New quality productive forces in energy represent a systemic transformation of the energy industry, current new quality productive development is characterized by a typical pattern of regional imbalance, hindering the overall progress of China's green energy transition. Taking the panel data from 30 provinces (autonomous regions, municipalities) in China spanning from 2008 to 2021, this study used the entropy evaluation method to assess the provincial development of new quality productive forces in energy. Specifically, the spatiotemporal evolution, inequality, and spatial convergence of new quality productive forces in energy were analyzed via the decomposition method of Dagum Gini coefficient and its subgroups, kernel density estimation, Markov chain, and u03B2 convergence testing models. Results reveal: u2460 The overall new quality productive forces in energy in China exhibited a fluctuating trend, with a slight increase from 2016 to 2021. u2461 The Dagum Gini coefficient and its subgroup decomposition revealed regional disparities in the development of new quality productive forces in energy, with intra-regional differences being the primary source. u2462 The Markov chain model demonstrated explicit "high-high" clustering and "low-low" club convergence in the new quality productive forces in energy, along with a Matthew effect. u2463 The u03B2 convergence test revealed the existence of u03B2 convergence in the new quality productive forces in energy. The data analysis results reveal the regional disparities and dynamic evolution patterns of China's new quality productive forces in energy, providing empirical evidence for formulating region-specific strategies to cultivate and develop new quality productive forces in energy.
The Bayan Obo deposit is the world's largest iron-rare earth-niobium polymetallic deposit, characterized by "low grade, fine grain size, complex composition, and disseminated distribution", and is intimately intergrown with rare earth and iron minerals, posing significant challenges to its efficient separation and extraction. This study reviews the current research progress, limitations, and improvement measures for Bayan Obo niobium resources in terms of physical beneficiation, hydrometallurgy, pyrometallurgy, and combined beneficiation-metallurgy processes, and compares the applicable scopes of various technological routes. The results indicate that physical beneficiation can achieve preliminary enrichment but is limited by low separation efficiency; metallurgical processes enable deep separation, yet suffer from high energy consumption and environmental concerns; and combined beneficiation-metallurgy and phase reconstruction represent key directions for synergistic recovery of polymetallic resources. Meanwhile, in response to the bottlenecks of economic utilization and green processing for low-grade resources, future development trends are proposed, including intelligent sorting, targeted reagent molecular design, and low-carbon metallurgy. The research findings may provide reference for the efficient utilization of refractory strategic metal resources in China.
Remote sensing technology provides crucial technical support for ecological restoration in mining areas. This paper, based on the entire lifecycle of ecological restoration in mining areas, summarizes the research status, challenges and prospects of remote sensing-enabled ecological restoration in these areas. The findings indicate that: ① Remote sensing-enabled ecological restoration in mining areas mainly includes five parts: basic investigation, environmental monitoring, problem diagnosis, planning and design, and effectiveness evaluation. ② Its technical level has gradually developed from the early stage, which focused on feature identification, range extraction, and single-element monitoring, to a rapid development stage characterized by multi-source fusion, intelligent interpretation, quantitative inversion, process characterization, and comprehensive diagnosis and evaluation. ③ The current common challenges include the limited timeliness of remote sensing image acquisition in mining areas, insufficient spatiotemporal resolution, insufficient accuracy of information extraction, and a lack of knowledge miningcapability. ④ In the future, there is an urgent need to enhance the real-time acquisition capability of remote sensing images through integrated sky-ground data fusion, improve the spatiotemporal resolution of remote sensing through multimodal data fusion, enhance the accuracy of remote sensing information processing through the fusion of deep learning and mechanistic models, and improve the knowledge mining capability through deepening multidisciplinary integration. In the future, efforts should be guided by the actual needs of ecological restoration in mining areas, strengthening industry-university-research collaborative innovation, promoting the deep integration of remote sensing and restoration engineering, so that remote sensing technology can better serve the ecological protection, and management of mine areas.
High-strength electric detonation (HEED) is a new type of permeability enhancement technology for physical coal seams. This study elaborates the technical principles and scientific connotation of HEED: "the precise control and directional release" of physical energy. We compared HEED with major permeability enhancement technologies of coal seams to highlight its technological advantages: precise energy control, ultra-low water consumption, and environmental friendliness. We then reviewed its development history and summarized the three-stage propagation of shock waves generated by the electro-hydraulic effect and their fracturing patterns on coal and rock. The performance and applicability of HEED under complex geological conditions were verified through representative engineering cases. This study also identified limitations in the engineering applications of HEED and its future research directions in fundamental theory, equipment series, technical processes, engineering applications and technological synergy, offering theoretical references for its standardization, engineering application and promotion.
With the large-scale exploitation of graphite resources, the output of graphite tailings in China has been continuously increasing. Long-term accumulation of these tailings has led to serious issues, including land occupation, ecological degradation, and potential environmental risks, making their resource utilization increasingly urgent. Influenced by the geological conditions of mineralization and beneficiation processes, graphite tailings are generally characterized by fine particle size, loose structure, low organic matter and nutrient content, pH imbalance, and potential heavy metal contamination. These characteristics limit their direct application in ecological restoration and engineering substrates. Based on the distribution and mineral composition of graphite tailings, this study systematically analyzes their chemical composition and physicochemical properties. Furthermore, differences in mineral composition and chemical characteristics among tailings from different regions are compared to evaluate their suitability for soilification improvement and the effectiveness of improvement measures. The development of physical, chemical, biological, and combined improvement technologies is reviewed. Finally, the future research directions for graphite tailings soilification improvement technology are presented.
This study aims to elucidate the mechanisms and control pathways of overburden environmental capacity loss during multi horizon mining of coal associated resources. In response to the coordinated development of coal, uranium, coalbed methane, and oil and gas resources in typical basins, the responses to overburden environmental disturbances induced by multi horizon resource development were analyzed. The concept of overburden environmental capacity was introduced to characterize the response limit and stability capacity of the geological environment under multi-horizon mining. A theoretical and technical framework for controlling environmental capacity loss was developed around the key processes of identification, assessment, control, and decision making. The results show that repeated mining and high-intensity disturbance intensify overburden movement, fracture propagation, and surface subsidence, thereby inducing instability of key strata load-bearing structures. The coupled evolution of stress, fracture, seepage, and energy fields further weakens the environmental carrying capacity of the overburden. A three-tier evaluation system was established by integrating near, intermediate, and far field disturbance criteria, capacity grading assessment, and identification of strongly disturbed zones. A technical pathway combining comprehensive assessment of capacity loss with global sensitivity analysis was developed. With minimization of environmental capacity loss as the optimization objective, the proposed framework supports optimization of mining layouts and proactive risk prevention and control. This study provides a theoretical basis and technical support for the safe, efficient, and coordinated development of coal associated resources and for green and low carbon mining.
As the key component of deep-environment coring equipment, the coring device connecting structure, directly affects the operational stability and safety of the equipment under complex conditions of high temperature and high geostress. Taking the connecting structure of the coring device used in deep mining as the research object, a finite element analysis model was established. Strength verification analyses were carried out under different temperatures, different internal pressures, and coupled high-temperature and high-pressure conditions. The response characteristics of stress, strain, displacement, as well as the load and deformation of each thread tooth, were systematically investigated, and the influence on the sealing performance was discussed. The results show that: ① Under internal pressure alone, within the range of 30-120 MPa, the stress, strain, and displacement at the threads exhibit a clear linear relationship with increasing pressure. Beyond 120 MPa, the local maximum stress exceeds the yield strength, driving the structure into the elastoplastic stage. The stress distribution across thread teeth is characterized by being "concave in the middle and convex at the ends." ② Under thermal loading alone, structural displacement increases approximately linearly with temperature, primarily manifesting as an overall thermal expansion effect. ③ Under coupled temperature and pressure, the stress response is dominated by internal pressure, while the displacement response represents an approximate superposition of thermal and pressure effects. The research results provide important support for the safe service of coring devices under deep engineering conditions.
With oil and gas exploration advancing towards deep, ultra-deep, and extra-deep reservoirs, complex geological environments have imposed stringent demands on drilling tools. This paper systematically reviews the rock-breaking mechanisms, failure modes, material and structural optimization, and the current status of intelligent development of Polycrystalline Diamond Compact (PDC) bits in deep complex formations, providing theoretical support and engineering references for high-efficiency bit design. By summarizing single-cutter experiments, numerical simulations, microstructural analyses, and field data studies, this paper analyzes plastic-brittle failure patterns of rocks under various formation conditions and their effects on cutting forces, mechanical specific energy (MSE), and cutting morphology. It systematically categorizes typical failure modes of PDC cutters, including wear, impact, and erosion. Furthermore, it evaluates recent progress in cutter material modification, shaped cutter design, global cutter layout, and hydraulic structure optimization technologies regarding their roles in enhancing rock-breaking efficiency and bit lifespan. The paper also outlines the research and application of smart bits and machine learning-based bit selection methods in deep drilling operations. Material and structural optimization can enhance the adaptability of PDC bits in deep oil and gas drilling, while intelligent technologies provide effective support for bit selection, lifespan prediction, and operational safety. The future development trend of PDC bit technology should focus on the deep synergy of materials, structures, and intelligence to achieve efficient rock breaking and optimize drilling operations in deep and complex formations.
This study reviews simulation model construction and validation to unveil the current research progress of simulation technologies for scraper conveyors. Simulation models were classified into four categories, namely, electro-mechanical coupling models, multi-body dynamics models, static analysis models and coal flow discrete element models, to elaborate their modeling approaches, application scenarios, respectively, and research progress in multi-model co-simulation. Two major model validation methods were then introduced, namely bench testing and small-scale prototype testing. This study also summarized existing challenges and future research opportunities. Results indicate that the four types of simulation models target at system dynamic characteristics, contact mechanics behavior, structural strength and coal flow impact respectively. Co-simulation could extend the functional boundaries of individual models, yet the degree of model integration remains limited and the operating condition settings are overly idealized. Bench testing mainly serves to validate the drive system, whereas small-scale prototype testing is employed for validating the overall macroscopic behavior of the machine, but a standardized validation framework covering the whole machine, its subsystems and components has yet to be established. This indicates that existing studies are limited in the construction of an efficient co-simulation framework, dynamic loads generation coupled with the coal mining process, and the building of a validation framework for hierarchical models, thus calling for future research.
Coal mining is gradually entering the stage of deep exploitation. The significant increase in mining depth further enhances high in-situ stress, and coupled with effects such as mining-induced stress relief, the rock mass surrounding gas drainage boreholes in deep coal seams is more susceptible to plastic failure, accompanied by severe propagation of micro-fractures, resulting in a rapid attenuation of coal seam gas drainage efficiency. Against this backdrop, the shortcomings of traditional solid-phase sealing materials for gas drainage boreholes have been gradually revealed. Over the years, extensive technical improvements have fully exploited the potential of the "solid sealing for gas" technology, and its effectiveness has reached its limit. Liquid-based sealing materials, with their excellent rheological properties, exhibit significant advantages in deep penetration into micro-pores, tight adhesion to borehole wall interfaces, adaptation to dynamic fracture evolution, and strong self-deformability, making them a research hotspot in the field of sealing materials in recent years. This paper systematically reviews the physicochemical properties and sealing mechanisms of various liquid-based sealing materials, summarizes three typical systems, namely bentonite-based suspensions, silicate-based gels, and resin-based modified solutions, and elaborates on the composite enhanced sealing mechanisms involving rheological regulation, fiber toughening, and particle support. Based on typical engineering cases, this paper demonstrates the excellent engineering performance of liquid-based sealing materials in improving gas drainage concentration and prolonging borehole drainage duration. Meanwhile, it identifies the key issues that need to be addressed in aspects such as precise stability control, long-term durability, and visual evaluation. Finally, it clarifies that the integrated technical path, which is based on the micro-fracture filling mechanism, centered on material rheological regulation, and supported by visual monitoring equipment, represents the future development direction of this field. The research findings provide a technical reference for the application of liquid-based sealing materials in gas drainage sealing under deep and complex geological conditions.
In mine cemented backfill, the pipeline transportation and mechanical properties of backfill materials are pivotal for the successful application of the backfill system. This study therefore investigates the self-flowing pipeline transportation and mechanical properties of full-tailings cemented backfill materials through L-pipe and strength tests. The variation patterns and microscopic mechanisms of backfill properties were analyzed and the feasibility of its industrial applications was discussed. Results show that increasing binder content and slurry mass concentration led to decreasing yield stress and increasing pipeline transportation resistance. As the viscosity and strength of backfill body increased, the maximum filling gradient was negatively correlated with pipeline transportation resistance. Intensified interparticle attraction and exacerbated interparticle friction were the intrinsic causes for the rise in yield stress and viscosity, as yield stress exerted a dominant influence on pipeline transportation resistance than viscosity. Individual or simultaneous increase in test factors leads to increased quantity of hydration products, reduced pore area, improved structural compactness and strength. With binder content of 210 kg/m3 and slurry mass concentration of 68 %, the system exhibited both industrial adaptability and economic efficiency, achieving a 4.11 % surplus in maximum filling gradient and 28 d strength of 2.08 %. This study offers references for self-flowing transportation theories and technologies of cemented backfill materials.
Under the context of intelligent coal mine development, this study reviews the research progress in optimizing the performance of gas extraction pipeline network and intelligent control for promoting efficient and intelligent gas extraction. Specifically, a composition framework for gas extraction pipeline network was established, and the fluid flow laws within the pipeline network were elucidated. A "static-dynamic" two-dimensional framework was established based on the existing performance optimization technologies for gas extraction pipelines. The static optimization technologies can enhance the system's inherent performance through pipe material selection, structural redesign, and fault diagnosis, while the dynamic optimization technologies can dynamically adjust pump and valve parameters based on multi-source data sensing and intelligent evaluation to ensure real-time optimal operation of the pipeline network system. The present performance optimization and intelligent control technologies face such limitations as the lack of a universal model for pipeline network topology design, insufficient visualization and verification of abnormal conditions, and weak coordination among intelligent algorithms. To address these challenges, this study proposed to determine optimal combinations of parameters such as pipe diameter and slope by combining orthogonal experiments with the Analytic Hierarchy Process; develop a testing platform for simulating abnormal operations and control of mine gas extraction pipeline to replicate operating conditions such as leaks, blockages, and deformation; integrate various data mining and neural network algorithms to establish more effective intelligent control models. This study can provide guidance and reference for promoting intelligent and efficient coalbed methane extraction and ensuring the safe and sustainable development of coal mines.
Direct air capture (DAC) removes CO2 directly from air and achieves net CO2 removal when coupled with transport and geological storage, thus becoming indispensable in global net-zero emissions pathways. This study proposes to identify demonstration regions and methods for cost reduction and performance improvement of direct air carbon capture and storage (DACCS) in China. We coupled life-cycle assessment (LCA) with DAC learning curves to evaluate and project the net removal efficiency and cost of liquid-solvent absorption and solid-sorbent adsorption. The results show that the national average net removal efficiencies for liquid-based DACCS vary across scenarios, ranging from 17.0% to 69.8%, whereas solid-based technology demonstrates relative stability (77.9% ~89.0%). National average net removal costs of DACCS decline with higher learning rates and larger deployment scales. By 2060, the costs are projected to be 1 336~1 970 RMB/t for liquid-based technology and 394~1 184 RMB/t for solid-based route. There are significant provincial disparities in net removal efficiency for liquid-based technology in 2035, with only Sichuan and Yunnan provinces exceeding 70%, theoretically qualifying them as pilot demonstration. The solid-based technology, in contrast, maintains a steady efficiency of 78.6% ~84.1% across all provinces. Declining energy-related carbon emissions improve the net removal efficiency of DACCS. From 2035 to 2060, the proportion of energy-related carbon emissions drops from 77.3% to 45.7% for the liquid-based technology, and from 68.3% to 22.9% for the solid-based route, indicating that the dominant contribution of the energy supply stage to full-chain carbon emissions gradually weakens. The cost structure of the liquid route is generally energy-dominated, whereas the dominant cost component of the solid route shifts from capture-side capital expenditure to CO2 transport and storage. This study thus suggests that DACCS demonstration projects be implemented in provinces with abundant non-fossil energy supply, and deployment should be expanded through scale effects and technological improvements to steadily reduce costs and expand adoption.
As fully-mechanized coal mining faces advance toward long-distance and high-throughput operations, long-distance, heavy-duty scraper conveyors are increasingly challenged by amplified self-weight, accumulated running resistance and insufficient intelligent closed-loop regulation. This study identified four technical routes by reviewing domestic and international studies for more efficient, reliable, and intelligent operations under complex working conditions: system-level lightweight design and energy-consumption optimization, drive control and multi-motor coordination, chain-drive failure and fault identification, and intelligent monitoring and closed-loop regulation, regarding their research development, key methods, and coupling relationships. Results reveal that existing studies are limited in the mechanisms of self-weight amplification and resistance accumulation under long-distance conditions, dynamic coupled control of multi-drive long-chain systems, the transformation of chain-drive failure mechanisms into engineering early-warning methods, and the implementation of intelligent closed-loop regulation in complex underground environments. This study therefore proposes future research directions based on the present industrial demands: low-carbon lightweight design, robust control under complex working conditions, AI-based predictive maintenance, and intelligent operation and maintenance supported by digital twins and underground 5G. This study provides references for research and engineering applications of key technologies for long-distance, heavy-duty scraper conveyors.
To achieve green and efficient mining of deeply buried thick coal seams under thin bedrock, this study takes the Zhaogu No.2 Mine as the engineering background and employs theoretical analysis, laboratory experiments, and field measurements. The technologies and equipment, technical difficulties and corresponding solutions, and economic benefit indicators under multi-slicing mining, large-cutting-height mining, and top-coal caving mining are compared. An adaptability evaluation model for mining methods is established based on economic and mining-technical indicators. A surface subsidence prediction method for extra-thick alluvium is proposed. Results show that top-coal caving mining exhibits the highest adaptability, followed by large-cutting-height mining and multi-slicing mining shows the weakest adaptability. The dynamic load method established based on the instability characteristics of the overburden caving arch can be used to guide the selection of hydraulic supports. Grouting-based modification and reinforcement at the bottom of the alluvium can enhance the integrity and water-resisting capacity of the thin bedrock-alluvium interface, promoting the formation of the towering roof beam structure, and weakening the concentrated transfer of thick alluvium load to the supports in the working face. The established surface subsidence prediction model reveals the mechanical mechanism of a surface subsidence exceeding 1.0. This study provides references for mining method selection, strata control, and subsidence mitigation in deeply buried thick coal seams under thin bedrock.
Coal and its associated resources serve as crucial non-traditional sources for recovering strategic rare metals, such as gallium (Ga), germanium (Ge), lithium (Li), and uranium (U). This paper provides an in-depth analysis of the occurrence mechanisms and extraction pathways of these four elements within coal-measure products. Utilizing sequential chemical extraction, micro-area in-situ characterization, and coupled thermal analysis, the study reveals that Ga is primarily hosted within the aluminosilicate lattice through isomorphous substitution of Al. In contrast, Ge exhibits strong organophilic affinity, existing as chelated states and demonstrating high volatility during thermal processing. Li is highly dispersed within clay minerals and prone to encapsulation by high-temperature glassy phases. The occurrence state of U evolves with coalification, undergoing a directional migration from organic complexation to inorganic mineral phases. In light of these complex occurrence characteristics, the core of the extraction process lies in matrix restructuring and element release. Pretreatment technologies, such as high-temperature decarbonization, complex salt roasting, and alkali roasting, can effectively disrupt stable mineral matrices or organic functional groups. During the separation stage, by employing gradient leaching, green organic acid dissolution, and highly selective resin adsorption, the optimal extraction efficiencies achieved for gallium, germanium, lithium, and uranium reached 98.00 %, 94.64 %, 99.64 %, and 95.80 %, respectively, demonstrating the feasibility of efficient multi-metal recovery and purification. Future research should focus on developing low-temperature activation additives, elucidating microscopic migration mechanisms, and establishing a green, clean, closed-loop recycling system across the entire industry chain.
Existing studies on roof cutting and pressure relief mainly focus on their process parameters and engineering applications. However, they are limited in their whole-process coordinated evaluation on the appropriateness, controllability and sustainability of pressure relief, resulting in failure to timely identify insufficient or excessive pressure relief. This study therefore proposes a multi-source coordinated evaluation framework incorporating pre-cutting baseline identification, dynamic feedback during roof cutting, post-cutting effect verification and long-term stability tracking to enhance the effect evaluation of roof cutting and pressure relief. It characterizes the pressure-relief effect from point-scale stress, regional fracturing, stress redistribution and continuous deformation by summarizing the evaluation indicators of the drilling cutting method, microseismic monitoring, stress monitoring, and distributed fiber-optic monitoring. Results indicate that, instead of adopting site-independent absolute thresholds, the effect evaluation of roof cutting and pressure relief should take into account the relative changes of areas with and without, before and after roof cutting and the consistency of multi-source monitoring in spatial location, temporal evolution, and variation trends. The research findings can provide valuable reference for the study and engineering practice of roof cutting and pressure relief technology in deep coal mines.
This study reviews the research progress and limitations of the safety standard system for blasting vibration in China to promote standard optimization and technological development. The core provisions of existing national standards and major industrial standards in water conservancy, railway, mining, and municipal engineering, with emphasis on major differences in vibration limits for various protected objects. Recent research progress was also reviewed regarding blast vibration propagation, safety criteria, structural response, intelligent prediction and vibration reduction technologies. Results show that the current standard system is limited in overlapping provisions, conflicting limits, and insufficient coverage of special geological conditions and emerging structural types. It is still dominated by static single-parameter control, posing deficiencies in frequency-velocity coupling framework and cumulative damage assessment. Despite significant advances in numerical simulation, machine learning prediction and electronic detonator precise delay technology, it is limited in the implementation of these research outcomes and insufficient validations. In this light, this study proposes the restructuring of the standard system into a "general basic + industry-specific" architecture by introducing dynamic, multi-parameter coupled control and intelligent monitoring systems to promote bidirectional translation among research, standards, engineering applications and enhance international alignment. This study provides references for the refined revision of blast vibration control standards and their engineering applications.
Insufficient safety investment on construction projects hinders their safety performance. The present study therefore proposes a theoretical framework of "Institutional Isomorphism, Safety Climate and Safety Investment" by integrating the Institutional Isomorphism Theory and the Safety Climate Theory. We employed correlation analysis and the random forest machine learning model on data from 953 valid questionnaires. Results demonstrate that safety climate serves as the core determinant of safety investment behavior, with organizational and team safety climate jointly accounting for over 86.00 % of the explanatory power. In contrast, institutional isomorphism exerts weak direct effect on safety investment. However, it poses significant mediating effect via safety climate. Its mediating pathway contributing 21.80 % to the total impact, with normative isomorphism and mimetic isomorphism demonstrating notable effects. The present random forest model achieves an R2 value of 0.814, outperforming conventional linear analysis approaches in unraveling the complex nonlinear coupling relationships across multiple variables. This study probes into the application of machine learning methods in construction safety management and delineates the transmission mechanism underlying "institutional pressure, cultural response and investment behavior". It provides theoretical and practical implications for construction enterprises to synergistically optimize institutional compliance and cultivate safety cultures, enhancing the efficiency of safety resource allocation.
As a critical parameter in electromagnetic detection for coal mine safety, the dielectric permittivity of coal is influenced by its structural characteristics. In addition, electromagnetic waves with terahertz(THz) frequencies have extensive application potential in coal mining. Therefore, in this study, the terahertz dielectric permittivity of coals with varying metamorphism degrees was measured using the terahertz time-domain spectroscopy, and its evolution mechanism was investigated through grey relational analysis based on proximate components. Experimental results indicate that the Landau-Lifshitz-Looyenga model provides the most accurate description of the dielectric behavior of coal tablets. Both the real and imaginary parts of the terahertz dielectric permittivity exhibit a decreasing trend with increasing metamorphism degrees. Due to the highest grey correlation, moisture and ash are the main factors affecting the dielectric properties of coal. Specifically, the decrease in moisture content with increasing coal rank primarily accounts for the decline in permittivity. Ash content is the key factor causing the increase in the real part of non-stick coal and imaginary part of long-flame coals due to its high dielectric permittivity and loss. These findings can enrich the theoretical understanding of coal's dielectric behavior and offer a valuable reference for the application of electromagnetic detection technologies in coal mining.
