Abstract:This paper addresses the bifurcation instability of deep roadway surrounding rock under the coupled effect of anisotropic tectonic stress and geometric non-coaxiality. Based on the higher-order Cosserat continuum theory, a nonlinear constitutive model with micro-structural rotational degrees of freedom is developed, and the bifurcation instability criterion considering the couple stress tensor is derived. Using analytical and numerical methods, the critical instability threshold of the roadway axis (N45°E) and maximum principal stress (N43°W) at an oblique intersection in the Dengjia Fireland section of Qingping Phosphate Mine is revealed. The study shows that when the anisotropic coefficient of tectonic stress χ＞0.35, the plastic zone of the surrounding rock expands in a bifurcation mode, with a critical stress threshold of 0.72σc. This work provides theoretical support for deep roadway stability control.
