Failure mechanism of severe deformation in gob-side entry rib and unloading-supporting coupling control technology

• Published in: Engineering failure analysis 2025-01, Vol.167, p.108973, Article 108973
• Main Authors: Ma, Xiang, Chen, Dongdong, Xie, Shengrong, Zou, Jun, Wu, Haodu, Sun, Aiguo, Wang, Zhiqiang
• Format: Article
• Language: English
• Subjects: Bag compression; Gob-side entry retaining (GER); Large-diameter pressure regulating hole (LPRH); Solid coal side pressure regulation; Stress transfer
• ISSN: 1350-6307
• DOI: 10.1016/j.engfailanal.2024.108973

•The applicability, advantages and disadvantages of three kinds of pressure-release technologies of roof-cutting [Fig. 1 (a)], large diameter drilling pressure-relief [Fig. 1 (b)] and roadside newly excavated pressure-relief roadway [Fig. 1 (c)] are compared and analyzed. A novel LPRH technology [Fig. 1(d)] of solid coal side in gob-side dynamic pressure roadway have been proposed, and its differences with the above three kinds of technologies and the advantages of LPRH technology in economy, principle and conditions are compared.•The mechanical hole-creating equipment with controllable space shape and coal output was introduced and reformed. A novel-type of pressure regulating monitoring system for bags which can be contracted and placed in the cavity-building space and inflated by injecting liquid is developed. By monitoring the deformation and closure degree of the LPRH and the loading pressure of the bag, it is found that about 40% of the variable space remains in the hole after the lag dynamic stress of the roadway along the goaf. The ability of the pressure-release hole to absorb deformation is very significant.•The impact degree of roof-cutting on the abutment pressure of the solid coal side, and the influence law of holes on the pressure-release result of GER under the influence of the position, length and spacing of LPRH in coal side are studied, and the optimal parameters are obtained.•Compared with the GER of similar geological units, the deformation of the experiment region of the “unloading-supporting” coupling regulate method is reduced by more than 65%, which ensures the reusability of the GER, avoids its brush expansion and refurbishment, and has an extremely obvious pressure-relief control effect. Given the problem of the solid coal side produces strong mine pressure in the stage of strong mining and lagging dynamic pressure in the gob-side entry retaining (GER). Using the W3233 ventilation roadway in the West-Third mining area as a case study, the research employs numerical simulation, field observation, and engineering analogy. Key findings include: (1) The optimal plan reduces maximum stress on the coal side and shifts it inward, primarily by severing the main roof and alleviating the gangue wall load, offering limited pressure relief on the solid coal rib. (2) When hole-creating depth is too close to the solid coal rib (b = 6 m), it compromises integrity. If the depth exceeds the stress maximum region (b = 10 m), it fails to effectivel