Permeability evolution and resistivity response of coal mass subjected to mining-induced stress

PENG Wei; ZHU Xiaole; ZHAO Yang; YE Mengqin; YU Saiyu

doi:10.11799/ce202602017

Abstract：To reveal the synergistic evolution mechanism of deformation,seepage,and electrical response in coal under complex mining conditions,a high-temperature and high-pressure triaxial seepage testing system was employed.Three mining stress paths with axial loading to confining pressure unloading ratios(load-unload ratios)of 2.5∶2,3∶2,and 3.5∶2 were designed.The dynamic evolution of deformation,permeability,and resistivity in bituminous coal and anthracite under these paths was investigated.The results show that:(1)The stress loading-unloading gradient ratio significantly influences the effective stress distribution and fracture propagation behavior of coal.Due to its layered structure and open pore characteristics,the strain increment of bituminous coal reached 41.32%～52.08%in the low confining pressure stage,with the peak strain increasing as the gradient ratio increased.For anthracite,with its dense structure due to high coalification rank,brittle fracture was activated after the critical stress,and the rate of strain surge was 16.24%higher than that of bituminous coal,exhibiting a nonlinear deformation response.(2)The permeability of anthracite was more sensitive to mining disturbance.Under the high load-unload ratio path(3.5∶2),the permeability increase reached 7.4 times,significantly higher than that of bituminous coal,indicating that a high load-unload ratio can significantly improve the seepage capacity of anthracite by intensifying fracture propagation.(3)Resistivity evolution sensitively reflects the damage accumulation process in coal.Under mining conditions,the resistivity of both coal types exhibited an exponential evolution trend.Notably,upon failure,the resistivity surge in anthracite reached 510%,far exceeding the 113%surge in bituminous coal,revealing the mechanism of sudden energy release due to fracture coalescence stemming from its brittle energy storage characteristics.In contrast,the resistivity change in bituminous coal was dominated by pore connectivity,with an increase of 110%under the 3∶2 load-unload ratio path,validating its effectiveness as a precursor information for disasters.The findings elucidate the synergistic mechanism of stress evolution and coal type differences on the seepage-electrical properties of coal under mining conditions,providing a theoretical basis for dynamic disaster warning,gas drainage,and coalbed methane development.