Study On Goaf Gas Migration Law And Ventilation Mode Optimization Of Working Face With Cutting Roof And Retaining Roadway

The technology of cutting roof and retaining roadway changes the roof pressure transmission mode and roof rock caving characteristics,causing the change of goaf permeability evolution law,resulting in a big difference between goaf air leakage law and traditional mining mode.For cutting the top left lane in different ventilation way（"W","Y"）under the goaf gas migration rule,the drainage condition of spontaneous combustion zones mingle change,based on the analysis of mined-out area,on the basis of overlying strata movement rule,build the cutting head for the"W","Y"type ventilation mode UDF of porosity and permeability of mined-out area,the main conclusions are as follows:Under the"Y"ventilation mode,the air leakage air flow in the goaf lane at the cutting top is close to the working face.The air leakage air flow in the goaf lane at the cutting top is combined with the air leakage air flow at the working face and moves to the deep part of the goaf.In the direction of goaf,the leakage of the cutting face increases with the increase of the porosity of the porous media,and the air leakage increases with the increase of the distance to the lower corner.With the increase of porosity of porous media,the air leakage amount in the goaf heading for the roadway is also larger,and the air leakage amount in the goaf heading for the roadway gradually decreases as the length of the working face increases.Due to the leakage air flow under the"Y"ventilation,the concentration of gas carried by the leakage air flow toward the goaf at the air inlet of the air lane is concentrated in the deep part of the goaf,and the spontaneous combustion zone near the working face and the roadway is larger.The"Y"ventilation has serious gas accumulation in the corner of the working face and the section at the end of the alley."W"type ventilation air leakage flow under is very different from"Y"type ventilation,machine lane near the working face machine lane to goaf under different air volume ratio,porosity,maximum leakage air volume 0.4 x 10^-1 m³/min,and the maximum"Y"type ventilation leakage air volume for 1.25 x 10^-1 m³/min,the"W"type ventilation leakage of working face goaf wind field and left lane into the wind to the mined-out area along the wind lane return after the leakage of romantic rendezvous.In the direction of"W"ventilation working face leakage to goaf increases with the porosity of plugging air material,and the air leakage also increases.The air leakage of"W"ventilation is more serious at 0～50m at the inlet of the retaining roadway,and the air leakage is small at the lower corner,and the gas concentration is more serious at the corner of the working face.According to the study on the gas migration law of the goaf working face under"W"and"Y"ventilation,the maximum porosity of the air leakage material on the side side of the goaf is 0.28～0.4×10^-1m³/min,and the maximum porosity of the air leakage material on the side side of the goaf is 0.2～0.68×10-²m³/min.And work under the"Y"type ventilation for goaf left lane side help plugging material porosity biggest wind leakage air volume in 0.52～1.25 x 10^-1m³/min,the mined-out area in the left lane to the side for help plugging material porosity under different wind maximum leakage air volume in 0.18～0.5 x 10^-2m³/min,considering the"W"type ventilation working face goaf,the left lane to goaf leakage air volume smaller than the"Y"type ventilation;Under the condition of drainage,the gas drainage effect of"W"type ventilating kilometer borehole and buried pipe is obvious,but the expansion of the spontaneous combustion belt on the working face and the side of the roadway is obvious.In the coal seam with high natural ignition,it is easy to spontaneous combustion.The drainage effect of"Y"type ventilating kilometer borehole is obvious and has a weak influence on the spontaneous combustion belt.At the same time,combined with the field measured gas concentration data,it can be seen that under the condition of using high borehole drainage,the"Y"type ventilation drainage effect is better than that of"W"type ventilation drainage effect.In the coal seam with low natural ignition,the buried pipe drainage can be used preferentially,and the buried pipe can be arranged in the asphyxiation belt as far as possible.However,no matter what drainage measures are adopted,it is necessary to strengthen the fire prevention monitoring and monitoring of the coal seam on the roadway side of the working face in the actual production process.