Study on Over-Long Bolt and Anchor Combined Support Technology of Large Cross Section Open-Off Cut Based on Thin Base Rock

According to the serious mine strata pressure behaviors of the open-off cut,large deformation of the surrounding rock,hard to maintain the surrounding rock and other problems in No.1105 high cutting coal mining face in the trial mine,with the theoretical analysis,numerical simulation and site experiment as the main study method,an optimized design was conducted on the support parameters of the open-off cut.The results showed that the conventional bolt and anchor combined support could not anchor in the stable rock strata.With the application of the new 5m over-long bolt and anchor combined support,the surrounding rock deformation of the open-off cut could be obviously controlled.The roof subsidence value was reduced from 212mm to 170mm,the deformation speed was highly reduced and the spalling of the two sidewalls was obvious small.