Search Results (2,139)

Aiming at the difficult problem of floor heave control in deep coal mine roadways, this paper took the 1224 transportation roadway of Shuguang Coal Mine in Shanxi as the engineering background and carried out the first underground industrial test of floor-slotting pressure relief technology by using special slotting equipment. The aim is to reveal the energy transfer law of the floor rock mass during slotting pressure relief and clarify its inherent connection with stress redistribution and floor heave deformation control. The research adopts a combination of theoretical analysis, numerical simulation, and field tests to systematically explore the energy accumulation characteristics of the floor and the induced mechanism of floor heave. Results show that the maximum energy accumulated in the floor after roadway excavation reaches 6.0 × 10⁵ J, which is the fundamental cause of floor heave. After optimizing the slotting parameters (depth 2.5 m, width 0.2 m), numerical simulation indicates that the surrounding rock stress concentration zone migrates to the deep part, the energy peak shifts down by 2.5 m, the floor plastic zone expands, and the range of the high-energy zone shrinks. Field test results show that the floor heave amount decreases from 30 cm to 20 cm, with a reduction rate of 33%. This study reveals the synergistic mechanism of “energy transfer–stress regulation–deformation control”, verifies the effectiveness and feasibility of the slotting pressure relief technology in the floor heave control of deep, high-stress roadways, and provides a guarantee for the safe and efficient advancement of the working face. Full article

This study presents an experimental investigation into the repair and seismic performance enhancement of earthquake-damaged reinforced concrete (RC) frame structures using high-strength cement mortar and viscous dampers. A 1/4-scale, four-story RC frame model—designed according to a seismic fortification intensity of 8 degrees (corresponding to 0.2 g PGA in China’s seismic code)—was subjected to shaking table tests under increasing levels of artificial seismic excitation. Following the first round of loading, the damaged structure was repaired using high-strength mortar infill, and 12 viscous dampers were installed for seismic upgrade. The second round of identical seismic loading was applied to evaluate the effectiveness of the repair strategy. Comparative analysis of structural responses before and after repair reveals that the combination of high-strength mortar and viscous dampers improved damping capacity. The initial natural frequencies of the repaired structure increased by 6% (X) and 24% (Y), and damping ratios rose—reaching 12.75% and 10.78% under rare ground motions (1.34 g). Peak acceleration and inter-story drift ratio (IDR) were effectively reduced under moderate seismic levels, although some increase in IDR was observed at higher intensities, all drift values remained within the seismic code limits. The viscous dampers significantly altered the inter-story deformation mechanism, reducing the deformation concentration factor (DCF) of the frame structure and resulting in a more uniform distribution of story drifts. In addition, the energy dissipation capacity of the dampers increased progressively with the intensity of seismic excitation. The results validate the feasibility and efficiency of integrating viscous dampers with high-strength mortar for seismic repair and retrofitting of RC frame structure. Full article

Conventional maintenance models often neglect the impact of pre-existing rutting on sealcoat performance, particularly in high-temperature regions like Chongqing in China, where rut-related failures are common. Existing ruts impose geometric constraints that significantly alter stress redistribution within the new sealcoat layer, yet this constraint mechanism remains poorly understood due to limitations in laboratory observation. This study developed a mesoscopic AC16 + MS3 composite discrete element model to simulate the mechanical behavior of a sealcoat applied over a rutted pavement. To replicate real-world conditions, a constant pressure of 0.7 MPa, representing the standard tire ground pressure in JTG E20-2011, was applied at a temperature of 70 °C, reflecting extreme high-temperature stability limits. Virtual rutting tests and contact force chain analyses were conducted across varying existing pavement rut depths, including 0 mm, 3 mm, 6 mm, and 10 mm. The results indicate that existing ruts redirect stress transfer paths, causing vertical compressive force chains to densify within the rutted zone and tensile stress to concentrate at rut edges. Mastic-mastic contacts transmit over 65% of the load, identifying asphalt mortar as the primary load-transfer phase. Notably, a 10 mm existing rut depth induces a tensile vacuum zone at depths of 15–40 mm, disrupting the standard U-shaped stress distribution. These findings clarify how pre-existing geometries govern structural degradation, suggesting that maintenance in high-temperature regions must prioritize asphalt mortar performance to mitigate edge cracking and deformation. Full article

Underground roadways are essential for personnel movement and equipment transport in coal mines, and the stability and deformation of surrounding rock are critical to mine safety. Traditional methods for monitoring surrounding rock deformation in underground coal mining are time-consuming, inefficient, and require on-site manual measurements. To improve monitoring efficiency and reduce acquisition time, a 3D laser scanning system was employed for deformation monitoring. However, in complex underground environments, 3D laser scanning is affected by multiple environmental factors. Controlled experiments were designed to simulate these conditions, and the effects of scanning resolution, object color, dust concentration, and scanner position on measurement errors were quantified to evaluate the feasibility of roadway measurements. A simulated roadway deformation environment was constructed, and point cloud data were used to monitor deformation and quantify the measurement error of the 3D laser scanner. A corresponding deformation monitoring system was developed to identify deformation patterns of surrounding rock in underground roadways. The proposed method was applied and validated at the Zouzhuang Coal Mine. The results indicate that the proposed approach can automatically acquire high-accuracy deformation data. Full article

Residual stress is an inherent consequence of the welding process and can significantly compromise the structural integrity of welded components. To clarify the high-temperature creep damage evolution of the 600 MPa-grade ship hull structural steel base metal, high-temperature creep tests were conducted, aiming to improve the understanding of its deformation behavior and to support reliable numerical predictions. The experimentally calibrated creep constitutive model was subsequently integrated into finite element simulations to analyze the residual stress evolution in welded joints and to quantitatively evaluate the effects of post-weld heat treatment (PWHT) and hammer peening. The results indicted that, within 450–550 °C, creep deformation of the steel was dominated by dislocation glide and climb, while creep damage was mainly associated with void and crack formation. The simulation results revealed that residual stresses were predominantly concentrated in the weld metal and the heat-affected zone, with the peak von Mises stress in the as-welded joint reaching 686.5 MPa, exceeding the material’s yield strength at the simulated temperature. PWHT exhibited superior stress-relief effectiveness compared with hammer peening, markedly reducing the peak residual stress. Moreover, the stress-relief behavior showed a nonlinear dependence on both holding time and heat-treatment temperature. In contrast, hammer peening produced a localized stress-relief effect, confined primarily to the mechanically impacted region. These findings provided a theoretical foundation for optimizing post-weld treatment strategies to mitigate residual stress in the high strength steel welded joints. Full article

Laser beam combining is essential for achieving high-power and high-radiance output. However, atmospheric turbulence induces independent tip–tilt aberrations across discrete sub-beams in laser array systems, which severely degrades the concentration of far-field energy. Traditional wavefront sensing techniques are primarily designed for the continuous wavefront of a single laser and are not directly applicable to laser array, whereas indirect optimization-based methods often suffer from slow convergence and limited real-time performance. To address these limitations, this study introduces a tip–tilt aberration compensation system for laser array propagation based on cooperative beacons with a shared-aperture transmit–receive configuration. The primary innovation consists of a modified Shack–Hartmann wavefront sensor (SHWFS) tailored to a discrete multi-beam layout, which facilitates the direct, independent, and simultaneous measurement of tip–tilt aberrations for each sub-beam. In conjunction with a segmented deformable mirror (SDM), the architecture can facilitate real-time closed-loop correction with high bandwidth and high precision. Numerical simulations of a 7-, 19-, and 37-beam laser array, together with validation experiments utilizing a 30-beam configuration, demonstrate that the proposed approach effectively suppresses tip–tilt error induced by turbulence. After closed-loop correction, the Strehl ratio (SR) increases above 0.92 ($r_0=5\mathrm{cm}$), while the beam quality factor β reduces below 1.37 ($r_0=5\mathrm{cm}$). Furthermore, the system retains performance stability as the number of sub-beams increases, demonstrating the scalability of the proposed method. In contrast to conventional approaches designed for a continuous wavefront, the proposed method offers a feasible approach for a discrete laser array system, providing robust and scalable tip–tilt correction under varying atmospheric conditions. Full article

The mechanical performance of joints in prefabricated subway stations is a key factor governing the overall structural stability. This study investigates the grouted mortise–tenon joint (GMTJ), which is widely used in prefabricated subway station structures. A refined finite element model was established by incorporating material nonlinearity and a cohesive–friction hybrid constitutive model for the grout–concrete interface, and the accuracy of the model was validated against experimental results. Using the prototype GMTJ from an engineering project as the baseline, parametric analyses were conducted considering three concrete strength grades (CSGs) and three longitudinal reinforcement ratios (LRRs). The results show that increasing the CSG improves the joint’s flexural capacity and delays crack propagation. Although a higher LRR enhances the overall deformation resistance, an excessively high LRR intensifies stress concentration in the tenon region due to the absence of reinforcement in this area. Therefore, merely increasing the LRR cannot effectively improve joint durability, and local reinforcement of critical components such as the tenon is recommended in practical engineering. These findings provide meaningful references and insights for the structural design of prefabricated subway station joints. Full article

Earthquakes induce significant mass redistribution, generating temporal gravity variations detectable by GRACE and GRACE-FO missions. However, the capability of different gravity field recovery strategies, particularly spherical harmonic (SH) and mass concentration (MASCON) solutions, to capture coseismic signals remains insufficiently quantified. This study investigates coseismic gravity changes associated with three Mw 9.0-class earthquakes, including the 2004 Sumatra–Andaman, 2010 Maule, and 2011 Tohoku events, using both SH and MASCON products and theoretical dislocation models. Spectral analysis indicates that recovered signals are dominated by long-wavelength components, while short-wavelength deformation is strongly attenuated. SH products exhibit higher sensitivity to large-scale mass redistribution but are more affected by striping noise and leakage, whereas MASCON products provide improved stability at the cost of signal attenuation. Overall, these findings highlight fundamental limitations of current GRACE-derived products in fully recovering coseismic deformation signals and emphasize the need for improved signal separation strategies. Full article

The combined arch theory provides an effective means for designing support parameters in roadways within loose and fractured surrounding rock. A clear understanding of the internal stress evolution during the load-bearing process of the combined arch is of guiding significance for optimizing roadway support. Taking the 11308 return airway of a mine in Inner Mongolia as the engineering background, this study adopts a combined research approach of theoretical calculation, numerical simulation and laboratory testing. It systematically investigates the internal stress evolution of the anchored combined arch load-bearing structure in roadways with loose and fractured surrounding rock. The load-bearing capacity and failure characteristics of the anchored combined arch under different roof support schemes are explored and analyzed. An optimized support scheme for the loose and fractured roof is proposed and applied in the field, and the monitoring results verify its effectiveness. The results indicate that bolt density is a key factor affecting the load-bearing performance of the combined arch. As bolt spacing decreases, the vertical stress concentration in the anchored structure increases, and its deformation resistance is enhanced. During the stage from load-bearing to failure of the combined arch, the changes in vertical and horizontal stresses within the arch become more stable, and the load-bearing capacity is significantly improved. Comparison between the model test results and theoretical calculations shows good agreement, verifying the rationality of the theoretical calculations. Pressure sensors were pre-installed in the laboratory model to monitor the vertical stress changes in the anchored structure throughout the loading process, and numerical simulations confirmed the stress concentration effect of the combined arch. It was also found that the instability of the anchored structure is controlled by the shear plane at the arch feet. Finally, the bolt spacing in the 11308 return airway of the Inner Mongolia mine was optimized to 0.7 m, and field monitoring was introduced. The maximum roof surface settlement displacement was 15 mm, and the maximum roof separation was 3 mm, confirming that these parameters can meet the roadway stability requirements. Full article

Permeability anisotropy, which is widely present in natural soil deposits, plays an important role in controlling groundwater flow patterns and ground deformation during deep excavation dewatering. However, isotropic assumptions are still commonly adopted in engineering practice, making it difficult to accurately capture realistic subsurface hydraulic conditions. In this study, a deep foundation pit of a metro station in Jinan, China, is taken as a case study. A three-dimensional excavation–dewatering model incorporating permeability anisotropy is established using PLAXIS 3D to systematically investigate the influence of the permeability ratio (Kx/Kz) ranging from 0.1 to 10 on the seepage field evolution, dewatering influence radius, ground surface settlement, and consolidation time history. The results indicate that increasing permeability anisotropy promotes a fundamental transition of the seepage regime from vertically concentrated recharge to laterally dominated radial flow. Correspondingly, the dewatering influence radius exhibits a pronounced non-monotonic response to Kx/Kz, decreasing significantly with increasing permeability ratio and reaching a minimum at approximately Kx/Kz ≈ 5, followed by a slight rebound. Meanwhile, surface settlement profiles evolve from a localized concentration pattern to a widely distributed form as permeability anisotropy increases, accompanied by a remarkable outward expansion of the settlement influence zone. Both the magnitude and spatial distribution of settlement show high sensitivity to variations in permeability anisotropy. Based on these findings, a three-stage conceptual seepage structure model accounting for permeability anisotropy is proposed, characterized by vertically dominated flow, a transitional competition regime, and horizontally dominated flow. The staged evolution of seepage structures is shown to govern the non-monotonic variation in the dewatering influence radius and the spatial–temporal response of ground settlement. The results indicate a dual-scale influence mechanism of permeability anisotropy on dewatering-induced hydro-mechanical behavior, providing a theoretical basis for refined dewatering design and environmental impact assessment in deep excavation projects. Full article

The structural safety of lithium-ion battery systems in electric vehicles (EVs) has become increasingly important with growing concerns over battery-related accidents. In particular, external impacts on the battery pack case (BPC) can cause cell deformation or short-circuiting, potentially leading to thermal runaway. In this study, the mechanical integrity of a commercial BPC was evaluated using both drop-weight impact tests and finite element method (FEM) simulations. A 10 kg hemispherical or cylindrical weight was dropped from a height of 7 m to generate high-energy vertical impacts. The deformation and potential failure of the BPC were examined experimentally, and equivalent FEM simulations were conducted to analyze stress and deformation responses. In both cases, the BPC maintained structural integrity without cracking or intrusion into the battery cell region. The hemispherical impact resulted in relatively shallow, distributed deformation, whereas the cylindrical impact produced more localized indentations due to stress concentrations. The close agreement between experiment and simulation confirms the suitability of FEM for pre-assessment of BPC impact on safety. These findings provide a useful basis for establishing mechanical design criteria and improving battery protection strategies for EV applications. Full article

Liquid hydrogen (LH₂) as an energy source is viewed as a potential path to achieve carbon neutral commercial aviation, albeit accompanied by a plethora of structural, thermal and safety challenges that still need to be resolved. With respect to a LH₂ tank’s structural integration aspect, static, damage tolerance and impact/crashworthiness responses need to be investigated. Ιn the present work, an efficient structural integration concept of LH₂ tanks into a Regional Commercial Aircraft fuselage is proposed, analyzed and preliminary designed, as part of the Clean Aviation project HERFUSE. The main purpose of the work is the feasibility assessment of introducing adhesively bonded solutions in the connection of LH₂ tanks to the aircraft fuselage. The initial design of the potential mounting system configuration was investigated via a finite element parametric simulation model that was developed for this purpose and used to analyze different variations in the proposed concept, under certification relevant load cases. Different variations in the mounting system were assessed, considering their effect on the stress concentrations developed in the fuselage and the tank structure, as well as induced deformations and potential joints debonding. The results indicated that the utilization of adhesive bonding elements in the design of an LH₂ tank integration system is conceptually efficient, although the specific configuration-related shortcomings that were identified need to be tackled. As far as the preliminary design study results are concerned, the minimum required number of joining elements were identified and an initial mass prediction of the mounting system was performed to be used as initial value in the entire hybrid–electric novel aircraft design loop. Future studies on the detailed design and sizing of the mounting system, as well as to incorporate dynamic crash analyses and implementation of energy absorbing elements are needed. 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 the deep mining of metal mines, the stability of pillar–backfill composite materials (PBCMs) under cyclic loading is crucial for preventing dynamic disasters in goafs. Although previous studies have extensively investigated backfill materials under static loading, the damage evolution mechanism of PBCM under cyclic disturbance—particularly the coupled effects of pillar width and disturbance amplitude—remains insufficiently understood. To address this gap, this study explored the mechanical properties and damage evolution of PBCM under cyclic loading using an indoor testing system. Tests were conducted on composite specimens with varying pillar widths (6, 9, 12, 15 mm) and disturbance amplitudes (3, 4, 5 MPa), combined with acoustic emission (AE), digital image correlation (DIC), and scanning electron microscopy (SEM). Results show that wide-pillar specimens (≥12 mm) exhibit significantly improved bearing strength and deformation modulus, with increases of nearly 90% and over 40%, respectively, compared to narrow-pillar specimens. Notably, wide pillars maintain over 95% strength stability even under 5 MPa cyclic disturbances. Narrow pillars are prone to localized damage concentration with high-frequency AE signals and shear failure, while wide pillars exhibit uniform damage development. Failure morphology confirms that pillar size dictates failure mode: narrow pillars undergo sudden through failure, whereas wide pillars display progressive composite failure, with fewer damage-induced cavities and directional crack propagation along maximum shear stress. These findings provide a theoretical basis for stope structure optimization and dynamic disaster prevention in deep mines. Full article

Artificial dams are key retaining structures in underground coal mine reservoirs, and their mechanical performance directly affects the safety and stability of underground water storage systems. This study investigates the effects of dam type, hydraulic pressure, and top boundary condition on dam behavior using three-dimensional finite element models developed in ABAQUS. Three representative dam types, namely flat slab, gravity, and arch dams, were analyzed under three upstream water pressures (0.5, 1.0, and 1.5 MPa) and three top boundary conditions (free, simply supported, and fixed), resulting in 27 numerical cases under an overburden pressure of 4 MPa. The results show that increasing water pressure consistently increases displacement and stress in all dam types, while the deformation mode and stress redistribution strongly depend on structural form and top restraint. The flat slab dam is more prone to edge cracking and local stress concentration, the gravity dam exhibits better overall stiffness and deformation stability, and the arch dam provides more efficient stress redistribution but shows stronger edge effects under restrained conditions. Overall, the gravity and arch dams demonstrate better mechanical adaptability than the flat slab dam. These findings provide a numerical basis for dam-type selection, structural optimization, and local reinforcement design in underground coal mine reservoirs. Full article