The deep-sea is rich in mineral resources, and deep-sea polymetallic nodules are considered to be the most likely resource for commercial exploitation. Since the discovery of polymetallic nodules by mankind, researchers around the world have made long and arduous explorations in the exploitation of deep-sea polymetallic nodules and have proposed various mining methods, such as the dragging bucket type, the continuous bucket rope type, the automatic shuttle boat type, and the pipeline -lifting type, and have carried out technical verification accordingly. In the collection of seabed polymetallic nodules, the development and testing of towed type, spiral-driven type, crawler self-propelled type, and suspended type technologies have been carried out, basically realizing the mining technology verification of seabed polymetallic nodules and providing technical support for commercial development. However, according to the demand for commercial development, there are still many technical difficulties in polymetallic nodule-collecting technology, and more focus needs to be placed on the efficiency, environmental protection, intelligence, safety, and reliability of the collecting system in the future. This paper compares the existing progress in collection technology and equipment, and provides ideas and references for the research and development of deep-sea polymetallic nodule-mining technology and equipment.

The vast seabed holds tremendous resource potential that can provide necessary materials for future human societal development. This study focuses on the mineralogy of seafloor manganese nodules off the coast of China in the Western Pacific and the primary techniques for extracting valuable metal elements from manganese nodules. The research indicates that the main valuable metal elements in the manganese nodules from this region include Cu, Co, Ni, Mn, Fe, etc. The key to extracting these valuable metals lies in reducing Mn(IV) to Mn(II) to disrupt the structure of the nodules, thereby releasing the valuable elements. The extraction processes for the main valuable metal elements of manganese nodules are mainly divided into two categories: pyrometallurgical–hydrometallurgical and solely hydrometallurgical. In order to cope with the challenges of environmental change and improve utilization efficiency, bioleaching, hydrogen metallurgy, and co-extraction are gaining increasing attention. For promoting commercialization, the future development of manganese nodule resources can refer to the technical route of efficient short-process extraction technology, the comprehensive recovery of associated resources, and tail-free utilization.

The conveying hose is an important piece of equipment in the field of Marine engineering. Its spatial configuration and force conditions affect the normal operation of the Marine engineering system. This paper proposes a flexible, fully hose-based conveyance method for the field of deep-sea mining and mainly uses Orcaflex software to simulate and analyze the characteristics of the conveying hose in this system. This paper studies the influences of the top spacing, incoming flow direction, and placement and recovery processes on the configuration characteristics and force conditions of the hose. The conclusion drawn is that the conveying hose studied in this paper can maintain a good spatial configuration underwater and has a stable force condition. When the top spacing is 20 m, the transition of the curved section at the bottom of the hose is relatively smooth. The top tension of the hose has a good adaptability to the top spacing and the direction of the incoming flow. The conveying hose can stably complete the deployment and recovery operations.

Understanding the interaction between submerged water jets and cohesive deep-sea sediment is critical for optimizing deep-sea polymetallic nodule hydraulic mining techniques. This research investigated the distinct erosion behavior of cohesive sediments through laboratory experiments and numerical simulations. Cohesive deep-sea sediments were simulated using bentonite–kaolinite mixtures. A series of laboratory experiments, including vane shear tests and viscosity tests under varying moisture content, were conducted to assess the sediments’ mechanical properties. Experimental submerged water jet erosion tests provided basic data for validating the numerical simulations. A Eulerian multi-fluid (EMF) model was implemented to capture sediment–water jet interactions under varying operational parameters, including jet velocities and nozzle heights. The erosion process was found to comprise three distinct stages, including rapid erosion, steady erosion, and stabilization. Two distinct erosion mechanisms were identified, depending on the jet intensity, which affected the depth and shape of the erosion pits. Quantitative analysis revealed that erosion depth exhibits an approximately linear relationship with jet velocity and nozzle height, whereas the erosion diameter shows nonlinear characteristics. These findings enhance the fundamental understanding of cohesive sediment responses under hydraulic disturbances, providing crucial insights for the design and optimization of efficient deep-sea mining systems.

This study examines the strongly nonlinear cross-media dynamics of a deep-sea umbilical cable–payload system during free-surface crossing under different sea states and lifting speeds. A two-dimensional time-domain lumped-mass model was established, in which the cable was discretized into node–axial elements. Morison-type hydrodynamic loading, added mass, and a continuous air–water parameter transition governed by an immersion factor were included for both the cable and the lower-end payload. To improve numerical robustness in long-duration simulations, a segmented ODE15s integration scheme was adopted, together with a smooth-start lifting–heave boundary condition and an adaptive lift-height correction procedure to ensure a stable cross-media response window. The results show a clear spatially segmented response: the upper cable remains nearly straight, whereas the middle and lower sections accommodate most of the lateral offset and curvature redistribution, which intensify under stronger environmental forcing. Top tension shows a gradually increasing mean component superimposed on quasi-periodic oscillations, while bottom tension, detrended vertical payload displacement, and vertical hydrodynamic force are more sensitive to sea-state severity and lifting speed. These results provide a comparative numerical basis for identifying response trends, screening lifting speed options, and interpreting cross-media load transfer mechanisms. Because the formulation is two-dimensional and has not yet been validated against model-scale or full-scale measurements, the results should not be interpreted as equipment-specific safety limits.