Gradient failure mechanism and control technology of deep roadways under the action of deviatoric stress field.

Deformation control of deep roadways is a major challenge for mine safety production. Taking a deep roadway with a burial depth of 965 m in a mine in North China as the engineering background, on-site investigation found that significant creep deformation occurred in the surrounding rock of the roadway. The original supporting U-shaped steel support failed due to insufficient supporting strength. The rock mass near the roadway experienced a transition from triaxial stress conditions to biaxial and even uniaxial stress states as a result of excavation and unloading, leading to a gradient stress distribution in the surrounding rock. From the perspective of the roadway's deviatoric stress field distribution, we investigated the gradient failure mechanism of the roadway and validated it through theoretical analysis and numerical simulations. The study found that the ratio of horizontal principal stress and vertical principal stress determines the distribution shape of the surrounding rock deviatoric stress field. The gradient distribution of the stress field in the roadway will cause time-related deformation of the roadway, which will lead to large deformation and failure of the roadway. Based on this, the control mechanism of roadway gradient failure was studied, and then a combined support technology of CFST supports with high bearing capacity was proposed.