Application of pillar-free self-formed roadway technology under the influence of reserse faults: Strata behavior law and surrounding rock control

To explore the influence of reverse fault activation on the stability of the application of the pillar-free self-formed roadway technology, this study systematically investigated the influencing scope and mechanisms of the reverse fault activation through theoretical analysis, numerical simulations, engineering practice, and field monitoring. The results show that, under the combined action of horizontal tectonic stress and dead weight stress, reverse faults have a significant influence on both the advanced abutment pressure of working faces and the pressure on the roadway roof after coal mining. The reverse fault was locally activated when the working face was close to the reverse fault. In contrast, it was completely activated when the working face reached the reverse fault due to the influence of intense coal mining along the working face. As a result, the advanced abutment pressure of the working face sharply increased, with a stress concentration coefficient of 4.75. After the reverse fault was exposed, the load of the overlying strata was transferred from the hanging wall of the reverse fault to the rear goaf, leading to an increase in the abutment pressure of the rear goaf. The simulation analysis indicates that the foot wall of the reverse fault had a significant influence on the stability of the surrounding rocks of the working face. The influencing scope was 85 m and was the key area for surrounding rock control. Using the constant resistance and large deformation anchor with supernormal mechanical characteristics, such as high and constant resistance, high elongation, and high preload, as well as precise roof pre-splitting for pressure relief and the combined support technology for roadway surrounding rocks, this study enabled the roadway surrounding rocks 150-190 m behind the working place to remain stable. Therefore, this technology can effectively control the instability and deformation of surrounding rocks.