Study on gas flow pressure caused airflow disorder in parallel downward ventilated roadways

The high-concentration of methane accumulating in a tilted roadway could produce gas flow pressure.This gas flow pressure can induce airflow disorder in the tilted roadway and its lateral roadways.In this paper,an experimental system was constructed for representing parallel downward ventilation roadways.With this system,a series of experiments were conducted to study the gas flow pressureinduced airflow disorder in coal mine roadways.The tilted roadway was saturated with 100% concentration methane while the lateral roadway was saturated with air for all experiments.The resistance coefficient of the tilted roadway and the lateral roadway were changed in different experiments.The experimental results indicate that the gas flow pressure could cause complex airflow changes in parallel downward ventilation roadways and lead to methane and airflow reciprocation in the roadways.A vibration model was developed based on a simplification of the experimental system.The vibration model can explain the effects of windage on the damping force of the vibration.Both the experiment and model results indicate that the windage increase of the tilted roadway or the lateral roadway can weaken the airflow vibration.Analysis of the methane movement in the experimental system indicates that for the tilted roadway and the lateral roadway an windage increase in one roadway is helpful for the airflow stability but harmful for its own gas discharge.If gas accumulation appears in an in situ downward ventilation roadway,the windage of the lateral roadway should be increased without delay to keep the system airflow stable and to discharge the accumulated methane as soon as possible.