Abstract: The construction of tunnels and related underground projects is increasingly faced with deep burial, high ground stress,complex geological conditions,etc. Among them,coal and gas outburst is a difficult problem that tunnels will encounter in coal measures strata. It is very important for tunnel design and construction to reserve safe coal pillars with appropriate thickness to facilitate comprehensive outburst elimination. Taking Zhaotong tunnel as the engineering background,aiming at the characteristics of deep burial,high ground stress and super large section,the influencing factors of reserved safety rock pillar are analyzed based on cusp catastrophe theory and slurry-stopping rock plate improvement method. The influence of tunnel equivalent height,elastic modulus,vertical ground stress and gas pressure on the critical rock pillar thickness is analyzed by numerical simulation method. The results show that the greater the gas pressure,the equivalent height of tunnel excavation and the vertical ground stress,the greater the thickness of the required reserved safety rock pillar. The elastic modulus has little effect on the thickness of the safety rock pillar and shows a fluctuation phenomenon. In terms of accurately calculating the thickness of the safety rock pillar,the improved method of the slurry-stopping rock plate performs better and is closer to the numerical simulation results. According to the research results,combined with the site geology and construction conditions,10 m was finally selected as the thickness of the reserved safe rock pillar in Zhaotong Tunnel,and the gas extraction work was successfully completed and the outburst coal seam was successfully crossed. 

Key words: deep tunnel,outburst coal seam,safety rock pillar,cusp catastrophe theory,slurry-stopping rock plate improvement method