Search Results (1,199)

Ultra-deep circular shafts are increasingly deployed in congested urban environments, yet their structural performance in highly sensitive soft clay remains susceptible to diaphragm wall panel joints, structural imperfections, and complex interactions with adjacent structures. This study presents a high-fidelity three-dimensional (3D) numerical investigation into the excavation behavior of an ultra-deep circular shaft with a diameter of 30 m and an excavation depth of 56.3 m in Shanghai soft clay by synthesizing high-resolution field monitoring with advanced finite element modeling. The numerical framework was established in PLAXIS 3D utilizing the Hardening Soil model with small-strain stiffness (HSS), explicitly incorporating an equivalent structural stiffness reduction scheme (0.8 vertically and 0.5 circumferentially) to capture panel segmentation, joint compliance, and concrete cracking. The reduced-stiffness model successfully reproduces the measured deep-seated bulging profiles and internal force distributions with high fidelity. The findings reveal exceptional deformation control capabilities of the circular geometry, yielding a maximum lateral wall deflection of merely 9.1 mm (0.016%H_e), which is significantly smaller than the normalized deformation ratio of 0.3%H_e observed in five analogous rectangular excavations in Shanghai. The numerical results indicate that circumferential compression governs the overall load transfer behavior, while vertical bending response remains relatively limited. Furthermore, a pronounced circumferential anisotropy in wall deformation is governed by asymmetric boundary conditions, where localized Metro Jet System (MJS) ground improvement significantly restrain movements, whereas the non-grouted area experience peak deflections. Crucially, interaction with the adjacent external diaphragm walls of ancillary structures induces a complex 3D stress redistribution rather than a beneficial shielding effect, amplifying the peak shaft wall displacement by nearly 62.8% (from 4.73 mm to 7.70 mm). These insights underscore the criticality of integrating small-strain soil mechanics, equivalent structural degradation, and adjacent structural boundaries into predictive design protocols for ultra-deep circular retaining systems. Full article

Early-age cracking severely limits concrete durability in hot, arid environments due to rapid plastic and drying shrinkage. This study evaluates the cracking sensitivity of cement-based materials incorporating four local supplementary cementitious materials (SCMs): limestone filler from Djebel Béchar, natural pozzolan, silica fume, and gypsum under simulated arid conditions (55 °C, 12% relative humidity, 10 km/h wind). Using a custom climatic chamber, prismatic cement-grout specimens with internal restraints were tested. SCMs were evaluated at substitution rates of 2% to 8%. Limestone was further tested at higher rates (up to 40%) and in binary combinations. Findings were validated using micro-concrete with limestone substitutions (0–35%) combined with 4% natural pozzolan. Cracking sensitivity was assessed using maximum crack width and a cracking index, along with setting times and mechanical strengths. Results indicate that limestone filler demonstrated the most favourable performance. A 4% limestone substitution yielded a single crack with a maximum width of 0.1 mm, while an 8% substitution resulted in five cracks of about 0.2 mm. The optimal cracking index was achieved at a 35% limestone substitution rate, which also successfully extended initial and final setting times. While binary SCM combinations significantly reduced cracking compared to the unsubstituted reference, they did not outperform the optimal 35% single limestone substitution. Furthermore, the 28-day compressive and flexural tensile strengths of the micro-concrete were effectively maintained at up to 35% limestone combined with 4% pozzolan. Overall, these preliminary findings demonstrate that crushed limestone fines from Djebel Béchar are highly promising as partial cement replacements to improve concrete durability in arid climates. Further durability assessments and statistical validation are recommended to confirm these benefits for practical field applications. Full article

Photovoltaic (PV) systems in arid regions experience substantial energy losses from dust accumulation, but automated cleaning can introduce risk when damaged modules are visually misclassified as dirty. Manual inspection is also impractical at utility scale. This study presents an edge-based cleaning-decision architecture in which vision proposes a cleaning request and independent electrical checks determine whether actuation is permitted. The prototype combines a YOLOv8n detector, INA219 voltage/current sensing, photodiode-based shading context, a Raspberry Pi 4, and an Arduino co-processor. Cleaning is allowed only when three conditions are satisfied: persistent dust detection, measured panel power below a predefined threshold, and the absence of an electrical structural-fault signature based on rolling-window voltage depression and instability. The detector was trained using 950 field-recorded frames containing 2850 annotated panel instances and achieved 77.3% mAP@0.5 on the validation set; across five retraining seeds, mAP@0.5 was $77.1\pm 1.1\%$. In a retrospective ablation of the recorded test campaign, the two verification gates reduced false or unsafe cleaning activations from five to one, while both unsafe activations involving the tested cracked module were vetoed. A 13.5 h three-day campaign recorded seven persistent visual dust requests; the power gate rejected six requests that did not justify cleaning, and the remaining request triggered a successful cleaning cycle. In that field event, panel power increased from 0.33 W to 7.48 W, corresponding to a 22.9-fold recovery. An assumption-based sensitivity analysis indicates potential water-cost savings from condition-based cleaning. An offline, template-constrained language model is used only for report generation and has no connection to actuation. Full article

This study comparatively investigates the coarse-grained heat-affected zone (CGHAZ) responses of two industrial X65 seamless pipeline steels with distinct composition–microstructure characteristics under simulated girth-welding thermal cycles. One steel exhibits a predominantly bainitic initial microstructure, whereas the other consists of a ferrite–bainite dual-phase microstructure. Low-temperature Charpy impact testing, microhardness measurements, scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron backscatter diffraction (EBSD), prior-austenite grain reconstruction, and JMatPro 13.0-based continuous cooling transformation (CCT) calculations were employed to evaluate their heat-input sensitivity and microstructural evolution. At heat inputs of 7–10 kJ/cm, both steels maintained high impact toughness at −20 °C, with average absorbed energies of approximately 250 J. A pronounced difference emerged at 15 kJ/cm the bainite-dominated steel retained relatively high impact toughness and higher crack-initiation and -propagation energies, whereas the ferrite–bainite steel exhibited a marked toughness reduction. At higher heat inputs of 20–30 kJ/cm, both steels showed substantial toughness deterioration associated with severe prior-austenite grain growth and coarsening of the bainitic transformation products. Microstructural and crystallographic analyses showed that the bainite-dominated steel generally retained finer prior-austenite grains and more refined crystallographic features under the investigated thermal cycles. Detailed characterization at 15 kJ/cm further revealed finer prior-austenite grain, packet, and block structures, together with more tortuous crack-propagation paths. JMatPro calculations predicted a lower bainitic transformation temperature for this steel, which is consistent with the experimentally observed tendency toward finer bainitic transformation products. The superior CGHAZ toughness retained by the bainite-dominated steel is therefore associated with the combined effects of alloy composition, initial metallurgical state, transformation behavior, and hierarchical crystallographic refinement rather than the initial microstructure alone. The results highlight the importance of coupled composition–transformation–microstructure effects in determining the welding heat-input tolerance of industrial X65 seamless pipeline steels. Full article

Ta-2.5W alloy is a promising liner material for high-performance shaped-charge warheads because of its high density and excellent dynamic mechanical properties. However, conventional machining and hot-forming routes suffer from low material utilization, limited dimensional accuracy, and oxidation-related defects. In this study, near-net-shape cold pressing and annealing treatments were investigated for Ta-2.5W liners. The initial microstructure and mechanical properties of the starting sheet were characterized, compression tests were performed to establish a room-temperature constitutive model, and 16 combinations of deformation and annealing temperature were designed to clarify the evolution of grain morphology and crack sensitivity. To compensate for elastic die deformation and blank springback, a coupled simulation-based die correction strategy was further developed. The results show that the starting alloy exhibits an excellent strength–ductility balance with weak anisotropy. Increasing cold deformation refines the grains, whereas increasing annealing temperature initially promotes grain refinement but subsequently causes grain coarsening. Excessive deformation combined with high annealing temperature increases crack susceptibility. Based on the single-specimen screening experiments in this study, a preliminary processing range of 20–40% cold deformation and 1200 °C annealing produced the most favorable microstructural condition without obvious cracking. After iterative die compensation, trial-manufactured parts satisfied the target contour requirements and showed uniform, crack-free microstructures after annealing. Full article

This study investigates the high-temperature high-cycle-fatigue behavior of TIG-welded Haynes 230 alloy using smooth and notched specimens (Kt = 3) at 850–950 °C. Both elevated temperature and notch effect significantly degrade fatigue performance. As temperature increases, thermally activated crack initiation and propagation accelerate, shifting the S–N curves downward. Notched specimens exhibit substantially shorter fatigue lives due to stress concentration-induced multi-source crack initiation, dispersed propagation zones, and fragmented sudden fracture zones. The alloy shows low notch sensitivity across the test temperature range, with the lowest value at 900 °C. A unified fatigue life prediction model is established using a temperature correction factor exp[P × ()], demonstrating high fitting accuracy. M-G curves of notched specimens shift downward and leftward, revealing the aggravating effect of the notch on creep–fatigue interaction. Fractographic analysis shows that with increasing temperature, smooth specimens exhibit expanded sudden fracture zones and degraded striations, while notched specimens display multi-source initiation and a composite morphology of striations with fine dimples, consistent with macroscopic mechanical behavior. This work delivers comparative experimental data and mechanism-oriented insights for TIG-welded Haynes 230 joints within 850–950 °C; the proposed temperature-corrected model is valid for the investigated test window and provides reference for component performance analysis. Full article

Ground-penetrating radar (GPR) and electrical resistivity tomography (ERT) provide complementary, but non-unique, observations of concrete and masonry conditions. GPR is primarily sensitive to dielectric contrasts, interfaces, reinforcement geometry and electromagnetic attenuation, whereas electrical measurements respond to ionic conduction, moisture state, material connectivity and electrode configuration. This paper presents a structured critical review updated to 21 July 2026. It distinguishes surface or bulk resistivity measurements from electrical resistance tomography around specimens and from multi-electrode geophysical ERT, an important terminological separation that is frequently blurred in the literature. This review’s contribution is a terminological separation of electrical measurement classes, an evidence-coding scheme that distinguishes corroboration from independent validation, and a staged, conditional research agenda built from that scheme; it is not a claim that GPR–ERT integration is routinely sufficient on its own. Verified evidence is synthesised across reinforced concrete, masonry, coastal infrastructure, laboratory calibration, field validation and forward modelling. The review shows that GPR is mature for reinforcement mapping and conditional detection of interfaces and delamination, while resistivity methods are well established for durability-related screening. True ERT can image spatial conductivity changes associated with moisture ingress and cracks, but inversion regularisation, electrode contact, reinforcement and three-dimensional effects limit resolution and quantitative recovery. Integrated GPR–ERT studies now include controlled masonry experiments, heritage structures, a field heritage pier and laboratory calibration on reinforced concrete; therefore, the principal remaining gap is not the absence of integration. It is the shortage of independent destructive field verification, scale-aware transfer rules and uncertainty-calibrated decision thresholds across structural types. A revised evidence matrix and detectability taxonomy show that neither method directly identifies active corrosion or chloride concentration. The paper concludes with a staged research agenda based on co-registration, physics-informed feature extraction, forward-modelled resolution assessment and targeted ground truth. Full article

The integration of complementary sensing modalities provides a basis for accurate crack identification in advanced aircraft structures. In this context, PZT transducers are sensitive to incipient damage through guided-wave interrogation, whereas strain gauges capture quasi-static deformation. Prevailing fusion paradigms, however, encounter an interpretability–adaptability dilemma. Model-based approaches lack robustness to sensor degradation, while data-driven attention methods sacrifice transparency. To resolve this trade-off, an Evidence-guided Attention Neural Network (EANN) is proposed. Its central methodological contribution lies in repositioning Dempster–Shafer (D-S) evidence theory from a terminal fusion operator to an upstream credibility feature extraction module. Evidence-derived credibility features, comprising belief entropy, inter-source similarity, and Kalman-filtered residuals, drive the attention weight optimization and endow the learned channel weights with physically interpretable evidential meaning. Ablation experiments confirm that the observed improvement arises from the interaction between the evidence-guided credibility representation and adaptive attention weighting, with neither component sufficient on its own. The framework fuses quasi-static strain measurements with active piezoelectric guided-wave interrogation, which offers high sensitivity to incipient damage but remains vulnerable to channel degradation. Experiments on aluminum tensile plates and trapezoidal wing skin specimens show that EANN maintains identification accuracy under simulated sensor anomalies and partial failures by attenuating compromised channels without explicit fault detection, providing an uncertainty-aware fusion framework for online structural health monitoring of aerospace structures. Full article

Reservoir impoundment can reactivate pre-existing landslides and reorganize slope topography, thereby changing seepage conditions and subsequent deformation. However, crack mapping, geomorphic interpretation, and hydrodynamic diagnosis are still often treated as separate tasks. This study investigates the Hemenkou (HMK) landslide in the Wudongde Reservoir area, China, using multi-scale space–air–ground observations, including multi-temporal optical satellite images, unmanned aerial vehicle (UAV) photogrammetry, pyramid scene parsing network (PSPNet)-based crack segmentation, global navigation satellite system (GNSS) monitoring, and convergent cross mapping (CCM). The remote sensing record shows a progressive damage sequence: cracks were mainly restricted to the upper source area in 2012, crown cracking intensified and propagated downslope by December 2020, and the UAV survey of 10 June 2024 revealed a mature tension-crack network concentrated in Zone II. ResNet-50-PSPNet achieved the best crack-extraction performance among the tested models, with Precision = 0.9120, Recall = 0.9041, F1 = 0.9081, and IoU = 0.8316. The mapped cracks are dominated by short, narrow, northeast–southwest-oriented tension cracks. GNSS monitoring reveals strong spatial heterogeneity, with stepwise deformation concentrated in Zone II. CCM provides strong directional evidence for the influence of reservoir water-level fluctuation on Zone II deformation, whereas the weaker rainfall signal is consistent with a secondary reinforcing role. The apparent increase in the rainfall-related CCM signal from 2021 to 2023 is consistent with progressive crack expansion and potentially enhanced hydraulic connectivity in Zone II. Taken together, these observations support the interpretation that post-deformation topography, particularly the tension-crack network and disturbed toe, may organise preferential seepage pathways and increase the sensitivity of the landslide to reservoir drawdown. The study provides an integrated remote sensing and monitoring framework for process-based interpretation of reservoir landslides. Full article

The structural application of 3D printed concrete (3DPC) is still constrained by the difficulty of qualifying a layered, process-dependent material using standards developed mainly for cast concrete and conventional masonry. This review examines 3DPC through masonry construction to clarify how interface-controlled behaviour should be interpreted, tested and standardised. The comparison is not based on material similarity, but on the shared structural role of joints, interfaces and assemblage-level load transfer. Most previous reviews mainly discuss printability, mixture design, material development or general mechanical performance. This review instead places the printed interface at the centre of structural qualification, using masonry only as a reference for interpreting joint-controlled load transfer. The review shows that compressive strength alone is insufficient for structural qualification, since printed elements may fail through interlayer debonding, direction-dependent cracking, filament instability, reinforcement discontinuity or connection weakness. Flexural, shear, cyclic and seismic responses are particularly sensitive to interlayer quality, loading orientation and print-path geometry. Existing concrete, mortar and masonry standards remain useful references, but require 3DPC-specific reporting and testing. Accordingly, a tiered qualification route is proposed, progressing from fresh-state characterisation to interface-dominated testing and structural-scale validation. Full article

Argillaceous siltstone forms water-sensitive weak layers in red-bed slopes, but its multiscale deterioration under wet–dry cycling remains incompletely understood. Specimens subjected to 0, 1, 3, 5, 7, and 9 cycles were examined through uniaxial compression, energy analysis, digital image correlation (DIC), and microstructural and mineralogical characterization. The mean unconfined compressive strength (UCS) decreased by 36.0% after the first cycle and then remained broadly stable, with modest fluctuations, from 1 to 5 cycles. At five cycles, the elastic modulus remained substantially below the natural-state value, and although total strain energy approached the natural-state level, elastic strain energy remained lower and the dissipated energy ratio more than doubled, indicating continued irreversible damage. The characteristic calcite diffraction peak was no longer detected in the X-ray diffraction (XRD) patterns, while microstructural observations showed redistributed fines within pores together with a temporary decrease in face porosity. With further cycling, the UCS declined again and was 59.0% below its initial level after nine cycles. Meanwhile, strain fields and failure patterns evolved from localized deformation and splitting to distributed cracking and surface spalling, while particle detachment reopened pores and increased face porosity to 14.37%. These observations are consistent with a dissolution–filling–detachment mechanism and suggest that the intermediate UCS stabilization reflected temporary maintenance of load-bearing capacity rather than recovery of the original rock skeleton. Full article

Automated airport pavement inspection requires reliable instance segmentation models for detecting and quantifying thin cracks under real operating conditions. Building on a previously established UAV-AI workflow for airport pavement crack detection and quantification, and on an earlier investigation of sealed-crack class definition using YOLO11, the present study addresses a subsequent research question by comparing two recent model configurations based on fundamentally different computer vision paradigms. YOLO26 was selected for its deployment-oriented convolutional architecture, computational efficiency, and mechanisms aimed at improving small-target handling, whereas RF-DETR was selected for its transformer-based architecture and DINOv2-pretrained backbone; these provide fine-grained visual representations and exploit broader contextual information. The two configurations were assessed using the same dataset of 24,768 annotated images and compared in terms of computational demands, independent test-set performance, and field-based crack length reliability. Field validation was performed on two airport taxiways representing different surface conditions: taxiway Nibbio, mainly affected by active longitudinal and transverse cracks with limited interference from sealed cracks, and taxiway November, characterized by the coexistence of active and sealed cracking patterns. YOLO26 showed a lower computational demand, requiring approximately one hour and 20 compute units, compared with approximately six hours and 80 compute units for RF-DETR. RF-DETR achieved a higher mAP50 and recall on the test set and lower model error index values on both taxiways, indicating better crack length recovery. However, on taxiway November, it also showed higher hallucination index values, revealing greater sensitivity to visually ambiguous sealed cracks. These findings indicate that model selection should consider pavement surface conditions, computational constraints, and the operational consequences of missed cracks and false-positive detections. The specific contribution of the present study is therefore the extension of the previously established UAV-AI framework from workflow development and class definition analysis to the comparative evaluation of recent convolutional and transformer-based model configurations under real airport pavement conditions. Full article

To address the issues of low mechanical rock-breaking efficiency and severe tool wear in hard rock, this study investigates the mechanical deterioration and abrasivity response of granite subjected to rapid flame-jet heating followed by liquid nitrogen cooling, with rock pre-treatment in thermal-assisted rock breaking as the background. Fine-grained granite specimens were heated by flame jet to temperatures ranging between 200 and 600 °C and then subjected to natural cooling or sudden liquid nitrogen cooling. Physical parameter measurements, uniaxial compression tests, Brazilian splitting tests, and CERCHAR abrasivity tests were conducted using national standards to investigate the evolution of thermal damage and the effect of cooling path. The results show that the damage degree of granite continuously increases with increasing heating temperature, and the damage induced by liquid nitrogen cooling is greater than that induced by natural cooling. Visible cracks begin to appear on the specimen surface after 300 °C, while crack propagation and structural deterioration become more pronounced at 500–600 °C. Among the measured physical parameters, P-wave velocity is the most sensitive to damage, with a maximum attenuation rate of 60.6%. The deterioration of the physical structure further reduces the load-bearing capacity and deformation performance of granite. After liquid nitrogen cooling at 600 °C, the uniaxial compressive strength, tensile strength, and elastic modulus decrease to 92.6 MPa, 1.42 MPa, and 17.4 GPa, respectively, corresponding to reductions of 56.0%, 87.7%, and 69.3% compared with the untreated specimens. The tensile strength is the most sensitive mechanical parameter to liquid nitrogen cooling. The CERCHAR abrasivity index decreases from 3.81 to 2.12. Liquid nitrogen cooling advances the transition of granite abrasivity from high to medium from 400–500 °C to 300–400 °C. The integrated analysis indicates that the non-uniform temperature field generated by rapid flame-jet heating and the differences in thermal deformation among minerals promote the initiation of initial cracks. The additional shrinkage stress induced by liquid nitrogen cooling further drives crack propagation and coalescence, eventually leading to the coupled reduction in the strength, stiffness, and abrasivity of granite. The results provide laboratory-scale evidence for evaluating granite pre-treatment under rapid flame-jet heating and liquid nitrogen cooling and offer a reference for thermal-assisted mechanical rock breaking and standardized abrasivity reduction. However, the relationship between CAI and actual tool wear still requires further verification. Full article

Laser Powder Bed Fusion (LPBF) has revolutionized high-end manufacturing, particularly in aerospace and biomedical fields. However, internal defects such as pores, cracks, and inclusions compromise the structural integrity and service reliability of LPBF components. Laser ultrasonics, a non-contact, broadband non-destructive testing (NDT) method, offers a promising solution for detecting and characterizing these defects. This study systematically investigated laser ultrasonic testing technology for LPBF-fabricated Ti6Al4V using a combined approach of physics-driven simulation modeling and experimental validation. To accurately model material anisotropy, a finite element model was developed that integrated Voronoi algorithm-generated polycrystalline microstructures with orientation-dependent elastic tensors, providing a comprehensive representation of the material’s microstructural heterogeneity. Simulation results revealed that while sub-100-μm defects yield weak ultrasonic scattering signals, the Synthetic Aperture Focusing Technique (SAFT) markedly improves the detection and imaging performance for such small-scale defects. Experimental validation using a laser ultrasonic system identified a 90 μm internal defect in the LPBF Ti6Al4V specimen, though a 75 μm defect was undetectable. This highlights the need for enhanced sensitivity. A signal processing method combining time-truncation principal component analysis (PCA) with targeted noise reduction and SAFT was proposed to reduce high-frequency noise and improve high-resolution imaging, enhancing defect detection accuracy. This study provides theoretical foundations and technical support for high-precision defect detection in metal additive manufacturing components, with significant implications for quality control in high-end equipment manufacturing. Full article

Prolonged underwater exposure degrades reinforced concrete (RC) structures, causing chloride-induced corrosion, spalling, cracking, and rebar exposure. Timely damage identification is critical for structural safety, but conventional non-destructive testing methods face severe limitations underwater due to restricted accessibility, image degradation, and weak-textured, irregular crack boundaries. Vision-based inspection offers a promising alternative but remains constrained by underwater optical degradation. This study proposes a two-stage detection framework for underwater RC based on YOLOv13 (YOLOv13-TSDD). First, an underwater color-detail enhancement network (UCDEN) performs color correction, detail recovery, and contour reconstruction through multi-channel color enhancement and multi-level feature refinement. Second, two detection modules are introduced: a pinwheel-shaped receptive field convolution (PRFConv), improving sensitivity to directional textures and local linear structural responses in shallow layers, and a crack-aware efficient multi-scale attention (CEMA) mechanism, enabling joint channel-spatial recalibration and multi-scale focus on crack-relevant regions. A fine-grained irregular crack IoU (FID-IoU) loss function is also developed, using auxiliary boundary boxes and piecewise weighted mapping to improve bounding-box regression for irregular cracks. Experimental results demonstrate that YOLOv13-TSDD not only achieves the best overall image enhancement performance among the evaluated methods but also delivers the highest detection performance. On the constructed underwater dataset, YOLOv13-TSDD achieves Precision, Recall, and mAP@0.50 of 93.63%, 88.97%, and 94.52%, respectively, demonstrating improved performance under complex underwater conditions. Full article