Search Results (241)

Surface water-groundwater interaction zones are critical ecohydrological interfaces in arid regions, yet quantitative spatiotemporal patterns and soil-vegetation responses under coupled water-salt-heat gradients remain poorly documented. Based on a one-year monitoring period (August 2024–August 2025) at four sites along a river-to-desert transect (LW3: 25 m, LW2: 200 m, LW1: 300 m, LW4: 400 m from the Niya River) in the hyper-arid Tarim Basin, this study reveals the following quantitative patterns. Groundwater depth increased with distance from the river and followed an annual decrease-increase trend, with an anomalous shallow peak in March 2025 (−20 cm) linked to precipitation recharge. Soil temperature stability increased with depth: the 20 cm layer recorded the widest annual fluctuation (e.g., −1.5 °C to 24 °C at LW1), whereas the 80 cm layer varied only between approximately −0.2 °C and 28 °C. Proximity to the river dampened thermal extremes. Shallow soil moisture was highly dynamic (with a coefficient of variation [CV] reaching 40–50% at LW1 and LW4), while deeper layers remained stable; LW3 near the river stayed saturated year-round (CV = 0). Soil electrical conductivity (EC) decreased with distance from the river: LW3 exhibited the highest surface values (5000–16,000 μS cm⁻¹), whereas LW1 recorded the lowest (1000–2700 μS cm⁻¹). Vegetation performance was governed by coupled water-salt conditions rather than moisture alone: P. australis at LW1 achieved the tallest growth (>200 cm) and highest photosynthetic rates (20.25–37.38 μmol m⁻² s⁻¹), outperforming LW3 (104 cm, winter photosynthesis dropping to 2.01) and LW4 (~100 cm). Correlation analysis further showed strong vertical temperature coupling (r > 0.96 across all depths) and depth-stratified water-salt relationships (e.g., EC-volumetric water content r = 0.95 at 20 cm in LW4), reflecting spatial differentiation driven by freeze-thaw cycles, evaporative enrichment, and homogeneous silt-textured soils (54–96% fine fraction). These quantitative findings provide a detailed observational baseline for riparian ecohydrology in hyper-arid inland rivers and underscore that sustainable vegetation management requires balancing water availability against salinity stress. Full article

Salt rock exhibits pronounced viscoelastic creep, continuously imposing radial extrusion loads on casing and threatening long-term well integrity. Field observations in the Missan Oilfield, Iraq, show that casing damage is concentrated near salt–non-salt interfaces, where lithologic contrasts intensify stress redistribution and mechanical coupling. This study integrates triaxial creep experiments, a calibrated modified Burgers model, UMAT implementation, and three-dimensional finite element simulations to investigate casing stress evolution and failure mechanisms. The calibrated model reproduces salt rock creep with a maximum relative strain error of 16.8%. Results show that post-cementing salt creep amplifies non-uniform radial loading at the interface, causing progressive casing stress concentration. At low inclination, the interface–casing intersection evolves into an elliptical annulus; the circumferential variation in equivalent wall thickness and stress-peak migration jointly weaken local stress concentration. However, when the inclination angle reaches approximately 45° at β = 0°, the peak Mises stress begins to exceed that under the vertical-well condition. When α ≥ 65°, the peak stress no longer decreases monotonically with azimuth but exhibits a decrease–increase trend. This indicates that eccentric loading and the additional bending moment dominate the transition from radial extrusion to coupled bending–shear–extrusion loading. A casing stress risk map and grade-selection chart are developed to support casing design in salt-interbedded formations. Full article

Background/Objectives: Patient-specific subperiosteal implants are increasingly used to treat severely atrophic ridges due to advances in digital planning and additive manufacturing. This study aimed to evaluate the effects of material type and implant configuration on stress distribution in subperiosteal implant systems and to compare their overall biomechanical performance using a multi-criteria decision framework. Methods: A three-dimensional model of a severely atrophic maxilla was reconstructed to simulate four clinical scenarios combining two configurations (one-piece and two-piece) and two materials (titanium and 60% carbon fiber-reinforced polyetheretherketone). Finite element analysis was conducted to assess stress distribution within the implant body, fixation screws, prosthetic framework, and surrounding bone under vertical and oblique loading conditions. Maximum and minimum principal stresses were evaluated in bone, whereas von Mises stresses were calculated for implant components. The resulting biomechanical indicators were subsequently integrated using an entropy weight–TOPSIS multi-criteria decision analysis. Results: Principal stresses in the surrounding bone showed minimal variation between titanium and 60% carbon fiber-reinforced polyetheretherketone across all configurations. Implant configuration had a more pronounced effect on implant body stress. Under oblique loading, the two-piece configuration demonstrated substantially higher implant stresses than the one-piece design, whereas under vertical loading, lower implant stresses were observed in the two-piece configuration. The multi-criteria analysis ranked the one-piece titanium model highest under oblique loading and the two-piece titanium model highest under vertical loading. Conclusions: Implant configuration and loading direction influenced biomechanical behavior more than material selection in patient-specific subperiosteal implants. Full article

Post-rotation jacking is a critical construction stage for load-path reconstruction and alignment adjustment in rotation-constructed bridges, particularly for ultra-wide double-deck composite girder systems. Taking a two-span continuous steel truss–concrete composite girder bridge with spans of 2 × 85 m as the engineering background, this study investigates the mechanical behavior during post-rotation jacking through theoretical derivation, finite element simulation, and on-site monitoring. Based on the force method of structural mechanics, a linear relationship between vertical synchronous jacking force and displacement is derived, and an analytical formulation for bearing reaction redistribution under laterally asynchronous jacking is established by considering the coupling effects of vertical bending, torsion, and transverse multi-bearing support. A full-bridge spatial finite element model was developed in MIDAS Civil NX 2024 V1.1 to analyze the redistribution of bearing reactions and the stress response of the concrete crossbeam under different jacking conditions. The results show that, for the investigated bridge, the jacking force–displacement response remains highly linear during synchronous jacking. The B-axis middle bearing is more sensitive to jacking displacement than the two side bearings, with its fitted stiffness being approximately 2.19 times the average stiffness of the side bearings. Eccentric jacking causes reaction concentration at the jacked point and reaction reduction at adjacent supports, and the magnitude of reaction variation increases approximately linearly with jacking displacement. When the transverse non-uniform jacking magnitude reaches 20 mm, a tensile stress of 0.3 MPa appears at the bottom flange of the concrete crossbeam; therefore, a project-specific stroke-difference limit of 20 mm is recommended for this bridge, while the actual construction achieved a stroke control accuracy of ±0.5 mm and a transverse elevation difference within 1 mm. Field monitoring results validate the proposed analytical and numerical methods. The Pearson correlation coefficients of the measured jacking forces with the finite element and theoretical results are 0.9987 and 0.9988, respectively, and the corresponding mean relative errors are 3.84% and 4.23%. For stress responses, the measured and calculated values show a strong correlation, with a Pearson correlation coefficient of 0.9980 and a mean relative error of 12.77%; the critical mid-span monitoring point shows a relative error of only 0.65%. The final bridge alignment deviation is controlled within ±3 cm. The overall mean verification coefficient is 0.968, with a 95% empirical agreement range of [0.888, 1.048], indicating that the proposed mechanical analysis framework and combined force–displacement control strategy can provide a useful reference for refined construction control of similar ultra-wide double-deck composite girder bridges with comparable span arrangement and transverse bearing layout. Full article

To address the challenges posed by complex Cretaceous(K) deep structural deformation and the poorly understood decoupling mechanism between deep and shallow structural layers in the foreland thrust belt of the Kuqa depression, Tarim Basin, this study integrates high-precision 3D seismic interpretation with balanced cross-section restoration techniques to systematically elucidate the controlling role of rheological heterogeneity within the Shushanhe Formation (K₁s) mudstone on the stress–lithology–structure coupling mechanism. Our findings demonstrate that variations in thickness and rheological properties of the Shushanhe Formation mudstone govern the structural segmentation along the Zhongqiu–Dongqiu transect. In the Dongqiu area, an exceptionally thick and highly ductile mudstone layer induces principal stress deflection and horizontal shearing, effectively absorbing vertical strain transmitted from deep-seated tectonic wedges. This results in pronounced decoupling between deep and shallow strata, giving rise to broad, gentle anticlines and ramp-flat imbricate structures at depth. Conversely, in the Zhongqiu area, the mudstone thins significantly and becomes more brittle, increasing the friction coefficient and impeding vertical stress transmission. Consequently, near-vertical stacking occurs in the proximal compressional segment, leading to the development of high-angle thrust faults and strike-slip-modified fault-bend folds. This study clarifies the genetic mechanism of non-coaxial structures controlled by the mudstone detachment layer and confirms that the plastic flow of this layer not only enhances lateral sealing capacity but also acts as an effective rheological barrier, thereby preserving the deep overpressured hydrocarbon reservoirs in the Yageliemu Formation (K₁y). These insights provide a robust theoretical foundation for shifting exploration strategies from shallow structural traps to deep, subtle lithologic–structural composite plays, offering critical guidance for sweet spot prediction in ultra-deep settings. Full article

Compacted loess is widely used as road subgrade filling in northwestern China, but its stability is threatened by traffic loads and repeated dry–wet cycles, leading to subgrade settlement or collapse. This study investigated the compression and resistivity characteristics of Q₃ Malan loess under 0–3 dry–wet cycles by incremental loading (IL) and constant rate of strain (CRS) tests. A self-developed consolidation chamber was used for the IL and CRS tests with the simultaneous monitoring of deformation and resistivity, with the moisture content controlled within the range of 1% to 29% to 15%. The results showed that loess compressibility increased rapidly after the first dry–wet cycle and became slow after other dry–wet cycles; The primary compression index C_c and secondary compression index C_α rose as vertical stress increased, and C_α stabilized at a vertical stress larger than 200 kPa. Resistivity decreased with stress and cycles, and sharply decreased after the first cycle (enhanced pore connectivity) and stabilized after two to three cycles, matching the compression stages. The compression and resistivity characteristics obtained by IL and CRS tests had consistent variation rules, confirming the reliability of the tests. This study provides a preliminary laboratory theoretical basis for exploring the feasibility of using resistivity in subgrade deformation monitoring. Full article

To address the longitudinal vibration issues in high-speed elevators induced by external excitations, this study constructs a high-precision multi-degree-of-freedom (MDOF) dynamic model to systematically analyze vertical dynamic response characteristics. Utilizing the substructure method, the complex traction system is decomposed into several subsystems, including the traction device, tensioning device, car and car frame, counterweight system, and segmented wire ropes. By integrating Lagrange’s equations with Newton’s second law, the governing differential equations of motion for each component are derived, establishing an adaptable global dynamic model. The forced vibration analysis focuses on the impacts of periodic excitation from traction sheave eccentricity, piecewise reverse braking torque, and vertical impacts from guide rail joints on car vibration response and wire rope dynamic stress. The results indicate that: traction sheave eccentricity leads to periodic fluctuations in car acceleration, with vibration peaks decreasing as the payload increases; reverse braking torque triggers impulsive acceleration overshoots, where the peak value under full-load conditions increases by approximately 15% compared to the no-load condition, accompanied by a longer duration of low-frequency vibrations; guide rail joint impacts produce instantaneous acceleration spikes, which increase by about 18% under high-speed operating conditions; and the wire rope stress exhibits significantly higher sensitivity to load variations within the low-load range of 0–0.2. Full article

The particle size distribution of backfill aggregate is a key factor affecting the performance of the -long-distance pipeline transport of backfill slurry. However, the understanding of its impact on slurry flow behavior, transportation resistance, and particle distribution mechanisms remains incomplete and calls for further investigation. This study first obtained the rheological parameters of slurry and their variation laws under the influence of particle size distribution through rheological experiments. Subsequently, CFD numerical simulations are used to investigate the flow characteristics of slurry under long-distance transportation conditions. The findings demonstrate that a reduction in the mixed aggregate particle size leads to a significant increase in both the yield stress and plastic viscosity of the backfill slurry. The conveying distance shows a positive correlation with the slurry transportation resistance. Furthermore, the slurry exhibits plug flow behavior in both the horizontal and vertical pipe sections, whereas this plug flow pattern is no longer observed in the bend section. The tailings particles exhibit a distinct stratified distribution within the pipeline. In the horizontal pipe section, the graded tailings predominantly settle at the bottom, whereas the fine tailings remain suspended near the top. In contrast, in the vertical pipe section, the graded tailings tend to accumulate in the central zone of the pipe, while the fine tailings are dispersed along the pipe wall. As the content of graded tailings increases from 30% to 50%, both the zones with increased and decreased particle volume fractions expand, while the steady flow zone correspondingly shrinks. Meanwhile, the volume fraction of graded tailings at the bottom of the pipe rises significantly from 0.12 to 0.61. This research provides important theoretical support for the optimized matching and rational application of tailings particle size distribution in the design of long-distance pipeline transportation systems for mine backfill. Full article

Tiankeng ecosystems are characterized by strong microenvironmental gradients that influence plant adaptation; however, the molecular mechanisms underlying plant responses to altitudinal variation remain poorly understood. In this study, transcriptome sequencing and bioinformatic analyses were conducted to investigate the environmental adaptation mechanisms of three representative plant species (Hydrangea strigosa Rehder, Pilea martini, and Pilea sinofasciata) distributed along the vertical gradient of the Hanzhong Tiankeng in Shaanxi Province, China. Differential gene expression and functional enrichment analyses were performed to explore transcriptional responses under different altitude conditions. The results showed that flower coloration in Hydrangea strigosa Rehder was associated with the activation of sugar metabolism and triterpenoid biosynthesis pathways, suggesting potential indirect roles in modulating cellular metabolism and physiological conditions linked to flower coloration, while poor growth at the tiankeng bottom was associated with enhanced cellular respiration under low-light conditions, suggesting a potential link between energy metabolism and growth performance. In contrast, Pilea martini and Pilea sinofasciata exhibited better growth in the pit-bottom environment. Pilea martini promoted growth through enhanced carbohydrate metabolism and tricarboxylic acid cycle activity, whereas Pilea sinofasciata responded to environmental stress through hormone signaling, triterpenoid biosynthesis, and light signaling pathways. These findings reveal species-specific molecular strategies for plant adaptation to altitude-related environmental gradients in tiankeng ecosystems and provide insights into plant survival mechanisms in karst habitats. Full article

This wind farm study provides a detailed and deep investigation into numerous aspects of both wind dynamics and the associated wind turbine performance via a wind data analysis utilizing an extrapolated timeframe of 50 years. The major wind characteristics assessed included wind speed and direction, flow inclination, turbulence intensity, and wind speed (average based on extremes) over the entire duration of the evaluated data set. A majority of study results indicated only narrow wind speed ranges (6.3 m/s to 7.0 m/s) for turbine operation within the wind farm. Higher turbine operation speeds than the average measured wind speed may significantly increase turbine energy output. Turbines were evaluated across numerous geographic locations, resulting in average flow inclination (−4.12° to 1.57°) from the vertical to horizontal directions. The variation in flow inclination indicates that there is a geographic component that likely creates a localized terrain impact on turbine performance. Similarly, the measurement of turbulence intensity was also assessed, which indicated elevated levels of turbine mechanical stress and additional requirements for turbine maintenance. Energy production analyses from each turbine in the wind farm exhibited various regions of energy loss, with the highest energy losses associated with select turbines. Full article

The load characteristics of the helicopter tail rotor system are critical to flight safety and handling performance, and flight testing remains the most direct and reliable means to obtain authentic load data. In this paper, the well-established Wheatstone bridge strain measurement method is adopted to carry out accurate load testing on the helicopter tail rotor system. The tail rotor assembly mainly consists of the tail rotor shaft, pitch link, and tail rotor blades, which undertake different load transfer tasks during flight. Under actual operating conditions, the tail rotor shaft bears significant axial tension as well as combined lateral and vertical bending moments; the pitch link is primarily subjected to alternating axial tension and compression; and the tail rotor blades withstand complex loads including flapping bending, lagwise bending, and torsional moments. According to the distinct stress characteristics and force transmission paths of each component, targeted flight test maneuvers are reasonably designed. These maneuvers include steady-level flight at low, medium, and high speeds, zigzag climbing flight, near-ground side-rear flight, as well as deceleration-to-sprint and obstacle slope maneuvers specified in ADS-33E. Key flight parameters are selected for in-depth analysis to reveal the load distribution and dynamic variation patterns of the tail rotor under typical operating conditions. On this basis, a helicopter load risk test point matrix is established to identify high-risk working conditions and key monitoring positions. This study provides a solid theoretical and data foundation for subsequent flight test monitoring and structural strength verification. It effectively reduces flight test risks, improves monitoring efficiency and accuracy, and helps cut down the human, material, and financial costs associated with flight test monitoring. The research results can also provide important references for the design optimization and safety evaluation of helicopter tail rotor systems. 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

To explore the stress-bearing characteristics of the “inner tensioned steel ring–segment–surrounding rock” composite structure in TBM (Tunnel Boring Machine) pressurized water conveyance tunnels, a 3D refined finite element model for this composite structure was established, with the Class V surrounding rock section of the TBM pressurized water conveyance tunnel in the Rongjiang-Guanbu water diversion project selected as the research subject. The effects of the internal water pressure, surrounding rock type and tunnel burial depth on the mechanical properties of the composite structures are studied. The findings demonstrate that reinforcing the tunnel structure with an inner tensile steel ring can effectively constrain tunnel deformation, diminish the tensile stress of segments and the extent of tensile zones, and enhance the bearing capacity of the composite structure. Under the effect of internal water pressure, the compressive stress of segments, vertical deformation, joint opening degree, stress of connecting bolts, stress of the inner tension ring, and stress of anchor rods all exhibit a reduction compared to the scenario without internal water pressure. Under the combined action of external water–soil pressure and internal water pressure, variations in surrounding rock types lead to respective increases of 37.16%, 15.75%, and 15.12% in the stress of connecting bolts, segment joint misalignment, and anchor bolt stress. As the tunnel burial depth increases, the stress of connecting bolts and the vertical deformation of segment and the joint misalignment of the pipe segment increase by 140%, 107% and 60.61%, respectively. In addition, under the combined action of external water and soil pressure and internal water pressure, the load-sharing ratios of the surrounding rock, pipe segment, inner tension ring and anchor rod are 34.87%, 34.59%, 21.59% and 8.95%, respectively, and the load-sharing ratio of the inner tensioned ring is 85.80% higher than that observed in the absence of internal water pressure, indicating that internal water pressure effectively enhances the load-sharing performance of the inner tensioned steel ring. In the composite structure, the load-sharing ratio of surrounding rock decreases as the surrounding rock class increases (from Class III to Class V). Under the same load condition, the load-sharing ratio of Class III surrounding rock is 7.14% higher than that of Class V. As the tunnel burial depth increases, the inner tensioned steel ring and anchor rods function more prominently as reserve-bearing components. When the tunnel burial depth reaches 71 m, the load-sharing ratio of the inner tension steel ring and anchor rod increases by 19.91% and 55.72%, respectively, compared with that of the buried depth of 31 m. The research results can provide a theoretical reference for the lining design and late reinforcement measures of similar tunnel projects. Full article

Ground subsidence and shaft lining deformation caused by compressed dewatered bottom aquifers in deep unconsolidated strata mining areas are critical engineering challenges, making the study of the seepage–soil deformation coupling mechanism during groundwater injection remediation vital. This study built a visual cylindrical model (1025 mm × 150 mm); formulated well-graded analogous materials based on the D₂₀ principle to simulate sandy gravel layers; embedded FBG sensors at 200/400/600 mm depths, combined with a dial indicator on the model top; and conducted two water injection–dewatering cycles. Results indicate: water injection generates excess pore water pressure, placing the entire model in a tensile stress state with top rebound; post-injection vertical stress redistributes (tension above the injection point, compression below, and an interlaced transitional band), validating the necessity of full-section injection; during the second injection–dewatering cycle, tensile strain at the upper monitoring point reaches 597.77 με, while compressive strain at lower depths reaches −253.90 με, internal deformation stabilizes within 6.5–10.0 days, injection improves the in situ stress state by reducing effective stress, and the deformation of the field strata remains in a stabilization period, with the stabilization time decreasing as the depth of the strata increases. This study clarifies the temporal evolution and representative spatial variation in internal strain at monitored depths during injection, providing theoretical and design references for optimizing water injection schemes to mitigate coal mine shaft damage. Full article

Turbulent structure and diffusion over different underlying surfaces are fundamental to understanding mass and momentum exchange in the atmospheric boundary layer. This study investigated these processes over six distinct surfaces—flat plate, sand, grass, small gravel, large gravel, and vegetation—through wind tunnel experiments combined with high-frequency velocity measurements. Quadrant analysis, Reynolds stress decomposition, and turbulence kinetic energy budget analysis were employed to elucidate the mechanisms driving variations in diffusion coefficients. The results reveal two distinct turbulence generation regimes: over rigid surfaces (flat plate, sand, gravel), turbulence is primarily generated by roughness elements, whereas over canopy surfaces (grass, vegetation), canopy-induced shear and wake dynamics dominate. Consequently, the vertical profiles of turbulent diffusion coefficients K_x and K_z exhibit markedly different patterns across surface types. For rigid surfaces, diffusion coefficients peak near the surface and decay monotonically with height. For canopy surfaces, diffusion coefficients reach their maximum at the canopy top, reflecting the dual influence of canopy-induced shear and energy dissipation within the canopy. These findings provide a mechanistic understanding of surface-induced variability in turbulent diffusion processes and offer quantitative parameterizations that can improve pollutant dispersion modeling over complex terrain. Full article