Based on the failure and instability of different structural transitions of offshore breakwater, this paper provides a basis for understanding the instability mechanism and also provides suggestions for engineering repair. Based on the breakwater project in the regulation of the bay of Shandong Province, physical model tests with a scale of 1:36 were carried out. This study revealed the wave characteristics, the force performance, and the instability mechanism in the transition. In the test, the relationships between 5°, 15°, 35°, and 75° oblique waves, the wave force, and the stable weight of the Accropode were simulated, revealing that the generation of a shock wave current is related to the wave direction angle, which results in the local wave height increasing by 2.05 times. The result that the design weight of the armour block is unstable and stable after optimization is obtained. The wave force of the caisson of the transition was concentrated in the anti-arc section of the superstructure, and the maximum horizontal force, buoyancy force, and impact pressure were 935.6 kN, 419.1 kN, and 65.9 kPa, respectively. The instability mechanism was determined as the poor connection between the accropode and the caisson, and the wave energy concentration. Compared with the calculation results of the standard formula, the correction coefficients of the overtopping volume, the wave crest elevation, the wave force, and the Accropode weight at the transition of breakwater were 1.95, 1.97, 1.60, and 4.0, respectively. The test results have solved the practical problems of the project and can also provide a reference for similar projects.

In order to ensure the safety and reliability of the submerged tunnel covering layer at the junction of an artificial island and tunnel under extremely bad conditions, the wave current characteristics and the stability of the protective structure in the variable slope section were studied. By conducting model tests, the coupling effect of wave and current is revealed in this study. The hydrodynamic field, including the varying angles between waves and currents, is simulated in the model test. The ratio ($H_{\mathrm{s}}^{\prime }/H_{\mathrm{s}}$) of the wave height and the ratio ($U^{\prime }/U$) of the velocity with and without the existence of a current, the relative velocity (U$/C$), the wave steepness ($H_{\mathrm{s}}/L$), the relative water depth ($d/L$) and the angle ($\alpha$) between wave and current are obtained, and the corresponding calculation expression is derived, by checking the test results, the empirical formula can better predict the changes of wave height and water flow after wave current coupling. The stable weight of the surface protection rock is obtained through an optimization test. Based on the relationship between the stable weight of the protection rock and the wave height under the wave–current coupling effect, a modified expression for calculating the stable weight of the armor block is derived. The modified calculation method can support estimating the stable weight of the armor rocks of an overburden structure of a similar immersed tunnel under the wave–current coupling effect. This study can not only solve the practical problems of major projects of the Shenzhen–Zhongshan channel but also provide valuable basic data and technical support for the construction of overburden of subsea-immersed tube tunnels in the future.

Based on the occurrence of floating and fracture accidents of FRP pipes on muddy seabeds in practical engineering combined with the water intake and drainage project of the 2 × 660 MW coal-fired power plant in the second phase along the coast of Vietnam, a model test study was carried out. The laboratory simulated the FRP pipe conditions during the construction and operation periods by configuring different densities of silt. The experiment results obtained are as follows: the FRP pipes floated up in the mud during the construction period; the thickness of sediment deposition when the FRP pipes are lifted up, as well as the entire lifting process time and maximum force, are all within 2 h and 70 kN/m; after adopting a cover layer design section during the operation period, the FRP pipes in the silt remain stable while obtaining a maximum force of 15 kN/m; and based on the experimental results, an empirical formula for the stress on FRP pipes and was derived and measures for FRP pipe stability were proposed. The research results not only solve practical problems in water intake and drainage engineering but also provide technical support for the promotion and application of FRP pipes.

Based on the project sea area where the large-scale sea-crossing bridge is located, the marine environment is facing the threat of severe marine environmental issues such as strong typhoons and big waves. In order to resist the impact of the super wave load, the research focuses on a new structure derived from soft computing techniques in a simulated environment. Since the conventional methods cannot be used for handling such an important problem, soft computing techniques can certainly help to provide simulated solutions. These solutions can be exploited in a real-time environment to test their viability. The overall physical model test of the wave with a scale of 1 : 40 is carried out in this research study by using the proposed methodology. By setting a series of groups such as different wave height, period, water level (pier foundation scouring depth), and wave-current coupling, it is studied that the wave height and period are in positive proportion to the wave force on the pier column structure. However, there is no obvious relationship with the water level change (scouring depth). The buoyancy of the pile cap structure is about 1.27 times greater than that of the pier structure. Compared with the combined wave force of the single wave and wave current, the sensitivity and the relationship have been studied. Using this study and several engineering results completed in the early stage and also verified by the measured data, the results show that the proposed soft computing technique has good accuracy and can provide a reference for the load estimation of large-scale foundation structures.

The construction of artificial islands not only alleviates the shortage of coastal land resources but also brings new environmental problems. This study focuses on the fundamental changes in the hydrodynamic environment and sediment transport caused by the construction of artificial islands, leading to imbalances in sediment distribution and beach erosion. This article takes the coast of Riyue Bay in Hainan Province, China, as an example and uses various methods such as field surveys and model experiments to explore the evolutionary mechanism of beach landforms under the influence of artificial islands. Based on this, an adaptive “cyclic maintenance” beach restoration plan is proposed. Reasonable distribution of beach sediment is achieved through experimental verification, effectively mitigating the coastal erosion caused by the construction of artificial islands. The expected goals were achieved after 2 years of implementation of the on-site restoration project. The results of this research not only solve practical engineering problems but also provide a good reference for the restoration of similar types of coastal beaches.

Due to the depletion of near-shore resources and the complex environment of offshore deep-water open port construction, a new barrel-pile foundation composite structure wharf is proposed. In order to provide technical support for the engineering design and application of the new structure, research is carried out on a physical model. Through setting up a series of group tests, on the basis of fully understanding the wave impact characteristics of the wharf panel of the new structure: (1) the relationship between the wave crest height, impact force, and various influence factors is established; (2) a calculation method and formula are put forward (compared with the physical model test data, the calculation formula results have good accuracy); (3) according to the formulas of wave crest height and panel impact force, a determination method for the wharf surface elevation of the new structure is given. In addition, due to the limitations of the test conditions, it is suggested that the physical model should be further verified for a complex transverse and longitudinal beam structure or extreme sea conditions, such as traveling wave breaking and wave inundation of the wharf.