非均匀应力下含缺陷砂岩失稳机制研究OA

Considering the non-uniform stress state and surrounding rock instability of rectangular roadways induced by the"small cantilever structure"in the roof,mechanical tests on rectangular-flawed sandstone specimens were conducted under three non-uniform stress loading conditions,namely"convex","ladder",and"concave"types.Based on the test results,the mechanical response characteristics and energy evolution laws were investigated,and the synergistic fracturing characteristics of rectangular-flawed sandstone under non-uniform stress were disclosed.The following results were obtained:Under the"ladder-type"loading condition,the sandstone specimen presents the highest peak stress,the longest linear stage,and a higher compressive strength compared to the"convex-type"loading condition,which demonstrates the advantage of"layered buffering".Under the"convex-type"loading condition,the sandstone specimen experiences rapid penetration of a single oblique crack,exhibits the weakest bearing capacity,and its acoustic emission energy drops sharply with a single peak,a mark of its limited energy dissipation.Under the"concave-type"loading condition,energy is gradually dissipated through the stepwise propagation of cracks,resulting in the highest cumulative acoustic emission energy.Under non-uniform stress,the evolution laws of stress,strain,and plastic zone in the rectangular-flawed sandstone specimen are consistent with stress distribution in the upper stress zone.The high-stress zone,which is the dominant area for internal damage in the specimen,witnesses the most intense evolutions.Non-uniform stress can induce local rapid instability in sandstone,and the non-uniform stress characteristics are correlated with the strength,shear failure proportion,and total energy.The research findings hold significant theoretical importance for the stability control and differentiated support of roadways under non-uniform stress conditions.