Surrounding rock control for the roadway driven under the goafs of small collieries and heading for adjacent...

Aiming at the problems of complex stress and large deformations in the surrounding rocks of the roadway driven under the goafs of small collieries and heading for adjacent advancing coal face, by numerical modeling and field practice, the failure characteristics of the overlying coal and rocks were investigated, and the stopping and resuming times of the roadway excavation were identified. A zoning-based reinforcement technique was put forward and applied in engineering practice. The results showed that (1) The roadway roof was divided into four zones: "Rolid coal zone", "Residual pillar zone", "Roof caved zone", and "Roof un-caved zone". (2) It was determined that the roadway excavation was stopped when the unmined distance between the return airway face and the 32,101 working face was 70 m. After the 32,101 working face passed the return airway face by 90 m, the roadway driving was restarted. (3) I.e. cable reinforcement for the "residual pillar zone" and bolt-wire mesh-cable-shotcreting-grouting reinforcement for the "roof failure zone" ("Roof caved zone" + "Roof un-caved zone"). The field observation results indicated that the maximum amount of the roof-to-floor convergence and the wall-to-wall convergence was 97 mm and 69 mm, respectively, which ensured the safety of roadway excavating.