Effect of Roof Cutting Technology on Broken Roof Rock Bulking and Abutment Stress Distribution: A Physical Model Test

The no-pillar longwall mining method (NPLM) by roof cutting technology (RCT) is an innovative longwall mining method proposed in China. Its essential technology is the employment of RCT to replace the chain pillar to safeguard the roadway. In this paper, a novel physical model test method is designed to investigate the protective mechanism of RCT for roadways in greater detail. Furthermore, the physical model test of RCT is conducted in consideration of the effect of broken roof rock bulking. Combined with numerical simulation, the results indicate that RCT can increase the degree of gangue bulking in goaf, hence providing effective support to the overlying strata and maintaining their integrity. Moreover, RCT can significantly reduce the abutment stress of the roadway roof and solid coal side, thereby ensuring the stability of roadway surrounding rock. This paper proposes three protection mechanisms of RCT for roadway based on the findings of the conducted research: I. Reducing the dimensions of roadway roof; II. Utilizing bulking gangue to support the overlying strata; III. Eliminating the cavities in the goaf adjacent to the roadway. The in situ application provides evidence that RCT is effective in controlling roadway deformation. This paper can serve as a reference for no-pillar mining and analogous geotechnical engineering physical model tests. Highlights A novel two-dimensional physical model test method is developed that can achieve bulking after failure. Three protection mechanisms of roof cutting technology for the gob-side roadway are elucidated. The effect of roof cutting technology on the bulking of broken roof rock is analyzed by experiment. In conjunction with the in-situ application, the key to no-pillar longwall mining by roof cutting technology is proposed.