Abstract:
Coal mine geothermal development presents significant advantages and considerable potential. The utilization of existing mine facilities for the co-development of coal and geothermal resources is crucial for local energy supply and national energy security. Currently, it faces two primary challenges: achieving efficient geothermal development within mining-disturbed rock strata, and maintaining the long-term stability of the rock strata during geothermal development. Recent advances in efficient geothermal development and rock strata control in coal mines are reviewed. In terms of efficient geothermal development, a multi-scale flow and heat transfer theory spanning from micro-pores to macro-fracture networks is summarized. The dynamic influence of mining-induced stress on the flow and heat transfer behavior of rock masses is revealed. Efficient geothermal development techniques that actively utilize or modify mining-induced spaces are reviewed, including backfilling heat extraction, water storage heat extraction, heat extraction using water-conducting structures, and mining-activated reservoir heat extraction techniques. Regarding rock strata control,the disaster mechanisms of water-conducting structure activation, floor failure-induced water inrush, and coal pillars failure under the combined disturbance of hydro-erosion, thermal cycling, and mining are clarified. Innovative control techniques suitable for high confined and dynamic hydrological environments are proposed, including hydrophobic high-strength multi-level grouting and grout-rock interface reinforcement grouting techniques. Advances in key materials are also summarized, particularly superhydrophobic nano-grouting materials adapted to high confined hydrological environments. Results indicate that the current researches have established a technological framework for efficient geothermal development and rock strata control in coal mines. However, shortcomings remain, including an incomplete understanding of the mining-induced stress within multi-field coupling theories, insufficient large-scale engineering validation for key techniques, and unclear performance evolution of control materials under sustained hydro-erosion and thermal cycling. In Future, coupled thermal-hydraulic-mechanical-chemical theoretical models that considering mining-induced stress are requires, along with multi-scale experimental validation methods. Precise intelligent control techniques based on detection-grouting feedback are needed. Long-term performance assessment and biomimetic structural design of control materials in extreme environments should be conducted. Engineering demonstrations in typical mining areas should be promoted to establish technical standards and evaluation systems , thereby enabling safe and efficient geothermal development in coal mines. .