| Cutting off roof to form roadway without coal pillar mining technology is a significant revolution in the development of coal industry technology,effectively reduce the workload of roadway drivage,increased coal mining rate,has been widely spread in the whole country,but its completion by cutting down the goaf roof collapse directly for lane help way to greatly increase the exposed area of goaf,increase the degree of the goaf air leakage,It is difficult to prevent and control goaf fire.Therefore,it is of great significance to study the law of air leakage in goaf and the distribution law of spontaneous combustion in three zones under the "Y" type ventilation condition of cut roof roadway,so as to provide effective guidance for the fire prevention and control of goaf under this condition.In this paper,taking 4303 working face of Shaqu No.2 mine as engineering background,the height of caving zone of goaf was determined by theoretical formula calculation,and a three-dimensional porosity distribution model of goaf was established.Set the goaf similar simulation experiment platform,the use of high precision wind speed sensor monitoring changes in goaf air leakage and air volume size and air distribution ratio on the goaf air leakage situation,combined with field can be measured and tracer technology analyzing law of air leakage is verified,law of goal air leakage were identified,the main air leakage part;At the same time,the CFD simulation software was used to simulate the gas distribution in goaf.Combined with the field measured results of beam tube monitoring,the three zones of spontaneous combustion in 4303 goaf were divided by oxygen concentration as an index.According to the air leakage law and the results of the three zones,the plugging measures of goaf under the "Y" type ventilation condition of the cutting roof roadway were worked out.The main conclusions are as follows:(1)Based on the key layer theory of the stope and the failure law of overlying rock in the three zones of goaf caving,considering the roof caving characteristics of goaf retaining roadway under roof pressure relief without coal pillar mining,combined with the physical and mechanical properties of overlying rock in the goaf of 4303 working face,the mathematical model of "three zones" height of overlying rock caving in the goaf of 4303 working face is constructed.The height of caving zone in goaf of 4303 working face is 14.28 m and the height of fracture zone is 30.61 m.(2)through the analog simulation study found that cut top lane "Y" type ventilation goaf air leakage parts distribution mainly in under the condition of working face two Angle and the side near the working face for front end,with the increase of the total air volume and air leakage range into the area of exponential growth,as the main,vice into air volume ratio increases,air leakage area into a rule of negative exponential growth;The main air leakage position was verified by energy level measurement technology,and it was found that the wind speed of side air leakage decreases with the increase of the distance from the working face.(3)in goaf caving height and porosity distribution of three zones model goaf based on numerical simulation of physical model,and import the UDF,simulates the goaf gas distribution,the simulation results with the field tube monitoring results,similar to oxygen content as indicators of goaf spontaneous combustion "three zones",the results combined with gob tube monitoring results and the numerical simulation results it is concluded that: The range of scattered zone in goaf of 4303 working face is 0 ～ 44 m on the main air inlet side,0～ 25 m on the central goaf,and 0 ～ 54 m on the return air retaining side.The oxidation zone ranges from 44 m to 88 m on the main air inlet side,from 25 m to 70 m in the central goaf,and from 54 m to 458 m on the return air side.For 4303 in shaqu coal mine goaf need to strengthen the special case of block,by using numerical simulation method of former chapters of the mined-out area of the main intake side and the side of the front end for plugging effect after the key block in main air leakage parts of simulation calculation,found that after the strengthening sealing parts,goaf air leakage wind speed is reduced,but not goaf oxygen distribution range contained,With the increase of the blocking length on the side of the goaf,the range of scattered zone and oxidation zone gradually decreases.When the side of the goaf is completely blocked,the oxygen distribution range of the goaf is significantly reduced,and the spontaneous combustion risk area of the goaf is effectively controlled.(4)Based on the above research conclusions,a set of plugging measures were formulated for the 4303 working face of Shaqu No.2 Mine.After the plugging effect test,the air leakage in the return air section of the retaining roadway was reduced by 50%,the range of spontaneous combustion three zones in the goaf moved forward to the working face,and the width of oxidation zone along the goaf retaining roadway was reduced by 262 m.The plugging measures achieved good results. |
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