Integrating geothermal extraction with mine heat hazard control: A thermal–hydraulic–mechanical-ventilation coupling model for deep mines

The modern mining industry faces severe challenges from mine heat hazards. Some scholars have proposed extracting heat from surrounding rocks as geothermal energy. However, existing research predominantly focuses on verifying this concept's feasibility from heat transfer perspectives, with limited investigation into how water injection disturbs the stratum stress field. This gap leaves the initiative without sufficient mechanical analysis to support its implementation. To address this, this paper developed a Thermal-Hydraulic-Mechanical-Ventilation (THMV) coupling model, designing 5 water injection schemes and 5 geological conditions. This framework systematically investigates the combined effects of injection temperature, injection volume, thermal expansion coefficient, and geothermal gradient on rock stress, geothermal extraction, and roadway cooling. The results demonstrate that: reducing injection temperature increases stress in the roadway area (peak stress grows from 10.6 MPa to 13.8 MPa) while enhancing both heat extraction and cooling performance; increasing injection volume reduces thermal stress accumulation but elevates pore pressure, maintaining Tresca stress around 6.7 MPa long-term and impairing sustainable geothermal extraction; both higher thermal expansion coefficients and geothermal gradients elevate stress, though the former negligibly affects thermal performance while the latter significantly enhances geothermal extraction, increasing cumulative heat production by 3.46 × 1013 J.