The Effects of Coal Floor Brittleness on the Risk of Water Inrushes from Underlying Aquifers: A Numerical Study

Abstract

Karst water in coal floors is the most common hazard in the coal fields of North China. Water inrush disasters always occur due to reductions in the efficacy of a coal floor’s water resistance ability, and have brought huge casualties and losses. The floor damage zone during mining disturbance is crucial to the formation of the water inrush pathway and is considered to be closely related with floor rock brittleness. To investigate the effects of coal floor brittleness on the hazard of water inrushes from underlying aquifers, four groups of numerical simulations are conducted in this study based on a finite-element method. These numerical simulations especially concern the contrastive analysis of brittle rock’s properties regarding the failure characteristics of rock samples, fracture development in layered rocks, the damage zone of the floor during mining disturbance, and the hazard of water inrush from the floor during mining. The results show that brittle rock is easier to destroy in comparison with ductile rock. Brittle layers are more likely to develop denser natural fractures than ductile layers. The more brittle the floor rock is, the larger the depth of floor damage will be. The brittle floor is verified to induce water inrush from an underlying aquifer more easily than the ductile floor. This study revealed the relationship between the brittle property of coal floors and the depth of mining-induced floor damage zones, providing a reference for hazard evaluation of water inrush from coal floors and control measures.