The Western-Pacific region contains abundant polymetallic nodule resources. Effectively exploiting these resources is of great significance for the metal resources supply in China. To verify the feasibility of deep-sea mining and achieve commercial mining, it is necessary to conduct in-situ sea trials of the mining system in the mining area and develop environmental monitoring procedures to assess the impact of the mining operations on the environment. This study focuses on the monitoring content and monitoring plans by establishing a set of environmental monitoring and impact assessment procedures. It details the environmental monitoring procedures for sea trials across pre-trial, in-progress, and post-trial phases. The results show that polymetallic nodule mining is feasible in the Western-Pacific region. However, the impacts of mining plumes and sediments on the bottom marine ecosystem should be considered carefully, alongside the formulation of effective mitigation measures.

To address the influence of multi-scale complex loads on the deep-sea mining transport system during operations, the Failure Modes and Effects Analysis (FMEA) method is improved based on the α-cut fuzzy numbers, resulting in an α-cut based Fuzzy FMEA model ( α-FFMEA). The evaluation criteria of failure modes, including occurrence ( O), severity ( S), and detectability ( D), are described by using linguistic terms, effectively overcoming the limitations of traditional methods in dealing with uncertainty. Analytic Hierarchy Process (AHP) and entropy theory are used to assign the weights of O, S, and D reasonably and objectively, ensuring the scientificity and accuracy of the risk assessment. The α-cut fuzzy numbers and centroid method are then used to calculate the risk priority number of each failure mode across different α-cuts, providing a quantitative basis for system failure prevention and optimization. Finally, the transport system in the deep-sea linkage system is analyzed to validate the effectiveness and applicability of the model, offering important theoretical basis and practical guidance for the optimization and failure prevention of the deep-sea mining transport system.

The aquaculture ship is one of the core equipment for the development of deep sea aquaculture, and the large aquaculture ship using recirculating water technology is one of the main technical route for the development of aquaculture ships in China. With recirculating water aquaculture system as the core, the factory aquaculture technology is adopted to improve the application scope and industrialization level of the aquaculture equipment. In view of the characteristics of this type of ship, a general design idea is proposed based on the development of some 80,000 m³ aquaculture ship, which focuses on the general arrangement, system design, structural design and overall performance analysis by taking the recirculating aquaculture system as the core. The design points of the recirculating aquaculture system, the water intake system, and the aquaculture comprehensive management and control system are discussed to provide references for the subsequent design of this type of ship.