Study On Gas Migration,Emission,Diffusion Law And Prevention Technology In Surrounding Rock Section Of Highway Tunnel With Coal Seam

With the continuous improvement of China’s economic and social development level,the construction scale of traffic facilities shows a trend of continuous and rapid development,and the construction scale of highway tunnels also shows an obvious growth.With the continuous expansion of highway tunnel construction scale,higher requirements are put forward for the construction safety level of the tunnel.Safety accidents often occur in the process of tunnel construction.In all kinds of disasters,gas disasters often cause serious consequences.Therefore,many scholars at home and abroad have done a lot of research on this issue,and have achieved fruitful results.However,these studies are mainly aimed at the prevention and control of tunnel gas disaster in coal measure area,while the comprehensive research results of gas migration and prevention in coal measure strata are very limited.The coal bearing strata are widely distributed in the southwest of China.There are a lot of harmful gases such as gas in the coal bearing strata.During the construction process,it is very easy to cause gas explosion,gas outburst and other disasters,resulting in serious casualties.Therefore,based on the engineering background of a highway tunnel in Southwest China,this paper systematically studies the gas source,migration law,diffusion law and gas disaster prevention and control technology in the strata section of the tunnel’s coal seam by means of site investigation,data collection,theoretical analysis and numerical simulation.The main research contents are as follows:(1)Based on the study of domestic and foreign research results on gas migration and disaster prevention in highway tunnel construction,this paper analyzes the gas occurrence form in the strata section of the coal seam with the tunnel engineering case in this paper,and studies the gas migration in the surrounding rock of the coal seam with the tunnel after excavation,based on the COMSOL Multiphysics physical simulation software is used to simulate the gas migration in the surrounding rock,which further verifies the gas migration law after the excavation of the tunnel surrounding rock.(2)Based on the analysis and recognition of the gas tunnel structure,stratum characteristics,hydrogeology and other basic conditions,the gas concentration of the gas occurrence section of the tunnel was detected.Based on the analysis of the gas concentration data obtained from the on-site monitoring,the relationship between the gas emission and the time,location,etc.is obtained,and then the gas emission distribution law after the tunnel excavation is obtained.(3)Aiming at the problem of gas diffusion in the tunnel after the surrounding rock of the tunnel adjoining the coal seam is excavated,this paper uses the fluent numerical simulation software,on the basis of in-depth analysis of the relevant principles and methods of numerical simulation calculation,calculates and analyzes the gas diffusion concentration distribution and spatial migration rule under different working conditions,and prevents and cures the gas disaster during the construction of the tunnel Theory provides some guidance.(4)This paper reviews and summarizes the main prevention and control measures of gas disaster in highway tunnel,including advance geological prediction of tunnel,gas drilling drainage,grouting and plugging of surrounding rock,strengthening tunnel ventilation,adding air tight materials behind the lining,etc.According to the monitoring data of gas concentration distribution in the tunnel site,the numerical simulation results of gas migration and emission obtained by advanced drilling,the gas control scheme for the coal seam section of the tunnel is determined,including the measures of drilling drainage,construction ventilation,etc.