Sandstone samples with precracks of different dip angles were collected from a coal mine roof and subjected to uniaxial compression tests, and acoustic emission (AE) and scanning electron microscopy (SEM) were used to study how the crack dip angle affected the fracture mechanism. In the precracked sandstone samples, as the dip angle between the crack line and loading direction decreased, so did the peak stress and its completion time. The SEM observations revealed a fracture transition from tensile cleavage to shear slip, which was manifested by a microstructure change from aggregate to staggered. According to energy conversion, a decreased crack dip angle results in gradually decreasing total and dissipative peak energies, whose variation amplitudes at different stages are consistent with those of the peak stress of the samples. The decreased crack dip angle lowered the stress required to trigger the first appearance of AE energy peaks and ring-down counts, as well as shortening the period before the occurrence of the first AE peak signal. However, the AE energy and ring-down count during the failure stage after the stress peak increased gradually. A stepped increase was observed in the AE ring-down count curves, with each step corresponding to a jump in the stress-strain curve. From the characteristics of the AE signal of the fracture of a precracked rock sample, the occurrence of joints or faults in the rock mass can be reasonably inferred. This is expected to provide a new method and approach for predicting coal and rock dynamic disasters.

The compound dynamic disaster of coal and gas outbursts and rockburst is a typical hazard jeopardizing the mining of the high gas content coal seam under a hard roof condition. In this study, the hard roof’s mechanism inducing this hazard is analyzed. Physical analog modeling experiments and in situ monitoring of mining-induced stress were performed during coal seam mining under a hard roof condition. The pattern of hard roof breakage effect on the stress-fissure field evolution was revealed. The elastic energy was released and propagated on both sides immediately after the hard roof breaking, leading to energy accumulation. Meanwhile, expansive roof collapse resulted in the intense weighting of the working face and rockburst. Thus, the coal and gas outburst occurred under the joint action of the impact energy generated by breaking the hard roof and gas expansion energy. In other words, the compound dynamic disaster happened. Synergistic stereoextraction integrating cross-seam drilling and along-seam drilling was combined with deep hole advanced presplitting blasting technology to cope with the compound dynamic disaster in the high gas coal seam under a hard roof condition.

To address the substantial mining pressure from unstable rock formations, impact compression tests were performed on coal–rock combination specimens of varying strengths using a split Hopkinson pressure bar (SHPB). The dynamic mechanical properties, energy dissipation patterns, and failure modes of the specimens were systematically analyzed, illuminating the mechanical behavior and energy conversion mechanisms of coal–rock combination under both dynamic and static loading conditions. The findings reveal a positive correlation between the proportion and strength of rocks within the coal–rock combination and its compressive strength as well as elastic modulus. From an energy perspective, at impact velocities below 10 m/s, the energy consumption due to the fragmentation of coal–rock combination of varying strengths rises significantly, ranging from 0.15 to 0.30. The greater the height and strength of the rocks within the coal–rock combination, the more pronounced the dynamic phenomena observed following the failure and instability of the coal–rock mass. The existence of a hard roof serves as a critical driving force for dynamic coal–rock disasters. For coal seams with identical strength, an increase in rock strength leads to greater energy expenditure in crushing the coal and rock mass under dynamic loading conditions. In engineering practice, coal seams beneath a hard roof are more susceptible to severe crushing under dynamic loading, thereby, increasing the likelihood of strong ground pressure events.

The abnormal structural state of the pantograph skateboard is a significant and highly concerning issue that has a significant impact on the safety of high-speed railway operation. In order to obtain real-time information on the abnormal state of the skateboard in advance, an intelligent defect identification model suitable to be used as a monitoring device for the pantograph skateboard was designed using a computer vision-based intelligent detection technology for pantograph skateboard defects, combined with an improved YOLO v8 model and traditional image processing algorithms such as edge extraction. The results show that the anomaly detection algorithm for the pantograph sliding plate structure has good robustness, maintaining recognition accuracy of 90% or above in complex scenes, and the average runtime is 12.32 ms. Railway field experiments have proven that the intelligent recognition model meets the actual detection requirements of railway sites and has strong practical application value.

The dynamic tensile strength of the coal is critical to the initiation and evolution of dynamic disasters such as coal bump and coal and gas outburst. To investigate mechanical and geometrical characteristics of the coal bump subjected to the variation of the shock pressure and water content, a split Hopkinson pressure bar (SHPB) with ultra-high-speed camera and fractal dimension were employed. The results show that the stress wave is the main controlling factor of a large number of micro damage structures and damage evolution of primary pores and voids in coal samples under impact load, and the coal rock fragmentation is a process of energy absorption and dissipation. With the increase of impact load, the dissipated energy density of coal samples increases linearly, but when the incident energy is small, the dissipated energy density of coal samples has little difference; The fractal dimension of samples increases with the increase of loading pressure, and the increasing rate has a decreasing trend. Under the same loading pressure, the fractal dimension of saturated coal sample is the largest, and that of dry coal sample is the smallest; The deformation and failure of coal samples are mainly tensile splitting, and the failure cracks develop along the loading direction, first in the middle of the disc, and then multiple secondary micro cracks are initiated. It is found that there are several main strain concentration regions in the middle of saturated coal sample under impact load, and the range gradually expands, and finally develops along the radial direction.