Influences of Gas Drainage Pipe Positions on Spontaneous Coal Combustion in the Gob: A Case Study of Baode Coal Mine in China

Abstract

ABSTRACT Gob buried pipe is a common technological means for gas extraction. This method can effectively address the transfinite gas problems on the working face. However, it may induce spontaneous coal combustion in the gob. In this study, the disturbance effect of the gob buried pipe’s entrance position on oxidation of residual coals in the gob is analyzed. A physical model with the same size as the 81307 fully mechanized caving face in the Baode Coal Mine in China is constructed. Then, the airflow leakage field and oxygen concentration field in the gob under different exploitation conditions are solved. Results demonstrate that extraction by buried pipe may change the airflow leakage field in the gob. Specifically, the gas penetration range into the gob is narrowed, which decreases the oxidation zone width in the gob to some extent. When the entrance is far from the working face, the return airway’s oxidation zone is small. With the increase in the distance from the entrance to the working face, the boundaries of the return airway’s oxidation zone also move backward, increasing risks. Combining with field practices, a gap of 100 m between the entrance and the working face can meet fire-resistance requirements of gob and decrease gas concentration at the corners of the return airway, achieving the best effect. The study could help to optimize gob buried pipe’s entrance position, prevent spontaneous coal combustion, so as to guarantee the safety of mining.