A novel conceptual model of fracture evolution patterns in the overlying strata during horizontal coal seam mining

The dynamic evolution of mining-induced fractures in overlying strata caused by mining has non-ignorable effects on engineering safety and water loss from an overlying aquifer. To clarify the evolutionary patterns of fractures due to the first and periodic weighting induced by coal mining, W-shaped fracture arch models are developed to explain and prevent water leakage during the mining process. With the conceptual hypothesis of a lopsided W-shaped fracture arch that may or may not consider the subsequent consolidation process from caving of the overlying strata, this model shows the evolutionary process of the morphological tendency in fracture arches and characteristics in different directions. Mining-induced fractures are found to evolve in W-shaped mode and develop both upward and forward with the advance of the mining face. Based on these models, we can identify the best developed parts of the overall fracture evolution, which are the key fracture paths for water to leak after the closure phase of fractures. Combined with a creative simulation experiment on similar materials including two comparative mining models, the normal mining model and the model of prefabricated fracture arches, the dome-shaped morphological evolution of this conceptual model is reflected well in the range of 20~40 m away from the initial mining location. The present models may help settle conflicts related to the dynamic evolution of mining-induced fractures and the loss of water resources during the mining process.