Search Results (127)

To investigate the impact of localized failure in the support structure on the overall safety performance of the excavation pit and the mechanism of subsequent chain failure, model tests were conducted on the failure of internal bracing in an asymmetrically excavated pit. Unlike previous progressive-collapse model tests, which have addressed symmetric excavations only, the present test captures the cross-pit load-transfer mechanisms that arise when the two sides of a pit are excavated to different depths. The crown displacement of the retaining structure, the earth pressure, and the redistribution of internal forces caused by the failure of internal support members were measured. The results show that when an internal support fails, the lateral stiffness of the retaining plate decreases and the plate moves inward toward the pit, causing settlement of the surrounding soil. The horizontal displacement on the deep-excavation side is larger than that on the shallow side. Failure of one support increases the axial force in the adjacent support while reducing the force in supports farther away. The earth pressure increases in regions far from the failed support, owing to the soil arching effect, but decreases in the adjacent region because the large lateral movement of the plate unloads the soil. Within the failed-support region, the retaining piles are more prone to bending failure on the shallow-excavation side. Full article

Gas-assisted discharge of granular materials plays a critical role in shaft furnaces, moving-bed reactors, and other industrial multiphase systems, where interstitial gas flow strongly influences arch stability and may induce progressive flow blockage. Existing analytical models generally neglect aerodynamic gas–particle interactions, whereas CFD–DEM simulations provide high predictive accuracy at the expense of substantial computational cost. To bridge this gap, the present study develops and validates a physically based Torque-Balance Model for predicting gas-assisted granular discharge, arch stability, and flow blockage. A comprehensive experimental investigation was performed using a quasi-two-dimensional transparent apparatus and a thermally stabilized shaft model operated under controlled conditions. Gas-assisted discharge was examined for different gas-flow directions, gas properties, outlet geometries, and particulate materials using hydrogen, helium, and air. High-speed imaging together with gravimetric measurements enabled detailed characterization of discharge regimes and arch evolution. The proposed analytical framework explicitly incorporates interparticle mechanical interactions, aerodynamic drag, outlet geometry, and gas-pressure effects within a unified torque-balance formulation. The model describes successive stages of the discharge process, including stable discharge, transition to blockage, and complete flow suppression, while maintaining computational efficiency suitable for engineering calculations. Experimental results demonstrated that gas-flow direction governs arch stability and discharge behavior. Co-current gas flow promoted repeated arch collapse and enhanced discharge, whereas counter-current flow progressively stabilized the granular arch and ultimately produced complete flow blockage. Validation against the complete experimental database demonstrated excellent agreement between theoretical predictions and experimental observations, yielding an average prediction error below 10%, a maximum deviation within ±20%, and a coefficient of determination of R² = 0.96. The proposed Torque-Balance Model provides a computationally efficient and physically interpretable engineering framework that bridges the gap between simplified empirical correlations and computationally intensive CFD–DEM simulations and can be applied to the prediction and optimization of gas-assisted granular discharge in industrial multiphase systems. Full article

Background: Orthodontic retreatment patients with a history of premolar extraction for Angle Class II malocclusion exhibit distinct dental arch morphologies; however, studies characterizing these features remain limited. This pilot study aimed to objectively assess baseline dental arch morphology and preliminary retreatment-related changes in this specific patient population. Methods: In this retrospective pilot investigation, a total of 21 subjects were consecutively enrolled and divided into two groups according to orthodontic history: the Retreatment Group (n = 9, patients with Class II malocclusion and a history of prior orthodontics with four-premolar extractions) and the Control Group (n = 12, first-time orthodontic patients with Class II malocclusion undergoing identical four-premolar extraction therapy during the current treatment). All participants were treated with a standardized 0.022-inch MBT self-ligating system. Pre-treatment (T0) and post-treatment (T1) CBCT data were analyzed to evaluate the following variables: intercanine width, interpremolar width (IPMW), intermolar width (IMW), anterior arch depth, total arch depth, arch perimeter, intercanine angle, mesiodistal angulation (MA), buccolingual inclination (BI), depth of the curve of Spee, overbite, and overjet. Arch width was designated as the primary outcome. Student’s t-tests were used for statistical analysis (α = 0.05). Results: At T0, the Retreatment Group had narrower posterior arches than the controls (p < 0.01; Hedges’ g = 1.55–1.94), with IPMW smaller by 4.9 ± 1.11 mm (maxillary) and 5.37 ± 1.25 mm (mandibular), and IMW smaller by 4.85 ± 1.06 mm (maxillary) and 4.17 ± 1.13 mm (mandibular). They also had greater overbite and overjet, greater maxillary anterior depth, smaller intercanine angle, and lower incisor BI and canine MA (p < 0.05). From T0 to T1, the main treatment changes included arch width expansion and adjustments in MA and BI. At T1, most parameters were similar between groups, but mandibular IPMW remained narrower in the Retreatment Group (p < 0.01). Conclusions: The Retreatment Group showed a distinct “arch collapse” pattern characterized by posterior constriction, increased overbite and overjet, an elongated and tapered arch, and abnormal incisor torque and canine angulation. Orthodontic retreatment corrected most of these features, but mandibular IPMW correction remained limited. Full article

The underground powerhouse of a hydropower station in Northwest China features a large height-to-span ratio and complex geological conditions, posing critical challenges for surrounding rock stability. This study employs a systematic framework of “parameter inversion–stability analysis–support optimization”. The main contributions are: (1) A forward-backward analysis method integrating monitoring data, numerical calculation, and parameter optimization was used to invert the physical and mechanical parameters of the surrounding rock, establishing a practice-consistent numerical model. (2) Considering complex geological conditions from a prior collapse, systematic analyses of deformation characteristics, stress distribution, and overall stability during subsequent bench excavation were conducted, revealing evolutionary patterns of deformation, reproducing the collapse mechanism, and evaluating rock mass safety. (3) An optimized reinforcement scheme was proposed, involving additional anchor cables at arch shoulders and two anchor bolts on each sidewall (Sidewalls 2), with comparative analysis confirming its feasibility. Key findings: (i) Based on the inversion of monitoring data, the obtained physical and mechanical parameters of the surrounding rock can effectively reflect the actual characteristics of the rock mass and align with monitoring trends. (ii) Stability analysis of subsequent layered excavation, accounting for prior collapse impacts, shows that while deformation at key points continued to increase, it remained below critical thresholds, maintaining overall stability—prestressed anchor cables significantly controlled deformation. (iii) The optimized support scheme yields comparatively favorable outcomes with respect to the containment of surrounding rock displacement and the internal forces within the supporting. These outcomes provide valuable references for the design and construction of similar underground powerhouses. Full article

Affected by moisture cohesion, wet rice seeds exhibit poor flowability and frequent arching blockage during silo discharging, which seriously restricts stable grain storage and conveying. To address this issue and reveal its intrinsic flow mechanism, this study establishes a discrete element method (DEM) model for wet rice seed-silo systems adopting the Hertz-Mindlin with Johnson-Kendall-Roberts (JKR) contact model, which incorporates surface energy to reflect moisture-induced cohesive effects. The model is verified via physical silo discharge tests, with consistent flow patterns, wall pressure error below 3.7% and discharge time error of 2.14%. EDEM parametric simulations are conducted to analyze velocity fluctuation at different silo heights. Coordination number and normalized contact force distribution are adopted to assess micro-contact force distribution in discharge areas, and a force chain extraction algorithm is used to explore variations in force chain length and orientation. Results demonstrate that during discharge, average particle velocity drops from silo bottom to top with growing fluctuation amplitude, presenting obvious stratified flow and intense upper-layer velocity pulsation. Weak contacts dominate wet rice seed groups and conform to exponential decay distribution. The force chain network undergoes three evolution phases: formation, force arch generation and collapse. Quantitative analysis reveals long force chain proportion falls steadily from 81.40% to 3.68% throughout discharge. Short force chains rise to 60.54% in the arch-forming stage and reach 96.32% after arch collapse. Horizontal force chains account for a maximum of 71.09% during arch formation, while vertical ones decline from 99.52% initially to 61.57% post collapse. This research offers mechanical references and quantitative parameters for the design and operation of silos for wet granular farm grains like rice seeds, and is particularly relevant to post-harvest engineering, grain storage safety, and agricultural machinery design. Full article

Reliable discharge of bulk granular materials is essential for the efficient operation of shaft furnaces, pneumatic conveying systems, and industrial dosing equipment, where uncontrolled arch formation can lead to flow instability and blockage. This study investigates the effect of gas velocity, direction, and configuration on arch formation and collapse during bulk granular material discharge through horizontal orifices. Experiments were conducted using cold quasi-2D (250 × 50 × 5 mm) and hot scale models (cylindrical shaft, D = 300 mm, H = 500 mm) with high-speed imaging (2000 fps, 1280 × 1024) across various materials. Uniform gas flow stabilizes arches, reducing the normalized mass flow rate $W_t/W_0$ to 0.20 ± 0.03 at critical gas velocity ratios $V_1/V_2\le 20$ and area ratios $L_1/L_2\ge 0.37.$ Conversely, localized gas jets increase $W_t/W_0$ to 1.45 ± 0.05. The scientific novelty lies in the development of a unified torque-balance model that, for the first time, predicts critical counter-current gas velocities $V_{kr}$ across different operating configurations with an error not exceeding ±28.9% (n = 3, p < 0.05). Three characteristic discharge regimes—continuous flow, pulsating discharge, and blockage-dominated flow—were identified and related to the stability of dynamically unstable arch structures. These findings provide a quantitative basis for the design and optimization of industrial systems such as shaft furnaces, pneumatic conveyors, and dosing units. Future work will focus on industrial-scale validation, extension to humid or cohesive materials, and investigation of more complex flow geometries to further improve gas-assisted flow control. Full article

Localized failures of structural components can lead to serious social, economic, and environmental consequences, such as the collapse of an entire structure or part of it. Therefore, it is important to thoroughly investigate and justify the acceptance criteria for these components, taking into account their performance in extreme conditions. However, the scientific literature lacks a systematic analysis of how various factors can affect the resistance of structures and influence acceptance criteria under extreme conditions. Therefore, this study investigates the typical substructures of reinforced concrete frame buildings in areas that are potentially prone to local collapse. To assess their resistance and structural robustness, an analytical model has been developed. The results of 22 tests on typical substructures of monolithic and precast frames, reported in various research studies, were used to validate this model. Further, this analytical model was used to conduct a parametric study on the impact of various factors on the performance of substructures under extreme conditions. These factors included the depth-to-span ratio of the beam, the strength of the bond between the steel reinforcement and the concrete, the stiffness of the horizontal bracing within the substructure, and the proportion of the effective depth to the total depth of the beam section. It has been found that the ultimate rotation angle in the plastic hinge of beams increases as the ratio of the beam’s cross-sectional depth to the span increases. An increase in the bond strength between the reinforcement and concrete leads to a decrease in the ultimate rotation angles in the plastic hinge at the flexural and arch stages of resistance and, in some cases, to reinforcement rupture without transitioning to the catenary stage of resistance. A decrease in the ratio of the effective depth of the beam section to its overall depth leads to an increase in the load-bearing capacity at the catenary stage of 19%. Full article

Türkiye has many historically rich cities that host structures of significant cultural value. These structures, especially masonry bridges, reflect the construction techniques and materials of the periods in which they were built. However, studies on the origins of these bridges and the structural deteriorations that develop over time are limited. This situation may lead to damage and even the risk of collapse if necessary precautions are not taken. In this study, stone and mortar samples were first collected from the historic Pamukçular (Şifalısu) Bridge in Bitlis, and the collected materials were analyzed. The structural behavior of the bridge under seismic effects was then investigated using the Finite Element Method (FEM). A three-dimensional geometric model of the bridge was created, and material parameters were defined based on values from the material analyses. Static analysis under self-weight and modal analysis were performed in the ABAQUS software (Version 6.14) to obtain the natural frequencies. Under the bridge’s self-weight, local stress concentrations were concentrated at the arch crown and pier-arch connections, with maximum tensile and compressive stresses reaching approximately 0.15 MPa and 0.27 MPa, respectively. These low stress levels demonstrate that the structure remains fully stable under static loading conditions. Finally, dynamic analyses in the time domain were carried out. In these analyses, records from the 2011 Van Earthquake and the 2023 Kahramanmaraş Earthquake were used to identify the bridge’s critical regions and evaluate its seismic performance. The results indicate that the overall structural stability is adequate; however, local stress concentrations occur in the arch crown and pier connection regions. The study provides engineering-based recommendations for preserving and strengthening historic masonry bridges. Full article

To address the issues of severe goaf collapse, difficulties in secondary extraction, and insufficient pillar stability encountered during the mining of high stopes north of Line 60 at the Dongguashan Copper Mine, this paper takes these high stopes as the research object. Based on an analysis of the engineering geological conditions, goaf failure characteristics, and current mining status in this area, a study on pillar stability and the mechanical behavior of combined mining is conducted. Given the susceptibility of pillars with high aspect ratios to bending instability, the secondary extraction pillar is simplified as a rod with fixed ends. A mechanical model for the triangular pillar’s stability is established, the critical instability equation is derived, and the influence of the reserved width on the pillar’s critical stress and safety factor is analyzed. Subsequently, based on the critical instability equation, the relationship between the reserved pillar width and critical stress is obtained to optimize the pillar dimensions. Simultaneously, to mitigate the adverse effects of primary stope collapse on secondary extraction, optimized schemes such as three-stope combined mining and two-stope combined mining are proposed. A mechanical model for combined mining is established based on the Protodyakonov’s arch theory to analyze the stress distribution characteristics of the surrounding rock in the goaf under different mining schemes. The calculated stress of the original rectangular pillar is 29.01 MPa. When the reserved width exceeds 4 m, the pillar safety factor becomes greater than 1.6, satisfying the stability requirement. In addition, three combined mining schemes were compared using Protodyakonov’s arch theory. The goaf spans of the three schemes are 40 m, 26.6 m, and 36 m, respectively. The results indicate that the two-stope combined mining scheme transfers the main roof load to the adjacent ore body and backfill, reducing the load borne by the barrier pillar and providing a better balance between safety and production efficiency. The proposed framework, integrating field goaf detection, pillar buckling analysis, reserved-width optimization, and combined mining comparison, provides a practical method for the stability control and secondary recovery of deep high stopes. Full article

Masonry arch bridges are critical assets in aging transportation networks, yet their Structural Health Monitoring (SHM) remains challenging. Smart bricks—piezoresistive sensing units compatible with masonry structures and capable of acting simultaneously as load-bearing components and strain sensors—offer a promising solution for embedding self-sensing capability directly within the masonry. While previous work by the authors has investigated their use in masonry walls, their application to arched structures remains unexplored. This gap is particularly significant given that arches, characterized by a predominantly compressive stress state, represent a natural context for smart-brick implementation. This study presents a numerical investigation assessing the potential of smart bricks for strain-based SHM of masonry arch bridges. A Finite Element (FE) model, derived from a validated experimental benchmark representative of typical Italian railway arch bridges, was used to virtually embed smart bricks at selected cross-sections along the arch. Damage progression was simulated through cyclic loading–unloading stages, enabling direct correlation between strain evolution and structural deterioration. Results demonstrate that smart bricks accurately capture damage-driven strain redistributions, closely mirroring both the sequence of damage formation and the associated collapse mechanism. These findings support the use of smart bricks for early detection of localized structural changes in masonry arches, providing a foundation for future experimental validation and real-world deployment of minimally invasive SHM systems. Full article

Flatfeet involve a collapse of the medial longitudinal arch, hindfoot valgus, and forefoot abduction. Flexible flatfoot is the most common type and can often be corrected with physiotherapy or orthotics. While some individuals remain asymptomatic, others develop symptoms for reasons that are not fully understood. This cross-sectional study compared plantar pressure distributions in 16 adults with asymptomatic and 16 with symptomatic flexible flatfeet (FPI-6 > 6; navicular drop > 5 mm), using a resistive-sensor-equipped pressure plate during walking and heel-strike running. During walking, symptomatic participants showed significantly higher total and peak forces at metatarsal 5 (p ≤ 0.003), and the midfoot (p ≤ 0.02146). The medial heel had significantly lower peak force (p = 0.00147), and metatarsal 4 showed higher peak force (p = 0.02539). Force ratios indicated a more lateralized pressure distribution in the symptomatic group. During heel-strike running, the symptomatic group exhibited higher total and peak forces at the fifth metatarsal, the midfoot, and the first metatarsal, with shorter time to peak force in the midfoot and the medial part of the heel. No significant ratio differences were found during running. Symptomatic individuals adopted a lateralized pressure distribution pattern, contrasting the traditional expectation of medial overload in flatfoot conditions. Full article

Background: Flatfoot is a condition brought on by trauma, persistent foot stress, obesity, and poor biomechanics. These factors result in the development of a flat foot, collapse of the foot arch, and malfunction of the posterior tibial tendon. This study aimed to assess the immediate effects of Kinesio Tape on static plantar foot pressure and force in young females with flexible flatfoot. Methods: A pilot study (pre-experimental study design) with a convenience sample of 20 female subjects from a university with flexible flatfoot (age = 20.1 ± 1.3 years, weight = 91.8 ± 14.4 kg, height = 162.2 ± 6.3 cm, BMI = 34.9 ± 5, foot posture index (FPI) = 8.8 ± 2.1) was selected. The TekScan MatScan^® system was used to measure the static plantar forces and pressures, foot contact area, and the mediolateral displacement of COF over time while standing (Boston, MA, USA) before and immediately after the application of Kinesio Tape (KT). Results: While there were no statistically significant changes in the foot peak or total pressure, paired-sample t-tests showed a statistically significant reduction in foot contact area (p < 0.05) and a statistically significant increase in midfoot maximum force (p < 0.05) following the application of KT. Furthermore, after applying KT, there was a statistically significant decrease in the mediolateral COF velocity, indicating greater lateral displacement of COF (p < 0.05). Conclusions: The results of this study concluded that Kinesio Tape was a useful intervention method for immediately redistributing pressure and forces in young females with flexible flat feet. Full article

Achieving lightweight representations of building mesh models with accurate geometry and fine structural details is a key challenge in urban 3D modelling. Most existing mesh simplification methods focus on minimizing geometric error while neglecting the specific characteristics of building models in terms of geometric structure and semantic hierarchy, thus leading to structural degradation and semantic inconsistencies. To address this issue, this paper proposes a structure–semantic dual-constrained edge-collapse decimation method for simplifying dense building mesh models reconstructed from point clouds. Our core innovation lies in the joint enforcement of geometric structural constraints and building semantic constraints to effectively preserve both geometric structural features and component-level semantic structures of the models. By incorporating these two constraints, we adaptively assign higher collapse penalties to key structural edges and semantic boundaries, achieving lightweight building model simplification while maintaining fine-level structural details even under high compression ratios. Our method is extensively validated on several datasets of varying scales and complexities, including single-building models from Sketchfab, the large-scale urban datasets SUM and STPLS3D, and the ArCH cultural heritage dataset. Experimental results demonstrate that our method achieves superior or comparable performance compared to the existing methods across all the test datasets, consistently achieving lower or on-par geometric errors measured by RMSE and MAE. Furthermore, our simplified results can be semantically organized and stored under the CityGML paradigm, which provides a unified data support for sharing, semantic retrieval, downstream analysis, and other applications of lightweight building models. Full article

Objectives: To investigate the association between calcaneal bump height and hindfoot radiographic parameters on weight-bearing lateral radiographs in adult males with Progressive Collapsing Foot Deformity (PCFD), and to determine whether posterior calcaneal morphology differs between feet with and without PCFD-related flatfoot alignment. Materials: We retrospectively reviewed 583 men (1166 feet), aged 17–46 years, who underwent standing weight-bearing lateral foot radiographs between 1 January 2024 and 31 August 2025. Radiographic measurements included calcaneal pitch, Meary’s angle, navicular height, tibiocalcaneal angle, Böhler’s angle, Fowler–Philip angle, calcaneal bump height, and additional calcaneal morphological indices. A flatfoot alignment consistent with PCFD was defined as a calcaneal pitch < 18°. Receiver operating characteristic (ROC) analysis and multivariable logistic regression were performed to assess diagnostic performance and identify parameters independently associated with flatfoot alignment. Results: Flatfoot alignment was identified in 232 feet (19.9%) from 153 patients (26.2%). Compared with normally aligned feet, the flatfoot group demonstrated significantly lower navicular height, calcaneal bump height, and Böhler’s angle, along with higher tibiocalcaneal and Meary’s angles (all p < 0.001). ROC analysis showed navicular height to be the most accurate diagnostic parameter (AUC = 0.75), followed by the tibiocalcaneal angle (AUC = 0.69). Multivariable logistic regression revealed that navicular height ≤ 52.7 mm, tibiocalcaneal angle > 64.6°, Böhler’s angle ≤ 32.9°, Meary’s angle > 4.9°, calcaneal bump height ≤ 3.9 mm, and Fowler–Philip angle > 61.1° were independently associated with flatfoot alignment (Nagelkerke R² = 0.293, p < 0.001). Conclusions: Calcaneal bump height is reduced in PCFD and reflects posterior calcaneal remodelling associated with hindfoot malalignment and medial arch collapse. Although not a primary diagnostic parameter, calcaneal bump height provides complementary morphological information that may inform surgical planning and osteotomy strategy aimed at restoring physiologic hindfoot biomechanics and Achilles tendon loading in patients with PCFD. Full article

Karst soil caves are prone to induce insufficient bearing capacity and excessive settlement of engineering foundations, which in turn trigger sudden ground surface collapse. In this study, multi-stage cyclic loads were designed to simulate traffic loads, and model tests were conducted to measure and analyze the variation laws of foundation settlement, peak vertical earth pressure within the foundation, and reinforcement strain at different positions under cyclic dynamic loading. The results show that the following: ① under cyclic dynamic loading, the collapse of soil caves significantly reduces the bearing capacity of reinforced foundations with an influence range of up to 3B; ② affected by karst soil caves, reinforced foundations only experience a short elastic compaction stage under cyclic loading, followed by rapid deformation until failure; ③ a critical value exists in the earth pressure distribution at a distance of 1B–2B from the soil cave to the foundation center, which governs the abrupt pressure drop behavior in the collapse zone; ④ under the same level of cyclic loading, the height and number of soil arches are independent of the number of loading cycles, and the soil arching effect exerts the most significant influence on the bearing capacity of reinforced foundations at the initial stage of loading application. Full article