Search Results (1,196)

A cold-sprayed Cr₂AlC coating was deposited on an H13 tool steel substrate, and the electrochemical corrosion behavior in 3.5 wt.% NaCl solution was experimentally investigated. Electrochemical tests, including open circuit potential and potentiodynamic polarization measurements, revealed that the Cr₂AlC coating significantly improved the corrosion resistance of H13 steel, exhibiting a more positive open circuit potential and a reduced corrosion current density compared with the bare H13 steel substrate. Post-corrosion surface morphology analysis by scanning electron microscopy showed extensive pitting corrosion on the substrate surface, while no obvious corrosion damage was observed on the coating surface. X-ray photoelectron spectroscopy (XPS) analysis further confirmed the formation of a passive film composed of chromium and aluminum oxides on the coating surface, indicating a protective passivation mechanism. The enhanced corrosion performance is attributed to a synergistic mechanism involving both a physical barrier provided by the coating and surface passivation induced by the Cr/Al-based oxide layer. This work highlights the potential of cold-sprayed Cr₂AlC coating as an effective corrosion protection solution for steel substrates in chloride-containing environments. Full article

Recently, interest has grown in using alternatives to cement and aggregates to improve concrete and reduce its environmental impact. This study explores the use of cherry pit waste (CPW) as a partial substitute for coarse aggregates in self-compacting concrete (SCC) at varying rates (0–25%). Rheological, compressive strength, and ultrasonic pulse velocity tests were conducted. The results showed that CPWs reduce flowability but increase cohesion. The 5% CPW mix achieved the highest compressive strength. All the mixes remained acceptable, with classifications from SF3 to SF1. Due to CPWs’ lower density, both wet and dry weights decreased, making this a viable lightweight concrete option. Full article

The performance of flux-cored Zn-Al filler metal is susceptible to corrosion-induced degradation, thereby impairing its brazability. In this study, flux-cored Zn-2Al filler metals are prepared, and the salt spray test is subsequently carried out on the prepared filler metals. Scanning transmission electron microscope is used to identify the phases in filler metals. An electrochemical workstation was employed to test the electrochemical performance of the filler metals. The corrosion pathways and evolution patterns of filler metals are analyzed. The findings demonstrate that the corrosion type of the filler metals is electrochemical corrosion, characterized primarily by the corrosion modes of pitting corrosion and intergranular corrosion. The cathode is the α-Al phase, which undergoes an oxygen-absorption corrosion reaction, while the anode is the η-Zn phase, which experiences corrosion and subsequent dissolution. The continuously distributed α-Al phase bands and discontinuously distributed large-sized rod-like α-Al phases accelerate the corrosion rate, and the corrosion propagation rate along the extrusion direction is higher than that in the radially inward direction. After 15 days of salt spray corrosion, the tensile strength of filler metals decreases by 16.2%, and the elongation rate decreases to 3.73%. Full article

Operational (short-term) planning in open-pit mining is a critical phase for ensuring grade control and production stability, particularly in complex geological environments. While long-term plans define the strategic goals, they often overlook shift-level variability and operational constraints of a shovel-truck system. This paper presents an optimization model based on a genetic algorithm (GA) for shift-by-shift operational planning. The model integrates real-world technological constraints of the equipment used, including fixed shift capacity (2000 t) and various constraints characteristic of active mining locations. The fitness function is designed to minimize the deviations from the targeted quality range for iron (Fe: 47–50%) and silica (SiO₂: ≤11%), while ensuring rational use of mineral reserves. The model was tested on a case study involving eight limonite ore open pits over a period of one production year (1000 shifts). The results show that the GA-generated plan reaches quality requirements in 98.1% of all shifts. This GA approach provides more balanced mining operations and confirms and ensures the achievement of goals from long-term plans, reducing the reliance on large-scale homogenization stockpiles. The developed tool is implemented in Excel/VBA and offers a practical framework for mining engineers to work with. Full article

In geotechnical engineering, operations such as foundation pit excavation, slope cutting, and tunnel boring often involve lateral unloading under plane strain conditions. This unloading pattern exhibits significant differences from the traditional axisymmetric triaxial loading path. To investigate the mechanical behavior of silt under such conditions, a series of plane strain tests were conducted using a self-designed plane strain apparatus, focusing on both vertical loading (constant lateral stress) and lateral unloading (constant vertical stress) paths. The results indicate that the failure of soil during unloading can be identified as the stage where the vertical deformation rate first increases and then decreases, corresponding to a distinct inflection in the stress–strain curve. The internal friction angle remained essentially constant regardless of the stress path, dry density, or consolidation stress ratio, while cohesion was higher under loading than under unloading. Failure deviatoric stress increased linearly with vertical consolidation stress and was unaffected by the consolidation stress ratio. The classical limit equilibrium condition remains valid for unloading under both isotropic and anisotropic consolidation. These findings provide a practical criterion for failure detection and highlight the necessity of adopting plane strain parameters in the design of lateral unloading engineering works. Full article

Pitting corrosion is a prevalent and highly detrimental form of localized corrosion, which can severely compromise the local load-bearing capacity of metallic materials and, in extreme cases, trigger structural failure. In response to the pronounced susceptibility of Q235 galvanized steel plates to localized pitting under the extreme service conditions of the South China Sea—characterized by high temperature, high salinity, high humidity, and coupled chemical corrosive effects—this study conducts a systematic investigation combining experimental characterization and numerical simulation. First, a novel accelerated pitting corrosion apparatus was designed and developed, and chloride ion cyclic corrosion (CICC) tests were performed on Q235 galvanized steel plates. The morphology and temporal evolution of pitting damage were comprehensively characterized. Subsequently, based on a coupled Cellular Automata (CA) and Finite Element Analysis (FEA) framework, a corrosion evolution model termed CAFE (Cellular Automata-Finite Element) was established. This model elucidates the initiation, growth, and corrosion product evolution of pitting pits under varying temperature and salinity conditions and further quantifies the spatial distributions of stress and temperature fields in the vicinity of pitting sites. Finally, experimental results were employed to validate the rationality and effectiveness of the proposed electro-thermo-mechanical-chemical (ETMC) multi-field coupling model. The results demonstrate that temperature and salinity are the dominant environmental parameters governing the evolution of localized pitting corrosion rates. A strong agreement between numerical predictions and experimental observations is achieved in both qualitative trends and quantitative metrics. Notably, the model reveals that under elevated current-driving conditions, localized plastic deformation plays a critical role in promoting pit propagation and accelerating the pitting corrosion process. Full article

Systematic, spatially explicit tree inventories are increasingly implemented in cities worldwide, as they are crucial for evidence-based green infrastructure planning. Currently, different approaches are adopted, which differ in methodological framework and parameter standardization, limiting comparative assessments and coordinated monitoring. This study presents a replicable protocol for a field-based digital street tree census, applied in a densely built central area and in a low-density suburban area of Rome. Field surveys documented a set of 15 parameters, including species identity, dendrometric and tree pit parameters, acquired using open-source QGIS/QField tools. Subsequent analysis evaluated floristic diversity, population structure, and climate suitability at the neighborhood scale, enabling the identification of context-specific vulnerabilities. The testing of the methodology shown in this work involved 13,017 georeferenced tree pits, pointing out substantial pit restoration needs and insufficient soil conditions in the most densely urbanized area, whereas the suburban area shows optimal conditions with extensive road verge green spaces. Joint interpretation of the considered parameters reveals that high floristic diversity alone does not guarantee climate resilience: high-diversity neighborhoods can exhibit substantial non-climate-resilient species and limited alignment with local species recommendations, demonstrating that comprehensive evaluation of street tree populations requires integrated analysis. The operationalized protocol establishes a replicable, municipally scalable methodological framework, providing policymakers with fine-scale, actionable insights enabling differentiated urban forestry strategies addressing both infrastructure deficits and long-term species climate suitability. Full article

Accurate determination of the physico-mechanical parameters of rock and soil masses is fundamental to the quantitative stability analysis and engineering mitigation of open-pit mine slopes. However, existing studies often rely on generalized parameters and lack systematic empirical data based on full-hole in situ core sampling to quantitatively verify the link between microscopic mineralogy and macroscopic instability. To address this gap, this study investigates the mineral composition, microstructure, and hydro-mechanical behavior of geotechnical materials, using the XG Open-pit Coal Mine in Inner Mongolia as a case study. Field drilling and sampling with a cumulative depth of 1500.7 m were conducted, combined with systematic laboratory tests. The results reveal significant lithological heterogeneity within the mining area. Specifically, hard rocks (e.g., fine sandstone) constitute the stable framework of the slope, whereas mudstones rich in hydrophilic clay minerals, along with low-strength coal seams, form potential weak sliding interfaces. Quantitative X-ray Diffraction (XRD) analysis reveals that the weak mudstone layers contain up to 32.4% hydrophilic expansive minerals (montmorillonite and illite/smectite). Scanning Electron Microscopy (SEM) and slake durability tests demonstrate that the mudstone is characterized by well-developed micropores (1–2 μm) and loose cementation. Theoretical analysis indicates that upon saturation, the strength of these weak layers is reduced by over 40%, causing the factor of safety (FoS) to drop from a stable 1.48 to a critical 0.89. Based on these findings, the slope instability mechanism driven by “Stiffness Mismatch and Hydro-Weakening” is elucidated. Consequently, targeted reinforcement and drainage measures are proposed to provide a scientific basis for safe mining operations. Full article

Excavation in soil–rock composite strata poses significant challenges in regard to deformation control due to stiffness contrast and interface discontinuity. Based on the optimization requirements of a foundation pit project in Jinan Metro Line 7, we evaluated an end-suspended pile support system without rock-socket support through physical model tests and numerical simulations. The results indicate that ground settlement exhibits a typical “trough-shaped” distribution with an influence range of approximately 20 m. The pattern of retaining wall displacement evolves from being “inverted-triangular” into a “vase-shaped” during staged excavation, with maximum displacement remaining within code limits. Bending-moment peaks can be observed near strut levels and approximately 1 m above the soil–rock interface, reflecting stress redistribution and differential constraint effects. Parametric analysis demonstrated that increased rock weathering reduces formation stiffness and amplifies deformation and strut forces, whereas moderately weathered rock provides more effective restraint. A steeper interface dip angle induces asymmetric deformation due to stiffness contrast, increasing overall structural demand. An increase in rock-socketed depth, particularly within 4.0–4.5 m, significantly enhances anchorage performance and deformation control. These findings provide quantitative support for optimizing suspended pile systems in soil–rock composite strata. Full article

In addressing the challenge that the settlement behavior of granite residual soil in South China during foundation pit dewatering cannot be fully understood due to its unsaturated characteristics, this study proposes and validates an unsaturated fluid–solid coupling calculation method for dewatering-induced settlement analysis. This method is implemented by compiling FISH language code within a finite difference software framework. Validation was carried out by comparing thes simulated groundwater drawdown–time response with the measured drawdown from a field pumping test, demonstrating the improved agreement of the proposed unsaturated coupling approach relative to the conventional coupling scheme. Furthermore, to elucidate the soil settlement mechanisms, a sensitivity analysis of the deformation behavior of granite residual soil during dewatering was performed. The results demonstrate that, compared to the traditional fluid–solid coupling method, the unsaturated fluid–solid coupling method exhibits superior agreement with field dewatering experiments. The sensitivity analysis reveals that the differential settlement observed in the soil surrounding a dewatering well under the same target drawdown is primarily attributed to variations in drainage consolidation time and pore water pressure dissipation. Finally, a normalized analysis correlating the dewatering depth at the well with the resulting soil settlement deformation was conducted, establishing a practical relationship applicable under similar ground conditions and dewatering durations. This analysis provides theoretical guidance for selecting appropriate dewatering schemes during engineering practice. Full article

In the field of magneto-optical imaging nondestructive testing for welding defects, multi-angle detection of welding defects has already been achieved. However, research on automatic defect recognition and contour extraction remains insufficient. Therefore, to enable automatic detection of welding defects using magneto-optical imaging technology, it is essential to address the key issues of defect recognition and contour extraction in magneto-optical images. The dataset in this article includes five types of images: defect-free, lack-of-fusion, cracks, pits, and Weld reinforcement. Firstly, the Mask R-CNN detection method is used to perform defect recognition and contour segmentation on the original magneto-optical image dataset. The detection results indicate that the recognition rate of lack-of-fusion and Weld reinforcement in the original magneto-optical image is not high, and the recognition accuracy of pits and cracks is extremely low. Subsequently, the magneto-optical image dataset was preprocessed using the differential level set method, and the mask R-CNN algorithm was used to identify defect types and segment defect contours. Comparing the results of two experiments, it was found that the detection accuracy of the preprocessed dataset was higher, and the overall recognition accuracy increased by $30\%$. Full article

During the excavation process of the foundation pit, soil parameters evolve dynamically. In order to improve the accuracy of soil parameter selection in foundation pit engineering and achieve accurate deformation prediction, this paper proposes a displacement inverse analysis method that combines the enhanced starfish optimization algorithm (ESFOA) and the hybrid kernel least squares support vector machine (LSSVM). The ESFOA improves the global search capability and convergence accuracy of the starfish optimization algorithm (SFOA) by optimizing the initial population and introducing a hunting mechanism. On this basis, the ESFOA was used to optimize the RBF kernel function width ($\sigma$), polynomial kernel coefficient ($q$), regularization penalty coefficient ($c$), and kernel function mixing weight ($\lambda$) of the hybrid kernel LSSVM model. Samples were obtained through finite element simulation and orthogonal experiments, and the optimized ESFOA-LSSVM model was used to establish the nonlinear mapping relationship between the horizontal displacement of the foundation pit excavation enclosure and the soil parameters. The horizontal displacement monitoring data of the foundation pit retaining structure is used to invert the soil parameters and predict the deformation of the retaining structure under subsequent conditions. The results show that (1) compared with other algorithms, the ESFOA has good global search capabilities and convergence accuracy; (2) the ESFOA-LSSVM model is tested through test samples, and the model has good accuracy and feasibility; (3) the parameters obtained by the inversion can effectively improve the prediction accuracy of foundation pit deformation, and the prediction results are closer to the actual monitoring values. Full article

The disposal of waste tyres presents a significant environmental challenge, necessitating sustainable, high-value recycling solutions. This study explores the incorporation of waste tyre metal fibre (WTMF) into hot mix asphalt (HMA) to enhance mechanical performance while reducing landfill burden. WTMF-modified mixes containing 0%, 0.375%, 0.75%, 1.125%, and 1.50% fibre were evaluated through Marshall and volumetric testing, indirect tensile strength (ITS) and tensile strength ratio (TSR) for moisture damage, stiffness modulus at varying temperatures, and fatigue life under cyclic loading. Microscopic analysis revealed WTMF’s irregular, rough surface with microcracks and pits, aiding crack-bridging and stress transfer. Marshall testing showed that the optimum binder content of WTMF-modified mixtures was approximately 5% higher than that of the control (conventional HMA without WTMF); however, stability decreased while flow increased, resulting in a reduced Marshall quotient due to fibre conglomeration affecting porosity and bulk specific gravity. ITS results indicated that the control mixture exhibited the highest cracking resistance, whereas WTMF-modified mixtures demonstrated improved moisture resistance (TSR > 80%). The maximum improvement was observed at 0.75% WTMF-induced HMA, with an 11% increase in TSR, while a slight reduction of 2.4% occurred at 1.50% WTMF-induced HMA. Stiffness testing showed that the mixture containing 0.375% WTMF achieved the highest modulus, exhibiting up to a 70% increase at 5 °C and more than a twofold increase at elevated temperatures compared to the control mixture. With increasing temperature, stiffness decreased by approximately 84% for the control mixture and 80% for the 0.375% WTMF-modified mixture. Fatigue analysis showed that the control mixture achieved a fatigue life of 115,529 loading cycles at low stress, followed by substantial reductions in fatigue life with increasing stress levels, whereas moderate WTMF contents improved strain performance; however, excessive fibre content increased permanent deformation under high stress. Stress- and strain-based empirical power-law relationships were established for predicting the fatigue life of each investigated mixture. Results demonstrate that WTMF’s controlled dosage within the optimum range of 0.375 to 0.75% has the potential to improve HMA’s performance indicators, offering a sustainable recycling pathway for waste tyres. Full article

With the intensive development of urban underground space, excavations adjacent to existing tunnels have become increasingly common. This study investigates the response of adjacent tunnels and surrounding soil to multi-step foundation pit excavation and the effect and mechanism of a new capsule technology. Centrifuge model tests and finite element analysis were conducted for models both with and without a capsule. The results show that the soil deformation caused by each excavation step is confined to an influence zone. As the excavation deepens, this influence zone progressively expands. Excavation causes the tunnel to move outward and the retaining wall to rotate clockwise. The results demonstrate that capsule pressurization can effectively reduce the maximum horizontal displacement of the adjacent tunnel by approximately 30–40% compared to the case without reinforcement. Capsule pressurization alters the earth pressure distribution on the retaining wall and reduces tunnel displacement. The effect of the capsule decays with increasing distance from the capsule to the tunnel. The excavation impact propagates to the tunnel via wall–soil and soil–tunnel interactions. Capsule pressurization mitigates the tunnel response by ensuring that the surrounding soil experiences a smaller reduction in horizontal stress and exhibits a higher modulus during subsequent excavation. This enhanced state of the soil produces smaller deformation, which ultimately transfers less of the excavation effect to the tunnel and controls its displacement. The study concludes that the active pressure control offered by the capsule technology is a promising method for protecting existing tunnels during adjacent deep excavations. Full article

Accurate estimation of snowpack microwave backscatter is critical for retrieving key physical properties of snow, such as snow depth (SD) and snow water equivalent (SWE), typically modeled using radiative transfer models (RTM). Among the various sources of uncertainty in RTM simulations, snow–ground reflectivity—used as a boundary condition—plays a critical role in influencing the accuracy of simulated backscatter. This study leverages high-resolution X- and Ku-band synthetic aperture radar (SAR) backscatter aircraft measurements using SWESARR and SnowSAR from NASA’s SnowEx campaigns, co-located with in situ snow pit observations in Grand Mesa, Colorado, and uses a Bayesian MCMC parameter optimization model with RTM framework to estimate the key ground parameters such as surface roughness, moisture content, and specular-to-total reflectivity ratio (STRR) governing the estimation of the snow–ground reflectivity and quantify the uncertainties associated with them. At the X-band, increasing ground surface roughness reduced the simulated backscatter by ~1.5 dB across the tested range, increasing the STRR produced an additional ~1.0 dB decrease while the dielectric properties of the ground are highly sensitive to the moisture content of frozen soil, and increasing the moisture content even by 2% increased the backscatter by 2–3 dB. The retrieval sensitivity to the STRR is minimized in the 0.6–0.7 range and it can be fixed at 0.65 without having discernible impact. The Bayesian inversion reveals that the extreme parameter values act as diagnostic indicators of unmodeled complexity rather than retrieval failures, with representativeness error often dominating over instrument noise. The study provides a robust methodology for the estimation of the snow–ground backscatter boundary condition for forward modeling, ultimately aiding SWE and SD retrieval from active microwave observations. While this study relied on Grand Mesa, the framework developed here is general and, along with the model uncertainty, is directly transferable and broadly applicable to other snow-dominated mountain regions where active microwave observations can be used for snowpack monitoring. Full article