Search Results (5,928)

Suction caisson anchor foundations have been widely applied in oil and gas platforms but remain in the exploratory stage for floating offshore wind power applications, where research on their anchor load-bearing characteristics is insufficient. This study focuses on the influence of length-to-diameter ratio, loading angle, and loading point depth on the anchor load-bearing characteristics of suction caisson anchor foundations. Through numerical simulation, the load–displacement curves, internal force distribution along the caisson body, movement mode transitions, and soil failure characteristics were obtained. The results indicate that loading point depth and loading angle alter the movement mode of the suction caisson anchor foundation, directly affecting its bearing capacity. Smaller loading angles result in higher bearing capacity, which initially increases with loading point depth, peaks at 0.6 L, and then decreases at 0.8 L due to a transition in the foundation’s movement mode. Similarly, as the length-to-diameter ratio decreases, the bearing capacity and overall movement amplitude of the foundation decrease, leading to a shift in the optimal loading point position. The circumferential soil pressure and horizontal soil resistance distributions vary significantly with loading angle and depth. The findings of this study provide valuable reference for the design and application of suction caisson anchor foundations. Full article

To study the vibration characteristics of viscoelastic slurry pipe structures under fluid–structure interaction (FSI), we constructed a three-dimensional FSI pipe model based on the finite element method to systematically investigate the effects of fluid effects, pipe length, and wall thickness on the vibrational characteristics of viscoelastic slurry pipes. A modal analysis demonstrated that fluid effects not only significantly reduced the natural frequency of the pipe but also disrupted the symmetry of the vibration modes and eliminated the phenomenon of frequency degeneracy. The frequency reduction caused by FSI reached 54%, which was dominant compared with the water-attached effects, and its impact intensified with the increasing vibration order. The water-attached effect exhibited differences between odd and even orders, attributed to the influence of vibration modes on the distribution of fluid inertial forces, with a contribution of 45.07% to 55.24% in the odd orders and of only 37.69% to 38.93% in the even orders. When the FSI and water-attached effects acted together, the frequency reduction was further aggravated, but the reduction ratio did not follow a simple linear superposition. The parametric analysis of the pipe showed that when the pipe length increased from 1 m to 3 m, the growth rate of its natural frequency was only 26.52% that of the shorter pipe, indicating that the longer the pipes, the slower the growth rate of frequency. When the wall thickness increased from 5 mm to 11 mm, the growth rate of the first-order natural frequency decreased from 15.43% to 7.44%, suggesting that the frequency improvement effect caused by the stiffness augmentation diminished with the increase in wall thickness. The research results hold significant guiding significance for the structural design of slurry pipe systems in practical engineering and the safe operation of pipe systems. Full article

Urban networks are a key force in reshaping regional resilience patterns. However, existing research has not yet systematically elucidated, from a physical–virtual integration perspective, the underlying mechanisms through which composite urban networks shape multidimensional urban resilience in regions confronted with severe environmental and infrastructural challenges. Northwest China, characterized by its extreme arid climate, pronounced core–periphery structure, and heavy reliance on overland transportation, provides an important empirical context for examining the unique relationship between network centrality and the mechanisms of resilience formation. Based on the panel data of 33 prefecture-level cities in northwest China from 2011 to 2023, this article empirically examines the impact of the composite urban network constructed by traffic and information flows on urban resilience from the perspective of network node centrality using a two-way fixed-effects model. It is found that (1) the spatial evolution of urban resilience in northwest China is characterized by “core leadership—gradient agglomeration”: provincial capitals demonstrate significantly the highest resilience levels, while non-provincial cities are predominantly characterized by medium resilience and contiguous distribution, and the growth rate of low-resilience cities is faster, which pushes down the relative gap in the region, but the absolute gap persists; (2) the urban network in this region is characterized by a highly centralized topology, which improves the efficiency of resource allocation yet simultaneously introduces systemic vulnerability due to its over-reliance on a limited number of core hubs; (3) urban network centrality exerts a significant positive impact on resilience enhancement (β = 0.002, p < 0.01) and the core nodes of the city through the control of resources to strengthen the economic, ecological, social, and infrastructural resilience; (4) multi-dimensional factors synergistically drive the resilience, with the financial development level, economic density, and informationization level as a positive pillar. The population size and rough water utilization significantly inhibit the resilience of the region. Accordingly, the optimization path of “multi-center resilience network reconstruction, classified measures to break resource constraints, regional wisdom, and collaborative governance” is proposed to provide theoretical support and a practical paradigm for the construction of resilient cities in northwest China. Full article

The seismic bearing capacity of water-saturated composite foundations adjacent to slopes is critical for engineering safety, yet it is significantly influenced by complex factors such as earthquakes and heavy rainfall. This paper establishes a failure mechanism model that involves both reinforced and non-reinforced zones, comprehensively considering the synergistic effects of seismic force, pore water pressure and group pile replacement rate, and thus addressing the issue that existing models struggle to account for the coupling effects of multiple factors. Based on the principle of virtual work, a general solution for ultimate bearing capacity is derived, and the optimal solution is obtained using the MATLAB R2023a exhaustive method. Findings reveal that pile group support substantially enhances bearing capacity: the improvement becomes more pronounced with higher soil strength parameters (φ, c) and replacement ratios. When the seismic acceleration coefficient increases from 0 to 0.3, the bearing capacity of the unreinforced foundation decreases by approximately 61.6% (from 134.71 kPa to 51.83 kPa), while group pile support can increase the bearing capacity by 433.2%. Notably, when soil strength is inherently high, the marginal benefit of pile group reinforcement diminishes. A case study in Fuzhou validates through numerical simulation that pile groups improve foundation stability by altering energy dissipation distribution, with the discrepancy between theoretical calculations and simulation results within 10%. The research results can directly guide the design of saturated composite foundations near slopes in earthquake-prone areas (such as Fujian and Guangdong) and enhance the seismic safety reserve by optimizing the replacement rate of group piles (recommended to be 0.2~0.3). Full article

This study develops a high-performance water-based mold release agent for polyurethane (PU) foaming applications. We demonstrate that incorporating octamethylcyclotetrasiloxane (D4) into a dimethyl silicone oil emulsion (5 vol% fixed concentration) significantly enhances key performance metrics. By systematically varying D4 content (0–15 vol%), we characterize droplet morphology, particle size distribution, contact angle, and viscosity to elucidate the underlying enhancement mechanism. Our findings reveal the following: (i) Optimal emulsion stability: At 5 vol% D4, the mold release agent exhibits a narrow particle size distribution (6–9 μm). (ii) Efficient processing: Film formation completes within 10 min, reducing demolding force and yielding PU foam with defect-free, non-adherent surfaces. (iii) Storage stability: After 60 days in ambient conditions, performance remains unchanged, with no phase separation observed under thermal stress (60 °C) or refrigeration (2–6 °C). This work explores an alternative pathway to mitigate key limitations—slow film formation and poor shelf-life—offering a prototype for next-generation release agents. Full article

This work develops an Updated Lagrangian Smoothed Particle Hydrodynamics (ULSPH) framework to simulate high-speed icebreaking by a hemispherically capped cylinder (HCC). Using a self-programmed C++ code with Drucker–Prager damage criteria, this work systematically analyzes how impact velocity (100–200 m/s), ice thickness (10–40 cm), and impact angle (60–90°) govern structural loads and ice failure modes. The head of the HCC is always the stress concentration area, and the peak value of the impact force increases non-linearly with increasing the initial velocity from 100 m/s to 200 m/s. The increase in ice layer thickness from 10 cm to 40 cm raises the peak value of the impact force by 18.1%. The ice layer deformation shows three-stage characteristics: collision depression, penetration perforation, and through-spray. When the impact angle α is non-vertical, the strain of the ice layer is asymmetrically distributed, and the component of the peak impact force along the y direction increases significantly with the decrease in the impact angle, reaching 129.3 kN at α = 60°. Results reveal velocity-driven nonlinear force amplification, asymmetric strain distribution at oblique angles, and critical stress concentration at the HCC head, providing design insights for polar equipment. Full article

The problem of quantifying prestress loss in the external tendons of in-service bridges is of immense practical importance, and the development of reliable, cost-effective methods is a commendable goal. Based on the principle of static equilibrium, this paper proposes a direct method for determining the effective stress in external prestressed tendons using the variation principle, whose calculation accuracy was validated by conducting experimental and theoretical analysis considering the prestressed tendon arrangement form. A transverse tensioning experiment of the prestressed tendons was carried out under four tension conditions of 50 kN, 80 kN, 110 kN and 170 kN at the anchorage end, and the theoretically calculated internal force of the prestressed tendons gradually approached the measured value as the transverse tension increased. Once the appropriate level of transverse tension was reached, stable and reliable results could be obtained. Ultimately, the error between them will stabilize below 5%. This method was used to detect stress loss in the external prestressed tendons of 20 m, 40 m and 50 m T-beams affected by both internal and external uncertain factors simultaneously, and the probability distribution hypothesis test of the stress loss rate was carried out, the results of which reveal that they all follow normal distribution. The ratio of stress at the bottom edge of the T-beam under self-weight and prestressed load to that under vehicle load is defined as the compressive stress reserve coefficient, which is a verified and reliable index for evaluating the external prestressed stress loss on the reinforcement effect of the bridge. Full article

This study investigates the anodization behavior and surface modification of Ti6Al4V (Ti64) alloy components fabricated via electron beam powder bed fusion (EB-PBF), aiming to enhance their performance in biomedical applications. Ti64 samples were manufactured using optimized EB-PBF parameters to produce a uniform microstructure and surface quality. Electrochemical anodization at 40 V and 60 V for 2 h generated self-organized TiO₂ nanotube layers, followed by a heat treatment at 550 °C to improve crystallinity while preserving the nanotube morphology. Characterization using scanning electron microscopy (SEM) and atomic force microscopy (AFM) revealed that a lower voltage produced uniform, compact nanotubes with moderate roughness and higher hardness, whereas a higher voltage generated thicker, less ordered nanotubes with larger diameters, increased roughness, and slightly reduced mechanical performance. X-ray diffraction (XRD) confirmed the presence of anatase TiO₂ phases, and energy-dispersive spectroscopy (EDS) analysis revealed a homogeneous distribution of Ti and O. Mechanical testing via nanoindentation and nanoscratch techniques demonstrated superior hardness and adhesion in nanotubes formed at lower voltage due to their compact structure. Electrochemical measurements indicated significantly enhanced corrosion resistance in anodized samples, attributed to the dense and chemically stable TiO₂ layer that acts as a barrier to aggressive ions and reduces active corrosion sites. In vitro bioactivity analysis further confirmed improved apatite formation on anodized surfaces. These results demonstrate the synergistic potential of EB-PBF and controlled anodization for modifying the surface properties of Ti64 implants, leading to improved mechanical behavior, corrosion resistance, and biological performance suitable for biomedical applications. Full article

As an important traffic and transportation roadway, tunnel engineering is widely used in important fields such as highways, railways, water conservancy, subways and mining. It is limited by complex geological conditions, harsh construction environments and poor robustness of the monitoring system. If the construction process and monitoring method are not properly designed, it will often directly induce disasters such as tunnel deformation, collapse, leakage and rockburst. This seriously threatens the safety of tunnel construction and operation and the protection of the regional ecological environment. Therefore, based on distributed fiber optic sensing technology, the full–cycle spatiotemporally continuous sensing information of the tunnel structure is obtained in real time. Accordingly, the health status of the tunnel is dynamically grasped, which is of great significance to ensure the intrinsic safety of the whole life cycle for the tunnel project. Firstly, this manuscript systematically sorts out the development and evolution process of the theory and technology of structural health monitoring in tunnel engineering. The scope of application, advantages and disadvantages of mainstream tunnel engineering monitoring equipment and main optical fiber technology are compared and analyzed from the two dimensions of equipment and technology. This provides a new path for clarifying the key points and difficulties of tunnel engineering monitoring. Secondly, the mechanism of action of four typical optical fiber sensing technologies and their application in tunnel engineering are introduced in detail. On this basis, a spatiotemporal continuous perception method for tunnel engineering based on DFOS is proposed. It provides new ideas for safety monitoring and early warning of tunnel engineering structures throughout the life cycle. Finally, a high–speed rail tunnel in northern China is used as the research object to carry out tunnel structure health monitoring. The dynamic changes in the average strain of the tunnel section measurement points during the pouring and curing period and the backfilling period are compared. The force deformation characteristics of different positions of tunnels in different periods have been mastered. Accordingly, scientific guidance is provided for the dynamic adjustment of tunnel engineering construction plans and disaster emergency prevention and control. At the same time, in view of the development and upgrading of new sensors, large models and support processes, an innovative tunnel engineering monitoring method integrating “acoustic, optical and electromagnetic” model is proposed, combining with various machine learning algorithms to train the long–term monitoring data of tunnel engineering. Based on this, a risk assessment model for potential hazards in tunnel engineering is developed. Thus, the potential and disaster effects of future disasters in tunnel engineering are predicted, and the level of disaster prevention, mitigation and relief of tunnel engineering is continuously improved. Full article

As one of the mooring foundation types for floating wind turbine platforms, research on the anchor pullout bearing characteristics of mooring pile foundations remains insufficient, and the underlying mechanism of anchor pullout bearing capacity needs further investigation and clarification. This paper conducts a numerical study on the bearing characteristics of mooring pile foundations under tensile anchoring forces with loading angles ranging from 0° to 90° and loading point depths of 0.2L, 0.4L, 0.6L, and 0.8L (where L is the pile length). The research findings indicate that the anchor pullout bearing capacity decreases as the loading angle increases from 0° to 90°, and exhibits a trend of first increasing and then decreasing with the increase in loading point depth. For rigid pile-anchors, the maximum anchor pullout bearing capacity occurs at a loading point depth of 0.6–0.8L, while for flexible piles, it appears at 0.4–0.6L. Both the bending moment and shear force of the pile shaft show abrupt changes at the loading point, where their maximum values also occur. This implies that the structural design at the loading point of the mooring pile foundation requires reinforcement. Meanwhile, the bending moment and shear force of the pile shaft gradually decrease with the increase in the loading angle, which is attributed to the gradual reduction of the horizontal load component. The axial force of the pile shaft also undergoes an abrupt change at the loading point, presenting characteristics where the upper section of the pile is under compression, the lower section is in tension, and both the pile top and pile tip are subjected to zero axial force. The depth of the loading point significantly influences the movement mode of the pile shaft. Shallow loading (0.2–0.4L) induces clockwise rotation, and the soil pressure around the pile is concentrated in the counterclockwise direction (90–270°). In the case of deep loading, counterclockwise rotation or pure translation of the pile shaft results in a more uniform stress distribution in the surrounding foundation soil, with the maximum soil pressure concentrated near the loading point. Full article

Low-cost ocean monitoring systems are increasingly needed to address data gaps in coastal environments, particularly in regions where traditional research infrastructure is limited. This paper presents the design, development, and field deployment of a biophysical ocean buoy (BOB)—a compact, solar-powered autonomous buoy system capable of measuring sea surface temperature, salinity (via electrical conductivity), total dissolved solids, pH, and GPS position. The system features real-time data transmission via the Iridium satellite, local data logging, and modular sensor integration. The BOB was deployed for three missions in the Seto Inland Sea, Japan, ranging from 26–56 h in duration. The system successfully recorded high-resolution environmental data, revealing coastal gradients, diurnal heating cycles, and tidal current reversals. Over 95% of the measurements were successfully recovered, and the Iridium communications exceeded 90% reliability. The temperature and salinity data captured fine-scale variations consistent with freshwater plume interactions and tidal forcing. With a total system cost under USD 2000 and minimal deployment requirements, the BOB offers a scalable solution for distributed ocean monitoring. Its performance suggests strong potential for use in aquaculture monitoring, coastal hazard detection, and climate change research, especially in data-sparse regions. This work contributes to the growing field of democratized ocean observation, combining affordability with operational reliability. Full article

Understanding the combined effects of edge width and cutter ring shape on the rock-breaking performance is critical for optimising disc cutter design. The intrusion test serves as an effective approach for investigating the rock-breaking mechanism of disc cutters. In this study, a two-dimensional discrete element method (DEM) model was established to simulate the intrusion process of a single disc cutter. Three commonly used disc cutter types were analysed: disc cutter with flat edge (FEDC), disc cutter with rounded edge (REDC) and disc cutter with alloy tooth (ATDC). The edge widths ranging from 10 mm to 24 mm were examined to assess their influence on rock crack propagation, stress distribution, cutting force and specific cutting energy. The FEDC and REDC exhibited face-contact extrusion breaking, whereas the ATDC was line-contact embedding breaking. The crack extension range, crack number, force chain intensity, stress distribution, rock-breaking force and specific cutting energy ranks are as follows: FEDC > REDC > ATDC. The ATDC generated a higher proportion of tensile cracks compared to the FEDC and REDC, though with fewer long cracks. The rock-breaking efficiency of the FEDC was lower, whereas the REDC and ATDC exhibited higher efficiency. With the increase in edge width, the force chain distribution became more concentrated, leading to greater internal rock damage, and the number and length of cracks increased significantly. Cracks initially expanded laterally at smaller edge widths but extended downward as edge width increased. The peak force and specific cutting energy increased with increasing edge width; the peak force at an edge width of 24 mm is approximately 3.5 times that of an edge width of 10 mm. The REDC is preferable in hard rock formations, and the ATDC is more effective in soft rock formations. The edge width should be determined based on rock properties and thrust capacity. Full article

The subject of the research in this article were experimental tests of the M-346 Master aircraft model, carried out in a wind tunnel using the 3D printing method (FDM) in terms of the impact of surface post-processing technology on its aerodynamic characteristics. The measurements of key aerodynamic parameters concerned forces and moments in various airflow conditions taking into account variable angles of attack at a constant sideslip angle. The main purpose of the work was to verify the hypothesis that properly performed surface treatment significantly affects the accuracy of actual aerodynamic measurements in terms of solving the research problem using the post-processing technology, to conduct selected tests in a wind tunnel and analyze the obtained results. The obtained results of the tests, which showed a significant impact of the technological parameters of 3D printing and surface treatment methods on the correctness of the representation of real aerodynamic characteristics, were used mainly to analyze the aerodynamic performance of the model, verify the distribution of forces and moments, and evaluate the behavior of the structure in various flight scenarios. The obtained research results, the analysis of the obtained results, and selected tests were used to present important observations and formulate practical conclusions. Full article

In this study, the impacts of various grouting methods and volumes on the vertical bearing characteristics of model piles in clay strata were investigated through indoor static load tests on one ungrouted model pile and two model piles with grouting at the pile tip, as well as two model piles with distributed grouting at the pile tip and along the pile side. These tests were performed in conjunction with data obtained from optical fiber sensors that monitored changes in the internal forces of the pile body. The results indicate that, compared to the ungrouted model pile Z1, the ultimate bearing capacities of the grouted model piles Z2 to Z5 were increased by 83.9%, 175.0%, 125.0%, and 253.6%, respectively. Additionally, the displacements at the pile tops after failure reached 57.6%, 62.3%, 69.5%, and 73.5% that of the ungrouted model pile Z1. These results demonstrate that post-grouting can significantly enhance the ultimate bearing capacity of model piles and reduce settlement at the pile top. Under various loads, the axial force of the pile body decreases gradually with the increasing depth of the pile foundation and increases with the increasing load at the pile top. The increase in the ultimate average side friction resistance and ultimate tip resistance of the grouted model piles (i.e., Z2 to Z5), in comparison to the ungrouted pile, was positively correlated with the grouting volume at the pile tip and along the pile side. All five model piles displayed the characteristics of friction piles. Full article

The active pile underpinning technology when a tunnel passes under a bridge involves complex force conditions, making construction monitoring and control extremely challenging. However, there is a lack of research on the laws governing the stress and deformation responses of bridges during the construction process. This paper takes an active pile underpinning project of a metro line passing under a bridge as a case study. Design and construction plans are taken as the basis, and on-site monitoring data are incorporated. A three-dimensional finite element simulation model is established. This model is used to analyze the distribution and variation laws of stress and settlement during the pile underpinning process. The results show that: considering the traffic conditions of the bridge and the requirements for additional stress, it is reasonable to suggest that the actual settlement of the bridge deck should be 2–3 mm; the determination of the jacking force should generally be greater than the load transmitted from the pier column to the underpinning beam and less than 75% of the maximum bearing capacity, which is more reasonable. Full article