Search Results (10)

Offshore wind energy is a key contributor to sustainable energy, yet its development faces significant technological challenges, particularly in the design of substructures that interface with the marine environment. In this study, a comprehensive numerical analysis was conducted to investigate the mechanical behavior of a high-rise pile cap foundation under hydrostatic loading conditions. A high batter pile bearing foundation model was employed to examine the effects of pile inclinations, embedment depths, lateral loads, and cap elevations on foundation performance. The results indicate that the displacement and bending moment at the pile head decrease significantly as the pile inclination gradually increases. Similarly, as the embedding depth increases gradually, both the displacement and bending moment decrease significantly. Additionally, a positive batter pile exhibits greater bending moments and displacements than a negative batter pile, with the maximum bending moment occurring in the lower one-third of pile below the mudline. These findings provide valuable theoretical guidance for the design of offshore wind turbine foundations, recommending an inclination angle of 8–12° and an embedment depth of 12–15 m to enhance structural stability, economic efficiency, and construction feasibility. Full article

Liquefaction and earthquake damage to coral sand sites can cause engineering structure failure. Both testing and analyzing the seismic response characteristics of pile groups on coral sand sites are highly important for the seismic design of engineering structures. To address the lack of research on the seismic dynamic response of group pile foundations in coral sand sites, this study analyzes the characteristics of the seismic dynamic response of vertical and batter pile foundations for bridges in coral sand liquefaction foundations via the shaking table model test and investigates the variation patterns of acceleration, excess pore water pressure (EPWP), and the bending moment and displacement of foundations, soil, and superstructures under different vibration intensities. Results show that the excitation wave type significantly affects liquefaction: at 0.1 g of peak acceleration, only high-frequency sine wave tests liquefied, with small EPWP ratios, while at 0.2 g, all tests liquefied. Vertical pile foundations had lower soil acceleration than batter piles due to differences in bearing mechanisms. Before liquefaction, batter piles had smaller EPWP ratios but experienced greater bending moments under the same horizontal force. Overall, batter piles showed higher dynamic stability and anti-tilt capabilities but endured larger bending moments compared to vertical piles in coral sand foundations. In conclusion, batter pile foundations demonstrate superior seismic performance in coral sand sites, offering enhanced stability and resistance to liquefaction-induced failures. Full article

Post-earthquake investigations have shown that piles in liquefiable soils are highly susceptible to damage, especially in sloping sites. This study examines the seismic performance of pile groups with lateral spreading through advanced numerical modeling. A three-dimensional finite element model, validated against large-scale shaking table test results, is implemented to capture the key mechanisms driving the dynamic response of pile groups under both inertial and kinematic loading conditions. Parametric seismic response analyses are conducted to compare the behavior of batter and vertical piles under varying ground motion intensities. The results indicate that batter piles experience increased axial compressive and tensile forces compared to vertical piles, up to 70% and 20%, respectively. However, batter piles provide enhanced lateral stiffness and shear resistance compared to vertical piles, reducing horizontal displacements by up to 20% and tilting the cap by 85% under strong ground motion. The results demonstrate that batter piles not only enhance the overall seismic stability of the structure but also mitigate the risk of liquefaction-induced lateral spreading in the near-field through pile-pinning effects. While vertical piles are more commonly used in practice, the distinct advantages of batter piles for seismic stability highlighted in this study may encourage using more advanced numerical modeling in engineering projects. Full article

The foundations of particular engineering structures, including marine and jetty structures, mooring systems for submerged platforms or those on the ocean surface, and transmission towers, are subjected to various external loads including compression, uplift, and lateral loads. In such cases, to improve the soil resistance below foundations, pile foundations such as helical piles, anchored piles, and batter piles are commonly preferred, depending on the in situ conditions. Helical piles, increasingly used as an alternative foundation to conventional piles, are placed in the soil body by rotating with torque. This paper deals with the contribution of a helical pile in improving loose sandy soil, and the main purpose is to study the effect of the helix-buried depth on the load-bearing capacity and failure mechanism. The investigated variables include the distance between helixes, the number of helixes, and the diameter of the upper helix. Physical model tests were conducted, and two- and three-dimensional numerical analyses were performed by using the finite element method with an advanced soil model to illustrate the failure mechanisms of helical piles. The aim was to reveal the efficiency of the finite element method in modelling helical piles placed in weak sandy soil. A simplified linear geometry for helixes was established in a two-dimensional finite element model whereas a real geometry for helixes, which was a more realistic approach, was created in a three-dimensional finite element model. The results show that the three-dimensional model indicates better agreement with the physical model compared to the two-dimensional model, and all investigated variables highly affect the load-bearing capacity of helical piles. Full article

Fiber-based finite element analysis (FB-FEA) has been widely recognized for its ability to reproduce experimental results and is also a reliable method for evaluating the nonlinear seismic response of pile-supported wharves (PSWs). Design practice often employs frame analysis (FA) due to its easy implementation. To precisely reproduce the nonlinear seismic response of PSW using FA, it is necessary to configure mechanical properties such as the hinge property correctly. However, it is unclear whether the hinge properties proposed in previous studies can be applied to PSWs with spun piles. In this study, a novel FA method was developed to investigate the nonlinear seismic response of PSWs with corroded spun piles considering PC bar area reduction, deteriorated material properties, the bending stiffness reduction factor, and the moment–curvature relationship of the spun pile. The nonlinear seismic response of corroded PSWs was determined by performing pushover analysis using three methods: FA using the method of the previous study (FA-1), the proposed FA method (FA-2), and FB-FEA. As regards PSW foundations, vertical pile and batter pile configurations were considered. The pushover analysis results were compared in terms of several parameters, such as the natural period, plastic hinge formation, and load capacity of the corroded PSWs. The FA-2 results agreed very well with the FB-FEA results, while the FA-1 results were less precise with respect to the natural periods and load capacities of corroded PSWs. The results indicated that the bending stiffness reduction factor, moment–curvature relationship, and axial load–bending moment (P–M) capacity of the corroded spun piles should be appropriately defined. Corrosion had greater negative impacts on the compressive axial load and bending moment capacities of the spun pile than on its tensile axial load capacity. Full article

The performance of passive battered piles resisting the embankment-induced lateral soil movements may differ from that of the active battered pile and axially loaded existing vertical piles adjacent to embankment constructions. This study was part of a preliminary feasibility investigation for a reinforcement plan of an actual embankment project, aiming to experimentally investigate the performance of passive battered piles under embankment-induced lateral soil movement. To this end, a sequence of reduced-scale model tests of battered piles near the surcharges was first designed in sandy soil with a similarity ratio of 1:30. The effects of pile inclinations (β = −20°, −10°, 0°, +10°, and +20°), surcharge magnitudes, and constraint conditions at the pile tip (free-tip and fixed-tip) on the responses of passive battered piles were explored. Finally, the response characteristics of battered piles resisting the embankment-induced lateral soil movement were analyzed to clarify the working mechanism of these battered piles. Full article

The purpose of this study is to grasp the behavior characteristics of a single batter pile under vertical load by performing a model test. The changes in the resistance of the pile, the bending moment, etc. by the slope of the pile and the relative density of the ground were analyzed. According to the results of the test, when the relative density of the ground was medium and high, the bearing capacity kept increasing when the angle of the pile moved from a vertical position to 20°, and then decreased gradually after 20°. The bending moment of the pile increased as the relative density of the ground and the batter angle of the pile increased. The position of the maximum bending moment came closer to the ground surface as the batter angle of the pile further increased, and it occurred at a point of 5.2~6.7 times the diameter of the pile from the ground surface. Full article

Under the action of vertical loading, batter piles rarely appear individually, as they undergo horizontal and vertical displacements at the same time and produce a sizeable additional bending moment. However, previous studies have mainly focused on a single batter pile, which is inconsistent with engineering practices. Although single pile tests can easily reveal its working behavior, they also ignore two important factors, namely, the internal force redistribution caused by the deformation limitation of the mirror-like pile, and the interaction between the symmetrical piles and “clamped” soil (the soil between two symmetrical piles). Therefore, this paper took symmetrical batter piles as the test object to explore the influence of the two factors on the load transfer mechanism. Moreover, the deformation mode, distribution of inertial forces, and group effect of symmetrical batter piles were also discussed. The results showed that the “clamping effect” caused by the pile deformation had a significant impact on the load transfer. Under vertical loading, the flexible symmetrical floating batter piles were the only deformation mode. Under the constraint of the cap and mirror-like batter piles, the symmetrical conformation partially compensated for the disadvantage of the additional bending moment. Full article

Pile-supported structures incorporating batter piles are commonly used, and can be installed both on the horizontal and inclined ground. Recent studies have considered the positive role of batter piles during earthquakes, highlighting their satisfactory contribution to structural seismic performance. However, in these structures, even though the dynamic system responses can vary greatly depending on the ground slope, few previous studies have evaluated the seismic performance of batter piles relative to the ground slope. Therefore, this study evaluates the seismic performance of pile-supported structures with batter piles, relative to the ground slope using dynamic centrifuge model tests. The acceleration, displacement, moment, and axial force of the system were experimentally derived and reviewed, and the pile moment and axial force (M–N) interaction diagrams of the pile cross-sections were analyzed. The installation of the batter piles resulted in a greater reduction in the system response in the inclined-ground model (acceleration: −48%, displacement: −50%, and moment: −84%) compared to that in the horizontal-ground model (acceleration: −27%, displacement: +650%, and moment: −77%). Overall, batter piles showed better seismic performance in the inclined-ground model than in the horizontal-ground model. Full article

A new form of retaining system for use in deep excavations in crowded cities is proposed in this paper. The new system, which we have coined the herringbone retaining system (HRS) involves the use of vertical and batter piles, capping beams, and wales. A numerical study was conducted (using the finite difference tool FLAC3D) to investigate various aspects of the behavior of the new system and reveal the mechanisms responsible for it. The HRS method was compared subsequently to two other commonly-used systems: the cantilever retaining structure (CRS) and horizontal-strutted retaining structure (HSRS). The results show that using the HRS method significantly reduces the deformation of the vertical piles and bending moments acting on them. More specifically, the maximum values of the deformation and bending moment were calculated to be 4.5% and 23.1% of the corresponding CRS values, respectively (the corresponding figures calculated for the HSRS method are 5.3% and 19.7%, respectively), so the HRS and HSRS methods provide similar levels of support. Finally, a real-world application of the system was presented to provide a valuable reference for the future use of HRS. Full article