No abstract

Long-hole blasting in mines is likely to cause strong vibration of surficial infrastructure, greatly damage the rock mass surrounding goaf near explosion center, and possibly induce blast vibration disasters. In this article, an improved method for multihole blasting seismic wave prediction is proposed to estimate far-field blast vibration. In this method, the fundamental vibration waveforms are firstly measured through the field blast with a single deck at an underground pilot area. The fundamental vibration waveforms are then used to simulate the vibration waveforms for a single-deck case in the production blast by considering the difference of the equivalent distances from the production blast site and the pilot area to the surface measuring point. The vibration waveforms for the single-deck case are linearly superposed to predict the possible vibration waveforms in production blast with multiple long holes and decks according to the designed delay time between decks. Based on these predicted waveforms, the blast vibration can be estimated and the blast design can be optimized to determine a rational delay time in accordance with the vibration limit. The proposed method was applied in pillar recovery of Hongling Polymetallic Mine to optimize the long-hole blast design to manage blast vibration. The rational delay time for the 716 production blast design was recommended as 26 ms. The practice showed that the blast vibration induced by the 716 production blast has been managed, and the predicted and the measured waveforms agree well. It provides an effective method for multihole blast design to control blast vibration.

In rock engineering problems, the rock is usually subjected to dynamic loads induced by drill, blast and rockburst. Therefore, understanding the dynamic response of rock benefit the safety and productivity of excavation activities. In this study, the response of rock panels under blast loadings is numerically investigated. The uniaxial and triaxial compression tests are firstly conducted in the laboratory to obtain the material property of four types of rocks, including Chuanshan limestone, Gaolishan sandstone, Mineralized limestone and Xixia limestone. Then, a total of 16 numerical simulations are carried out in which each type of rock panel is subjected to TNT blast loadings with four scaled distances, i.e., 0.15 m/kg1/3, 0.30 m/kg1/3, 0.60 m/kg1/3, 1.20 m/kg1/3. The damage distribution, which is characterized by the effective plastic strain, within the rock panels is quantitatively and qualitatively analyzed. The modelling results demonstrate that the effect of blast loading on the rock is material dependent. For a given scaled distance, the Gaolishan sandstone damages most severely, followed by Xixia limestone, Chuanshan limestone, and mineralized limestone. A critical scaled distance is observed on the limestone panels. When the scaled distance is smaller than the critical value, the damage of limestone panels increases with increasing the scaled distance. Once exceeding the critical value, the damage of limestone panels decreases with the increase of scaled distance. However, such a transitional scaled distance is not observed in the sandstone panels, of which damage decreases gradually with the increases of scaled distance.