Strength Reduction of Coal Pillar after CO2 Sequestration in Abandoned Coal Mines

Self Cite

Based on the blasting principle of the cutting seam cartridge, smooth blasting with the charge structures of the usual cartridge and cutting seam cartridge has been designed and implemented, respectively, for different peripheral holes in the same face. Meanwhile, the blasting vibration has been monitored. Through the analysis of the frequency spectrum of blasting vibration signals, it is found that the maximum blasting vibration velocity of the cutting seam cartridge charge is lower than that of the usual cartridge charge, from 0.21 m/s to 0.12 m/s. Moreover, the blasting energy distribution is more balanced. Especially in the low-frequency part, the blasting energy is less, and there is a transferring trend to the high-frequency part, which shows that the cutting seam cartridge charge has a better optimization effect. Furthermore, using wavelet packet analysis, the cutting seam cartridge charge could effectively reduce the energy concentration in the low-frequency part. The energy distribution is much more dispersed, and the disturbance to the structure could be less, which is conducive to the stability of the structure. According to the blasting effect, the overbreak and underexcavation quantity at the cutting seam cartridge charge is better than that at the usual cartridge charge.

Section: Discussionmentioning

confidence: 99%

Frequency Spectrum and Wavelet Packet Analyses of Blasting Vibration Signals for Different Charge Structures in Blasting Peripheral Holes

Man¹,

Liu²,

Song³

2020

Self Cite

“…Some researchers considered rockburst as microseismic events that result in severe damage to rock mass structure with sudden or intensive acoustic emissions [25][26][27]. Microseismic monitoring technology has been widely used in rock mechanics and provides a feasible way to predict or prewarn rockburst [28][29][30][31]. Feng et al proposed a neural network prediction model based on the microseismic monitoring information [1].…”

Section: Introductionmentioning

confidence: 99%

Decision Tree Model for Rockburst Prediction Based on Microseismic Monitoring

Zhao

Chen

Zhu

2021

Rockburst is an extremely complex dynamic instability phenomenon for rock underground excavation. It is difficult to predict and evaluate the rank level of rockburst in practice. Microseismic monitoring technology has been adopted to obtain microseismic events of microcrack in rock mass for rockburst. The possibility of rockburst can be reflected by microseismic monitoring data. In this study, a decision tree was used to extract the knowledge of rockburst from microseismic monitoring data. The predictive model of rockburst was built based on microseismic monitoring data using a decision tree algorithm. The predictive results were compared with the real rank of rockburst. The relationship between rockburst and microseismic feature data was investigated using the developed decision tree model. The results show that the decision tree can extract the rockburst feature from the microseismic monitoring data. The rockburst is predictable based on microseismic monitoring data. The decision tree provides a feasible and promising approach to predict and evaluate rockburst.

“…erefore, it is very important to select an appropriate detonator and identify the accurate delay time. Furthermore, the appropriate detonator section and delay time should be selected based on the cross section of the tunnel, the layout of blasting boreholes and geological conditions, and so on [12][13][14][15][16][17][18][19][20]. Most importantly, it plays a vital role in the improvement of blasting footage and the control of vibration.…”

Section: Introductionmentioning

confidence: 99%

Identifying Delay Time of Detonator for a Millisecond Blasting

Song

Man

Liu

2021

Based on wavelet transform, the blasting vibration signals are analyzed here. For millisecond blasting, the blasting effect is mostly affected by the actual delay time. Local characteristics of the analyzed signals could be highlighted by the wavelet transform. The simultaneous initiation of large explosive quantity could be avoided by the use of multistage detonators, while the vibration resistance effect could be better. For the same level of detonator segment, the larger the arranged time interval, the less the possibility of initiation at the same time, which is not conducive to the vibration resistance. Therefore, it is suggested to use high-level detonators with detonating cord or high-precision digital electronic detonators to minimize the initiation error. Furthermore, by identifying the delay time using wavelet transform, the interval delay time of different detonator segments could be obtained. Moreover, the nominal delay time, actual delay time, and interval delay time are further compared and analyzed. It is suggested that the millisecond delay series of detonators should be selected in the whole section blasting, and the segment should be jumped as much as possible, so as to increase the secondary breakage time. Detonators with longer interval delay time should be avoided to the full.