Experimental investigation of fire extinguishment using expansion foam in the underground goaf

Mine fire is a serious environment, health, and safety hazard throughout the world. Through analyzing the drawbacks of traditional extinguishing techniques on dealing with fire at top of goaf, we propose a new foam preparation method to make extinguishing foam. It uses a jet device to add foaming agent and a foam generator to produce foam. The driving powers are water pressure and compressed gas, which have strong intrinsic safety for application in underground coal mines. Testing results show that foam diffuses fast at the initial stage of infusion in the goaf, while the foam diffusion velocity finally maintains at 0.0084–0.0087 m/s. With a large tensile deformation, the foam flowing through a fracture aisle is within 0.4 s. The expansion foam accumulates upwards until it extinguishes fire at top of the goaf, making a sharp decrease on the fire source temperatures. It is feasible that foam is infused into the goaf discontinuously with an interval time less than the foam half-life to get a reasonable economic cost input and a good foam accumulation in the goaf.