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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]

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]

The construction of deep-sea and offshore wind farms is key to the development of offshore wind power. Since the forms of bottom supporting structures and their installation methods greatly affect the overall cost of electrical platform, the latest developments in this filed were reviewed, based on which a novel integrated floating method was introduced. First, by incorporating the advantages of the integrated offshore wind turbine and the installation method for suction bucket foundation, the idea of integrated floating and quick installation based on a four-bucket jacket foundation was proposed. Second, the process of integrated wet towing of the four-bucket jacket foundation was described, which was further verified via indoor model experiments and numerical simulations. Results show that under 2 m wave height and level 5 sea conditions, the proposed four-bucket jacket foundation can be wet towed and floated at a speed of 5 knots under the optimum draft depth. [ABSTRACT FROM AUTHOR]

This study investigates the impact of assimilating conventional weather observations on the wind forecast over the nearshore region of the East China Sea. Multi-level wind measurements in the boundary layer from five masts near the coast were used to verify the numerical model forecasts. Four numerical experiments with a rapid update cycle were performed to forecast the wind field over the masts. The observation shows that the characteristics of the wind field are distinct between the onshore and offshore masts. The numerical forecasts were able to reproduce the main features of the observed wind field both onshore and offshore. However, the wind forecasts of the offshore masts showed larger BIAS and MAE than those onshore. The forecast skill was shown to be sensitive to different weather events and the choice of control variables in the assimilation. The use of new momentum control variables allows a smaller observation-minus-analysis field compared with the traditional control variables, and the resultant wind forecast showed significant improvements. Further tuning of the new control variable scheme showed little improvement of the wind forecast which demonstrates the importance of maintaining the balance between large-scale and small-scale fields in the analysis. The larger forecast error at the offshore masts was likely due to the distribution of conventional observations and the uncertainties in representing the marine boundary layer in numerical models. [ABSTRACT FROM AUTHOR]