as roadbed filler faces challenges due to the variable mechanical properties caused by fragile recycled brick aggregates. This study elucidates the breakage mechanism of CDW fillers under compaction effort through a combination of standardized laboratory compaction tests and discrete element method (DEM) simulations. Furthermore, the breakage evolution patterns of mixed fills comprising recycled concrete and brick aggregates at various mixing ratios were revealed. A DEM model was developed to characterize recycled concrete and brick aggregates, adopting polygonal clumps for particles >4.75 mm and spherical clumps for finer fractions. The results indicate that particle breakage progresses through three distinct stages: linear fragment stage (0–200 kJ/m³, 50% of total breakage), deceleration growth stage (200–1000 kJ/m³, 38% of total breakage), and residual crushing stage (1000–2684.9 kJ/m³, 12% of total breakage). Recycled concrete aggregates form a skeleton restraining deep cracks, while brick aggregates enhance stability through energy dissipation and void filling. However, exceeding 30% brick content impedes skeleton development. Critically, a 30% brick content optimizes performance, achieving peak dry density with 25% lower compression deformation than concrete-only fillers, while limiting breakage index rise. These results provide a science-based strategy to optimize CDW roadbed design, improving recycling efficiency and supporting sustainable infrastructure. Full article

This study investigates the motion and fragmentation of non-spherical particles in pipeline pneumatic conveying, using gangue particles as the research object. The effects of airflow velocity and particle shape on the picking characteristics, as well as the influence of elbow angle, airflow velocity, particle size, and air pressure on particle crushing, were analyzed through a combination of Computational Fluid Dynamics and Discrete Element Method (CFD-DEM) coupled simulations and experiments. Orthogonal experiments were conducted to determine the optimal combination of parameters for minimizing particle breakage rates and pipeline pressure drops. The results show that the airflow velocity significantly affects the pick-up rate of particles, while particle shape also plays a key role, with higher sphericity resulting in lower pick-up rates. Among the factors influencing particle breakage, airflow velocity has the most pronounced effect, followed by elbow angle and particle size, whereas air pressure has a relatively minor impact. In terms of the pressure drop inside the pipeline, all factors—airflow velocity, elbow angle, particle size, and air pressure—exert considerable influence, with air pressure being the most critical factor. The optimal configuration for minimizing both particle breakage and pressure drop was determined to be an elbow angle of 150°, particle size ranging from 7 to 11 mm, airflow velocity of 20 m/s, and air pressure of 0.4 MPa. Full article

Typical greisen-type ore samples from northeastern Tasmania were investigated for their critical metal potential. The samples contain zinnwaldite (KLiFe²⁺Al(AlSi₃O₁₀)(F,OH)₂), a lithium-bearing mica that is prone to excessive breakage during conventional processing, leading to the generation of very-fine-sized particles (i.e., slimes, <20 µm), eventually ending up in tailings and resulting in lithium (Li) loss. To assess whether the natural grain size of valuable minerals could be preserved, the samples were processed using electric pulse fragmentation (EPF). The results indicate that EPF preferentially fragmented along mica-rich veins, maintaining coarse grain sizes, although a lower degree of liberation was observed in fine-grained, massive samples. In addition, the critical metal distribution within zinnwaldite was examined using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) techniques. The results reveal differences in Li content between groundmass zinnwaldite and vein-hosted zinnwaldite and that the zinnwaldite contains the critical elements rubidium (Rb), cesium (Cs), and rare earth elements (REEs: La, Ce, Pr, and Nd). Vein-hosted zinnwaldite has a higher average Li content, whereas groundmass mica contains higher concentrations of Rb, Cs, and REEs. Both mica types host inclusions of bismuth–copper–thorium–arsenic (Bi-Cu-Th-As), which are more abundant in vein-hosted mica. In some of the samples, Bi, Cu, Th, and REEs also occur along the mica cleavage planes, as well as in mineral inclusions. The Li, Rb, and Cs grades are comparable to those of European deposits, such as Cínovec and the Zinnwald Lithium Project. Full article

Due to the widespread prevalence of respiratory diseases such as COVID-19 and H1N1, the use of disposable masks has increased significantly. Consequently, the environmental issues arising from their accumulation have become increasingly severe. This study, therefore, aims to investigate the potential of using masks as soil reinforcement materials. This study conducted triaxial and seepage tests on mask–calcareous sand mixtures with varying ratios to examine the effects of mask content on the strength, modulus, particle fragmentation, and permeability coefficient of calcareous sand, as well as the influence of different mask sizes on shear strength and shear dilation. The results demonstrate that with an increase in mask content, the peak stress ratio of the mask–calcareous sand mixture increases by 4% per level, and the internal friction angle rises by approximately 1.6% per level. Conversely, water permeability and shear swelling are reduced, and particle loss decreases by over 70%. The reinforcing effect of the mask is attributed to the high friction between the mask and the calcareous sand at the contact interface, which restricts the movement of soil particles during deformation, thereby enhancing the overall strength of the mixture. Among the three mask sizes, the smallest mask–calcareous sand mixture exhibited the greatest improvement in shear strength, and the shear shrinkage effect was more pronounced. This indicates that particle size also significantly influences the mechanical properties of the mixtures. The reinforcing effect of the mask on the soil results from the high friction at the interface between the mask and the calcareous sand. When the soil deforms, the mask enhances the overall strength of the mixture by restricting the movement of soil particles. Considering the impact of masks on the performance of calcareous sand, it can be concluded that the optimal mass content of masks is 0.3%. This study offers a new perspective on the reuse of discarded masks in civil engineering applications. Full article

The scarcity of natural aggregates and the growing accumulation of waste materials have driven the demand for sustainable and circular economy solutions in transportation infrastructure, and this has led to the utilization of waste materials in transport infrastructure, such as recycled rubber. Although numerous laboratory experiments have been conducted on granular mixtures mixed with rubber, predicting the complex stress–strain behaviour of these mixtures mathematically and capturing the influence of rubber on the geotechnical properties of waste mixtures are imperative. This paper presents a comprehensive review of the constitutive models developed to predict the stress–strain behaviour, dilatancy, and shear strength of rubber-mixed waste materials, including sand–rubber, coal wash–steel furnace slag–rubber crumbs, and coal wash–rubber crumbs in various transport infrastructure applications under static loading. This paper also highlights the innovations and limitations of these existing constitutive models on rubber-mixed materials. It was found that existing constitutive models based on hyperbolic, hypoplastic, critical state, and bounding surface plasticity approaches can capture the behaviour of these materials under static loading conditions. However, further developments are required to incorporate the influence of the type and size of the rubber, particle breakage, and damping properties and also account for train-induced cyclic loading in models developed for railway substructures. This paper contributes to advancing future research aimed at deepening the fundamental understanding of rubber-mixed materials used in transportation infrastructure. Full article

Chert gravel, a byproduct of sand quarrying, remains an underutilized material in construction due to its low microwave (MW) absorption and high mechanical strength. The present study deals with the potential of MW irradiation as a novel, energy-efficient method for processing chert gravel into high-quality aggregates, reducing reliance on virgin materials. The research systematically examines MW exposure duration (1–2.5 min), rock size (150–800 g), moisture conditions, and cooling methods (air vs. water quenching) to optimize fragmentation. Experimental results indicate that larger rock sizes (600–800 g) yield coarser, less uniform aggregates, while prolonged MW exposure (>2 min) induces extensive micro-fracturing, producing finer, well-graded particles. Water quenching significantly intensifies fragmentation, generating irregular but highly fragmented aggregates, whereas pre-wetted samples exhibit finer and more uniform breakage than dry samples. The findings introduce a novel approach for optimizing chert gravel fragmentation, a material previously considered unsuitable for MW treatment. The study proposed a customizable methodology for tailoring aggregate properties through precise control of MW parameters, offering a sustainable alternative to conventional crushing. The results contribute to resource conservation, reduced energy consumption, and climate change mitigation, paving the way for more sustainable construction practices. Full article

Many underground projects are built in cohesionless soil regions, where soil strength is crucial for stability. Particle size greatly influences the mechanical behavior of cohesionless soil. To investigate the relationship between particle size (as a single internal variable) and the strength behavior of cohesionless soil, this study employed idealized spherical glass beads of varying sizes as an experimental material. A series of consolidated-drained triaxial compression tests, including both conventional and large-scale tests, were conducted on specimens with different particle sizes. The correlation between particle size and stress-strain behavior, as well as strength characteristics, was analyzed. Additionally, the influence of particle size variations on the macroscopic strength characteristics was investigated. Results indicated that for both small-sized (2 mm–6 mm) or large-sized (10 mm–30 mm) granular materials, the peak shear stress and internal friction angle increased with increased particle size. The strength of large-sized granular materials was significantly higher than that of small-sized ones. During the shear process of large-sized particles, the particle breakage rate initially increased and then decreased with increasing particle size. The internal friction angle rose monotonically with particle size, but showed insensitivity in the 4 mm–5 mm and 20 mm–25 mm particle size ranges. This insensitivity reflects a macroscopic effect resulting from the interplay between the number of inter-particle contacts and the micro-area of their surface, which reaches an extremum. These findings provide valuable insights into the micromechanical interactions governing the strength of behavior of cohesionless soils and highlight the importance considering particle size effects in geotechnical analysis. The derived particle-interaction framework provides theoretical underpinnings for optimizing design methodologies in underground infrastructure projects involving granular media. Full article

To investigate the mechanical response characteristics of damming rockfill materials under different confining pressure conditions, this study integrates laboratory triaxial compression tests and PFC^2D numerical simulations to systematically analyze their deformation evolution and failure mechanisms from both macroscopic and microscopic perspectives. Laboratory triaxial test results demonstrate that as the confining pressure increases, the peak deviatoric stress rises significantly, with the shear strength of specimens increasing from 769.43 kPa to 2140.98 kPa. Under low confining pressure, rockfill exhibits pronounced dilative behavior, whereas at high confining pressure, it transitions to contractive behavior. Additionally, particle breakage intensifies with increasing confinement, with the breakage rate rising from 4.25% to 8.33%. This particle fragmentation alters the granular skeleton structure, thereby affecting the overall mechanical properties and leading to a reduction in shear strength. Numerical simulations further reveal the micromechanical mechanisms governing rockfill behavior. The simulation results show a shear strength increase from 572.39 kPa to 2059.26 kPa, exhibiting a trend consistent with experimental findings. The shear failure mode manifests as a characteristic “X-shaped” shear band distribution, while at high confining pressures, shear fracture propagation is effectively inhibited, enhancing the overall structural stability. Furthermore, increasing confining pressure promotes denser interparticle contacts, with contact numbers increasing from 16,140 to 18,932 and the maximum contact force rising from 12.19 kN to 59.83 kN. The quantity and frequency of both strong and weak force chains also increase significantly, further influencing the mechanical response of the material. These findings provide deeper insights into the mechanical behavior of rockfill materials under varying confining pressures and offer theoretical guidance and engineering references for dam stability assessment and construction optimization. Full article