Response law of three-dimensional complexity of faults in coal mine working face

As a crucial geological structure in coal mine, faults directly affect the stability of mining operations and the occurrence of fault-related disasters. To address the current limitation that mine-scale fault complexity assessments cannot effectively quantify the impact of faults on working face operations, a new method is proposed by integrating transparent geological model with numerical simulation to calculate the three-dimensional(3D) faults complexity at the working face scale. On one hand, based on a transparent geological model of the working face, the spatial curvature features of fault plane are extracted through mathematical analysis using recursive search algorithms and the least squares method. On the other hand, a numerical model of the fault-containing working face is constructed using the Anderson fault model and the Mohr-Coulomb (M-C) failure criterion. This model simulates the regional stress accumulation patterns in the rock mass under mining conditions, reflecting the degree of fault zone activation. Subsequently, the entropy weight method is used to integrate the two types of fault features, compensating for the statistical characteristics of the fault structure. The 3D fractal dimension is then employed as the framework to compute the overall 3D faults complexity of the working face under mining-induced conditions. Taking the 40103 working face in the Dafosi Coal Mine of the Binchang mining area as the engineering background, the 3D complexity of fault was calculated at mining distances of 100, 80, 60, 40, 20 and 0 m from the DF5 reverse fault. Combined with fault spatial distribution and microseismic data, the variation trends of fault complexity at different mining positions were analyzed. The results indicate that the overall 3D fault complexity increases as mining approaches the DF5 reverse fault. The complexity changes mainly because the fault enters an unstable state during mining, which propagates both laterally and longitudinally as the mining face advances-particularly when approaching the fault. Additionally, zones with intersecting multiple faults are more strongly affected by mining disturbances than those with a single fault, with fault structures evolving from single to intersecting patterns. Furthermore, high-energy microseismic events are predominantly concentrated in areas of higher fault complexity. The evolution of these events closely mirrors the trend of increasing fault complexity, indicating that the more structurally complex a fault is, the more uneven the spatial distribution of microseismic events and the higher the frequency of high-energy occurrences. This highlights the correlation between changes in regional rock stress and the fault instability state reflected by the 3D faults complexity model under mining conditions.