Distribution pattern and influencing factors of in-situ stress for deep levels in Shoushan No.1 Coal Mine

Abstract

To investigate the distribution pattern and influencing factors of in-situ stress for deep levels in the Shoushan No.1 Mine, according to the measured in-situ stress data of the mine, the tectonophysics and rock mechanics and numerical simulation methods were applied to study the type, magnitude and direction distribution pattern of in-situ stress. The distribution characteristics of in-situ stress field was simulated. The effect of buried depth, lithology and geological structure on the in-situ stress distribution was analyzed. The main factor of in-situ stress distribution was determined. The research shows that the in-situ stress values obtained by the multiple regression analysis of inversion method are consistent with the measured values. The relative error is less than 20% and the results are reliable. The coal and rock mass of mine is in a state of three-dimensional compressive stress. The principal stresses relation of coal seam is SH > SV > Sh. The in-situ stress increases firstly, then decreases and finally increases from the north to the south of the mine. The magnitude of in-situ stress is 28−44 MPa and belongs to the high stress level. The in-situ stress direction is NEE. The buried depth controls the magnitude and type distribution of the in-situ stress. With the increase of buried depth, the principal stress is increasing and the stress field type has the changing tendency from the dynamic stress field to quasi-hydrostatic pressure field. The lithology has a closely relationship with the in-situ stress. From mudstone to sandstone or limestone, the in-situ stress is increasing. The larger the elasticity module is, the higher the in-situ stress is. The difference of stratum lithology causes the discrete distribution of in-situ stress and the deflection angle of in-situ stress direction is less than 10°. The relation between the in-situ stress and the buried depth and the elasticity modulus is expressed as σH=0.0350H+0.4681E−8.5513 in the mine. The geological structure is the main controlling factor of in-situ stress in the mine. The fold shape controls the horizontal stress distribution of the in-situ stress. The in-situ stress of the syncline inner arc is more than that of the anticline inner arc. With the increase of the fold crook degree, the in-situ stress of inner arc increases gradually, and its stress gradient increases gradually. The in-situ stress of fault zone is decreasing and the in-situ stress of the fault pinch-out side is greater. The in-situ stress direction deflects along the fault strike. The larger the angle between maximum horizontal principal stress and the fault strike is, the greater deflection angle of maximum horizontal principal stress direction is. The in-situ stress of the tectonic association zone of fault and syncline is more than that of the tectonic association of fault and anticline. The tectonic association causes the undirectional distribution of the in-situ stress direction.

Keywords

• in-situ stress measurement
• stress relief method
• tectonophysics
• shoushan no.1 coal mine