Study on intensified control technology of large span open-off cut surrounding rock

In order to have the failure features of the large span open off cut in the thick seam and to effectively control the surrounding rock stability,an analysis was C onducted on the high convergence between the two sidewalls ,serious roof subsidence and other conditions occurred in the driving process of the large span open-off cut in No.705 coal mining face of Pangpangta Coal Mine. With the analysis on the deformation and failure inducements of the surrounding rock,in combination with the support r ole mechanism of the anchor truss to the roof,a large span strengthened beam control technology was provided based on a bolt I steel mesh 1 anchor + truss combined sup port. The application results showed that during the excavation period of the pilot hole,a max convergence between the roof and floor of the gateway was90 mm,a max con vergence between the two sidewalls was 100 mm and the relative stable period of the pilot hole excavation was about 15 days. During the reaming period of the gateway,a max convergence between the roof and floor was about 95 mm,a max convergence between the two sidewalls was 65 mm,the roof could be stbilized 20 days,the two side walls could be stabilized about 10 days and the deformation of the surrounding rock could be effectively controlled.