Study On Safety Numerical Simulation And Monitoring And Early Warning Method Of Tunnel Construction In Goaf Of Coal Mine

China is a major coal and coal mining area scattered in many areas..When the road tunnel go into the mountain,The mined out area at the upper part or the lower part of the tunnel will have a bad influence on the stability of rock.Even if the geological prospecting has been proven in the mountain area,but in order to meet the requirements of the highway,highway tunnel is inevitable to wear mined out area.In this paper,taking the key project of Chongqing as an example,the paper studies the stability of the surrounding rock of the tunnel through the theoretical derivation,numerical simulation and field measurement data,and gives the mining goaf tunnel construction phase matching monitoring and early warning method.The main research results are as follows:(1)According to the principle of the formation of the coal mining area,the formation mechanism of the goaf under the three forms(0 degree horizontal coal seams,30 degree gently inclined seams and 60 degree steep coal seams)is fully considered.By analyzing the stress distribution of the forming process of the goaf and the influence range of the goaf,mechanical model of mined out area is determined,which provides a theoretical basis for the numerical simulation.The net distance between the tunnel and the mined out area is L,the size of the mined out area and the different position of the goaf are used as variables,and the mechanical model of the construction under the influence of a single variable is put forward by considering the two cases of the tunnel through the mined out area at the upper part or the lower part:Mechanical model of tunnel construction under different net distance between the goaf and tunnel,the mechanical model of tunnel construction in different sizes of coal mining area and the tunnel construction mechanics model under different space position conditions.(2)The influence of the net distance between the tunnel and the goaf L?Size of mined out area S and Mined out area in different locations on the stability of the rock is studied by simulating the working conditions of the tunnel and the tunnel under the goaf.The results show that the larger the inclination of the coal seam,the greater the vertical displacement of the rock,and the influence of the goaf on the vertical displacement is larger than the horizontal displacement.The smaller the net distance from the L or the larger the size of S,the greater the influence of the plastic zone of the surrounding rock of the tunnel,and the influence of the region is mainly concentrated in the surrounding rock of the near coal seam.1)When the tunnel under mined plastic zone area has the following rules:Dip angle of coal seam to 0 degree,spacing L=0.5D or mined out area size S=D×3.In the upper part of the tunnel by the left and the right arch waist to mined out area edge rock appeared "triangle" and through the region;coal seam dip angle is 30 degree,spacing L=1D or mined out area size S=0.9D×3,between the tunnel and mined out area of surrounding rock plastic zone through;coal seam dip angle is 60 degree,spacing L=2D or mined out area size S=0.7D×3,between the tunnel and mined out area appeared through the region.2)When tunnel through mining the empty zone: coal seam dip angle is 0 degree,net distance L=0.3D or mined out area size S=D×3.In the upper part of the tunnel surrounding rock appears plastic penetration area;coal seam dip angle is 30 degree,the spacing L=1.5D or mined out area size S=0.7D×3,between the tunnel and mined out area of surrounding rock plastic penetration area;coal seam dip angle is 60 degree,spacing L=2D or mined out area size S=0.6D×3,between the tunnel and mined out area appeared through the region.3)At the same time,based on the strength reduction method,the stability of surrounding rock is studied under the condition of 60 degree inclined angle coal seam,and the safety factor of the tunnel under 4 conditions is obtained.(3)This section to China rock tunnel ZK1+567 gob area to monitor quantity measuring the measured data and numerical simulation Comparison of the results,that the rules are basically the same,in addition for mining gob and tunnel between the three relative position,specified in the original standard monitoring and measuring based on proposed mined out section surrounding rock monitoring and measurement method,and the mechanism of monitoring and early warning ratings,to enhance the sense of crisis of all parties participating in the construction,at the same time also is same geological structure of tunnel construction to provide a reference.