Search Results (655)

In mechanical material evaluation and biomechanical studies, Young’s modulus is commonly used to describe the elastic response of materials. Existing measurement approaches are mainly based on contact loading or large-scale experimental instruments, which may limit excitation controllability and system integration in practical applications. In this work, a Young’s modulus measurement system based on electromagnetic excitation and capacitive sensing is designed and experimentally implemented. The system is composed of an electromagnetic driving unit and a capacitive sensing unit. In the driving unit, a coaxial copper wire coil is arranged with a ring-shaped neodymium–iron–boron permanent magnet assembly. When a square-wave electrical signal is applied, the coil generates a Lorentz force, which produces transient mechanical excitation on the tested sample. The resulting micro-scale deformation of the material surface is monitored using a coaxial passive capacitive sensor. The sensor records the relative capacitance variation (ΔC/C₀) induced by deformation during excitation. Based on the measured capacitance response, a force–capacitance coupling model is established to relate the electrical signal to the mechanical behavior of the material, enabling the inverse calculation of Young’s modulus. Commercial standard hardness blocks were used for system calibration and performance verification. The experimentally obtained Young’s modulus values are consistent with reference data within an acceptable deviation range, indicating that the proposed system can be used for quantitative evaluation of elastic properties. Due to its compact configuration and controllable excitation, the system is suitable for non-invasive surface mechanical characterization of soft materials, including biological tissues. Full article

The multi-cycle high-rate injection and production operations in Underground Gas Storage (UGS) facilities converted from depleted fracture-pore carbonate gas reservoirs induce complex rock–fluid interactions that threaten long-term integrity and performance. This study experimentally investigates the petrophysical responses of the Xiangguosi (XGS) UGS carbonate reservoirs in China using multi-cycle stress sensitivity tests, fines migration experiments, and water evaporation–salt precipitation analyses. SEM observations distinguish the contributions of crack closure and matrix compression to permeability evolution. Results show a sharp contrast in mechanical damage: high-quality rocks present negligible permanent deformation (<8% Young’s modulus reduction), whereas poor-quality rocks suffer catastrophic deterioration (>60%). Fines migration exhibits a three-stage behavior under cyclic flow, with water saturation significantly aggravating permeability impairment. A critical salinity threshold (220,000 ppm) is identified for the transition between drying-enhanced storage and salt plugging. Permeability declines sharply despite a slight porosity increase due to selective salt clogging of key pore throats, revealing a clear porosity–permeability decoupling. Salt deposition under movable water conditions can reduce UGS capacity by up to 1.45%. Reservoir heterogeneity, microfractures, karst structures, and initial petrophysical properties dominate the storage and flow space evolution. This work provides a predictive framework for optimizing injection–production strategies and improving the performance of complex carbonate UGS. Full article

Under long-term cyclic loading, the cumulative plastic deformation of unsaturated sandy subgrade is a key control factor for the pavement’s service performance. However, its evolution mechanism and quantitative characterization still lack a universal model. In this study, based on the GDS dynamic triaxial system, a series of cyclic tests were conducted under different conditions: matric suction from 0 to 90 kPa, net confining pressure from 30 to 120 kPa, dynamic stress amplitude from 60 to 240 kPa, and compaction degrees of 87–96%, reaching a total of 10,000 cycles. The results reveal that the permanent deformation of unsaturated sandy subgrade material evolves through three stages: fast, slow, and stable. The deformation is exponentially negatively correlated with matric suction, net confining pressure, and compaction degree, and exponentially positively correlated with dynamic stress amplitude. A coupling prediction model was developed by embedding matric suction and compaction degree factors into the Karg model. This model incorporates net confining pressure, dynamic stress amplitude, matric suction, and compaction degree. By using a normalized master curve method, the permanent deformation curves under different working conditions were compressed into a unique dimensionless function. The parameters have clear physical significance and allow for a unified description across stress, suction, state, and soil types. Experimental data, along with data from the literature, were used to validate the model, showing prediction errors of less than 10% and R² > 0.95. The model provides a simple, high-precision, and transferable theoretical tool for long-service-life subgrade deformation control. Full article

This study investigates the synergistic effects of combining polyphosphoric acid (PPA) and styrene–butadiene–styrene (SBS) as modifiers in asphalt binders to enhance their performance. The research focuses on optimizing the concentrations of PPA and SBS to improve the resistance to permanent deformation, cracking at intermediate and low temperatures, and resistance to aging. A series of empirical and rheological tests, including penetration, softening point, elastic recovery, dynamic shear rheometer (DSR), multiple stress creep recovery (MSCR), and bending beam rheometer (BBR), were conducted to evaluate the rheological and engineering properties of the modified binders. The results indicate that PPA can partially replace SBS, offering comparable improvements in high-temperature performance and creep resistance. The MSCR test revealed a statistically significant synergistic effect between PPA and SBS, resulting in improved recovery and reduced non-recoverable compliance. However, PPA alone shows limited effectiveness at low temperatures and in properties that are governed by elastic response. This study highlights the potential for optimizing asphalt modifiers by leveraging the complementary properties of PPA and SBS in hybrid systems, particularly regarding high-temperature properties and dynamic loading. Full article

In this study, an L₁₆(4³) orthogonal experimental design was employed to optimize the preparation process of rubber-modified asphalt, and a series of rheological tests were conducted using a dynamic shear rheometer to systematically investigate the compatibility mechanisms among the four components: base asphalt and rubber particles. The results indicate that process parameters exert varying degrees of influence on performance. The optimal combination determined was: base bitumen temperature of 170 °C, shear rate of 4000 r/min, and shear time of 40 min, followed by isothermal curing at 170 °C for 60 min. Rheological analysis indicates that resin and asphalt are the key components determining the high-temperature rheological properties of rubber-modified asphalt; notably, L74, which has the highest asphalt content, exhibits excellent high-temperature performance. Grey correlation analysis shows that the correlation coefficient between resin content and creep recovery capacity is 0.82, while the correlation coefficient between asphalt content and resistance to permanent deformation is 0.86. Furthermore, the goodness-of-fit value of the multiple regression model exceeded 0.99, further confirming the reliability of the research results. This study provides a precise characterization of compatibility, thereby offering a theoretical foundation and technical support for material selection and process control in the application of rubber-modified asphalt. Full article

This study investigates the thermo-mechanical response of geocell-reinforced concrete pavements through scaled model tests and three-dimensional finite element analyses. Static, thermal, traffic, and coupled temperature–loading tests were conducted to clarify the deformation evolution, strain distribution, and damage-related response of the reinforced structure. The results show that, under static loading, pavement settlement evolves through three stages, namely initial compaction, plastic development, and stable strengthening, indicating progressive mobilization of geocell confinement. Under thermal loading, slab strain exhibits pronounced spatial and temporal non-uniformity, and the slab center is identified as the thermally sensitive zone. Under coupled temperature–loading conditions, both strain and settlement show a non-monotonic response near 1.1–1.3 kN, suggesting a potential damage-initiation range. Post-test crack observations further provide direct qualitative evidence that local cracking damage occurred in the slab under representative loading conditions. Under traffic loading, permanent deformation accumulates with load repetitions and is highly sensitive to load amplitude, indicating a load-sensitive transition in cumulative deformation behavior rather than a definitive fatigue threshold. Numerical results further show that geocell reinforcement reduces central settlement by 17.4% relative to plain concrete pavement and by 7.6% relative to doweled pavement, while producing a smoother deflection basin and a more uniform stress distribution. Parametric analyses indicate that the optimum geocell height is approximately one-third of the slab thickness; beyond this range, the marginal reinforcement benefit decreases. Overall, the results demonstrate that geocell reinforcement can effectively improve load transfer, deformation compatibility, and thermo-mechanical stability of concrete pavements under the investigated conditions. Full article

This work experimentally evaluates the geometry-driven structural efficiency and normative performance of sandwich-type composite roofing tiles composed of a miriti wood core and fiberglass-reinforced polymer faces. Trapezoidal-profile tiles were manufactured by hand lay-up and assessed according to ABNT NBR 16753, including visual inspection, fiber content, water absorption, apparent flexural behavior, deformation resistance, and impact resistance. The miriti core exhibited an extremely low mean density of 0.091 ± 0.008 g/cm³ (CV ≈ 8.8%), enabling lightweight sandwich configurations with an average overall thickness of approximately 8 mm. Fiberglass contents ranged from 27.5% to 32.1% by mass. Sealed sandwich specimens showed median water uptake values of approximately 2.5% after 2 h and 6.0% after 24 h immersion. Deformation resistance tests indicated admissible deflections of 15.0–15.75 mm (L/40), supported by applied masses between 39.6 and 104.3 kg (≈388–1023 N) without rupture or permanent damage. Apparent flexural stresses ranged from 6.7 to 9.3 MPa, with apparent moduli between 0.7 and 1.9 GPa. All tiles achieved 100% approval in deformation, impact (2–8 J), and visual criteria. The results demonstrate that geometric effects dominate structural performance, validating miriti wood as an efficient and sustainable core for normatively compliant composite roofing systems. Full article

Long-term safety assessment of deep geological repositories for spent nuclear fuel requires explicit evaluation of thermo-mechanical (TM) processes induced by decay heat and their influence on fractured host rock. A safety-relevant, though low-probability, scenario concerns shear reactivation of fractures intersecting deposition holes, which could compromise canister integrity if displacement exceeds design limits. This study presents a three-dimensional discrete element modelling approach to analyze the thermal evolution of the Forsmark repository (Sweden) and the associated long-term response of a discrete fracture network (DFN) during the post-closure phase. The model explicitly represents repository panel, deterministic deformation zones, and a stochastically generated fracture network embedded in a bonded particle assembly representing the rock for Particle Flow Code (PFC) numerical simulations. Time-dependent heat release from spent nuclear fuel canisters is implemented using a physically based decay power function. A deposition panel-scale heat-loading formulation accounts for deposition-hole and tunnel spacing. Two emplacement scenarios are analyzed: (a) a simultaneous all-panel heating scenario, used as a conservative bounding case, and (b) a sequential panel heating scenario representing staged emplacement and closure. The simulations show that temperature and thermally induced stress evolution are sensitive to the emplacement and closure sequence. Sequential heating produces a more gradual thermal build-up and lower peak temperatures than simultaneous heating, indicating that thermal and stress perturbations in the host rock can be influenced not only through repository design, but also by operational strategy. Thermally induced fracture shear displacement displays a systematic temporal response. Fractures located within the deposition panel footprint develop shear displacement rapidly during the early post-closure period, reaching peak values at approximately 200 years, followed by gradual relaxation as temperatures decline. The average peak shear displacement on fractures is on the order of 2–3 mm, while fractures outside the panel footprint show smaller early-time displacements and a more prolonged long-term response. All simulated shear displacements remain more than one order of magnitude below the commonly cited canister damage threshold for Forsmark of approximately 50 mm, even for the conservative simultaneous heating case. These results indicate that thermally induced fracture shear is unlikely to cause direct mechanical damage to canisters. At the same time, the persistence of residual shear displacement after heating implies permanent fracture dilation, which may influence long-term hydraulic properties and indirectly affect processes such as groundwater flow and canister corrosion. The modelling framework and results presented here were conducted for review purposes independently from the Swedish safety case, and provide a mechanistic basis for evaluating thermally induced fracture deformation in crystalline rock repositories and contribute to bounding the role of thermo-mechanical processes in the safety assessment of spent nuclear fuel disposal at Forsmark. Full article

The integration of vertical greenery systems (VGSs) into existing reinforced concrete (RC) buildings raises questions regarding interface kinematics and the permanent displacement of soil-retaining elements under seismic excitation. This study experimentally investigates the residual displacement of façade-mounted living walls and rooftop planter pods anchored to a deficient RC frame under shake table excitation. A 1:3 scale reinforced concrete frame was tested in two distinct phases: initially as a deficient, unretrofitted structure (Phase A), and subsequently as a retrofitted system integrated with vertical greenery elements (Phase B). High-precision terrestrial laser scanning (TLS) was employed before and after successive seismic excitation stages to generate dense three-dimensional point clouds. Cloud-to-cloud comparison techniques were used to quantify global structural displacement and local kinematic behavior of greenery components, while results were validated against conventional displacement sensors. The RC frame exhibited millimeter-scale permanent displacements consistent with draw-wire measurements. In contrast, planter pods demonstrated configuration-dependent behavior, including up to 8 cm translational sliding and rotational responses reaching 13° under repeated excitation, whereas living wall panels remained stable. Notably, a 95% reduction in point cloud density reproduced global deformation patterns with an RMSE of 3.03 mm and quantified peak displacements with only ~2% deviation from full-resolution results. The findings demonstrate the capability of TLS-based monitoring to detect differential kinematic behavior of integrated VGSs, while highlighting the variability in performance of friction-based rooftop anchorage utilizing different robust planter pod fixing systems. Full article

Asphalt pavements are frequently subjected to fatigue cracking, rutting, and surface wear, which accelerate maintenance needs and shorten service life. This study evaluates the performance enhancement of NHA Class B dense-graded asphalt mixtures (12.5 mm NMAS) prepared with a 60/70 penetration grade binder through carbon fiber (CF) reinforcement. Chopped fibers (~12.7 mm) were incorporated via the dry mixing process at dosages of 0.5%, 1.0%, and 1.5% by binder weight. The results indicate that the 1.0% CF mixture delivered optimal performance, with ITS increasing by 51.9%, Marshall stability improving by 38.4%, resilient modulus rising by 42.6%, and rut depth decreasing by 69.2% compared to the unmodified control. Dynamic stability reached 33,750 passes/mm, demonstrating substantial resistance to permanent deformation. Statistical analysis using one-way ANOVA confirmed that all improvements were significant (p < 0.05). Despite a ~6.7% increase in initial cost, the CF-modified mix exhibited strong economic viability, achieving a benefit–cost ratio of 4.79 and significant life-cycle savings over 20 years. These findings underscore carbon fiber as an effective modifier for developing durable, high-performance asphalt composites with reduced maintenance requirements. This work contributes to the advancement of smart and sustainable pavement technologies for resilient transportation infrastructure. Full article

Ventricular septal defect (VSD) occluders commonly rely on permanent nitinol frameworks, which may contribute to long-term mechanical mismatch and late complications. Here, we developed a tissue-compliant composite membrane by embedding a 3D-printed poly(vinyl alcohol) (PVA) grid within a shape-memory poly(glycerol dodecanedioate) (PGD) matrix. Grid spacing was varied from 0.1 to 0.5 mm to tune reinforcement density. FTIR indicated that PVA was incorporated mainly through physical interlocking rather than new covalent bonding. The composite preserved near-body-temperature shape recovery. In water at 37 °C, PVA reinforcement increased tensile modulus and fracture strength, although swelling also increased. Finite-element analysis and benchtop occlusion testing consistently showed lower deformation, less strain localization, and smaller bulge height for PGD–PVA than for PGD alone. In vitro assays showed low cytotoxicity, low hemolysis, and prolonged plasma recalcification time. A 12-week pilot degradation study showed that the faster mass loss observed in initial samples was mainly caused by exposed PVA cut edges; after switching to a fully encapsulated design, static mass loss became similar across groups, and dynamic PBS agitation produced about 10% mass loss at 12 weeks. These results support PGD–PVA as a reinforced membrane strategy for polymeric occluders. Full article

Permanent deformation, manifested as rutting, remains one of the most critical threats to the structural integrity and functional performance of flexible pavements. The Mechanistic–Empirical Pavement Design Guide (MEPDG) includes rutting models that are highly sensitive to the dynamic modulus (E*) of asphalt mixtures—a parameter that can be determined experimentally or predicted by analytical models. In this study, the influence of E* prediction error on rutting estimation is systematically evaluated by comparing laboratory-measured E* values with those predicted by two models: NCHRP 1-37A and a locally calibrated model. The dynamic pavement behavior and rut depth predictions were determined using the finite layer program 3D-Move under standard traffic loads. Comparative analysis revealed that the NCHRP 1-37A model tends to underestimate E*, leading to significant overestimation of vertical strains and accumulated permanent deformation. In contrast, the locally calibrated model provided predictions that closely matched the laboratory measurements, resulting in minimal deviation in rut depth estimates. The results highlight the importance of local calibration and model selection to improve the reliability of mechanistic–empirical pavement predictions, enabling smarter pavement performance evaluation and supporting more sustainable pavement management practices, especially when laboratory testing is not feasible. Full article

Reinforced concrete (RC) structures in marine environments face severe durability challenges due to chloride-induced corrosion. This study investigates the corrosion mechanism and degradation of axial compressive performance in RC columns under the combined effects of sustained loading and corrosion, taking the permanent–temporary integrated RC columns of the Pinglu Canal project as an example. The experimental variables included different sustained load levels and degrees of corrosion. Twelve rectangular RC columns were designed and tested. A specialized setup was developed to simultaneously apply sustained load and induce corrosion to the columns, while monitoring their creep deformation. The columns were subjected to accelerated electrochemical corrosion in a 5% NaCl solution, concurrently under sustained loads of 0, 0.3, and 0.6 times their designed axial compressive capacity, with exposure durations of 0, 30, 60, and 120 days, respectively. The study examined the effects of sustained load level and corrosion degree on the failure mode, concrete creep deformation, and load–displacement curves of the corroded RC columns. The results indicated that sustained loading shortened the duration of concrete expansion deformation and reduced its peak value. Furthermore, the expansion deformation of concrete delayed the creep of corroded columns by 25 to 35 days; after the expansion recovery, the creep rate increased significantly. For corroded columns without sustained loading, the ultimate bearing capacity decreased by 32.0% to 47.8%, with degradations in both stiffness and ductility. The application of sustained loading alleviated the degradation in the ultimate bearing capacity and stiffness of the corroded columns but exacerbated the degradation of their ductility. Finally, considering the effects of concrete expansion deformation and steel corrosion, a predictive model for the creep of RC columns under the coupled action of sustained loading and corrosion was proposed, aiming to provide a theoretical basis for the durability design and maintenance of RC structures in the Pinglu Canal project. Full article

The performance of ballasted railway tracks under cyclic loading is a critical issue in urban railway systems, where high traffic frequency and geometric constraints accelerate track degradation, leading to the accumulation of plastic deformations that may reduce operational efficiency. This study presents a numerical framework for rail track performance assessment based on two complementary modeling approaches: a fully continuous Finite Difference Method (FDM) model, and a hybrid Discrete Element Method–Finite Difference Method (DEM–FDM) model. The continuous FDM simulations are employed to evaluate the global mechanical response of the track support system and to compute conventional stability indicators, including the factor of safety (FS). In parallel, the hybrid DEM–FDM simulations explicitly represent the ballast layer using DEM to capture inter-particle interactions, accumulation of permanent deformation, and particle fragmentation under cyclic loading, while rails, sleepers, sub-ballast, and subgrade are modeled using FDM to describe system-level load transfer. Ballast performance is assessed by linking safety factors obtained from the continuous models with mechanically derived permanent deformation and stress measures extracted from the hybrid simulations. The proposed dual-modeling framework enables a systematic investigation of the influence of ballast layer thickness and material type on deformation accumulation, stress transmission, and granular degradation mechanisms. The results reveal distinct behavioral trends among different ballast materials, showing that increased ballast thickness generally improves track performance, while material-specific degradation mechanisms govern the evolution of permanent deformation under repeated loading. The proposed approach establishes a quantitative bridge between traditional stability-based design metrics and deformation-based performance indicators, providing a rational basis for performance-based evaluation, comparison, and optimization of ballast configurations through a set of robust numerically derived relationships for railway track design. Full article

Structural evaluation of railway tracks in operation requires the integration of field measurements and numerical models capable of adequately representing the mechanical behavior of permanent railway pavement components. In this context, this study presents the structural analysis of a railway segment based on the combination of field instrumentation, laboratory testing, and numerical simulations grounded in the Finite Element Method, adopting linear elastic and resilient material behavior for all track components, using SysTrain software (v.1.88).The objective of this work is to assess the application of a back-analysis methodology based on field instrumentation and numerical modeling, as well as to verify the structural conditions of an in-service railway pavement. The back-analysis was conducted using the SysTrain software, with a focus on calibrating the ballast resilient modulus (RM) and analyzing its effects on the propagation of stresses, internal forces, and displacements throughout the track structure. To this end, field-measured deflections obtained from LVDT sensors installed at the sleeper ends were used, together with the geotechnical, resilient, and permanent deformation (PD) characterization of the underlying soil layers obtained in the laboratory. The results indicated that the calibration of the numerical model requires a ballast resilient modulus in the order of 1500 MPa, suggesting a condition of high layer stiffness. The simulations showed vertical stress levels below 100 kPa in the lower layers, while laboratory tests revealed the high susceptibility of the soils to PD, particularly under moisture variations. It is concluded that the applied methodology enables a consistent assessment of the structural conditions of the track and contributes to a more robust understanding of the ballast response under repeated loading, providing support for railway design, maintenance, and management criteria. Full article