Water inrush disaster is one of the major disasters affecting the production safety of coal mines following roof caving, fire, gas outburst, and dust explosion disasters. It is urgent to reveal the water inrush mechanism and take effective measures to prevent the disasters. More than 80% of water inrush accidents occur around geological structural zones such as faults and karst collapse columns (KCCs). The water inrush events from KCCs caused huge economic losses and heavy casualties, and the water inrush process often shows certain hysteresis characteristics. Taking the water inrush disaster from a KCC during roadway excavation in PanEr Coal Mine of Huainan Mining Area as the case study, the delayed inrush mechanism of KCC was analyzed from the aspects of floor failure, KCC activation, seepage transition, and water inrush development characteristics. The results show that the rock mechanical properties and the excavation depth are the main factors affecting the floor failure characteristics. The seepage transformation from pore flow to fracture flow and pipeline flow, with the change in internal composition structure, is the internal mechanism of the delayed water inrush from KCC. The research is of great significance for the prediction and prevention of water inrush disasters from KCCs.

Coal and gas outburst is a complex dynamic phenomenon happened in the underground of coal mines, and it has been a serious threat to the safe and efficient production of mines. To investigate the intricate mechanisms at play, a large-scale coal and gas outburst test was conducted based on the prototype of outbursts induced by coal uncovering. Coal samples were obtained through isometric excavation, grinding, and sieving, followed by an analysis of their pore structure and gas adsorption properties. Furthermore, the microscopic mechanisms underlying the disaster caused by the deterioration of coal due to the combined effects of in-situ stress and gas pressure were examined using fracture mechanics theory. The research findings aim to enhance the foundational theory of coal and gas outbursts and provide technical references for prevention efforts.

The mechanism of force chain deflection and instability-caused disaster in the deep surrounding rock of large-scale stopes was examined in this study using theoretical analyses, laboratory experiments, PFC3D numerical simulations, and other comprehensive research methods based on a discrete element theory that included force chain research as the main line. The results indicated that the overburden strata of the stope presented an arched force chain in both the strike and the inclined direction of the working face. In addition, a force chain shell composed of strong chains similar to “ellipsoid” in shape had been formed in the overburden strata space of the entire stope. The main mechanical characteristics of the force chain shell were as follows: the strength levels of the force chains within the shell were the largest; the strength levels of the force chains inside and outside the shell were relatively low and had evolved with the advancement of the working face; the directions of the force chains in different areas of the surrounding rock masses of the stope were deflected, forming an anisotropic characteristic with a certain deflection angle which was distributed in the vertical direction at the shell base; the force chains at the shell shoulder were angled in the horizontal direction, and the force chain at the shell top had an obvious horizontal direction; finally, the strong chain clusters of the surrounding rock masses of the stope formed a force chain shell in the stope space, and the stress shell was the macroscopic embodiment of the force transference in the force chain shell formed by the force chain clusters, which revealed not only the mechanical mechanism of the force chain shell formed by the surrounding rock but also the relationship between the macro stress shell and the stress chain shell. The stability of the shell determines the stability of the surrounding rock, and the instability of the shell will lead to dynamic disasters such as strong dynamic pressure or rock burst.

In deep coal mine strata, characterized by high ground stress and extensive fracturing, predicting the strength of fractured rock masses is crucial for stability analysis of the surrounding rock in coal mine strata. In this study, rock samples were obtained from construction sites in deep coal mine strata and intact, as well as fissured, rock specimens were prepared and subjected to triaxial compression tests. A numerical model based on the discrete element method was then established and the micro-parameters were calibrated. A total of 288 triaxial compression tests on the rock specimens under different conditions of confining pressure, loading rate, fissure dip angle, and fissure length, were conducted to obtain the triaxial compressive strength of the fractured rock specimens under different conditions. To address the limitations of traditional back propagation (BP) neural networks in solving stochastic problems, a modified BP neural network model was developed using a random factor and an interlayer mean square error corrected network model evaluation function. The traditional and modified BP neural network models were then employed to predict the triaxial compressive strength of the fractured rock specimens. Through comparative analysis, it was found that the modified BP neural network prediction model exhibited smaller errors and significantly reduced overfitting, making it an effective tool for predicting the strength of fractured rocks in deep coal mine strata.