Characteristics of in-situ stress field in Xinji coal mine

Mine dynamic phenomena such as deformation and destruction of roadway, coal-gas outburst and water inrush from floor, are closely related to initial ground stress. The hydraulic fracturing method was used to measure in-situ stress of Xinji mine, confirmed in-situ stress state of surrounding rock in deep autochthonous system, the magnitude and orientation of in-situ stress, occurrence regularity and essential characteristics of in-situ stress in mining area have been put forward by the study. The analysis of measuring results indicated:the horizontal stress dominated the field stress of Xinji mine and had obvious tectonic stress features; The vertical, maximum and minimum principal stress would be increased with the mine depth, represented approximate linear growth; Ratio of maximum to minor horizontal principal stresses ranged from 1.01 to 1.29, Xinji mining area was relatively constant under the action of geologic structure. Lateral pressure coefficient ranged from 0.98 to 1.3, changed inconspicuously with burial depth; The maximum horizontal principal stresses of Xinji mining area was close to EW under the function of stretching stress in EW direction of fault F10. At last, the reason for difference between in-situ stress direction of diverse tectonic positions in autochthonous system was discussed, the analysis suggested that Fuyang-Fengtai nappe was the principal factor.