For the ecological risks of sediment plumes induced by deep-sea mining disturbances, a high-fidelity numerical simulation framework was developed based on the Navier-Stokes equations, integrating high-resolution 3D topography, seawater density stratification, unsteady tidal dynamics, and multi-scale circulation constraints. A typical seamount mining area southwest of the Canary Islands in the Atlantic Ocean was taken as the research subject, and the multi-stage coupled evolution mechanism of the plume from initial disturbance to long-range ocean current transport was revealed after Spearman data validation. The study found that, constrained by the complex seamount topography and the geostrophic deflection effect, the horizontal path of the plume deflects significantly and exhibits a rotational diffusion pattern, which prolongs the residence time of particulate matter in the local water body. Modulated by the flow-around dynamic field of the seamount and the rotational shear mechanism, the plume evolves from a near-field point source discharge into a far-field anisotropic stretching structure. Due to the inhibitory effect of the stable deep-sea density stratification, the plume spatially exhibits a hierarchical dilution pattern.

Aiming at the erosion failure problem of 90° elbows in deep-sea mining systems, a study was carried out on the wear evolution mechanism under the coupling action of solid-liquid two-phase flow. In combining with the CFD-DEM two-way coupling method and analysis of variance (ANOVA), the influence weights of pipe-to-particle diameter ratio, initial fluid velocity, and particle shape on pipe wear were quantitatively evaluated. The results show that the influence of single factors on the maximum wear rate of the pipe is in the following descending order:pipe-to-particle diameter ratio > initial fluid velocity > particle shape; while the influence of multi-factor interactions on the maximum wear rate is also in the following descending order:initial fluid velocity and pipe-to-particle diameter ratio > particle shape and pipe-to-particle diameter ratio > initial fluid velocity and particle shape. With a lower pipe-to-particle diameter ratio, the elbow suffers severe overall wear, with peak wear concentrated in the middle section of the elbow; with a higher pipe-to-particle diameter ratio, the elbow has its peak wear presenting in the upstream impingement section, with the wear rate in the middle and rear sections of the elbow in an obvious declining trend.

A process consisting of reduction roasting and sulfuric acid leaching was adopted to extract manganese from manganese nodules, and the microstructure evolution and phase transformation during the processes from raw ore, roasting to sulfuric acid leaching were explored. It is found that the reduction rate of manganese can reach 99.29% after 2 h reduction process at 750 ℃. After 6 h leaching with 0.5 mL/g of sulfuric acid at 60 ℃, the leaching rate of manganese is 90.53%. It is shown that part of manganese replaces iron to form acid-insoluble minerals such as jarosite and manganese-iron olivine, which are difficult to be leached out. This study provides a technical reference for preparing electrolytic manganese with low-grade manganese nodules.

To investigate the heave compensation capability of a wave compensation hoisting device, a simulation test bench for the hoisting device was built by using an ordinary hydraulic cylinder and an ordinary accumulator to replace dedicated compensation cylinders and accumulator, and a simulation model was then established based on AMESim. Experiments and simulations were performed to compare the compensation rate and energy consumption of the hoisting device under passive, semi-active and active compensation modes. In the passive compensation mode, the simulated compensation rate was 14.64% and the experimental value was 13.51%; in the semi-active compensation mode, the simulated compensation rate was 91.01% and the experimental value was 89.80%; the simulated compensation rate reaches 94.44% under the active compensation mode. Both simulation and experimental data prove that this alternative scheme can deliver high compensation rate with low energy consumption. It is regarded as a low-cost and efficient solution for testing wave compensation hoisting device, providing a verification platform for subsequent design and optimization of wave compensation hoisting device.

To address the lack of long-term continuous monitoring methods for evaluating the impact of deep-sea polymetallic nodule mining on the near-bottom (with height less than 1 m above the seafloor) ecological environment, a novel near-bottom long-term monitoring platform has been designed and developed. It adopts a passive self-righting design by a "upward-buoyancy and downward-gravity", and has solved the problem of uncontrolled landing attitude during untethered deployment. A novel "sleep-wake" intermittent working mode was proposed to achieve long-term continuous monitoring under limited battery capacity. Deep-sea tests were successfully completed in Block A-5 of the Eastern Pacific. The at-sea test results show that the platform maintained a stable landing attitude and successfully acquired the pH value (average 7.50), flow velocity (average 0.003 3 m/s), and turbidity (1.17-1.25 FTU) of the near-bottom seawater during the testing period, verifying the reliability and effectiveness of the platform in the extreme deep-sea environment.

To address the optimization of stope structural parameters for the deep complex geological orebody beneath the abandoned MSESA open pit in the DRC, an analytical method was proposed, integrating the 3D rock mass quality Q-value model and the Mathews stability graph method. Through rock mechanics tests, a 3D rock mass quality Q-value model of the mining area was constructed. Based on the Mathews stability graph method, the quantitative relationship between the stope hydraulic radius and the stability factor was established, and reasonable stope structural parameters under the condition of the critical allowable hydraulic radius were selected. The results show that for the area north of the+500 exploration line, where the sublevel open stoping with subsequent backfilling method is adopted, the structural parameters should be 35 m × 8 m × 45 m when the stope is arranged perpendicular to the strike under unsupported conditions, and 20 m × 9 m × 45 m when arranged along the strike. In the area south of the+500 exploration line, roof support is required and the optimal stope structural parameters should be 17 m × 8 m × 15 m.

The bench slope within the elevation range from+793 m to+817 m near Line 29 of the Dabaoshan open-pit slope in Guangdong was taken as the research object, and a 3D fracture network model of the slope was firstly established based on relevant geological data and was used to conduct a 3D deconstruction analysis of the rock mass structure of the bench slope. Thereby the data on the location and distribution of blocks within the slope body were obtained. Secondly, a 3D discrete fracture network model of the bench slope was constructed to analyze the displacement and deformation of the slope under the action of fractures and gravity, delineating the potential sliding areas of the bench slope. Thirdly, the dangerous block 1 and dangerous block 2 were identified by combining the block location and distribution information with the potential sliding areas. Finally, the stability of the dangerous blocks was analyzed using the stereographic projection method. The analysis results show that the dangerous block 1 may experience wedge sliding, while the dangerous block 2 may experience double-plane sliding but with a low probability. Since the overall stability of the slope is poor, it is recommended that a combined measure of grouting, anchor cables and lattice beams should be adopted for slope prevention and control.

To address the challenge of freeze-thaw instability of rock slopes in alpine mining areas, the andesite from a slope in a mining area in Ngari of Xizang was taken as the research object. Through freeze-thaw cycle tests, uniaxial compression tests, and triaxial compression tests, the deterioration laws of the mechanical properties of freeze-thaw andesite under different confining pressures were obtained. The results show that with an increase in the number of freeze-thaw cycles, both the compressive strength and shear parameters of the andesite exhibit a decreasing trend, and the deterioration degree gradually increases. Under unconfined conditions, the failure mode of the andesite evolves from splitting failure to mixed splitting-shear failure with an increase in the number of freeze-thaw cycles, accompanied by an increase in cracks. When confining pressure is applied, it enhances the compressive capacity of the rock to a certain extent. As the confining pressure increases, the failure mode gradually transitions from brittle failure to shear-slip failure. After a higher number of freeze-thaw cycles, radial crack propagation develops, accompanied by obvious spalling phenomena.

The iron tailings in Hubei contains 0.058% copper and 9.26% sulfur. It is recovered by bulk flotation followed by separation on site, but the flotation indices of copper and sulfur are unsatisfactory. In order to improve the comprehensive resource utilization rate, experiments on flotation with new reagents were carried out for such iron tailings. With tailings at a grinding fineness of -0.074 mm 64.81%, a bulk floatation was performed with a new collector Xiexin 930 and frother No. two oil; a separation flotation was conducted with activated carbon as an activator, Xiexin 950 as a copper collector, and slaked lime as a sulfur depressant added in stages. As a result, the experiment produced a copper concentrate grading 17.77% Cu at recovery of 60.07%, and a sulfur concentrate grading 38.16% S at recovery of 34.48%. Compared with the on-site reagent regime, the separation indices are improved, with recoveries increased by 17.60 percentage points and 12.28 percentage points, respectively. It is shown that copper and sulfur resources in such iron tailings can be effectively recovered. This experimental study can provide a theoretical reference for the efficient recovery of other similar low-grade ores.

Systematic process mineralogy studies were conducted on a refractory copper-molybdenum polysulfide ore in Yunnan, and a new collector KMC531 was developed according to its properties. The effect of KMC531 on its collection performance in copper and molybdenum was clarified. The results show that under optimized conditions, a closed-circuit flotation test on the raw ore assaying 0.28% Cu and 0.011% Mo yielded a copper-molybdenum bulk concentrate grading 23.51% Cu and 0.92% Mo with recoveries of 82.86% Cu and 86.17% Mo, indicating efficient enrichment of copper and molybdenum.