Cause Analysis and Treatment Technology of Gas Overlimit in Close Range Rock Drivage

In view of the problem that gas overlimit in close range rock drivage process,taking 1302 floor rock roadway in Yuxi Coal Mine as the research object,the stress and displacement distribution of surrounding rock roadway was simulated by FLAC^3D numerical simulation software.The results show that the serious deformation of surrounding rock is the direct cause of gas overlimit in rock roadway,and the low air volume is the indirect cause of gas overlimit in rock roadway.Some gas control technologies were put forward,including ventilation technology,pre-pumping technology for long drilling of 1 000 m drilling rig and the technology that extraction gas using drilling network to cut off gas etc.,the application results show that after adopting gas comprehensive treatment technology,the gas concentration (methane volume fraction) in the roadway decreases,ranging from 0.10% to 0.50%,it is from 0.73% to 0.96% previously,there is no gas overlimit;the progress of rock drivage increases from 100 m per month to more than 200 m per month,with an increase of 100%.It can provide reference for gas control under similar geological conditions.