There is no mature method for identifying and monitoring the broken rock zone. Taking the two-level west wing track roadway of Chengjiao Coal Mine as the engineering background, the model tests with four schemes were carried out, and the broken rock zone was identified by ultrasonic waves, strain bricks, digital photography, and parallel electrical methods. Based on 3DEC numerical calculation, the evolution and displacement of plastic zone and broken rock zone were analyzed to verify the effectiveness of each monitoring technology. The results show that the digital photography method can identify the generation location of cracks and the distribution of broken rock zone. The parallel electrical method can identify the distribution of the broken rock zone, plastic zone, and original rock stress zone in the failure process of the surrounding rock. In the numerical calculation, the cloud map of the plastic zone of the surrounding rock exhibited a similar trend to the displacement cloud map of the digital photography method. The range of the plastic zone and the broken rock zone can be determined according to the maximum principal stress difference method. Finally, it is recommended to use digital photography and the parallel electrical method to comprehensively determine the scope and size of broken rock zone.

To learn more about the problem of blast weakening in shallow-buried and extra-thick coal seams, Panjin coal mine was used to provide the engineering background for this study. The influence of blast weakening technology on the vibration of ground buildings was investigated. Based on monitoring the vibration data from the final 400 m of the working face, we established the Sadovsky formula for this coal mine through regression. The maximum safe charge of one blast at different distances was obtained. A numerical model was established and compared with field monitoring data to verify its accuracy. This numerical model was used to analyze the influence of blast weakening vibrations on ground buildings during the final mining stage. Finally, the maximum safe charge for one blast at advancing distances from the working face was derived based on numerical calculation results. It was compared with the maximum safe charge obtained from field measurements. The results show that both exhibit significant consistency, and the maximum safe charge of one blast decreases as the working face advances. In addition, the peak vibration velocity at each monitoring point does not exceed 0.2 cm/s for the remaining 400 m of the measured working face, which is lower than the allowable safety value for blasting vibrations. In the numerical simulation of the final mining stage at 200 m, the ground vibration velocity is largest for the district office, second-largest for the chimney, and smallest for the science and technology building. The maximum vibration velocity and effective stress in the three directions of the three buildings are within the allowable range, indicating that the buildings remained in a safe state.