Reinforcement and Anti-seepage Performance of Binder in Fractured Coal in Underground Reservoirs under True Triaxial Stress Condition

Underground caving zones formed by longwall mining are used as water reservoirs to protect mine water resources. The presence of fractured coal mass within the caving zone impacts the stability and seepage behaviors during the circulation, storage, and discharge phases of the reservoir. The binder has been used to improve the fractured coal to enhance its strength and lower its permeability. This paper reports the mechanical and permeability behaviors of briquette coals with different binder contents under true triaxial stress conditions. These results suggest that with the increasing binder content, the elastic modulus and peak strength of briquette coal also rise. The binder increases the tangent modulus of the stress–strain curves in both pre-peak and post-peak stages, showing a transition from strain-softening to stress drop. As the binder content increases, the initial permeability and the minimum permeability of the briquette coal decrease, as well as the change rate of permeability curves.