Research on stope equivalent hole model and rotation law of principal stress

Aiming at the problems of serious asymmetric damage phenomenon of roadway on the side of stope and unclear rotation law of principal stress around roadway, the relationship between the rotation of principal stress around roadway and the asymmetric damage of roadway is expounded based on boundary equation of plastic zone around non-isobaric circular hole under the rotation of principal stress and butterfly failure theory. A theoretical model of stope equivalent hole is established to study the evolution laws of the rotation of stope lateral principal stress under different initial lateral stress coefficients. Under the engineering background of the 22205 working face in the Buertai Colliery, equivalent hole fitting is carried out for different positions of stope along the advancing direction. The reliability of the stope equivalent hole has been proved through theoretical analysis and numerical simulation, providing a new idea for determining the rotation angle of the principal stress on the side of the stope. The results show that: ① When the roadway is in the butterfly risk zone, the rotation of the principal stress direction around it will cause the rotation of the butterfly plastic zone, which affects the stability of the roadway. A theoretical model of stope equivalent hole is established, which can be used to calculate the rotation angle of stope lateral principal stress. The numerical simulation results are in good agreement with the theoretical calculation. ② The direction of stope lateral principal stress in a certain range before and after the stope will rotate, and the rotation angle of principal stress is determined by the original state around the stope and the equivalent hole radius of the stope. When the initial lateral stress coefficient is greater than 1, the maximum principal stress gradually rotates from vertical direction to horizontal direction, and the hidden equation of principal stress rotation 45° can be used to determine the position of rotation 45° on the side of the stope. When the initial lateral stress coefficient is less than 1, the maximum principal stress first rotates to the horizontal direction by a certain angle from the vertical direction, and then turns to the vertical direction. The radius of stope equivalent hole represents the influence range of stope. The larger the radius, the larger the influence range of stope will be.