Study on the formation mechanism and mechanical properties of composite foam slurry material for mine plugging

The development of tough, energy and shock absorbing materials is the key to solving the problem of long-term sealing of air leakage to prevent and control coal spontaneous combustion. To study the mechanical behavior and energy absorption characteristics of composite foam slurry material (CFSM) for mine plugging, the effect of activator on the properties of CFSM was investigated, and the whole process of CFSM under uniaxial compression were analyzed systematically. The results indicated that activator could improve the compressive strength of CFSM by dissolving the vitreous structure of slag and generating more hydration products, further improving the structural compactness. Moreover, CFSM exhibited the unique deformation damage patterns and energy absorption effects during stress loading. Based on the uniaxial compressive stress-strain curve, the damage failure pattern of CFSM was mainly caused by shear stress and exhibited three main characteristic stages, including elastic-plastic stage, plateau stage and crush compact stage. The material showed elastic deformation of the bubble pores and local micro cracks in the elastic-plastic stage. The platform stage was characterized by the development of fissures until complete penetration. The bubble pores of the material were gradually compacted and became dense in the compacting stage, and ultimately retained a certain compressive strength. Unlike the direct splitting damage of traditional grouting materials, CFSM showed obvious energy and shock absorption effect in the process of compression. Part of the energy was transformed into the elastic energy of the bubble pore for releasing when disturbed by external impact, resulting in deformation of the bubble pore. The other part of the pressure was transformed into plastic fracture energy, causing cracks in the bubble hole or collapse. The findings of this study can help for better understanding of the mechanism of long-lasting prevention coal spontaneous combustion by foamed gelling plugging materials, and eventually provide more ideas for the development of green and safe mine plugging materials.