Abstract: To solve the problem of safe fully-mechanized mining in steeply dipped thick soft coal seam, physical modelling integrated with digital image correlation (DIC), acoustic emission (AE) and distributed optical fiber sensing (DOFS) technology, and the numerical simulations were conducted in this study. Based on the geological and engineering conditions of the 1212 (3) working face of Panbei Mine in Huainan mining area, the evolution of the fracture tendency zone of the regenerated roof during the lower slice mining was studied. The acoustic emission characteristics and the fiber strain responses of the regenerated rock mass were deeply investigated. The results show that the caving of regenerated roof consists of rock slippage, fracture of the low and mid-level cantilever beams and high-level articulated rock beams. Furthermore, the fracture of the double-beams is the key to the instability of the support in lower slice. The acoustic emission energies from the upper and middle parts of the lower slice are highly concentrated with short durations. Moreover, the fiber strain results indicate that the breakage occurs in the low cantilever beam and the high strain peak appears in the upper and middle parts. The middle and upper parts of the lower slice are the key areas for the stability control of the support and the regenerated roof. The lower part of the regenerated roof is densely filled with fragmented rock with much smaller grain size, where the rock leakage between and in front of the shelf is commonly encountered. A high-stress arch is formed in the regenerated roof of the lower slice, which is approximately 30 m in height from the goaf. The fracture of the double-beams mainly occurs in the arch, and the rock breakage in the arch has a certain collapse effect on the support.

Key words: steeply dipping coal seam, lower slicing mining, surrounding rock failure, similar simulation, numerical simulation