Self-bearing Characteristics and Control Strategy of a Cataclastic Regenerated Rock Mass in a Roadway Roof with Top Remains: A Case Study

A roadway roof has compound and cataclastic features when tunneling a roadway under a gob with top remains in downward mining. To identify the self-bearing characteristics and to develop a control strategy for a regenerated roadway roof with top remains (RRRTR), mechanical and numerical models of a RRRTR were built on the basis of a structural model of a compound and cataclastic roof. Through a theoretical analysis and numerical simulations, the formation and instability criterion of a three-hinged arch in a RRRTR were analyzed. Meanwhile, the self-bearing characteristics of a RRRTR with various crack spacing values in the top remains were studied. On this basis, a bolt-net-belt (BNB) support scenario was proposed to control the RRRTR and an on-site roof subsidence monitoring task was conducted. The theoretical and numerical analyses both indicate that a three-hinged arch exists in the roadway top remains, and it has a certain bearing capacity. The compressive failure of the hinge points is an instability trigger of a three-hinged arch that would trigger the entire failure of the RRRTR. The crack spacing values of the top remains influenced the formation and bearing capacity of the three-hinged arch. The three-hinged arch is easier to establish and has a better bearing effect when the top remains have a larger crack spacing value. The BNB support scenario could not only control the roof subsidence but also facilitate the potential self-bearing capability of the RRRTR.