Non-uniform failure mechanism and stability control of mining roadway under deviatoric stress field

Based on the elastic-plastic theory, the analytical formula of the second invariant J2 of deviatoric stress at any point around the circular roadway under the non-uniform stress field is derived. The distribution law of J2 of surrounding rock under the three-dimensional non-isobaric stress field is studied by theoretical analysis and numerical simulation. Combined with the butterfly failure theory of surrounding rock of roadway, the close relationship between the distribution pattern of J2 and the distribution pattern of plastic zone is found, and the failure mechanism of surrounding rock is revealed. The results show that the distribution form of the second invariant J2 of deviatoric stress is closely related to the distribution form of plastic zone. When the distribution of J2 of surrounding rock shows 'round', 'oval' and 'butterfly', the plastic zone shows the corresponding consistent form. When the second invariant J2 of deviatoric stress produces stress concentration, the surrounding rock of roadway will produce large-scale damage. When the stress concentration is high, it may lead to malignant expansion of surrounding rock of roadway. The distribution of the second invariant J2 of deviatoric stress is directional. When the principal stress rotates over a certain angle, the second invariant J2 of deviatoric stress rotates over the same angle as the plastic zone. Under the influence of superimposed mining, the second invariant deviatoric stress J2 of the wind tunnel of Yangchangwan 160,206 working face presents butterfly distribution, and the stress butterfly leaves present a certain degree of rotation. Based on the failure mode of plastic zone, the corresponding optimization support scheme is proposed, and the engineering effect is good.