The precursor of rock failure around a hole has always been one of the research hotspots in the field of rock mechanics, and the distribution of the plastic zone is often adopted to reflect the location and form of rock failure. The shape of the plastic zone around a hole before rock failure can guide the mechanism of and early warning methods for geotechnical engineering disasters, while previous theoretical research and numerical simulation results show that the shape of the plastic zone around the hole is butterfly shaped under specific stress, which is referred to as butterfly failure theory. Studies also indicate that the butterfly shape of the plastic zone around a hole is considered to be the main cause of many disasters, which signifies the importance of studying the morphology of the plastic zone near rock failure. Therefore, this study is committed to finding the specific shape of the plastic zone near rock failure through relatively accurate and a high number of AE event location results, and the final experimental results show that the plastic zone around the hole is basically a butterfly shape near rock failure. This study verifies the correctness of the butterfly failure theory and provides an important reference for the study of geotechnical engineering disaster mechanisms and monitoring methods. The fact that the plastic zone in the early stage of rock failure in this study tends to be butterfly shaped preliminarily indicates the fractal law of rock failure. In the moment before rock failure, the distribution of AE events is more regular, which leads to large-scale collapse type failure.

The main frequency of microseismic signals has recently been identified as a dominant indicator for characterizing vibration events because it reflects the energy level of these events. Frequency information directly determines whether effective signals can be collected, which has a significant impact on the accuracy of predicting rock burst disasters. In this study, we adopted a characterizing method and developed a monitoring system for capturing rock failure events at various strata in an underground coal mine. Based on the rock break mechanism and energy release level, three types of rock failure events, namely, high roof breaking, low roof breaking, and coal fracture events, were evaluated separately using specific sensors and monitoring systems to optimize the monitoring accuracy and reduce the general cost. The captured vibration signals were processed and statistically analyzed to characterize the main frequency features for different rock failure events. It was found that the main frequency distribution ranges of low roof breaking, high roof breaking, and coal fracture events are 20–400 Hz, 1–180 Hz, and 1–800 Hz, respectively. Therefore, these frequency ranges are proposed to monitor different vibration events to improve detection accuracy and reduce the test and analysis times. The failure mechanism in a high roof is quite different from that of low roof failure and coal fracturing, with the main frequency and amplitude clustering in a limited zone close to the origin. Coal fracturing and lower roof failure show a synergistic effect both in the maximum amplitude and main frequency, which could be an indicator to distinguish failure locations in the vertical direction. This result can support the selection and optimization of the measurement range and main frequency parameters of microseismic monitoring systems. This study also discussed the distribution law of the maximum amplitude and main frequency of different events and the variation in test values with the measurement distance, which are of great significance in expanding the application of optimized microseismic monitoring systems for rock burst monitoring and prevention.

Built-in multi-sensor measurement-while-drilling (MWD) modules on roof bolters can record torque, thrust, rotational speed, and displacement during drilling. This study examines whether identical rock types produce consistent MWD responses when tested through different boreholes in separate composite specimens. Three laboratory-scale composite specimens containing yellow sandstone (YS), dark-colored red sandstone (DCRS), and light-colored red sandstone (LCRS) were drilled with the same integrated rig, and the sensor responses and specific energy were compared using descriptive distributions, mean values, and relative differences. The results descriptively indicate that torque and thrust respond more clearly to lithological changes than rotational speed, while torque is generally the most stable indicator. Under nominally identical lithological conditions, responses varied across boreholes in separate composite specimens, with reported relative differences reaching approximately 30% in some comparisons. Because one borehole was drilled per specimen, this preliminary study identifies a cross-specimen reproducibility limitation only; it does not estimate within-rock-mass variability or validate a transferable prediction model. The practical implication is limited to showing that single-borehole formulas should not be transferred without calibration, while normalization, hierarchical modeling, and larger multi-borehole validation remain future research directions.

Previous research results preliminarily indicated that the Coal Failure Events (CFEs) that occurred during the process of Underground Pressure Relief Drilling (UPRD) represented the phenomenon of coal fracture and energy release. The research results had excellent value for the monitoring and response of pressure relief drilling while drilling, but there were still some special situations that needed to be analyzed and studied in actual on-site testing. So, through on-site testing and data statistical analysis, the study investigated the applicability of the innovative external Monitoring-While-Drilling (MWD) method for UPRD with more coal failure events and made a quantitative statistic of the CFEs and their relationship with abutment pressure to reveal the applicability of the external MWD method and characteristic of CFEs. The results showed that hundreds of CFEs were produced in the UPRD process, which must be removed to ensure the accuracy of the MWD method. Although CFEs bring recognition difficulties, they also provide conditions for studying their own distribution and characteristics. Results showed that more CFEs were produced in the depth of difficult drilling, which indicated that there was a positive correlation between the degree of difficulty in drilling and the number of CFEs. In addition, spectrum analysis showed that the depths with more CFE occurrence were more likely to produce high-frequency events. When the surrounding stress of drilling rocks is high, the occurrence of small fractures with a higher main frequency may become more frequent and consistent; more fractures with similar failure forms would occur, which may have a lower fractal dimension and promote the generation of more failure. The research results were of great significance for the MWD method for UPRD, a quantitative study of CFEs and their generation characteristics during UPRD construction.

The behavior of anchor cables in response to stress disturbances directly influences the effectiveness and interference resistance of their support system. This study developed and executed a non-destructive testing method to evaluate and compare the dynamic responses of anchor cables made from various materials under stress disturbances. The methodology utilized two vibration sensors in conjunction with a single data acquisition instrument. The vibration sensors were responsible for capturing the vibrational signals of the anchor cable, while the acquisition instrument facilitated synchronous data collection. The anti-interference ability was compared by the collected vibration signals of different anchor cables under the influence of the same stress disturbance. The results showed that the IREA anchor cable exhibited lower vibration intensity and stronger anti-interference ability than the ordinary anchor cable under the same stress disturbance, which could be quantitatively compared by the proposed method. Across 16 disturbance events, the vibration amplitude ratio of the ordinary anchor cable to the IREA anchor cable ranged from 1.3 to 5.3, with an average ratio of 2.45. The method was conceptually straightforward and easily implementable, and the field measurement data demonstrated promising results.

The measurement-while-drilling (MWD) method of roof bolter plays an important role in explaining the structure of roadway roof, especially the soft hard relationship of rock layers. One of the key factors for the MWD method of roof bolter is to ensure the accuracy of monitoring, which greatly depends on the optimized selection and matching of indexes. Therefore, this study first analyzed the source of monitoring indexes data to see how they relate to normal distribution, and then evaluated their reliability for subsequent feedback. After that, the receiver operating characteristics (ROC) quantitative calculation and analysis method was used to obtain the specific accuracy values of commonly used individual indexes and comprehensive index of specific energy. The quantitative results showed that the performances of individual thrust and torque indexes were relatively excellent, and unexpectedly exceeded that of the comprehensive index of specific energy. The research results have important reference value for the subsequent selection of MWD indexes for roof bolter. It is necessary to use indexes with better feedback results to comprehensively reflect the medium, and to furthermore improve the accuracy of feedback.