Research On Gas Movement Law And Construction Technology Of Highway Tunnel Through Coal Stratigraphic System

Since the reform and opening up,the speed of China’s economic development has changed with each passing day.The demand for the scale of public transport construction is increasing,and the demand for highway tunnels is also increasing.However,the geological conditions of tunnel construction are complex,and the corresponding construction technology and safety control put forward higher requirements.In the actual construction process of the tunnel,all kinds of accidents emerge one after another,among which the safety accidents caused by gas disaster are the most serious.Once they occur,the damage to the construction personnel is immeasurable.So far,a large number of researchers have studied and analyzed the problem of gas emission in tunnel through various ways,and obtained a large number of research results.However,most scholars study the gas disaster prevention measures for tunnels passing through coal measures,and lack the research on the law of gas migration and seepage.However,the geological situation in Southwest China is complex and changeable,and there are a large number of tunnels passing through coal measure strata.These tunnels are prone to gas infiltration during construction,resulting in gas disasters.Based on the research background of a highway tunnel passing through coal measure strata in Southwest China,this paper analyzes and calculates the gas migration law in the process of tunnel construction,the change of gas infiltration concentration distribution before and after grouting and the numerical simulation of gas disposal effect after ventilation on the basis of data collection and theoretical analysis.The comprehensive treatment measures for gas in highway tunnels crossing coal measures are put forward.The main research contents are as follows:(1)By consulting the research results of experts and scholars at home and abroad on the road tunnels crossing the coal formation,combined with the actual working conditions of the highway tunnels selected in this paper,the storage form and transport of gas gas in the surrounding rock of the tunnel are analyzed and studied,and the transport of gas gas in the surrounding rock is simulated by Fluents numerical simulation software,and the transport and diffusion of gas in the surrounding rock after tunnel excavation is obtained: in the case of no ventilation in the tunnel,the gas will spread to the whole tunnel over time.In particular,the concentration of gas near the palm face is very high.During the construction of the tunnel,the surrounding rock is disturbed,and the development and expansion of the fissures increase the gas seepage path in the surrounding rock,and the gas will spread at a faster rate.(2)According to the migration law of gas in surrounding rock,reasonable construction disposal measures are put forward,and air ducts are arranged in the tunnel for ventilation.Under the wind speed of 1m / s,the tunnel returns to the normal construction standard requirements after 1h,indicating that ventilation can effectively improve the tunnel environment.At the same time,grouting reinforcement is carried out on the surrounding rock of the tunnel on the basis of ventilation,which changes the mechanical properties of the surrounding rock,reduces the pores and the permeability coefficient.Based on numerical simulation,the change of gas concentration before and after surrounding rock grouting is analyzed and studied.The simulation results show that after grouting in the surrounding rock,the gas concentration is about 0.69% after stabilization,which is far lower than the maximum safety range.Compared with 13%of the gas concentration in the tunnel before grouting,the gas concentration in the tunnel is greatly improved.After grouting reinforcement of surrounding rock,the normal construction of tunnel can be ensured.It can provide some guidance for the prevention and treatment of gas disaster during tunnel construction.(3)Based on FLAC3 D finite difference software,the three-dimensional model of tunnel is established.By comparing and analyzing the stability and stress characteristics of tunnel support system excavated by full section method and bench method under the conditions of grouting reinforcement and non grouting reinforcement,this paper expounds the influence of stratum grouting on tunnel support system;(4)By reading a large number of literature on prevention and control measures of gas tunnel at home and abroad,this paper adopts advanced geological prediction,surrounding rock grouting reinforcement and tunnel ventilation treatment to comprehensively control the gas existing in the tunnel.The feasibility of comprehensive treatment measures is verified according to the way of on-site monitoring of gas concentration.Figure [46] Table [9] Reference [85]...