Underground coal fires waste resources, pollute the environment, and compound gas and water hazards—but much research still targets isolated techniques rather than whole-process governance. Wang et al. (2023), Sustainability, combine CiteSpace bibliometrics with a complexity-science framework to summarize multi-field coupling literature and propose management elements and principles. Below is a structured reading note—not a substitute for the full paper.

Paper highlights

  • 773 WoS papers (1992–2022) show rapid growth after 2011 and divergent but clustered topics;
  • Hotspots span spontaneous combustion kinetics, detection/monitoring, prevention, and environmental impact;
  • Macro disasters couple temperature, seepage, concentration, and stress–strain fields via void/fracture networks;
  • Underground coal fires qualify as complex systems (stochastic, nonlinear, socio-technical);
  • Three governance elements and three principles aim at full-process scientific management.

1. Problem background

1.1 Why methodology matters

Underground coal fires occur worldwide (China, US, India, Australia, etc.). They cause direct coal loss, ground subsidence and fissures, greenhouse and toxic gas release (CO₂, CO, SO₂, H₂S, NOx), soil damage, and can amplify gas and water compound disasters. Existing work emphasizes inert gas/foam injection, gob sealing, “three-zone” zoning, and even heat utilization—but generalization is weak because causes, geometry, and re-ignition risk are highly site-specific.

1.2 Research gap

Technical solutions abound; method-level guidance for building a prevention-and-control system is scarce. The authors adopt complexity science—already used in environmental and urban disaster governance—as a paradigm for underground coal fire management.

2. Bibliometric overview (CiteSpace 6.1.R6)

Data: Web of Science, search terms “underground coal fire” and “coalfield fire”, 1992–2022.

2.1 Publication trend

| Stage | Period | Papers | Note | |-------|--------|--------|------| | Initial | ≤2010 | 128 | Foundational reviews (e.g. global coal fires, detection/suppression) | | Growth | 2011–2022 | 645 | ~5× increase; China-focused comprehensive reviews |

Average ~26 papers/year overall; post-2011 acceleration tracks large-scale mining and environmental concern.

2.2 Research subjects

  • Top authors (English corpus): Deng Jun (Xi’an Univ. of Science & Technology), Hower James C. (Univ. of Kentucky), Wang Deming, Zhou Fubao, Liang Handong—Chinese scholars dominate (~80% of top 10).
  • Top institutions: China University of Mining and Technology (147 papers), CUMTB, IIT (India); dense collaboration links among CUMT, CAS, and Kentucky.

2.3 Topics and keywords

Keyword co-occurrence network density 0.0177 (relatively divergent topics). Clusters cover:

  • Coal combustion kinetics and thermodynamics;
  • Environmental and health impacts;
  • Detection, monitoring, prevention, and suppression (recent emergence not fully captured in older keyword windows).

Takeaway: rich engineering literature, but little explicit complex-system theory for governance.

3. Literature synthesis: micro to macro

3.1 Microscopic combustion

Thermal analysis (TGA/DSC, etc.) and material characterization reveal stage-dependent coal–oxygen kinetics, heat release, mass/microstructure change, and product evolution—different ranks and stages behave differently. Micro mechanisms explain autonomous heat accumulation leading to spontaneous ignition.

3.2 Macroscopic multi-field coupling

Underground fires are thermodynamic hazards under coupled fields:

| Field | Role | |-------|------| | Temperature | Accelerates oxidation; creates gradients that alter gas flow | | Seepage / airflow | Supplies O₂; ventilation volume, speed, and mode reshape fire zones | | Concentration | CO₂, CO, etc. feedback on reaction and diffusion | | Stress–strain | High temperature deforms strata; changes void connectivity |

Void/fracture networks in mined areas and overburden are the main O₂ and heat/mass paths—and the route for toxic gases to the surface. Recent work (including Wang’s team at Central South University) models void ratio distribution after horizontal/inclined mining under combustion disturbance, linking geometry to multi-field evolution.

3.3 Open challenge

Many variables interact nonlinearly; fully predictive laws remain difficult—motivating a complexity-based management view rather than pure reductionism.

4. Complexity judgment and system traits

Using accepted complex-problem criteria, underground coal fires are:

  • Stochastic — uncertain ignition locus, hard-to-estimate severity;
  • Nonlinear — void ratio, temperature, composition, and airflow lack simple linear maps (e.g. Darcy flow gains temperature-driven nonlinearity);
  • Socio-technical — people, communities, regulations, and technology co-evolve in governance.

Four manifested complexity traits:

| Trait | Meaning | |-------|---------| | Compound cause | Nested cause–effect chains (e.g. airflow ↔ heat ↔ temperature ↔ airflow) | | Dynamic process | Slow or abrupt evolution of heat, flow, deformation, oxidation | | Nonlinear evolution | Chaos-prone multi-field coupling | | Unpredictable outcome | Fracture growth, heterogeneity, and human factors limit forecastability |

5. Governance elements and principles

Under the complex systems research paradigm, the authors propose:

5.1 Three elements

  1. Complex network relationships — fields and management subsystems as nodes; couplings and workflows as edges; protect key nodes whose failure breaks the network.
  2. Spatiotemporal dynamic evolution — factors accumulate and feedback in “spiraling” escalation after thresholds; governance must track space–time loops.
  3. System integrity — combine vertical (reductionist decomposition) and horizontal (holistic interaction) views; balance top-down control with bottom-up self-organization.

5.2 Three principles

  1. Focus on network relations, not isolated nodes — maintain synergy and balance across the governance network.
  2. Spiral cycle governance — cyclic monitoring and plan refinement to counter re-ignition and long horizons.
  3. Align micro research with macro governance — microscopic mechanism studies inform macro policy; macro systems constrain and support micro measures—avoid pure reductionism or disconnected tactics.

6. Engineering takeaways

  • Treat underground coal fires as open, multi-field, socio-technical systems, not single-parameter fires.
  • Bibliometrics confirm technical depth but methodological thinness—useful for positioning monitoring/ML tools inside a governance network.
  • Void/fracture topology is a cross-cutting variable linking physics models and field sealing priorities.
  • Prefer spiral, whole-process management (detect → intervene → verify → adapt) over one-shot suppression.
  • Pair micro kinetics (lab TGA, radicals, pores) with macro zoning (three zones, injection, surface cracks).
  • High model scores or single-sensor alerts do not replace network-level redundancy and human confirmation.

7. Limits

  1. Bibliometrics: English WoS only; Chinese domestic literature underrepresented.
  2. Conceptual framework: elements/principles are qualitative—operational KPIs and case validation are left to follow-on work.
  3. Not a field experiment or ML paper: no new datasets; value is synthesis and governance framing.
  4. Site specificity remains: principles must be instantiated per mine geology, mining method, and regulatory context.

Reference

Wang, S.; Guo, S.; Yang, Y. Complexity Study on Multi-Field Coupling Systems for Underground Coal Fires. Sustainability 2023, 15(17), 12918.