Risk analysis of spontaneous coal combustion in steeply inclined longwall gobs using a scaled-down experimental set-up

•An inclination-adjustable working face gob model was developed.•The oxygen concentration in steeply inclined longwall gobs was analyzed.•The spontaneous coal combustion risk zones in steeply inclined longwall gobs were drawn.•A simple practical method was proposed for risk analysis. Spontaneous coal combustion in longwall gobs which are formed via underground mining is responsible for the loss of coal resources and impairs the ecological environment. Few studies are focused on risk analysis of spontaneous coal combustion in steeply inclined longwall gobs with experiments. In this work, an inclination-adjustable longwall gob model was developed to analyze the effects of airflow direction and ventilation rate on the oxygen concentration in steeply inclined longwall gobs (inclination angles of ±55°). According to the oxygen concentration gradients, the Spontaneous Coal Combustion Risk Zone (SCCRZ) was drawn. Furthermore, a simple practical method was proposed to quantitatively determine the risk of spontaneous coal combustion in steeply inclined longwall gobs. The results show that the SCCRZ mainly focuses on the lower side regardless of airflow direction. When the working face airflow direction is from the lower side to the upper side, the risk of spontaneous coal combustion tends to be stable with increasing ventilation rate. In case of the opposite airflow direction, the risk of spontaneous coal combustion increases significantly with increasing ventilation rate.