A bulking control method for controlling surface subsidence based on technology of automatic roadway formation without coal pillars

Abstract In the mining technology of automatic roadway formation without coal pillars (ARFCP), the capacity of gangue from collapsed roof to completely fill goaf and create a stable pressure-bearing structure is crucial for controlling surface subsidence. This study first proposed the ARFCP mining theory based on bulking equilibrium. Subsequently, using PFC2D, it analyzed the mechanical characteristics of gangue structure from three perspectives: force chain evolution, fracture development, and particle displacement under different load conditions. Based on this analysis, the bulking control method (BCM) based on gangue bearing characteristics was proposed, including deep and shallow hole coupled energy accumulation blasting (DSAB), dual-control pre-cracked holes (DCCH) and cyclic loading and unloading of supports (CAUS). Three types of bulking monitoring methods were then proposed to assess bulking characteristics. Finally, taking the 1310 working face of Zhujiamao Coal Mine as an example, engineering comparative experiments were conducted on different sections of the site. The results show that after the application of BCM, the bulking coefficient and residual bulking coefficient increased to 1.79 and 1.39, respectively, while surface subsidence decreased from 0.36 m to 0.04 m. The surrounding rock of the retained roadway did not exhibit significant subsidence or floor heave, meeting the safety production requirements.