Pillar Stability Analysis in Underground Coal Mining

The stability of coal pillars in underground coal mining is pivotal to maintaining the integrity of mine workings and protecting overlying strata. Pillar stability analysis encompasses the assessment of load-bearing capacity, deformation behaviour and potential failure mechanisms under varied geological conditions. Coal pillars support the overburden—rock and soil layers above the excavations—which may exhibit complex stress distributions influenced by mining geometry, in situ stress regimes and time-dependent effects such as creep. Analytical methods range from empirical pillar strength equations derived from case histories to numerical simulations employing finite-element or discrete-element techniques. Empirical approaches offer expedient design guidelines but often fail to capture site-specific factors such as horizontal stresses, pillar–goaf interactions and progressive failure modes. Advanced numerical models, calibrated against laboratory tests and field observations, enable the investigation of cooperative load-sharing between pillar groups and adjacent goaf zones. Modern studies increasingly consider long-term stability, accounting for creep, strain softening and environmental degradation in abandoned workings. The synthesis of empirical, analytical and numerical methods underpins robust pillar design for diverse mining layouts, including room-and-pillar and partial extraction systems, while informing risk mitigation strategies to prevent subsidence and catastrophic collapse.

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Pillar Stability Analysis in Underground Coal Mining publication trend

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Technical terms

Coal pillar: A block of coal left in place to support the roof and overburden in underground mining.

Overburden: The layers of rock and soil that lie above a coal seam and exert pressure on underground excavations.

Goaf: The fragmented and caved rock mass that fills voids after coal extraction.

Empirical pillar strength equation: A formula derived from case histories relating pillar dimensions and load conditions to strength estimates.

Pillar peeling: Progressive failure of pillar margins under sustained loading, characterised by successive flaking of material.

References

1. Limitations and potential design risks when applying empirically derived coal pillar strength equations to real-life mine stability problems. International Journal of Mining Science and Technology (2019).
2. Subsidence Mechanism and Stability Assessment Methods for Partial Extraction Mines for Sustainable Development of Mining Cities—A Review. Sustainability (2018).
3. Long-Term Stability Evaluation and Pillar Design Criterion for Room-and-Pillar Mines. Energies (2017).
4. Cooperative load‐bearing characteristics of a pillar group and a gob pile in partially caved areas at shallow depth. Energy Science & Engineering (2019).