Search Results (101)

This paper proposes an intelligent analysis method of rock sheet based on the segment anything model (SAM) with zero samples, which combines small sample training with deep learning to realize high-precision automatic identification and segmentation of rock minerals, and then converts the segmentation results into vectorized data by using image processing technology to construct the numerical model of rock minerals, and ultimately realizes rock sheet from image identification to physical and mechanical research. The results show that the SAM-based zero-sample segmentation method can accurately and efficiently identify different mineral components in multi-component complex rock flakes. Numerical simulation results show that the numerical model of rock minerals generated by the method can effectively reflect the microstructural characteristics of rocks and accurately predict their mechanical behaviors, and the resulting elastic modulus matches well with the existing literature data, with a relative error of only 3.4%, suggesting that the proposed method provides reasonable predictive capability for rock mechanical behavior. Compared with the traditional measurement methods, this method realizes the automation and intelligence of rock thin-section analysis and enhances the adaptability to different rock samples, providing an efficient tool means for geological exploration, petroleum engineering, and geotechnical research. Full article

This study addresses the complexity and high cost associated with traditional temporary formwork in post-cast strips. An innovative use of fish-scale mesh as a permanent interface material is proposed. This material serves as both construction framework and a connector during the service phase. The study investigates the enhancement mechanism of fish-scale mesh on the interfacial bond between new and old concrete. A multi-parameter experimental framework combined with full-field strain measurement was employed. Three specimen types with varying hole heights and numbers were designed and fabricated. Macro-mechanical properties were evaluated through double-shear and splitting-tensile tests. The interfacial strain field was quantified with high precision and visual clarity using Digital Image-Correlation (DIC) technology. Results show that introducing fish-scale mesh alters the interface failure mode. In mesh-free specimens, failure occurs through brittle interfacial delamination. With fish-scale mesh, failure transitions to ductile rupture within the concrete body. The number of holes has the greatest effect on shear strength, followed by hole height. Among all configurations, the fish-scale mesh with a hole height of 6 mm and 30 holes demonstrated the best performance. The shear strength and splitting strength increase by about 32% and 13%, respectively, compared to mesh-free specimens. Based on experimental results and theoretical derivation, a shear-bearing capacity formula for the fish-scale mesh interface is proposed. This model innovatively incorporates the shear key area of the fish-scale mesh, along with weakening and disturbance coefficients derived from experimental data. The theoretical model was validated against experimental results, showing a good agreement and supporting the use of fish-scale mesh as a permanent interface material. Full article

In order to conduct a comprehensive investigation into the effects of ground granulated blast furnace slag (GGBFS) on the dynamic mechanical properties and mesoscopic damage mechanisms of recycled aggregate concrete (RAC), a combined approach integrating material testing, microscopic characterization techniques, and theoretical analysis was adopted in this study. Two GGBFS replacement rates (0% and 35%) were considered. Uniaxial compression tests were performed to obtain data at different curing ages (T = 7 d, 28 d, 56 d, and 150 d) and strain rates ($\dot{\epsilon }$ = 10⁻⁵/s, 10⁻⁴/s, 10⁻³/s, and 10⁻²/s). The obtained data were complemented by nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM) analyses to characterize the evolution of the microstructure and pore characteristics of the specimens. The findings demonstrated that prolonging the curing period continuously densified the microstructure of the specimens, resulting in a commensurate improvement in their initial macro-mechanical behavior. At curing ages exceeding 28 d, the secondary hydration reaction of GGBFS was found to generate additional C-S-H gel, which filled the internal microvoids within the specimens, reduced porosity, and further improved the initial macroscopic mechanical properties. Concurrently, the microstructural characteristics observed at different curing ages, in conjunction with the crack propagation and the fracture toughness effects associated with strain rate, further influenced the initiation, propagation patterns and paths of microcracks during uniaxial compression, as well as the adjustment of the effective stress framework. Furthermore, characteristic parameters describing the evolution of mesoscopic fracturing and yielding damage exhibited regular variations with curing age and strain rate. For specimens cured for 56 d, compared to those with a GGBFS replacement rate of 0%, specimens containing 35% GGBFS exhibited a 4.13% increase in peak stress and a 0.29% decrease in peak strain at $\dot{\epsilon }$ = 10⁻⁵/s. At a replacement rate of 35%, as the strain rate increased from $\dot{\epsilon }$ = 10⁻⁵/s to $\dot{\epsilon }$ = 10⁻²/s, the peak stress rose from −50.37 MPa to −60.74 MPa, whereas the peak strain dropped from −23.87 × 10⁻⁴ to −22.15 × 10⁻⁴. This study provides significant scientific evidence and a theoretical framework for the engineering application of GGBFS-modified RAC under varying strain rate conditions. Full article

Engineered cementitious composites (ECCs) reinforced with imported polyvinyl alcohol (PVA) or polyethylene (PE) fibers exhibit high tensile deformability, but the fiber cost limits the wider application of ECCs. In this study, locally produced PVA and PE fibers were used to develop lower-cost ECC, and PVA–PE fiber hybridization was adopted to improve tensile deformability. Based on matrices with various fly ash volumes, the single-fiber pullout behavior was first investigated at the micromechanical level. The results showed that PVA and PE fibers failed mainly by rupture and pullout, respectively, and that the chemical bonding between PVA fibers and the surrounding matrix decreased with increasing fly ash volume. The effects of single-fiber addition and hybrid-fiber addition on the macromechanical properties of ECC were then examined. The results indicated that ECC reinforced with hybrid PVA–PE fibers exhibited enhanced tensile performance compared with ECC reinforced with either PVA or PE fibers alone, with an ultimate tensile strain exceeding 5.3%, an average crack width below 39 μm, and hybrid reinforcing effect coefficients of 1.17–1.30, indicating a positive hybrid effect. Overall, the lower-cost ECC incorporating hybrid local fibers developed in this study demonstrates promising tensile deformability and crack-control capacity. Full article

In this study, the influence of thermal loading in a supersonic flight environment on the mechanical stiffness of elastic structures and the corresponding aeroelastic stability limits is investigated analytically. Recognizing that elevated temperatures inherently alter constituent elastic properties, a temperature-dependent continuous elasticity framework is incorporated directly into the governing differential operators of the structural domain. The macro-mechanical behavior of representative panel- and wing-type elements is modeled utilizing the Euler–Bernoulli beam formulation, while high-speed supersonic aerodynamic effects are represented through linearized first-order piston theory. The continuous spatial displacement fields are discretized by means of a modal expansion, and the coupled aeroelastic system is subsequently transformed into a finite set of dynamic state-space equations using the Ritz–Galerkin truncation method. The numerical and analytical outputs demonstrate that aerothermal softening not only induces continuous erosion in the material stiffness but also directly modulates the aeroelastic pole trajectories, thereby prematurely contracting the safe supersonic flight envelope. The primary novelty of the proposed framework lies in the derivation of explicit analytical expressions that directly map temperature-dependent stiffness variations onto supersonic aeroelastic instability boundaries. Because this approach is formulated in a generalized analytical form, it can be applied across diverse material systems, geometric profiles, and thermal conditions with reduced computational overhead compared to full fluid–structure interaction solvers, thereby providing a theoretical basis for preliminary stability assessment of supersonic aerospace configurations operating under high-temperature conditions. Full article

This study examines the complex interplay between dynamic response and mineralogical microstructures across various geological formations, particularly differentiating between mineralized and metamorphic rocks. Utilizing a comprehensive vibration-based approach, in conjunction with petrographic analysis and ultrasonic wave propagation, the study clarifies the significant impact of microstructural features, such as disseminated sulfides and foliated planes, on the complex’s global dynamic behavior. This study investigates six representative rock samples from mineralized and metamorphic geological zones using integrated petrographic analysis, ultrasonic wave velocity testing, density and physical property measurements, and free-vibration dynamic analysis. The results show that the composition and mechanical properties differ significantly. Mineralized rocks contain a high proportion of sulfide minerals, reaching approximately 75% in some samples, and exhibit significantly higher densities, with the APZ sample reaching 3950 kg/m³. In contrast, metamorphic rocks have an average density of 2700 kg/m³. This difference in composition leads to different dynamic responses. Mineralized zones have dynamic elastic moduli that are much higher than those of metamorphic rocks, with Young’s Modulus reaching up to 134.17 GPa and shear moduli ranging from 49.78 GPa to 56.14 GPa, which is about 50% higher than metamorphic rocks (28.9 GPa to 30.5 GPa). However, macro-mechanical deflection tests show that highly foliated metamorphic rocks (like PFT) exhibit the largest deflection of 0.52 mm, while demineralized rocks (like CP) exhibit the smallest deflection of 0.26 mm. Dynamic vibration analysis shows that microstructural “flaws” significantly affect energy dissipation. For example, the Transitional Phase Zone (TPZ) in mineralized rocks has the highest damping ratio (1.67%) and the lowest natural frequency (270 Hz) in its suite. This is different from the more rigid Advanced Pyritization Zone (APZ), which has a damping ratio of 1.1% and a frequency of 395 Hz. These new correlations provide a more accurate basis for the non-destructive assessment of structural stability in mineralized settings, highlighting that local micro-stiffness does not necessarily indicate macroscopic dynamic rigidity. Full article

This study investigates the influence of nano-alumina (nano-Al₂O₃) on the compressive properties and damage mechanisms of epoxy matrix composites across a wide strain rate range. Composites with varying nano-Al₂O₃ contents (0, 1, 3, 5, 10, 15 wt%) were tested under quasi-static (0.001~0.1 s⁻¹) and dynamic (2500~4800 s⁻¹) conditions using a universal testing machine and a Split Hopkinson Pressure Bar, respectively. The phase, the microstructure, and their effects on macro-mechanical performance and micro-damage were characterized by XRD, SEM, and TEM. Results indicate that the incorporated nano-Al₂O₃ is highly crystalline, single-phase lamellar α-Al₂O₃. Its addition significantly modulates the compressive properties, with effects dependent on both content and strain rate. Under quasi-static compression, yield strength increased monotonically with nano-Al₂O₃ content at 0.1 and 0.01 s⁻¹, reaching a maximum increase of ~9.5% at 15 wt%. However, at 0.001 s⁻¹, optimal strength occurred at 10 wt%, beyond which agglomeration caused degradation. Dynamic tests revealed a positive strain rate effect. The 10 wt% composite exhibited optimal overall performance, combining high peak stress and a stable stress plateau, whereas the 15 wt% sample showed higher peak stress but poor post-peak load-bearing capacity. Microstructural analysis showed that 10 wt% nano-Al₂O₃ dispersed uniformly, enhancing toughness by inhibiting crack propagation via interfacial bonding and microstructural refinement. In contrast, at 15 wt%, particle agglomeration induced interfacial defects, promoting debonding and brittle fracture. This work provides insights into the wide-strain-rate mechanical behavior of nanoparticle-reinforced polymers and supports the design of high-performance, impact-resistant epoxy composites. Full article

The development of green building materials and high-performance concrete has promoted the use of manufactured sand (MS) in self-compacting concrete (SCC). To investigate the effect of MS lithology on concrete performance, this study prepared C40-SCC using basalt, limestone, and granite manufactured sand, as well as river sand. Workability and mechanical properties were measured via macro-scale tests. A meso-scale random aggregate model, including mortar, aggregate, and interfacial transition zone (ITZ), was established to simulate uniaxial compression. The macro-test results indicate that workability decreases in the order of river sand, granite, limestone, and basalt, while mechanical strength decreases in the order of granite, limestone, basalt, and river sand. The meso-scale simulation reveals that damage initiates at the ITZ and extends into mortar. The simulated stress–strain curves match the experimental data in the ascending branch, with peak stress errors between 1.1% and 6.9%. The failure modes also align with experimental observations. The consistency between the simulation and experimental results verifies the reliability of the meso-scale model. By combining macro-experiments and meso-simulation, this study compares concrete performance and explains the differences from the perspective of damage evolution. The results indicate that MS lithology affects interfacial properties and damage development, thereby determining macro-mechanical behavior. This research provides a theoretical basis for the appropriate selection of MS in SCC. Full article

Asphalt rheological properties are fundamental to pavement performance, yet their accurate assessment requires multi-scale characterization due to asphalt’s inherent complexity. This article reviews the connections between asphalt rheology across chemical, microstructural, and macro-mechanical scales, employing a methodological analysis of supramolecular and colloidal models for micro-scale behavior and dynamic shear rheometry for macro-scale properties. Current research confirms asphalt as a complex multiphase continuum, where micro-scale rheology is explained by intermolecular interactions and colloidal structures, while macro-scale analysis successfully characterizes linear viscoelasticity through established empirical and mechanical models. However, the study identifies critical gaps: nonlinear viscoelastic characterization under large-amplitude oscillatory shear (LAOS) remains underdeveloped, and fundamental issues like directly probing molecular interactions and the origin of microstructures like the “bee structure” are unresolved. The primary conclusion is that a comprehensive understanding of asphalt rheology hinges on future research that integrates experimental and simulation data across these scales to bridge the gaps between chemical composition, microstructure, and macroscopic performance. Full article

To determine the optimal mix proportion of steel fiber-reinforced concrete in cold regions, this study adopted a multi-factor orthogonal experimental design method. A series of mix proportion schemes was formulated based on different water-to-binder ratios, steel fiber volume fractions, and combinations of mineral admixtures such as silica fume. Mechanical performance tests and freeze–thaw cycle tests were conducted to obtain the strength, deformation characteristics, and durability degradation patterns of specimens with different mix proportions before and after freeze–thaw exposure. Meanwhile, scanning electron microscopy (SEM) was employed to observe the microscopic surface morphology of specimens, both pre- and post-freeze–thaw cycles, and to analyze the damage evolution in pore structures and the fiber–matrix interfacial transition zone, thereby elucidating the microscopic mechanism of freeze–thaw damage. Ultimately, by comprehensively comparing the macro-mechanical properties, freeze–thaw durability, and microstructural characteristics, the experimental results of different groups were evaluated to identify the optimal mix proportion for steel fiber-reinforced concrete, which exhibits excellent mechanical performance and durability under freeze–thaw conditions. The results indicated that freeze–thaw cycles significantly reduced the mechanical properties of the concrete. The optimal mix proportion was achieved with a water-to-binder ratio of 0.4, a silica fume content of 10%, and a steel fiber volume fraction of 1.5%. This optimal mix proportion can provide a direct reference for the material design and application of steel fiber-reinforced concrete in engineering projects located in cold regions. Full article

Rockfall typically involves repeated impacts that induce progressive damage and fragmentation in rock masses. To investigate the mechanism governing this process under different impact velocities, a series of controlled impact tests were conducted using a newly developed compressed gas-driven rock impact apparatus. This study systematically examined the effect of impact velocities and number on rock damage, distinguishing between internal damage (<10.0 m/s) and local failure (10.0 m/s–20.0 m/s). At the internal damage level, uniaxial compression tests with acoustic emission monitoring were employed to analyze the macro-mechanical properties and micro-failure processes of granite. At the local failure level, the repeated impact number required to transition from localized to complete failure was recorded, and polarizing microscopy was used to characterize microstructural evolution. The results show that damage and failure mechanisms are strongly influenced by both impact velocity and repeated impact number. Specifically, higher impact velocities and repeated impacts promote a shift toward brittle failure, with threshold behaviors observed at 5.0 m/s (fourth impact) and 7.5 m/s (third impact). A quantitative analysis further correlates impact conditions with mechanical degradation and energy evolution, providing insight into the underlying processes controlling rockfall fragmentation. Full article

Understanding the mechanical responses of layered rock masses at both macro and micro scales, particularly under diverse confining pressures and bedding directions, is crucial for evaluating their stability and optimizing resource extraction. This study employs PFC2D numerical models, calibrated with laboratory data from Xinjiang Barkol oil shale, to investigate how confining pressure and bedding direction control the mechanical properties of layered rock masses during biaxial compression. The results demonstrate distinct failure modes, shifting from splitting in Per bedding (beddings perpendicular to the loading direction) to shear-tension and shear-slip failures in inclined bedding. A U-shaped distribution of compressive strength across bedding directions is observed, with strength increasing under higher confining pressure. A novel microfracture connection algorithm is proposed to quantify microfracture parameters, such as quantity, length, and angle, shedding light on the complex microfracture evolution mechanisms. Fewer persistent microfractures in Par (i.e., beddings are parallel to the loading direction) and Per beddings explain their higher compressive strength compared to inclined bedding. Additionally, microfracture length evolution demonstrates a shift from brittle to ductile macro-failure as bedding direction changes. Microfractures primarily develop parallel to the loading direction, while confining pressure slightly affects microfracture characteristics. These findings establish a new framework for predicting the behavior of layered rock masses under complex loading, providing theoretical insights and practical guidance for engineering applications. Full article

This study aims to resolve the “secondary activation” challenge when erecting structures over goaf zones by employing a novel grouting and filling material. It delves into the performance degradation of the innovative ECS soil grouting filling material (ESGF material) within the goaf’s ionic erosion context. Erosion tests were performed on ESGF material specimens with varying mix designs to mimic the sulfate and chloride erosion scenarios commonly encountered in practical engineering. The macro-mechanical properties and microstructural changes of ESGF materials under ionic erosion environment were systematically investigated by various testing methods, such as unconfined compressive strength (UCS), SEM, XRD, TG, FTIR, and Raman. The findings indicate that both sulfate and chloride erosion lead to a reduction in the strength of the ESGF material. As erosion progresses, the specimens experience a mass increase followed by a decrease, with their strength exhibiting a consistent downward trend. In sulfate erosion conditions, the buildup of expansion product like ettringite (AFt) and thaumasite (TSA) inflicts substantial internal structural damage. Conversely, Friedel’s salt, the primary product of chloride erosion, exhibits relatively weaker expansiveness, and chloride concentration exerts a less pronounced effect on material degradation. Moreover, the cementitious material content and the proportion of quick-setting component play a significant role in determining the ESGF material’s resistance to erosion. By adjusting the quick-setting components ratio in response to changes in the water content of soft soil, the anti-ion erosion performance of solidified soil can be effectively enhanced. Notably, curing with a 5% sulfate maintenance could significantly improve the erosion resistance of ESGF material. This suggests that ESGF materials can be used without concern for curing issues in high-salinity environments during grouting. The research addresses the root cause of goaf subsidence while facilitating the recycling of solid waste, offering an environmentally friendly solution. Full article

This study describes the effect of electron radiation on the macro- and micro-mechanical and tribological properties of composite polypropylene filled with 25% glass fiber. Micro-mechanical and tribological properties were investigated both on the sample surface and at various depths below the surface. Polypropylene was irradiated with radiation doses of 15, 33, 45, 66 and 99 kGy. As the results show, electron radiation has an influence on the change in PP’s structure, in which due to the electron radiation, a crosslinked phase and an increase in crystallinity are formed. These changes in morphology are reflected in an enhancement of micro-mechanical and tribological properties both at the surface and in deeper layers below the surface. More crosslinking and recrystallization occur across the sample’s cross-section up to a depth of 2 mm, where greater micro-mechanical and tribological properties are also measured. The difference between the surface and the center of the material can be up to 32%. The optimum radiation dose appears to be 45 kGy, where the maximum crosslinking, highest crystallinity and best micro-mechanical and tribological properties are found. The difference between non-irradiated and irradiated filled PP is 52% in indentation hardness. In terms of macro-mechanical properties, the tensile modulus increased by 44% (45 kGy). This translates into higher surface wear resistance and the overall stiffness of the part. Higher doses of radiation cause the beginning of degradation processes, which are manifested by a decrease in the degree of embedding, crystallinity and thus micro-mechanical and tribological properties. Full article

Reinforced concrete walls (RC walls) are widely used in transportation, building structures, and civil air defence engineering. RC walls are vulnerable to low-velocity impact, such as the fall of components caused by earthquakes or explosions, for example, and the impact from road objects, such as vehicles, during their service life. When subjected to instantaneous high-energy impact, RC walls at key positions are prone to severe damage, which can further lead to structural collapse. Therefore, it is necessary to consider improving the impact resistance of key RC walls in a structure. Using a porous honeycomb structure with excellent energy absorption performance to provide impact protection for key RC walls is an effective way to reduce the damage of RC walls and thereby enhance the impact resistance of a structure. Therefore, based on the author’s previous series of experimental and numerical studies on the impact resistance of RC walls, as well as the high-mass pendulum impact experimental study on the honeycomb sandwich panel composite RC wall (HSP-RC wall), this paper adopts a multi-scale modelling method in micro-mechanics and macro-mechanics to establish a pendulum impact finite element model (FEM) for the HSP-RC wall. The representative volume element (RVE) and periodic boundary condition (PBC) are used to calculate the elastic property parameters of the honeycomb, which guide the establishment of the FEMs for the HSP-RC wall. The FEMs can avoid the computational difficulty caused by refined simulation, analyse the impact damage of the HSP-RC walls more accurately, quantify the impact protection effect of the honeycomb sandwich panel, and thus facilitate the parametric analysis of the impact resistance of HSP-RC walls with different honeycomb panel structural parameters in subsequent studies. Full article