Search Results (992)

The post-peak failure and softening mechanisms of surrounding rock in common tunnel, mine shaft, and roadway engineering primarily include radial tensile softening, shear sliding softening, and circumferential compressive–shear softening. Given the distinct post-peak failure and softening mechanisms, the softening coefficient in self-similarity analytical algorithms for stability analysis should differ accordingly. In this paper, to address the limitation of the existing self-similarity numerical algorithms for the deformation and failure of rock surrounding circular excavations—which typically employ only the plastic shear strain as the softening coefficient—we extend the self-similarity numerical algorithm by incorporating two additional softening coefficients: the maximum and minimum plastic principal strain. We validated the extended algorithm’s accuracy and reliability by comparing its stress, displacement, and plastic zone radius predictions with those obtained through numerical simulation and engineering monitoring and examined its sensitivity to step length variations under various softening coefficients and yield criteria. According to the validation and comparison with existing algorithms, the extended algorithm extends the applicability scope of the original self-similarity numerical algorithm and significantly improves the accuracy of the calculated results. Finally, using the extended algorithm, we systematically compared and quantitatively analyzed the stress, deformation, and failure characteristics around a circular excavation across different softening coefficient categories, including their critical values, revealing the influence patterns of the softening coefficients and their critical values on the stability of engineering surrounding rock. Full article

Ultra-high-molecular-weight polyethylene (UHMWPE) thin films are considered promising shielding materials against hypervelocity microparticle impacts in space environments. In this study, a finite element-smoothed particle hydrodynamics (FEM-SPH) adaptive coupling simulation method was developed to reveal the damage mechanisms of UHMWPE films impacted by alumina (Al₂O₃) particles with a diameter of 10 μm. A 100 μm thick single-layer UHMWPE film was subjected to normal impacts at velocities ranging from 1 to 30 km/s. The morphology and characteristics of craters formed on the film surface were analyzed, revealing the velocity-dependent transition from plastic deformation to complete perforation. At 10 km/s, additional oblique impact simulations at 30°, 45°, 60° and 75° were performed to assess the effect of impact angle on damage morphology. Furthermore, the damage evolution in double-layer UHMWPE films was examined under impact velocities of 5, 10, 15, 20 and 25 km/s, showing enhanced protective performance compared to single-layer films. Finally, the critical influence parameters for UHMWPE failure were discussed, providing criteria for evaluating the shielding limits. This work offers computational methods and predictive tools for assessing hypervelocity microparticle impact and contributes to the structural protection design of spacecraft operating in the harsh space environment. Full article

This study investigates the flexural behavior and practical application of Reinforced Concrete (RC) beams strengthened with Ultra-High Performance Concrete (UHPC). Flexural tests were conducted on ten beam specimens to systematically analyze the effects of steel fiber dosage, reinforcement ratio, and beam height on the failure modes, load-bearing capacity, and deformation characteristics of the strengthened beams. The results were compared with those of unstrengthened control beams (CB). Experimental observations indicated excellent interfacial bonding between the UHPC layer and the RC beam, with no debonding failure occurred. All specimens exhibited typical under-reinforced flexural failure characteristics, and their load–deformation curves displayed three distinct stages. Compared to the control beams, the ultimate load-bearing capacities of the strengthened beams increased by 9.5–15.7% with varying steel fiber dosages, 16.4–110.2% with varying reinforcement ratios, and 6.2–518.8% with varying beam heights. Furthermore, the UHPC layer significantly enhanced the flexural stiffness of the beams. Although ductility was slightly reduced, all strengthened beams demonstrated clear yield characteristics prior to failure, avoiding brittle fracture. Additionally, nonlinear numerical simulations performed using MATLAB R2020a showed high agreement with the experimental results, verifying the accuracy of the analytical procedure. Based on the validated model, a parametric study was conducted to further investigate the influence of beam height, reinforcement ratio, and interface coefficients on flexural performance. The findings confirm the reliability and effectiveness of the UHPC strengthening technique. Full article

Polyester yarn bundle geogrids are widely used materials in flexible retaining structures due to their high toughness and high-strength mechanical properties. To investigate the mechanical characteristics and the interfacial mechanical properties of these geogrids, a series of pull-out tests were conducted under different pull-out rates and filling water contents. Based on the test results, a DEM-FDM coupled numerical model for pull-out behavior was established to analyze the pull-out deformation behavior of the geogrids. Combined with the theoretical analysis of the load-bearing characteristics of the geogrids, the reinforcement mechanism of polyester yarn bundle geogrids was revealed. The results show that there exists a critical pull-out rate of 1 mm/min that maximizes the pull-out resistance; the interface friction angle decreases with an increase in pull-out rate, while the interface cohesion shows an opposite trend. The filling water content presents a more significant weakening effect on the soil–geogrid interface strength under low stress, resulting in a strain-softening type of pull-out curve. Unlike fine-ribbed plastic geogrids, the sliding frictional resistance of polyester yarn bundle geogrids accounts for 80% of the total pull-out resistance during the pull-out process. The mechanical interlocking force, which arises from the bulges on the mid-section of transverse ribs and the downward bending of longitudinal rib edges, is subject to dynamic changes in the course of the pull-out process. The geogrid exhibits overall shear failure under low normal stress (${\sigma }_n<$ 200 kPa) and penetration shear failure under high normal stress (${\sigma }_n\ge$ 200 kPa). In practical engineering installation, polyester yarn bundle geogrids should be placed as parallel as possible to maximize the frictional resistance with filled soil and should take care of the geogrid joints for enhanced durability of the geogrids. Full article

To address the difficulty of controlling surrounding rock subjected to repeated repair-induced disturbances, the characteristics of the roadway surrounding rock and its deformation–failure mechanisms were examined. An experimental scheme for surrounding-rock control was formulated, and a three-dimensional numerical model was established. Four support schemes were evaluated to identify a rational support method and corresponding parameters: (a) rock bolts and cable bolts; (b) rock bolts, cable bolts, and floor cable bolts; (c) rock bolts, cable bolts, floor cable bolts, and U-shaped closed steel sets; and (d) rock bolts, cable bolts, floor cable bolts, U-shaped closed steel sets, and grouting. Comparative analyses were conducted in terms of plastic-zone evolution, stress-field distribution, surrounding-rock displacement, and the mechanical response of the support structures. The results indicate that, in roadways experiencing multiple repair disturbances and supported only by rock bolts and cable bolts, distinct stress-concentration zones develop within the supported surrounding rock, suggesting that reliance solely on bolts and cables is unfavorable for effective rock-mass control. Grouting improves the overall integrity and self-bearing capacity of the surrounding rock. Both the U-shaped closed support and the combined U-shaped closed support with grouting effectively restrain surrounding-rock deformation, and the corresponding stress distribution shows no pronounced stress-concentration zones. Based on the analyses of surrounding-rock displacement, support-structure loading, and incremental shear strain, the effectiveness of the support schemes in mitigating roof and floor displacement ranks, in descending order, as (d), (c), (b), and (a). Engineering practice further demonstrates that the combined support system consisting of 29U-type sets, grouted bolts, and bundle-type grouted cable bolts provides effective control over the deformation and failure of the roadway surrounding rock. Full article

Volcanic Scoria Lightweight Aggregate Concrete (VSLAC) has been identified as a material with considerable potential for use in carbon-neutral construction; however, its application is often hindered by two main issues. Firstly, the low density of scoria often results in aggregate segregation and stratification. Secondly, its high hygroscopicity can lead to shrinkage cracking. In order to address the aforementioned issues, this study proposes a multi-scale modification strategy. The cementitious matrix was first strengthened using a binary blend of Fly Ash and Ground Granulated Blast Furnace Slag (GGBS), followed by the incorporation of a ternary admixture system containing Styrene-Acrylic Emulsion (SAE), a foaming agent (FA), and alkali-treated Straw Fibres (SF) to enhance workability and durability. The findings of this study demonstrate that a mineral admixture comprising 10% Fly Ash and 10% GGBS results in a substantial enhancement of matrix compactness, culminating in a 20% increase in compressive strength. An orthogonal test was conducted to identify the optimal formulation (D13), which was found to contain 4% SAE, 0.1% FA, and 5% SF. This formulation yielded a compressive strength of 35.2 MPa, a flexural strength of 7.5 MPa, and reduced water absorption to 8.0%. A comparative analysis was conducted between the mineral admixture mix ratio (Control group) and the Optimal mix ratio (Optimization group). The results of this analysis reveal that the Optimization group exhibited superior durability and thermal characteristics. Specifically, the water penetration depth of the optimized composite was successfully restricted to within 3.18 mm, while its thermal insulation performance demonstrated a significant enhancement of 12.3%. In the context of freeze–thaw cycles, the modified concrete demonstrated notable durability, exhibiting a 51.4% reduction in strength loss and a marginal 0.64% restriction in mass loss. SEM analysis revealed that the interaction between SAE and the FA resulted in the densification of the Interfacial Transition Zone (ITZ). In addition, the 3D network formed by SF redistributed internal stresses, thereby shifting the failure mode from brittle fracture to ductile deformation. The findings demonstrate that modifying VSLAC at both micro- and macro-levels can effectively balance structural integrity with thermal efficiency for sustainable construction applications. Full article

To support intelligent and sustainable mine engineering, this geotechnics-based study integrates laboratory testing, three-dimensional numerical simulation, and field monitoring to optimize roadway support and improve resource efficiency. This study investigates the geotechnical behavior of the surrounding rock in coalmine roadways under single-face unloading conditions, aiming to provide theoretical and practical support for surrounding rock control in underground coal mining. Excavation of the roadway creates a free surface, leading to unloading, which makes timely support crucial for preventing instability. True-triaxial single-face unloading tests and mechanical tests on hole-containing coal specimens show that the coal exhibits four characteristic stages, namely fissure compaction (closure), elastic deformation, yielding, and residual strength. Under a confining stress of 4 MPa, the peak strength of Coal Seam No. 3 in the true-triaxial single-face unloading test reached 32.4 MPa, whereas the peak strength of the hole-containing coal specimen was only 17.1 MPa, and failure occurred as instantaneous global instability with an “X”-shaped conjugate shear pattern. Numerical simulations were conducted to optimize the roadway’s surrounding rock control scheme, indicating that increasing the bolt length increases the proportion of the load carried by the rock bolts while reducing the load borne by the cable bolts. In addition, advance abutment pressure increases the forces in the support system and amplifies deformation of the solid rib, coal-pillar rib, and roof; roadway surface convergence is dominated by floor heave. Full article

Background: Takotsubo cardiomyopathy (TTC) has been historically considered a contraindication for heart donation due to its transient left ventricular dysfunction. However, emerging evidence supports that hearts from donors with fully recovered Takotsubo Cardiomyopathy can be safely transplanted. Methods: This case series describes seven heart transplantations performed between January 2022 and September 2025 using donors with previously diagnosed Takotsubo cardiomyopathy. Donor characteristics, intraoperative data, echocardiography data and postoperative outcomes were analyzed. Results: The mean donor age was 33.5 years (range 18–58), with a male-to-female ratio of 6:1. All donors exhibited echocardiographic evidence of Takotsubo Cardiomyopathy at the time of brain death, with full or partial recovery before procurement. Coronary angiography excluded obstructive coronary disease. Echocardiographic follow-up demonstrated the mean LVEF increased to 52 ± 6%, reaching 58 ± 4% at 12 months, global longitudinal strain (GLS) improved progressively (from −14.2 ± 2.8% to −18.5 ± 1.9%), confirming normalization of myocardial deformation and the right ventricular function, assessed by TAPSE, rose from 15 ± 3 mm at discharge to 20 ± 2 mm at 12 months. All patients transplanted with donors who had Takotsubo cardiomyopathy are alive at the 12-month follow-up. Conclusions: Hearts from donors with resolved Takotsubo Cardiomyopathy can be safely used for transplantation without compromising early- or mid-term outcomes. Expanding donor eligibility criteria to include selected TTC donors may contribute to mitigating organ shortages in advanced heart failure patients. Full article

This study investigates the creep behavior and acoustic emission (AE) characteristics of bedded coal samples under acidic water environments. Uniaxial graded creep tests coupled with AE monitoring were conducted on samples with bedding angles of 0°, 30°, 60°, and 90°, respectively. The anisotropic mechanical behavior and acoustic emission characteristics in terms of stress–strain, deformation, AE count, AE energy, and spectrum characteristics were revealed. The experimental results show that the strength of the coal samples gradually decreases as the saturation duration increases. At the same axial stress level, the axial deformation of the coal samples becomes larger with increasing saturation duration. The mechanical strength exhibits a distinct “U-shaped” relationship with the bedding angle, initially decreasing and then increasing. Correspondingly, axial deformation at a given stress level first increases and then decreases as the bedding angle increases. AE activity, particularly the AE ring count and energy, peaks at specimen failure, indicating significant fracture development. Spectral analysis revealed that under conditions of severe strength degradation (e.g., 0° bedding after 60-day saturation or 60° bedding after 30-day saturation), high-frequency, high-amplitude AE signals were absent. This suggests a shift in the dominant fracture mechanism from small-scale cracking to larger-scale fracture propagation in weakened samples. These findings offer valuable theoretical insights for the prevention and early warning of coal mine disasters. Full article

Background/Objectives: Adult spinal deformity (ASD) management often requires pelvic fixation, with S2 alar–iliac (S2AI) screws emerging as an alternative to traditional iliac screws. Despite multiple meta-analyses comparing these techniques, the methodological quality of these syntheses and technical heterogeneity across primary studies significantly impact their conclusions and subsequent clinical decision-making. This systematic review evaluates the evidence quality of meta-analyses comparing S2AI with traditional iliac screws for ASD management, focusing on methodological rigor, primary study overlap, and clinical heterogeneity. Methods: PubMed, Cochrane, and Epistemonikos were searched for meta-analyses comparing S2AI with iliac screws for patients with ASD. The Quality of Reporting of Meta-analyses (QUOROM) checklist and the revised Assessment of Multiple Systematic Reviews (AMSTAR 2) tool were adopted to assess the methodological quality. Primary study overlap was evaluated using the Corrected Covered Area (CCA) method. Clinical heterogeneity was assessed by examining characteristics of studies included in ≥67% of meta-analyses. Results: From a total of 29 publications, six meta-analyses met the inclusion criteria (4807 patients; mean age: 59 years; 33% female). All included meta-analyses exhibited critically low methodological quality per AMSTAR-2, with common flaws including failure to provide lists of excluded studies and lack of a priori protocols. Very high primary study overlap was observed (CCA: 31%), with only 11% (2 of 19) primary studies included in all meta-analyses, whereas 42% (8 of 19) primary studies were included by only a single meta-analysis. Substantial clinical heterogeneity existed regarding patient characteristics, surgical techniques, and outcome definitions. Conclusions: This systematic review of meta-analyses identified critically low methodological quality, high primary study overlap, and substantial clinical heterogeneity in the existing evidence comparing pelvic fixation techniques for ASD. While published meta-analyses generally favor S2AI screws, these significant limitations prevent drawing definitive conclusions about superiority. Future research should prioritize high-quality prospective studies with standardized reporting to generate more reliable evidence for improving surgical outcomes in ASD management. Full article

To evaluate the stability of fiber-reinforced cemented foamed backfill (FCFB) in complex underground mining environments, this study investigates the synergistic effects of fiber content and modified coal gangue (MCG) under acidic and high-temperature conditions. Through a systematic analysis of hydration processes, compressive strength, and deformation characteristics, the research identifies critical mechanisms for optimizing backfill performance. Calcination of MCG at 700 °C enhances gelling activity via amorphous phase formation, while modified aluminum dross (MAD) treated at 950 °C develops dense α-Al₂O₃ and spinel phases, significantly improving chemical stability. In acidic environments, the suppression of calcium silicate hydrate (C-S-H) is offset by the development of Al³⁺-driven C-A-S-H gels. These gels adopt a tobermorite-like structure, substantially increasing acid resistance. Mechanical testing reveals that while 1% fiber reinforcement promotes nucleation and densification, a 2% concentration hinders hydration. Compressive strength at 28 days shows constrained growth due to pore inhibition, and failure modes transition from multi-crack parallel failure (3-day) to single-crack tensile-shear failure. Under acidic conditions, strain concentration in the upper sample highlights a competitive mechanism between Al³⁺ migration and fiber anchorage. Ultimately, the coordinated regulation of MCG/MAD and fiber content provides a robust solution for roof support in challenging thermo-chemical mining environments. Full article

The Yutian region at the southwestern termination of the Altyn Tagh Fault has experienced four moderate-to-strong earthquakes since 2008, providing an opportunity to investigate fault interactions within a transtensional tectonic setting. In this study, we derive the coseismic deformation and slip model of the 2020 Mw 6.3 Yutian earthquake using ascending and descending Sentinel-1 InSAR data. The deformation field exhibits a characteristic subsidence–uplift pattern consistent with normal faulting, and the preferred slip model indicates a north–south-striking fault with slip concentrated at depths of 6–9 km. To place this event in a broader tectonic context, we incorporate published slip models for the 2008 and 2014 earthquakes together with a simplified finite-fault model for the 2012 event to construct a unified four-event source framework. Static Coulomb stress calculations reveal complex interactions among the four earthquakes. Localized positive loading from the 2012 event partially counteracts the negative $\Delta CFS$ imposed by the 2008 and 2014 earthquakes, reshaping the stress field rather than simply promoting or inhibiting failure. The cumulative stress evolution shows persistent unclamping and repeated shear-stress reversals, indicating that the 2020 earthquake resulted from long-term extensional loading superimposed on multi-stage coseismic stress redistribution. These results demonstrate that multi-event stress analysis provides a more reliable framework for assessing seismic hazards in regions with complex local stress fields. Full article

This study investigated the use of Marine Recyclable Aggregate (MRA), synthesized from Recycled Particles from Paste (RPPs) obtained from construction waste, seawater, and alkali activator (Na₂O∙3.3SiO₂, NS), for reinforcing marine soft clay. RPP is a laboratory-prepared material used to simulate construction waste. The physicochemical properties of MRA were characterized using X-ray diffraction (XRD), thermal field emission scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and thermogravimetric analysis (TGA). The results revealed that the key hydration products in MRA are Friedel’s salt (3CaO·Al₂O₃·CaCl₂·10H₂O, FS), xCaO·SiO₂·nH₂O (C-S-H), and CaO·Al₂O₃·2SiO₂·4H₂O (C-A-S-H). The formation of these hydration products enables MRA to maintain stability in marine environments. The deformation characteristics of MRA-reinforced soft clay under various conditions were investigated by integrating X-ray computed tomography with triaxial compression tests, allowing for the three-dimensional visualization and reconstruction of the failure process. The application of MRA for soft clay reinforcement in seawater environments enhances the bearing capacity of the clay and provided significant environmental benefits. Full article

High rock slopes are extensively distributed in areas of major engineering constructions, such as transportation infrastructure, hydraulic projects, and mining operations. The stability and failure evolution mechanism during their multi-stage excavation process have consistently been a crucial research topic in geotechnical engineering. In this paper, a series of two-dimensional rock slope models, incorporating various combinations of slope height and slope angle, were established utilizing the Discrete Element Method (DEM) software PFC2D. This systematic investigation delves into the meso-mechanical response of the slopes during multi-stage excavation. The Parallel Bond Model (PBM) was employed to simulate the contact and fracture behavior between particles. Parameter calibration was performed to ensure that the simulation results align with the actual mechanical properties of the rock mass. The research primarily focuses on analyzing the evolution of displacement, the failure modes, and the changing characteristics of the force chain structure under different geometric conditions. The results indicate that as both the slope height and slope angle increase, the inter-particle deformation of the slope intensifies significantly, and the shear band progressively extends deeper into the slope mass. The failure mode transitions from shallow localized sliding to deep-seated overall failure. Prior to instability, the force chain system exhibits an evolutionary pattern characterized by “bundling–reconfiguration–fracturing,” serving as a critical indicator for characterizing the micro-scale failure mechanism of the slope body. Full article

This paper presents an experimental and numerical investigation of continuous reinforced concrete (RC) beams made of self-compacting concrete (SCC) strengthened with fiber-reinforced polymer (FRP) bars using the Near-Surface Mounted (NSM) method. While the majority of previous studies have focused on simply supported beams, this work examines two-span continuous beams, which are more representative of real structural behavior. Four SCC beams were tested under static loading to evaluate the influence of the FRP reinforcement position on flexural capacity and deformational characteristics. The beams were strengthened using glass FRP (GFRP) bars embedded in epoxy adhesive within pre-cut grooves in the concrete cover. Experimental results showed that FRP reinforcement significantly increased the ultimate load capacity, while excessive reinforcement reduced ductility, leading to a more brittle failure mode. A three-dimensional finite element model was developed in Abaqus/Standard using the Concrete Damage Plasticity (CDP) model to simulate the nonlinear behavior of concrete and the bond–slip interaction at the epoxy–concrete interface. The numerical predictions closely matched the experimental load–deflection responses, with a maximum deviation of less than 3%. The validated model provides a reliable tool for parametric analysis and can serve as a reference for optimizing the design of continuous SCC beams strengthened by the NSM FRP method. Full article