Identification and application of the formation time of new free surface in tunnel blasting
LIU Xiangyu1，GONG Min1，YANG Renshu1，WU Haojun1，WU Xiaodong1，QIU Yikeke1，ZHOU Shijun2
1.School of Civil and Resource Engineering, University of Science and Technology Beijing, Beijing 100083, China;
2.Chongqing Zhonghuan Construction Co., Ltd., Chongqing 401120, China
Abstract：The formation of new free surface in tunnel blasting has an important influence on changing the explosive energy release process in the cutting area, which can significantly reduce the blasting vibration intensity. However, it is difficult to obtain the accurate formation time of new free surface due to the transient nature of the blasting process and the great difficulty in testing. A method to identify the formation time of new free surface is proposed: two groups of contrast waveforms were obtained based on the precise initiation characteristics of electronic detonator. The two groups of waveforms were as follows: measured vibration waveform affected by new free surface is obtained by short delay cut blasting test; calculated vibration wave was obtained based on the superposition theory according to the initiation time sequence, without considering the influence of new free surface. The accumulated energy of two groups of waveforms was calculated by HHT, and the difference characteristic points were taken as the formation time of new free surface. The formation time determined by this method is 43.5 ms. After the formation of the new free surface, there are three stages: rapid increase to the maximum, continuous stability and gradual decrease. By comparing and analyzing the calculated vibration velocity and cumulative energy under the condition of short delay time (< 10 ms) and long delay time (> 10 ms), it is determined that 16~19 ms is the better delay time between cut holes.
刘翔宇1，龚敏1，杨仁树1，吴昊骏1，吴晓东1，邱燚可可1，周世均2. 隧道爆破新自由面形成时间的识别与应用[J]. 振动与冲击, 2023, 42(10): 15-22.
LIU Xiangyu1，GONG Min1，YANG Renshu1，WU Haojun1，WU Xiaodong1，QIU Yikeke1，ZHOU Shijun2. Identification and application of the formation time of new free surface in tunnel blasting. JOURNAL OF VIBRATION AND SHOCK, 2023, 42(10): 15-22.
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