Absorbent Bag Type Horizontal Drilling And Sealing Technology And Its Application In The Study Of The Width Of Stress-relief Zone Of The Coal Body Beside Tunnel

In the process of the production process of the mine,the surrounding rock in the mining space is decompressed and damaged,and a large number of cracks are generated.The stress-relief gas enters the mining space through the pores and cracks in the stressrelief coal body,which reduces the pressure and content of the stress-relief coal body gas.Theories and practices show that mining operations in the stress-relief zone will eliminate coal and gas outburst accidents.Therefore,Determine the width of the stressrelief zone in the mining space in advance,and gob-side entry driving in the pressure relief zone,which can prevent coal and gas outburst accidents,effectively reduce the amount of gas emission,and ensure the safety of tunnel construction.This paper uses theoretical analysis,field measurement,and COMSOL numerical simulation to research the width of the stress-relief zone beside the tunnel,and provides a theoretical basis for the setting of the coal pillar width and the safe driving of the gob-side entry driven.First,theoretically analyzed the stress distribution of the coal body beside the tunnel under the influence of mining,discussed the formation and division of the stressrelief zone,the concentrated stress zone,and the original stress zone,and develop the evolution law of the size of each zone over time,and the support of the coal body in each zone.Research on the law of stress and Permeability changes with mining,as well as the law of gas occurrence and migration in coal bodies in various districts,and explore the law of dynamic evolution of the width of the stress-relief zone.Secondly,through theoretical analysis,it is found that the main influencing factors of the width of the stress-relief zone are geo stress,gas pressure,and coal mechanical properties.The deeper the coal seam is,the greater the gas pressure,the smaller the internal friction angle and cohesion,and the width of the stress-relief zone is larger.According to the field measurement and analysis of the on-site residual gas pressure and content,the coal Permeability of the stress-relief zone increases,and the gas content decreases;while the coal Permeability of the concentrated stress zone decreases.The above theoretical analysis and field measurement provides a basis for determining the width of the stress-relief zone.Thirdly,based on the conventional horizontal borehole gas pressure measurement method,an absorbent bag's horizontal drilling and sealing technology were developed.Compared with traditional technologies,it has obvious advantages and makes up for the shortcomings of traditional technologies.At the same time,the absorbent bags horizontal borehole sealing pressure measurement method was used to measure the residual gas pressure,residual gas content and the amount of drill cuttings per meter of the coal body beside the tunnel,The regression analysis showed that the width of the stress-relief zone in the process of mining evolves with the time elapse of mining exposure is that the longer the mining exposure time,the larger the stress-relief zone width,provided that it is within a certain time range.When the working face is mined to 500 m and there are about 330 days from the beginning of the tunnel excavation.the width of the stress-relief zone in the second coal seam affected by mining is at least 35 m.It can provide a basis for rationally arranging production plans for the mine,and deciding whether to take stress-relief and outburst prevention measures and strengthen tunnel support.Finally,using the multi-physics simulation software COMSOL as a tool,combined with the properties of the overlying strata in the 21106 working face of the Chengjiao Coalmine,a three-dimensional geometric model is established,the measured width of the pressure relief zone was simulated,and verified,and the stress distribution of the coal body beside the tunnel and the evolution of the width of the stress-relief zone in the process of the mining process are established.A simulation analysis was performed.The study concluded that the width of the stress-relief zone beside the tunnel in the mining stage has an exponential relationship with the mining process;At the same time,the width of the stress-relief zone of the coal body beside the tunnel dynamically evolves with the time of mining exposure,when dividing the width of the stress-relief zone of the coal body beside tunnel,it is necessary to consider the stages of the mining process;The simulation of the COMSOL numerical model can be used as a fast and reliable method to determine the width of the stress-relief zone of the coal body beside tunnel.Besides,the width of the stress-relief zone beside the tunnel expands slowly with the passage of mining exposure time,which is far less severe than the impact caused by mining disturbance.By the time the working face of 21106 was mined to 500 m,the width of the stress-relief zone beside the tunnel of the 2nd coal seam of Chengjiao Coalmine was 35 m,and 5 m small coal pillar width in gob-side entry driving is reasonable.