Consolidation grouting technology for fire prevention in mined‐out areas of working face with large inclined angle and its application

Summary The phenomenon of linear flow of slurry in mined‐out areas of working face with large inclined angle is a crucial issue that hinders grouting for fire prevention. The traditional way of grouting exerts a poor effect on inhibiting coal spontaneous combustion, so it is in urgent need of a suitable grouting technology for fire prevention in mined‐out areas with large inclined angle working face. This paper brings up the consolidation grouting method for fire prevention for the first time and conducts a systematic study on the flow characteristics of slurry and sedimentation characteristics of slurry in mined‐out areas with large inclined angle working face. Consolidation slurry materials and their ratio are optimized by experiments. Test platform has been established, and effectiveness of the consolidation grouting for fire prevention has been simulated. The results show that settling velocity of yellow mud increases at first and then decreases as the concentration of consolidation slurry materials ascends. The optimum mass concentration is 0.2%–0.8%. The flow speed of mud is greatly reduced by laying consolidation slurry materials (The decreasing range is approaching 50%). The retention of yellow mud in mined‐out areas has significantly increased. Finally, technology in working site has been developed; meanwhile, compressed air and spray between frames have been used during the period of working face, and the consolidated way of expansion bags in wood crib to lay consolidation slurry materials has been adopted during the period of stopping work. Field application shows that CO concentration at upper corner decreases significantly and eliminates signs of spontaneous combustion. Besides, the flowing water becomes clearer, and effectiveness of the consolidation grouting is remarkable after laying consolidation slurry material band. Research results can provide theoretical guidance to technology for fire hazard prevention in mined‐out areas with large inclined angle. Copyright © 2016 John Wiley & Sons, Ltd.