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The tetrapod jacket foundation is one of the most common types of foundations used for offshore structures. Although the static bearing capacity of the jacket foundation is important, a safe design must be taken into consideration for accumulative deformation and stiffness degradation during cycles. To address this, a set of centrifuge model tests of a tetrapod jacket foundation subjected to cyclic and monotonic loading was conducted in Kaolin. The test results mainly reveal: (1) the influence of loading history on the lateral bearing capacity of the jacket foundation; (2) the evolution of accumulative deformation of the jacket foundation during cycles; (3) the stiffness degradation of soil-pile interaction under cyclic loading. Compared typical p-y curve approaches with test results, a hyperbolic tangent p-y curve method proposed by Zhu et al. (2017) is adopted to calculate the soil-pile interaction of the jacket foundation. The values of the p-multiplies of leading-row and trailing-row piles in soft soils are clearly lower than that in sands. Finally, a cyclic p-y curve method related to cycles and embedded depths is developed for the jacket foundation in the hope of providing guidance for the design of the jacket foundation in soft soil.

A number of image filtering algorithms based on nonlocal means have been proposed in recent years which take advantage of the high degree of redundancy of any natural image. The block-matching with 3D transform domain collaborative filtering (BM3D) proposed in [1] achieves excellent performance in image denoising. But the choice of shrinkage operator in block-matching step is not discussed, only given the threshold by experience in its related papers. In this work, we introduce an improved version of BM3D with adaptive block-match thresholds. The proposed method firstly seeks the relationship between the Structural Similarity index (SSIM) [2] and match distance in blocks and obtains the data with fine SSIM values. Then, compute the Noise level and Gradient values in blocks of the same block size. Finally, surface fitting is adopted to get a formula which applies weak thresholds for flat blocks and strong thresholds for detail blocks. Experiment results are given to demonstrate the same class of denoising performance with less time-consuming to slightly noisy image and good improvement in denoising performance to seriously noisy image.

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