Several finite element numerical simulations were conducted on laterally loaded piles in Geba sand to investigate how pile shape, loading direction, and pile length impact lateral load transfer curves and pile-soil interaction. The stress–strain behavior of Geba sand was defined using the hypoplastic constitutive model within the finite element software via the UMAT subroutine. The accuracy of the finite element model was confirmed through a comparison with the centrifuge test findings from prior research. Using the validated finite element model, we examined the behavior of circular and square piles subjected to lateral loads at 0° and 45° angles. The findings indicate that square piles exhibit greater lateral bearing capacity compared to circular piles. The change in the loading direction of square piles changes the pile-soil interaction mode. Square piles with a loading direction of 45° can mobilize a wider range of soil, therefore, the lateral bearing capacity is higher than that of 0° loading direction. The increase in pile length changes the deformation mode of the pile, which can significantly reduce the influence of the shape and loading direction of the pile on the deformation of the laterally loaded pile. When the pile length exceeds 7D, the deformation of the pile below the depth of 6 m is almost 0.

Deep-sea-resource development and marine engineering represent cutting-edge global research priorities. As a typical deep-sea region in the Western Pacific, the physical–mechanical properties of the South China Sea’s deep-sea sediments have critical implications for regional and global deep-sea engineering design and the safety assessments of resource exploitation. However, due to extreme environmental conditions and sampling technology limitations, studies on the mechanical behavior and microstructural control mechanisms of sediments in complex marine environments exceeding 2000 m in depth remain insufficient worldwide, hindering precise engineering design and risk management. This study systematically investigates the physical–mechanical properties, microstructure, and mechanical behavior of intact sediments acquired at a depth of 2060 m in the South China Sea. Through physical property tests, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), one-dimensional consolidation, and triaxial shear tests, combined with comparisons with nearshore soft soils and other deep-sea sediments, we acquired the following results: The sediments primarily consist of muscovite, quartz, and calcite. Triaxial shear tests revealed initial dilation followed by shear consolidation, reaching critical conditions with an effective cohesion of 19.58 kPa and an effective internal friction angle of 27.32°. One-dimensional consolidation tests indicated a short principal consolidation time, wherein the consolidation coefficient first decreased under loading before slowly increasing, while the secondary consolidation coefficient stabilized after vertical pressure exceeded 400 kPa. The research results not only provide a direct reference for designing deep-sea engineering projects in the South China Sea, calculating the penetration resistance of deep-sea drilling rigs, and predicting the foundation settlement of offshore wind power but also furnish typical cases and key data support for the study of the mechanical properties of global deep-sea high-organic-matter sediments and engineering applications.

Several finite element numerical simulations were conducted in this study to investigate the laterally loaded response of pile foundations under general scour conditions in clay, the finite element model was verified by centrifuge tests, and the “model change” method was used to simulate the formation process of general scour and its impact on the lateral bearing response of pile foundations. The effects of overall scour and progressive scour on the load-displacement relationship, pile-soil deformation and failure mode, bending moment, displacement of circular and square pile foundations with equal cross-sectional areas under the same scour depth were analyzed. The results show that under no scour and two general scour conditions, the lateral bearing capacity of square-section pile foundations is higher than that of circular pile foundations with equal cross-sections; the general scour changes the pile-soil deformation and failure mode of laterally loaded pile foundations and reduces the wedge-shaped failure zone of soil around the pile; the wedge-shaped failure area of the soil around laterally loaded square cross-section piles is larger than that of circular cross-section piles of equal cross-sectional area; when the scour depth is the same, one overall scour and progressive scour have less impact on the lateral bearing capacity of the pile foundation; under the same scour depth conditions, one overall scour and distribution scour have less impact on the lateral bearing capacity of the pile foundation.

With the advancement in deep-sea resource development, the creep behavior of deep-sea remolded sediments under coupled temperature, confining pressure (σ₃), and stress effects has become a critical issue threatening engineering stability. The traditional Singh–Mitchell model, limited by its neglect of temperature effects and prediction of infinite strain, struggles to meet deep-sea environmental requirements. Based on low-temperature, high-pressure triaxial tests (with temperatures ranging from 4 to 40 °C and confining pressures ranging from 100 to 300 kPa), this study proposes a modified model incorporating temperature–stress–time coupling. The model introduces a hyperbolic creep strain rate decay function to achieve strain convergence, establishes a saturated strain–stress exponential relationship, and quantifies the effect of temperature on characteristic time via coupling through the Arrhenius equation. The modified model demonstrates R² values > 0.96 for full-condition creep curves. The results show several key findings: a 10 °C increase in temperature leads to a 30–50% growth in the steady-state creep rate; a 100 kPa increase in confining pressure enhances long-term strength by 20–30%. 20 °C serves as a critical temperature point. At this point, strain amplification reaches 2.1 times that of low-temperature ranges. These experimental findings provide crucial theoretical foundations and technical support for incorporating soil creep effects in deep-sea engineering design.