Study On Spontaneous Combustion Characteristics Of Goaf Coal Under Disturbed Airflow

Spontaneous combustion of residual coal in goaf is one of the most common disasters in underground coal mines,which brings serious threats and damage to the health and safety of underground workers.Based on the research background of periodic disturbed air flow generated by driving roadway,this paper explores the influence of disturbed airflow on working face air volume and goaf by combining theoretical analysis,laboratory experiment,and numerical simulation,and makes the following main research achievements:Through the establishment of the periodic disturbance air flow experimental model,the disturbance airflow experiment was carried out in the driving roadway,and the variable speed ventilation was carried out in the driving roadway.It was concluded that after the variable speed ventilation was carried out in the local ventilator,the air volume of the working face connected with the local ventilator decreased first and then increased,and the air volume variation of the two was negatively correlated.When the total return air volume is low,the influence of the heading air volume on the working face air volume will be increased.With the increase of the total return air volume,the air volume at the working face increases rapidly and still meets the negative correlation with the air volume of the heading roadway.When the length of the heading roadway is changed and the total return air volume is low,the roadway length has little influence on the disturbance at the working face,and the total return air volume is increased.With the increase of heading length,the influence on the air volume at the working face is increased,and the disturbance amplitude is more obvious.The relationship between the total return air volume and the heading roadway and the working face air volume is established.Because the air leakage in the goaf is related to the air volume at the working face,the goaf will also be affected by periodic disturbance airflow.Through numerical simulation,it can be concluded that: in the fluctuating process from steady wind speed to periodically disturbed wind speed,"periodic deceleration" ventilation will make the goaf wind speed field and oxygen concentration field move forward towards the working face,and then recover and move forward again."Periodic acceleration" ventilation has the opposite effect;The maximum temperature of goaf is positively correlated with the variation period of wind speed.The temperature of the fixed monitoring point and the maximum temperature of the goaf increase with the increase of the disturbed wind speed.The fitting formula of the disturbance wind speed with the temperature of the monitoring point and the maximum temperature of the goaf is obtained.The spontaneous combustion area of coal is positively correlated with the variation of periodic disturbance wind speed,and it is more sensitive to "periodic deceleration" ventilation.The change of gas concentration in the return air side is not linearly related to the change value of wind speed and the change period of wind speed but is affected by the temperature effect and wind speed effect at the same time.In a short period,even if the wind speed value is increased,the temperature effect is great and the gas parsing amount is increased,the gas concentration in the return air side may still be greater than the gas concentration in the normal ventilation period or even the gas overrun phenomenon may occur.In a long period,when the value of wind speed increases,the concentration of gas decreases obviously after being diluted,and the effect of wind speed is stronger than that of temperature.This study can provide some theoretical support for the monitoring of working face air volume and the prediction and early warning of spontaneous combustion of coal in goaf under the condition of periodically disturbed airflow.There are 33 figures,3 tables,and 114 references in this dissertation.