Comparative analysis and verification on broken rock zone of model test based on multiple testing methods

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.