Simultaneous Drifting Gateway Technology of Medium Guide Hole Advanced Excavation for Large Cross Section Open-Off Cut

Abstract：In order to solve the high roof subsidence and serious floor heave problems occurred in the excavation process of the large cross section open-off cut, the simultaneous drifting gateway technology of medium guide hole advanced excavation for the large cross section open-off cut was proposed. A Midas/GTS numerical simulation was applied to study the surrounding rock deformation features and the stress distribution features of the open-off cut under the condition of simultaneous drifting gateway technology of medium guide hole ad- vanced excavation and the secondary drifting gateway with the cross section slicing. The study results showed that with the simultaneous drifting gateway technology of medium guide hole advanced excavation, the roof subsidence value was reduced by 43 mm, the floor heave value was reduced by 110 mm, the plasticity zone of the surrounding rock was small, the gateway stress were even and would be favorable to the stability of the surrounding rock. The simultaneous drifting gateway technology of medium guide hole advanced excavation was ap- plied to the construction of the open-off cut for No. 4502 coal mining face in Xinyao Mine. The monitoring and measuring results of the mine strata pressure showed that the roof subsidence value was 98 mm, the floor heave value was 172 mm, the surrounding rock deforma-tion were within the control range and the stability of the gateway could be maintained.