A discussion on collaborative development of low-altitude economy (LAE) and mining & metallurgical engineering (MME), as well as the two-way empowerment mechanism is presented. Low-altitude technologies, such as unmanned aerial vehicle (UAV) and electric vertical take-off and landing aircraft (eVTOL), can be used to reshape MME, while MME can provide core materials for low-altitude aircraft. However, the collaboration between them is limited by disciplinary barriers and talent gaps, so it is necessary to build a dual system of “technology chain－talent chain”. This can be achieved by adding interdisciplinary courses, establishing actual flight certification bases in mining areas, promoting integration of relevant qualification certifications, and accelerating incubation of key technologies based on low-altitude economic industrial parks. These measures can break down discipline barriers, shorten the cycle of technology transformation, and provide support for the in-depth integration and collaborative development of LAE and MME.

In order to accurately know the progress in frontier technologies and research hotspots in environmental monitoring and protection during deep-sea mining, after the patents and academic literature from January 1, 2005 to April 14, 2025 in the filed of deep-sea mining were retrieved with IncoPat and Web of Science, a statistical analysis was performed with bibliometric methods for 542 published patents and 469 academic literature, and then the development trend in this field was also discussed. It is shown that a synchronous increase in both patents and academic literature highlights the support of basic research for technological innovation. By formulating corresponding policies and through institutional collaboration, China has shifted its place from following others to keeping pace and even leading the pack in theoretical research. China has also put emphasis on the technologies of environmental monitoring and protection in its scientific research on deep-sea mining, and established a technical system and theoretical framework with in situ observation technologies for environmental impacts during deep-sea mining at the core. As a result, the research perspective has shifted toward understanding of complex system mechanisms. In the future, the environmental monitoring and protection system for deep-sea mining will be composed of four core modules, including environmental monitoring, environmental assessment, environmental management and environmental protection, and form an ecological risk supervision and management framework through the whole mining process, which will also be continually updated.

Several pieces of hard paper with different numbers, dip angles and widths were embedded into specimens to simulate structure of closed joint in rock masses and prepare rock mass models with different joints. Effect of joints on blast-induced failure characteristics of rock mass was analyzed with a high-speed camera and a 3D laser scanner, so as to explore the rules of crack propagation and fragment size distribution during rock blast. It is found that joints can disperse blasting energy and hinder crack penetration, leading to a decrease in the average size of blast-induced fragments as the number of joints increases. Wider joints can make diffraction and reflection of stress waves much more complicated, intensify energy dissipation, and also hinder crack propagation；while joints with small width are prone to make blast-induced fragments smaller in size. The interaction between joint dip angle and the propagation direction of the blast stress wave can significantly affect the crack propagation mode, and excessively large dip angles can easily hinder stress wave propagation.

As for backfill slurry transported through reducing bends, the effect of bend angle, inlet flow velocity, mass fraction and average particle size of slurry, mass flow rate, particle shape factor and particle impact angle on the erosive wear of reducing bends were analyzed with Fluent software. The results show that the inlet flow velocity of slurry exerts the most significant impact on the erosion-prone areas of pipeline. With the inlet flow velocity up from 0.8 m/s to 2.0 m/s, the erosion rate in the erosion-prone areas of the pipeline surges approximately 43 times. The average particle size of the slurry ranks second in terms of its impact on the pipeline's erosion-prone areas, while the bend angle and particle impact angle have relatively minor effects. It is found that the erosion rate in pipeline is related to the kinetic energy of slurry；the greater the kinetic energy of the slurry, the more severe the erosion. The erosive wear locations of pipeline are primarily distributed at the inlet, the inner and outer wall surfaces of the bend, and reducing section and the straight section to the elbow, with the connection between the reducing section and the outlet section worn most severely.

As for rainfall-induced landslides in Mayang, Yuanling and Luxi counties within the red-bed region of the Yuanma Basin in Hunan Province, a correlation between landslides and rainfall were analyzed. Based on the E-D threshold model, the daily rainfall (R) was introduced as a third indicator to construct an E-D-R threshold model, thereby rainfall thresholds were determined for the Yuanma Basin. The study area was divided into warning units with the Thiessen Polygon method, enabling a county-level, unit-based graded warning response. The results show that the period from four days before a landslide to the day of the landslide represents the critical rainfall period for inducing landslides in the Yuanma Basin, and it is deemed appropriate for the effectiveness coefficient (α) of the rainfall to be 0.5. Compared to the two-dimensional E-D threshold model, the three-dimensional E-D-R threshold model demonstrates higher precision and offers greater accuracy and reliability in landslide risk assessment. The grid-based and refined division of warning units not only enhances the refined management and control capabilities of meteorological warnings for landslide disasters, but also facilitates unit-specific differentiated warnings in future forecasting by integrating predicted rainfall and rain information.

As for the slope collapse at bench merging section in an open-pit mine, engineering geological analysis, analysis with stereographic projection and mechanical analysis were employed to comprehensively explore the main factors inducing slope collapse. Based on the causes and instability characteristics of slope collapse, a management scheme was proposed and thoroughly demonstrated. The results show that the collapse of bench slope occurs under the combined effects of rainfall infiltration and excavation at bench merging section, and induced effects of rock mass properties and weathering fracture surfaces. A management scheme of “gravity retaining wall foot pressure + gravel soil backfilling + shotcrete and rock bolt support” was proposed. The overall stability coefficient of the slope after management is 1.39, meeting the safety standard requirements.

Wavelet analysis was performed for the collected pressure signals of gas-liquid two-phase flow in a vertical pipe in an air lift test. The optimal wavelet basis functions were determined by improving the signal-to-noise ratio (SNR). The range of decomposition levels was determined based on changes in energy of detail coefficients, and optimal decomposition levels were determined by the entropy weight method together with SNR, root mean square error and smoothness. After denoise with wavelet thresholding, three-level decomposition of signal was performed with the wavelet packet method, and then flow patterns were identified for gas-liquid two-phase flow with the energy ratio in the 1st and 2nd frequency bands and entropy values as feature vectors. The flow pattern recognition based on 389 sets of pressure signals shows that the extraction feature vector combined with random subspace decision tree can efficiently identify and classify gas-liquid two-phase flow patterns, and the overall mean recognition rate is up to 98.08% by adopting the improved wavelet thresholding.

To address the issue of volumetric locking encountered in the slope stability analysis with three-node triangular elements in upper bound finite element method (UBFEM), a six-directional triangular mesh (P6) with weak velocity discontinuity line characteristics was proposed based on the mechanical equivalence effect between velocity discontinuity lines and conjugate triangular elements located in the same position. The P6 is utilized in conjunction with a six-node triangular (T6) element in UBFEM for slope stability analysis. The results show that the potential slip surface of the slope obtained using the P6 combined with T6 elements is clearly defined, with a smooth transition in dissipated energy density. As the mesh density increases, the effect of weak velocity discontinuity lines strengthens, leading to an improved accuracy in the upper bound solution of the slope stability coefficient (N_s). With the combined influences of factors such as the internal friction angle and slope gradient into consideration, the upper bound solutions of N_s obtained with P6 outperform those from three-directional triangular meshes and Delaunay triangular meshes. The uniform mesh generated by the P6 UBFEM in a single computational framework yields favorable results, facilitating batch processing operations such as strength reduction upper bound analysis. Additionally, its application scope can be extended by integrating it with adaptive mesh refinement techniques.

To explore the mechanism of phosphogypsum in modification of grouting materials for mines, grouting materials were prepared with different proportion of ingredients. Performance indicators including fluidity, permeability, strength parameters and leaching rates of heavy metals were analyzed, and the microscopic mechanism of phosphogypsum-modified grouting material was also explored with scanning electron microscopy and X-ray diffraction. Results show that an addition of phosphogypsum in grouting materials can not only actualize effective utilization of resource, but also improve fluidity of grouting material. It is shown that by adding 30% of phosphogypsum, the grouting material exhibits better fluidity and impermeability, significantly enhanced compressive and flexural strength, and reduced leaching rates of heavy metals. Furthermore, phosphogypsum can promote secondary hydration reaction, leading to more calcium-silicate-hydrate gel, which thereby can improve structural stability and engineering performance of grouting material.

Based on the unascertained measure theory, ten influencing factors, including hydrological and engineering geological conditions, slope height, slope gradient, foundation pit depth, drainage facilities, adjacent loads, distance from adjacent loads to the pit edge, maximum daily rainfall, support method and construction method, were selected. The weight of each indicator was determined by using the entropy weight method, and an unascertained measure theory model for a certain foundation pit slope was established. Then the slope's stability level was determined by adopting Euclidean distance discriminant method. The results indicate that when there is heavy rainfall and both drainage facilities and support methods are poor, the foundation pit slope is instable. When there is no rainfall and both drainage facilities and support schemes are good, the slope is relatively stable. It is shown that drainage facilities and support schemes have a significant impact on slope stability. Field monitoring data show that the evaluation results are consistent with the actual situation, demonstrating high reliability of the proposed unascertained measure theory and Euclidean distance discriminant method for evaluating foundation pit slope stability.