Abstract:
In response to issues such as limited operating space and high labor intensity associated with advanced hydraulic support in fully mechanized top-coal caving faces with large mining height, this study takes the auxiliary transport roadway of the 507 working face in Madiliang Coal Mine as the research object and proposes a support scheme that uses active advanced support with reinforcement anchor cables to replace advanced hydraulic support. The TS-C1201 type borehole imaging device for mining was used to observe fractures within the coal and rock mass. The results showed that a small number of vertical fractures were present in the shallow part of the roof of the 507 top-coal caving face, while fractures were not developed in other areas, indicating that the overall roof integrity was good and the conditions were suitable for implementing active advanced support. Based on the above observation results, an active advanced support scheme using bolts (cables) was designed. A combined support system of “bolts + cables + steel strips” was adopted for the roof, with the installation of seven left-handed deformed-thread steel bolts without longitudinal ribs and three cables, in combination with M3-type steel strips. Four full-thread bolts were installed on the left sidewall, and four fiberglass bolts were installed on the right sidewall. Theoretical calculations indicated that the reinforcement anchor cables used in the active advanced support system enhanced the strength of the support system and met the support requirements for the advanced section of the roadway. Numerical simulation results showed that during the mining of the 507 fully mechanized top-coal caving face, under the original active advanced support scheme, significant stress concentration occurred within 10 meters ahead of the working face, with a maximum vertical stress of 4.5 MPa and a maximum roof subsidence of approximately 35 mm. Within 30 meters ahead of the working face, the maximum vertical stress reached approximately 5.5 MPa. After the implementation of reinforcement support with bolts (cables), the vertical stress in the roadway decreased slightly, and the distribution of the vertical stress field was optimized. However, there was no significant change in the maximum roof subsidence within the 10–30 m range ahead of the working face. These findings demonstrated that replacing advanced hydraulic supports with active advanced support using reinforcement bolts (cables) could meet the requirements for advanced support. Industrial test results showed that the reinforcement anchor cables remained stable under a load of approximately 81 kN. The maximum displacements of the roadway roof and floor, and of the two sidewalls, were 41 mm and 37 mm respectively. No separation was observed in the roof, indicating that the support scheme meets the requirements for safe production.