Existing reviews on deep-sea polymetallic nodule mining focus only on structural optimization of individual equipment, lacking a systematic analysis of full-chain key technologies oriented to the core dual goals of ‘‘cost reduction and efficiency enhancement”, which cannot support the commercialization process. To fill this gap, this paper systematically sorts out the technological progress and bottlenecks in three core stages (seabed mining vehicle mobility, mineral collection, and ore lifting) based on the full-chain technical framework of ‘‘precise seabed nodule collection – long-distance stable transport”, and explores feasible cost-saving and efficiency-enhancing solutions. The results show that the unique soft sediment properties in nodule-rich areas (water content 312%–577%, internal friction angle < 8°, undrained shear strength 4.0–15.5 kPa) are the primary factors limiting equipment stability. Optimized sharp triangular track shoes increase maximum traction by 120% under typical working conditions (15% slip ratio, 0.6 m/s travel speed), while thick triangular ones achieve 70.4% higher traction with 18% weight reduction. Hydraulic collection dominates current technologies, with the Coandă effect scheme reaching 87% maximum efficiency, and multi-stage centrifugal hydraulic lifting is the engineering focus. Innovatively, the synergy of mining and carbon sequestration increases unit revenue by 606.3% and reduces CO₂ sequestration cost by 62.8%, while the ORC system for wastewater energy recovery covers 15%–20% of total mining electricity demand. Core commercialization obstacles include uncoordinated mobility-collection systems, unstable pipeline transport, poor material adaptability to extreme conditions, and high costs. This paper clarifies key breakthrough directions for full-chain optimization, providing a systematic framework and technical reference for the industrialization of deep-sea polymetallic nodule mining technologies.

The quantitative regulation mechanisms of injection temperature and pressure on the spatiotemporal multi-field evolution in in-situ coal-to-hydrogen (ISCH) conversion remain poorly understood. We developed a coupled thermal–hydraulic-chemical (THC) model and performed full-factorial simulations to elucidate the competitive interactions between these parameters. Results demonstrate a distinct functional differentiation: injection pressure serves as the decisive lever for the spatial expansion rate, where increasing pressure from 8 MPa to 10 MPa surged the average expansion rate by 200.0%; conversely, injection temperature predominantly governs the induction period, with an increase from 673.15 K to 873.15 K reducing the initiation time by 59.2%. While the system exhibited convergence toward a quasi-steady configuration regardless of initial conditions, high-energy injection strategies effectively suppressed the localized accumulation of carbon byproducts by intensifying fluid transport. Crucially, this study identifies ‘‘heat–mass spatial decoupling”—characterized by the spatiotemporal mismatch between the high-temperature core and the reactant field—as the fundamental bottleneck restricting initial hydrogen production efficiency, rather than thermal energy depletion. Accordingly, this study suggests that enhancing spatiotemporal overlap through dynamic pressure modulation and gradient steam-to-oxygen regulation is essential for maximizing ISCH yield.

Rock fragment size distribution (FSD) plays an important role in various engineering applications, such as mining, tunnelling, and other underground construction scenarios. While vision-based deep learning approaches have been increasingly applied to FSD analysis, they are often case-specific, showing limited cross-site generalization despite their accuracy. To address these challenges, FragSAM, an end-to-end, fully automated framework is proposed for near real-time rock fragment segmentation and FSD analysis across diverse engineering environments. FragSAM integrates the generalization power of Segment Anything Model (SAM) with a context-aware prompting mechanism and lightweight architecture for efficient dense fragment segmentation. In Stage 1, an enhanced SAM automatically generates high-quality annotations, which are used to train a modified CenterNet for precise centroid prediction. In Stage 2, these centroids serve as prompts for EdgeSAM, a lightweight SAM variant optimized for real-time inference. This two-stage design eliminates dense grid prompting and reduces reliance on heavy post-processing, enabling efficient and scalable segmentation. Experimental results show that FragSAM achieves competitive segmentation performance with significantly lower latency and model complexity compared to existing SAM-based methods. In comparison with supervised learning approaches, it also demonstrates superior generalization and performs better in low-quality or unseen scenarios. Furthermore, case studies on blasting fragmentation, TBM muck, and coastal rock surfaces confirm its robustness and seamless cross-site adaptability, requiring no tuning or retraining, making it highly practical for on-site applications.

During the operation of the drilling cuttings method, frequent occurrences of suction and sticking phenomena lead to the loss of drilling tools and failure to achieve the designed borehole depth. resulting in inaccurate risk assessment for coal seam rockbursts. To address these challenges, a mechanical analysis of cuttings transport via the spiral drill pipe was conducted. This analysis identified the primary factors contributing to suction and sticking phenomena in spiral drill pipes and proposed a targeted approach for mitigating these issues. Based on this analysis, an intelligent drilling cuttings method drill rig (IDCMDR) was developed, and field experiments were conducted. The experimental results demonstrate that when suction occurs, adjusting the rotational and drilling speeds of the IDCMDR effectively controls the phenomenon. When sticking occurs, the stuck drill pipe can be addressed by injecting high-pressure gas into the borehole bottom through the hollow structure of the spiral drill pipe or by reversing its rotation. During operation, characteristic patterns in the needle movements of the thrust and torque hydraulic gauges on the IDCMDR enable the identification of suction and sticking phenomena. The development and field validation of the IDCMDR confirm the feasibility of the theoretically proposed mitigation methods.

Damage evolution and seepage behavior variations of rock salt under cyclic loading directly affect the long-term safety of the storage, especially the unclear damage-permeation coupling mechanism of impure rock salt. Through cyclic loading and hydrogen permeation tests, this study systematically investigated the damage evolution and permeability change patterns of impurity rock salt under different stress levels and cycle counts. Results show that the damage evolution presents the stage characteristics of ‘‘initial intense damage-gradual stable damage-final rapid damage”. High stress promotes the development of shear cracks and significantly increases the cumulative acoustic emission energy. Permeability increases nonlinearly with stress level and cycle number. Stress level determines the type of damage mechanism, while cycle number determines the degree of damage accumulation. And shear crack penetration is the main controlling factor for the formation of seepage channels. A permeability prediction model based on cumulative acoustic emission energy is established, enabling effective characterization of the damage-permeation coupling relationship. The research provides important theoretical basis for the sealing integrity and safe operation of salt cavern hydrogen storage.

Previous studies about natural disasters proved the crucial influence of fault geometrical complexity. The laboratory tests were conducted to investigate its effect, and the fault misalignment ratio was used to quantify fault geometrical complexity. Samples with different fault misalignment ratios were compressed under uniaxial and triaxial conditions, with a distributed optical fiber sensor (DOFS) being applied to obtain full-field deformation across the sample surface. The entire process of deformation localization was quantified by the Gini coefficient. Moreover, the acoustic emission (AE) was used to capture fracture signals during the entire process. The difference in failure processes, influenced by various fault geometries, was compared based on mechanical and deformation characteristics. Results show that fault networks with simple geometrical characteristics facilitate strain delocalization with slow and small stress drops, which may originate from slow fault slip. However, strain localization dominates the entire deformation process with sudden and larger stress drops for fault networks with complex geometry. The analysis of deformation localization and stress drops indicates that a crucial fault misalignment ratio, significantly changing the failure mechanism, may appear between 0.2 and 0.4. The CT images show that crack propagation controls the deformation process, and the potential mechanism was explored to explain this difference.

Air leakage through the crushed zone surrounding boreholes is a critical bottleneck constraining efficient gas extraction, yet its underlying mechanisms remain unclear. This study employed a CT visual compaction apparatus, enabling, for the first time, the visualization and quantitative investigation of leakage pathways within the crushed zone. The main findings are as follows: (1) Particle re-crushing exhibits significant spatial non-uniformity, with its re-crushing degree descending in the order of upper zone, middle zone, lower zone. (2) As increasing stress, the void network evolves from a mesovoids-dominated system to one dominated by small voids and microvoids, whose combined proportion ultimately reaching 85%, and the voidage decays exponentially with increasing stress. (3) Under the stress, particle morphology evolves toward greater regularity and roughness, evidenced by an average increase of 224.7% in specific surface area, along with increases of 6.6% in flatness and 5.4% in elongation. (4) Based on this non-uniform evolution mechanism, an adaptive sealing strategy is proposed to guide the development of materials with dynamic responsiveness, enabling precise and persistent sealing of evolving leakage channels. The established visual-quantitative framework elucidates the microscopic mechanisms of air leakage and provides a crucial theoretical foundation for the development of adaptive sealing technologies.

Accurate in-situ identification of coal and gangue is critical for intelligent mining, particularly in longwall top coal caving (LTCC) mining, where it enables precise control of the gangue mixed ratio and enhances resource recovery. This study introduces a Secondary Intervention strategy to augment the conventional ‘‘liquid intervention + infrared detection” approach. Results demonstrate that Secondary Intervention can consistently enhance the thermal contrast between coal and gangue, and the average accuracy of infrared image recognition for coal and gangue increased from 79.14% after the First Intervention to 93.75% after the Secondary Intervention, representing an improvement of 14.61%. Furthermore, the average contact angle difference between coal and gangue expanded from 16.64° after the First Intervention to 33.80° after the Secondary Intervention, an increase of 17.16°. Meanwhile, the area difference between coal and gangue increased by 4.94 times. Moreover, based on comprehensive analysis of the temperature difference, accuracy of morphological identification, as well as the contact angle and area of droplets, the eco-friendly compound surfactant (EFCS) of Soapnut Saponin (SS) + CTAB with a concentration of 0.06 wt% demonstrated optimal performance. These findings advance liquid intervention techniques for infrared-based recognition and support the development of greener, more intelligent coal production systems.

The mining-induced self-forming roadway without advance tunnelling (MSRWAT) method is an innovative longwall mining technique developed in China. In this method, the roadway is formed automatically by the coal shearer during coal extraction, eliminating the need for chain pillars and all advance roadway excavation. This study investigates the stability of MSRWAT roadway, with a particular focus on its unique formation mechanism. The results show that the average convergence between the roof and floor in MSRWAT roadway is 11.34% lower than in gob-side entry retaining by roof cutting (GERBRC) roadway, primarily because the MSRWAT roadway avoids the abutment stress ahead of the mining face. Compared to conventional rectangular roadways, the cambered side of the MSRWAT roadways reduce failure depth by 5% to 40% across different conditions. This cambered geometry optimizes the stress distribution, minimizing the development of tensile stress in the surrounding rock. Based on these findings, corresponding engineering recommendations were proposed and successfully validated in the field. Field monitoring shows that the surrounding rock deformation in MSRWAT roadway is 73.67% less than that in GERBRC roadway. This work confirms the superior stability of MSRWAT roadways and offers practical guidance for implementing no pillar mining technology in underground coal mines.

To address the critical gaps in modeling the failure of gas-bearing coal under realistic multi-source disturbances, this study developed, for the first time, a systematically integrated dual-disturbance damage mechanics model. The model uniquely synthesizes a modified Nishihara-NVPB creep framework with partitioned damage evolution laws to concurrently account for gas adsorption, long-term axial static stress, and the synergistic effects of superimposed cyclic and impact dynamic loads. The core innovation is this strategic damage-partitioning integration, where damage from gas and static load is embedded into the elastic element, and damage from dynamic disturbances is embedded into the viscous and plastic elements, enabling a unified representation of complex multi-factor coupling. This integrated constitutive model was successfully embedded into the GDEM continuum-discontinuum software. A full engineering-scale numerical simulation of a coal and gas outburst was conducted. The results, including the excavation outburst initiation distance, in-situ stress evolution at monitoring points, and outburst coal volume, showed high consistency with benchmark results from a large-scale physical simulation test. This work verifies the model’s reliability and applicability at the engineering scale and provides a novel analytical framework and computational tool for investigating the disaster mechanisms of coal and rock dynamic disasters under dual disturbances.

Although hydraulic fracturing of water-bearing tight sandstone gas reservoirs has been extensively investigated, little attention has been paid to the influence of water saturation (w_s) on pore structure and fluid infiltration behavior during the fracturing process. To address this gap, hydraulic fracturing experiments were conducted on sandstone specimens with different water saturations (w_s = 0, 25%, 50%, 75%, and 100%) using a real-time nuclear magnetic resonance (NMR) system. Results show that increasing w_s reduces both breakdown pressure and breakdown time. Fluid injection promotes progressive micropores dilation and their transformation into mesopores and macropores at w_s = 0–50%, while higher saturation enhances macropores modification by coalescence of pre-existing smaller pores. Capillary tension at dry-wet interfaces and clay mineral dissolution are suggested as dominant mechanisms governing pore-scale damage at low and high w_s, respectively. Fluid infiltration is enhanced at low w_s due to improved pore connectivity and strong water absorption effect, but is suppressed at high w_s owing to water-locking effects. An apparent transition in mesopore evolution and preferential infiltration direction is observed between w_s = 50% and 75%. These findings provide mechanistic insights into the role of w_s in hydraulic fracturing of water-bearing tight sandstone gas reservoirs.