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A rigorous theoretical solution is presented for torsional vibration response of a pipe pile embedded in radial heterogeneous transversely isotropic saturated soil. The method was successfully verified against the analytical solution to a pile embedded in transversely isotropic saturated soil and the analytical solution to a pile embedded in radially inhomogeneous saturated soil. The influence of the construction disturbance effect, the wall thickness of the pipe pile, and especially the soil transverse isotropy on the complex impedance, twist angle, and torque of the pipe pile in the frequency domain were investigated comprehensively. The results revealed that (1) if the influence of the soil transverse isotropy is neglected, the maximum deviation rate of both dynamic stiffness KT and dynamic damping CT can reach 40%, and may result in 25% underestimation and 40% overestimation of the twist angle at pile head, and 40% underestimation and 104% overestimation at pile midsection; (2) ignoring the effect of the construction disturbance, the overestimation rate of CT can reach 42% and 167% for f=15 and 30 Hz, respectively; and (3) using a solid pile to simulate a pipe pile with wall thickness of 0.01 m, the average underestimation deviation rate of KT would be 71% in the range 0–30 Hz, and CT would be underestimated by 82%–360%. The deviation rate of the twist angle at the pile top and the torque at the pile end were approximately 250%–320% and 1,900%–2,900%, respectively. The present solution is applicable for identifying various pile defects through torsional reflection analysis of pipe piles. [ABSTRACT FROM AUTHOR]

In recent years, offshore wind farms have frequently encountered engineering geological disasters such as seabed liquefaction and scouring. Consequently, in situ monitoring has become essential for the safe siting, construction, and operation of these installations. Current technologies are hampered by limitations in single-parameter monitoring and insufficient probe-penetration depth, hindering comprehensive multi-parameter dynamic monitoring of seabed sediments. To address these challenges, we propose a foldable multi-sensor probe and establish an underwater adaptive continuous penetration system capable of concurrently measuring seabed elevation changes and sediment pore water pressure profiles. The reliability of the equipment design is confirmed through static analysis of the frame structure and sealed cabin. Furthermore, laboratory tests validate the stability and accuracy of the electrical and mechanical sensor measurements. Preliminary tests conducted in a harbor environment demonstrate the system's effectiveness. [ABSTRACT FROM AUTHOR]

This paper aims to investigate the ultimate lateral capacity of suction caissons embedded in clay with spatially varying undrained shear strength in the framework of probabilistic analysis for the first time. A non-stationary three-dimensional random field is used to represent the undrained shear strength with a linearly increasing trend with depths below the mudline. The stochastic finite difference method is employed to determine the probabilistic ultimate lateral capacity of suction caissons. The influences of the clay undrained strength heterogeneity κ, the coefficient of variation of undrained strength COVsu, and the autocorrelation distances on the probability density function (PDF) curves and cumulative distribution function (CDF) curves of the normalized ultimate lateral capacity Nh are investigated. It is found that both the mean and standard deviation of normalized ultimate lateral capacity Nh increase with the undrained strength heterogeneity κ, but the coefficient of variation of Nh does not. Besides, the small autocorrelation distance of clay results in the low variability of normalized ultimate lateral capacity. This indicates the significance of probabilistic site characterization of the undrained strength of clay. [ABSTRACT FROM AUTHOR]

In this study, a diagnostic model for evaporation ducts was established based on the Coupled Ocean–Atmosphere–Wave–Sediment Transport (COAWST) and the Naval Postgraduate School (NPS) models. Utilizing this model, four sensitivity tests were conducted over the South China Sea from 21 September to 5 October 2008, when four tropical cyclones affected the study domain. These tests were designed with different roughness schemes to investigate the impact mechanisms of wave processes on evaporation duct simulation under extreme weather conditions. The results indicated that wave processes primarily influenced the evaporation duct heights by altering sea surface roughness and dynamical factors. The indirect impacts of waves without dynamical factors were rather weak. Generally, a decrease in local roughness led to increased wind speed, decreased humidity, and a reduced air–sea temperature difference, resulting in the formation of evaporation ducts at higher altitudes. However, this affecting mechanism between roughness and evaporation ducts was also greatly influenced by changes in regional circulation. In the eastern open sea areas of the South China Sea, changes in evaporative ducts were more closely aligned with local impact mechanisms, whereas the changes in the central and western areas demonstrated greater complexity and fewer local impacts due to variations in regional circulation. [ABSTRACT FROM AUTHOR]

Monopile foundations are extensively utilized in the rapidly expanding offshore wind power industry, and the stability of these foundations has become a crucial factor for ensuring the safety of offshore wind power projects. Such foundations are subjected to a myriad of complex environmental loads during their operational lifespan. Whilst current research predominantly concentrates on the effects of wind, wave, and current loads on monopile stability in extreme environments, it is imperative to consider the potential influence of unexpected submarine landslide loads. In this study, we provide a comprehensive overview of wind, wave, current, and submarine landslide loads on monopile foundations in extreme environments. Subsequently, we establish a finite element model for analyzing the stability of monopiles under complex lateral loads, and validate the accuracy of the model by comparing it with the previous numerical findings. A case study is performed with reference to the Xiangshui Wind Farm project to analyze the effects of varying submarine landslide densities, velocities, impact heights, and seabed sediment strengths on pile head horizontal displacement, pile rotation at the mudline, and maximum bending moment. The findings indicate that the increase in submarine landslide density, velocity, and impact height leads to an increase in horizontal displacement at the pile head, pile rotation at the mudline, and maximum bending moments, and a horizontal failure mode is observed in seabed sediments. Furthermore, under the same load conditions, a decrease in seabed sediment strength and internal friction angle triggers instability in monopiles, with a noteworthy transition from horizontal failure to deep-seated seabed sediment failure. Finally, we propose a criterion for monopile instability under diverse loading conditions. [ABSTRACT FROM AUTHOR]

The three-dimensional topography of the seabed has a significant influence on the wave field and the failure characteristics of the sloping seabed. Nevertheless, previous experimental studies were predominantly limited to two-dimensional wave conditions. In this study, a series of regular wave experiments (including a rigid-slope seabed and a sandy-slope seabed) have been done in a large-scale three-dimensional harbor basin to investigate the three-dimensional wave field in the Zhoushan sea area and the response characteristics of the sloping seabed under the wave actions, respectively. The results of the rigid-seabed tests show that the wave field has obvious three-dimensional characteristics under the influence of three-dimensional topography. During the process of propagation, wave shoaling occurs which leads to wave breaking finally. At the same time, the wave will reflect when it meets the topography, and the reflected wave will affect the wave field in turn. The pore water pressure response and three-dimensional failure modes of sandy sloping seabed under the wave actions are obtained by the sandy-seabed experiment. Three-dimensional seabed topography of typical sea area is established in the harbor basin. The characteristics of the three-dimensional wave field and the response of submarine slope under the three-dimensional wave actions were investigated. The three-dimensional topography of sandy sloping seabed after wave actions was captured. [ABSTRACT FROM AUTHOR]

AbstractUnderstanding the volume change behavior of deep-water sediments is essential for the safety design of deep-water engineering structures. In this study, the volume change behaviors of marine sediments from the South China Sea were studied through oedometer and isotropic compression tests. Scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) tests have been conducted to investigate the microstructure evolution of two types of sediments under loads. The experimental results showed that the structural anisotropy of intact specimens is more pronounced in oedometer tests with the increase of stress, however, depolarization occurs in the isotropic consolidation test. The volume change after yield in the oedometer and isotropic consolidation tests comes from inter-aggregate pore variations associated with the adjustment of the soil fabric. The reconstituted specimen presents a more uniform distribution of pores than that of the intact specimen, and the macropores are more easily compressed for the reconstituted specimen than those of the intact specimen. With increasing stress, the oedometer compression and isotropic consolidation curves of intact specimens gradually approach those of the reconstituted specimen. The deformation mechanism under high stresses is that soil particles are reoriented and the variation of micropores. [ABSTRACT FROM AUTHOR]