Abstract: In order to solve the support problem of roadways at large cross-section intersection points in underground coal mines, especially the problem of stability maintenance of the surrounding rock of the wedge-shaped wall with broken "ox nose" at the intersection points of special sections under isolated island pillars, combined with the engineering example of cross-cut intersection point of Xutuan Coal Mine-500 horizontal track, the failure and deformation characteristics and causes of the "ox nose" wedge-shaped wall of roadways at large cross-section intersection points are analyzed and summarized. Based on the theoretical analysis of the model, it is proposed that the stability of the wedge-shaped wall and rock pillar is the main factor controlling the overall instability of the roadway at the intersection point, and a new grouting pre-reinforcement technology for the broken wedge-shaped wall and the reinforcement support for the tension anchor cables are proposed. Engineering practice shows that the technology can effectively reinforce and control the deformation of the surrounding rock of the wedge-shaped wall broken at the large cross-section intersection point under the isolated island coal pillar, improve the overall stability of the intersection roadway, and play the mutual control effect between the top and bottom of the intersection roadway; after 70 days of repair, the deformation of the intersection point tends to be stable, the displacement of the two sides is less than 100 mm, and the displacement of the roof and floor is less than 85mm.

Key words: Mutual control effect among roof, side and floor.