In the dredging industry, the automation and accuracy of the Dredging Perception System (DPS) are vital for operational efficiency and environmental safety. Current DPS implementations face challenges with sensor fault tolerance, leading to system unreliability and increased false alarm rates that can disrupt dredging operations. We propose a Hybrid Redundancy Sensor Fault Tolerance (HRSFT) strategy that integrates matching physical sensors (PS) with two distinct types of virtual sensors (VS) driven by multi-sensor association and time-series prediction models. The HRSFT employs a voting-cold storage strategy to address the false alarm issues commonly associated with single virtual sensor systems. Through experimental validation, the HRSFT strategy has demonstrated its capability to provide accurate replacement information during both single and multi-sensor failure scenarios, effectively managing abnormal sensor data and enhancing the operational reliability of the DPS. The implementation of the HRSFT strategy significantly improves the accuracy and stability of the DPS, suggesting a substantial advancement in sensor fault tolerance that could be applied to similar systems in various industries, leading to safer and more reliable operations.

In marine environment, floating photovoltaic (FPV) plants are subjected to wind, wave and current loadings. Waves are the primary source of fatigue damage for FPVs. The climate change may accumulatively affect the wave conditions, which may result in the overestimation or underestimation of fatigue damage. This paper aims to present a projection method to evaluate the climate change impact on fatigue damage of offshore FPVs in the future. Firstly, climate scenarios are selected to project the global radiative forcing level over decadal or century time scales. Secondly, global climate models are coupled to wind driven wave models to project the long-term sea states in the future. At last, fatigue assessment is conducted to evaluate the impact of climate change on fatigue damage of FPVs. A case study is demonstrated in the North Sea. A global-local method of fatigue calculation is utilized to calculate the annual fatigue damage on the FPVs’ joints. The conclusions indicate that there are decreasing trends of significant wave height and annual fatigue damage in the North Sea with the high emission of greenhouse gases. The fatigue design of FPVs based on the current wave scatter diagrams may be conservative in the future. The manufacture cost of FPVs can be reduced to some extent, which is beneficial to the FPV manufacturers.

Cutter suction dredger is one of the ship types widely used in dredging engineering, especially for rock dredging, this ship type has more obvious advantages. Compared with dredging of sediment, rock excavation requires higher performance of cutterhead. Therefore, the determination of cutting force and the research of excavation effect in the process of cutting rock with cutter teeth have important guiding significance for the design of cutterhead and dredging construction. In view of the heterogeneity of natural rock material, complex internal mechanical properties and poor regularity and repeatability of tests, concrete samples were innovatively prepared to replace natural rock samples. A large scale model test platform was used to test the linear cutting of rock by cutter teeth. The cutting resistance of cutter teeth and the groove shape of the rock sample under different cutting angles and cutting depths were compared and analyzed. The test results show that in the process of rock cutting, cutting resistance of cutter teeth varied linearly with cutting depth, but the regularity was not obvious when cutting depth was small. The dimensionless cutting specific energy (SEQ) decreased with the increase of cutting depth, and it decreased rapidly when the cutting depth was small; when the cutting depth reached a certain value, SEQ basically did not change. The cutting width increased with the increase of cutting depth while they were linearly correlated, and the fitting curves under different cutting angles were basically the same.

A jet pump is used to transport a variety of working media and is especially suitable for dredged soil transporting. In this study, a three-dimensional numerical study of a jet pump that is used for slurry delivery was carried out. The characteristics of the internal flow field of the mixing chamber with different working parameters were comprehensively analyzed. The results indicate that the pressure of the axial line decreases with increasing flow ratio (ratio of suction flux and inlet flux) while the pressure of the injected slurry shows a downward trend. With the increase in the flow ratio, the pressure ratio (difference between inlet pressure and suction pressure divided by the difference between exit pressure and suction pressure) falls off while the efficiency presents a parabolic distribution. The pressure ratio can be promoted by properly increasing the length of the mixing chamber so that the available efficiency is broadened. When the mixing chamber length is L = 2.5D_n~4.0D_n (D_n is nozzle outlet diameter), the highly efficient area is wide; in particular, when L = 3.5D_n, the jet slurry pump with the highest efficiency of 27.6% has the best performance.

Slurry transport is a very important means of transporting solids through a pipeline. To improve the efficiency of slurry transport, especially in coarse particle transport, which is subject to problems such as strong resistance and easy blockage, more of the internal structure of the flow must be known. Empirical and analytical models are inadequate for this purpose. Therefore, in this study, a coupling mechanism is established between the computational fluid dynamics (CFD) and discrete element method (DEM). The CFD-DEM coupling was applied and research was conducted on the internal flow structure characteristics of microscopic motion and flow transition for coarse particles in a pipeline. The flow-regime transition processes of coarse 10-mm particles were analyzed qualitatively at velocities of 2 m·s ⁻¹ , 5 m·s ⁻¹ , 8 m·s ⁻¹ and 10 m·s ⁻¹ in a 0.1524-m diameter pipe, and quantitative analyses were performed on both the concentration distribution and the pressure gradient of particles in regimes of fixed bed flow, sliding bed flow and heterogeneous flow. Moreover, from the perspective of force analysis of particles, the law of sedimentation movement of particles is discussed, and the reason for the change in concentration distribution is explained. The research presented here provides insight into the internal structure of the flow and gives quantitative indications of pressure gradient and concentration distributions.

Currently, a fundamental relation between cohesion and adhesion in cohesive soils has not been established. Yet, it is of great importance to get a better understanding of the relationship between cohesive and adhesive forces, because the large surfaces on dredging tools can generate a lot of resistance, meanwhile limiting the production for materials with increasing adhesion. Because the relationship is not exactly known, the adhesive strength of a clay is usually expressed as a fixed fraction of the cohesive strength, varying between 60% for hard clays and 100% for soft clays. Material tests of cohesive soil have been undertaken to detect the actual relation between the adhesion and cohesion of cohesive soil. The experimental results can directly help the implementation of the Delft sand, clay and rock cutting model, as a result the optimal cutting angle in dredging practice can be calculated. In this way, the designs of dredging tools are improved, which can help to increase the overall production rate in dredging operations. This paper gives detailed description of the experiment setup and results.

Transportation of the coarse materials is one of the major challenges in slurry transport for dredging. Unfavorable situations may occur, e.g., the strong hydraulic resistance and the blocking in the pipe. In this study, An Eulerian-Lagrangian coupled algorithm is implemented to model the pipeline transport process of coarse particles. Codes of computational fluid dynamics (CFD) and discrete element modeling (DEM) are utilized for simulating the fluid and the solid behavior respectively. The numerical modeling of particles with a diameter of 10mm transported in a pipeline with a diameter of 15.24cm is carried out under three different conveying line speeds. Qualitative study is made on the transitions between different flow regimes, and quantitative analysis is made on the volumetric concentration and the hydraulic gradient in the pipe.

The behavior of fully-suspended slurry flow in horizontal pipeline can be simulated through two very distinct models, the Computational Fluid Dynamics (CFD) model and the Delft Head Loss & Limit Deposit Velocity (DHLLDV) model. The predicted results from simulations are compared with a series of experiment data from the literature, involving the effects of different particles volume concentration (9–42%), particle size (90–440 μm), mixture velocity (1–9 m/s), and pipe diameter (51.5–263 mm) on hydraulic gradient and particles concentration distribution, and revealing excellent agreements between two model predictions and the experimental data. Both CFD and DHLLDV, however, still have some deviations in the near-wall concentration distribution as for larger particles. Though it is observed that the accuracy for CFD will decline when particle size increases and further research is needed for improving the accuracy of the models for the near-wall flow of larger particles, it can be concluded that both CFD model and DHLLDV model apply to calculations for fully-suspended flow.