Explore the vast range of titles available.

A novel scour protection approach for pipeline using the Ionic Soil Stabilizer (ISS) solidified soil was proposed in this study. The ISS-solidified slurry can be poured adjacent to the pipeline immediately after it was placed, or in the growing scour holes. In the present study, the first type was utilized as the scour protection layer around the pipeline. A series of laboratory flume tests were conducted to validate the protective capacity of ISS-solidified slurry for the pipeline in waves and combined waves and current. Then, the scanning electron microscope (SEM) tests and pore size tests were carried out, respectively, to investigate the mechanism of ISS-solidified slurry for scour protection around the pipeline. Finally, the effects of the ISS-solidified layer for liquefaction stability of non-cohesive subsoil were evaluated. The results indicated that the ISS-solidified slurry is a reliable, economic approach for scour protection around pipelines in the ocean environment. It is noteworthy that if a non-cohesive soil layer underlies the ISS-solidified slurry, it is vulnerable to suffer accumulated liquefaction due to the dense crust structure of the ISS-solidified layer, so the adverse effects for accumulated liquefaction should be considered carefully due to the set of the ISS-solidified layer.

A series of laboratory experiments were conducted in a wave-current flume to investigate the scour evolution and scour morphology around tripod in combined waves and current. The tripod model was made using the 3D printing technology, and it was installed in seabed with three installation angles α = 0°, 90°and 180° respectively. In the present study, the scour evolution and scour characteristic were first analyzed. Then, the equilibrium scour depth Seq was investigated. Furthermore, a parametric study was carried out to study the effects of Froude number Fr and Euler number Eu on equilibrium scour depth Seq respectively. Finally, the effects of tripod’s structural elements on Seq were discussed. The results indicate that the maximum scour hole appeared underneath the main column for installation angle α = 0°, 90° and 180°. The Seq for α = 90° was greater than the case of α = 0° and α = 180°, implying the tripod suffered from more severe scour for α = 90°. When KC was fixed, the dimensionless time scale T* for α = 90° was slightly larger than the case of α = 0° and α = 180° and the T* was linearly correlated with Ucw in the range of 0.347 < Ucw < 0.739. The higher Fr and Eu both resulted in the greater scour depth for tripod in combined waves and current. The logarithmic formula can depict the general trend of Seq and Fr (Eu) for tripod in combined waves and current.

In this study, the local scour around tripods in random waves is numerically investigated. The seabed-tripod-fluid numerical model with an RNG k−ε turbulence model is built and validated. Following that, the scour characteristics and flow velocity distribution are analyzed using the present numerical model. Finally, a revised stochastic model is proposed to predict the equilibrium scour depth, Seq, around tripods in random waves. The results indicate that the present seabed-tripod-fluid numerical model is capable of depicting the scour process and of capturing the flow field around tripods with high accuracy. Due to the blockage effects of the main column and structural elements, there is enhanced flow acceleration underneath the main column and the lower diagonal braces, which increases the turbulence intensity and seabed shear stress, causing more particles to be mobilized and transported, resulting in more severe scour at the site. The revised stochastic model shows the best agreement with the numerical and experimental results when n = 20, but more experimental data and numerical results are still needed to verify the adaptation of the revised stochastic model for larger Keulegan–Carpenter (KC) number conditions (KCrms,a > 4).

Local scour around offshore wind turbine foundations presents a considerable challenge due to its potential influence on structural stability, driven by hydrodynamic forces. While research has made strides in comprehending scouring mechanisms, notable complexities persist, specifically with newer foundation types. Addressing these limitations is vital for advancing our understanding of scour mechanisms and for improving mitigation strategies in offshore wind energy development. This review synthesizes current findings on local scour across various offshore foundations, encompassing field observations, data-driven approaches, turbulence-sediment interactions, scour evolution processes, influencing factors, and numerical model advancements. The objective is to enrich our understanding of local scour mechanisms. In addition, future research directions are outlined, including the development of robust artificial intelligence models for accurate predictions, the exploration of vortex structure characteristics, and the refinement of numerical models to strengthen prediction capabilities while minimizing computational efforts.

This study presents an innovative theoretical approach to predicting the scour depth around a foundation in large-scale model tests based on small-scale model tests under combined waves and currents. In the present approach, the hydrodynamic parameters were designed based on the Froude similitude criteria. To avoid the cohesive behavior, we scaled the sediment size based on the settling velocity similarity, i.e. , the suspended load similarity. Then, a series of different scale model tests was conducted to obtain the scour depth around the pile in combined waves and currents. The fitting formula of scour depth from the small-scale model tests was used to predict the results of large-scale tests. The accuracy of the present approach was validated by comparing the prediction values with experimental data of large-scale tests. Moreover, the correctness and accuracy of the present approach for foundations with complex shapes, e.g. , the tripod foundation, was further checked. The results indicated that the fitting line from small-scale model tests slightly overestimated the experimental data of large-scale model tests, and the errors can be accepted. In general, the present approach was applied to predict the maximum or equilibrium scour depth of the large-scale model tests around single piles and tripods.

A series of numerical simulation were conducted to study the local scour around umbrella suction anchor foundation (USAF) under random waves. In this study, the validation was carried out firstly to verify the accuracy of the present model. Furthermore, the scour evolution and scour mechanism were analyzed respectively. In addition, two revised models were proposed to predict the equilibrium scour depth Seq around USAF. At last, a parametric study was carried out to study the effects of the Froude number Fr and Euler number Eu for the Seq. The results indicate that the present numerical model is accurate and reasonable for depicting the scour morphology under random waves. The revised Raaijmakers’s model shows good agreement with the simulating results of the present study when KCs,p < 8. The predicting results of the revised stochastic model are the most favorable for n = 10 when KCrms,a < 4. The higher Fr and Eu both lead to the more intensive horseshoe vortex and larger Seq.

Local scour around a submarine piggyback pipeline in combined waves and current is investigated experimentally. Based on the experimental results, the scour evolution and scour morphology are firstly analyzed. Then, a comparison with the equilibrium scour depth Seq between the present experimental data and predicted results is conducted. After that, the correlation between the dimensionless scour timescale T* and the maximum Shields parameter θcw is investigated, and a formula is obtained to describe the variation trend between T* and θcw for different gap ratios G/D. Furthermore, the parametric study is carried out to study the effects of Reynolds number Red and θcw on Seq, respectively. The results indicate that the Seq below the piggyback pipeline increases when the gap ratio G/D increases from 0 to 0.1, and it gradually decreases when G/D > 0.1. For a given KC, the Seq increases with the increase of the ratio of velocities Ucw. In addition, when Ucw is fixed, a higher KC results in a greater Seq. The T* is closely related to θcw and G/D. The higher Red and θcw both tend to result in the greater scour depth below a piggyback pipeline in combined waves and current.

The displacement of monopile supporting offshore wind turbines needs to be strictly controlled, and the influence of local scour can not be ignored. Using p–y curves to simulate the pile–soil interaction and the finite difference method to calculate iteratively, a numerical frame for analysis of lateral loaded pile was discussed and then verified. On the basis of the field data from Dafeng Offshore Wind Farm in Jiangsu Province, the local scour characteristics of large diameter monopile were concluded, and a new method of considering scour effect applicable to large diameter monopile was put forward. The results show that, for scour of large diameter monopiles, there was no obvious scour pit, but local erosion and deposition. Under the test conditions, the displacement errors between the proposed and traditional method were 46.4%. By the proposed method, the p–y curves of monopile considering the scour effect were obtained through ABAQUS, and the deformation of large diameter monopile under scour was analyzed by the proposed frame. The results show that, with the increase of scour depth, the horizontal displacement of the pile head increases nonlinearly, the depth of rotation point moves downward, and both of the changes are related to the load level. Under the test conditions, the horizontal displacement of the pile head after scour could reach 1.4~3.6 times of that before scour. Finally, for different pile parameters, the pile head displacement was compared, and further, the susceptibility to scour was quantified by a proposed concept of scour sensitivity. The analysis indicates that increasing pile length is a more reasonable way than pile diameter and wall thickness to limit the scour effect on the displacement of large diameter pile.

In landslide control engineering, anti-slip piles are the most commonly used means. This article established a numerical model of the interaction between fully weathered granite landslides and anti-slip piles based on the strength reduction method. Firstly, five pile-soil interaction models with different pile spacing were established using Abaqus software, and individual components were generated and assembled using the stretching function. The friction surface is used between the pile and soil, and the normal and tangential contact characteristics are both Penalties. Secondly, the strength reduction method based on displacement criteria is used to reduce the rock and soil parameters to the unstable stage before failure, while calculating the slope safety factor. Then, the influence of anti-slip pile spacing on slope stability, pile shear force, bending moment, and soil arch effect are studied. The strength reduction method and pile-soil interaction model used in this article can effectively avoid single pile effects and have high accuracy in characterizing soil arching effects. The results afford certain application and promotion values by providing theoretical references and technical guidance for similar anti-slide pile reinforced slope projects.

The hydrodynamic loads exerted on offshore wind structures are intricate, and primarily influenced by marine dynamics. The interaction between waves and seabed soil can lead to liquefaction, posing a threat to the secure functioning of offshore installations. This study focuses on the silty seabed, investigating the soil surrounding the monopile through pore pressure response tests conducted in a specially designed wave tank. The research delves into the pore pressure response patterns at various depths and positions of the piles. The findings reveal that the amplitude of pore pressure elevation preceding the introduction of a pile is greater than the post-pile values. Moreover, there is a notable escalation in pore pressure amplitude with increasing depth. Consequently, in practical applications, safeguarding the deeper region in front of the monopile assumes paramount importance. These research outcomes offer valuable insights for enhancing the safety protocols governing offshore wind turbine operations. The emphasis on shielding the deeper sections preceding the monopile, as suggested by this study, holds practical significance in optimizing the operational safety of offshore wind power installations.