Study on roof structure evolution process and surrounding rock control technology of gob-side roadway

In order to solve the problem of the surrounding rock control of the gob-side roadway with thick hard roof under influence of the double mining operations,the method of combining theoretical analysis, numerical simulation and field practice were applied to study the evolution process of roof structure along the roadway and the control technology. The results show that:①A three-hinged arch structure is formed on both sides of the coal pillar during the second mining. The superposition of the double mining pressures causes the former working face side of the broken block above the coal pillar to rotate downward and compress the coal pillar, resulting in the deterioration of stress environment of surrounding rock of roadway.②Mechanical analysis results show that the pressure on the coal pillar is linear with the length of the basic roof above and load it bears. The lateral overhang length of main roof and increase of load of main roof in time-advance section during the secondary mining are main causes of serious deformation of surrounding rock along roadway. ③Numerical simulation results show that vertical stress distribution on both sides of roadway show different deflections during the double mining operations, and the coal pillars still remain a certain bearing capacity in the first mining, the vertical stress distribution of coal pillar side of roadway is larger than that of mining side, and coal pillar deformation and damage are serious in the secondary mining, which makes the vertical stress distribution of mining side of roadway larger than that of coal pillar side, and the asymmetry is obvious; ④Surrounding rock control along gobs must not only change the roof structure to optimize the surrounding rock stress environment, but also increase the support strength and strengthen the bearing capacity of surrounding rock to influence mining. Based on this,the stress optimization technology of surrounding rock of gob-side roadway with thick hard basic roof is put forward. After the scheme is applied to field practice, mine pressure along gob decreases significantly, and the deformation is effectively controlled. The research results provide a reference for surrounding rock control of roadways under similar engineering geological conditions.