Determination of the permeability coefficient in backfill with coal tailings

Abstract

The coal mining activity in southern Brazil plays an important role in society, the economy, and the environment. The deposition of tailings on the surface requires significant investments of time and financial resources in projects and environmental licensing. The Structural Safety ACP (Analysis and Control Plan) became part of this context, with mineral backfill technology—or simply ‘backfill’—emerging as a technique capable of ensuring not only the long-term stability of pillars but also reducing the effects of post-mining backfill, particularly in mitigating the risk of potential water inflows during operation and after closure. Aiming to contribute to the aspects mentioned above and in alignment with the Just Energy Transition (JET) process, this study evaluated the permeability and mechanical behavior of pure coal tailings hydraulic backfill samples undergoing final consolidation in an underground coal mine in Santa Catarina. It was concluded that pure hydraulic backfill acts as a hydraulic insulator, positively contributing to the post-closure hydrogeological context of the mine. Structurally, the confinement of pillars provided by pure hydraulic backfill enhances the integrity of the roof and pillars, serving as a short-, medium-, and long-term structural reinforcement.