Analysis On The Delay Time Of Electronic Detonator To Decrease Subway Tunnel Blasting Vibration

With the vigorous development of China’s urban rail transit business, the tunnel project beneath the sensitive area of the city is more and more. Blasting is still the most effective and the most economical way in hard rock tunnel, However, strongly blasting vibration caused by blasting poses a serious threat to surrounding buildings and facilities.That about how to predict and control the blasting vibration, achieving the active control of the whole process of blasting and reducing the impact of blasting operations on the environment, has become a major problem of the urban construction of the tunnel blasting.Practice shows that application of electronic detonator blasting can effectively reduce the blasting vibration, and the delay time to choose proper, also can realize the interference effects of vibration reduction, further enhance the vibration reduction of space.This paper based on extensive testing and engineering vibration monitoring data, detailed analyse of the delay time of blasting on the impact of the waveform, combinate theoretical analysis and numerical simulation studies to find the best way to determine the delay time of the electronic detonators.The classical theory of wave mechanics shows that electronic detonators’ implementation mechanism of interference vibration reduction stems from the principle of superposition of elastic waves and interference, electronic detonator delay time is closely related to the main vibration period, and the effectively delay interval is [T/3,2T/3].The line 16 of beijing subway tunnel blasting experiments determines the single-hole wave main vibration period in 14 ms,he delay in the range of 5～9ms. Conducted group holes blasting experiments delay of 5～9ms respectively between hole, the results showed that 7ms delay gets the optimal effects of vibration reduction, the superimposed waveform is relatively uniform, performes high-frequency low amplitude vibration state.Using LS-DYNA to simulate delay initiation process between two blast holes, With the increase of the delay time, firstly, the peak velocity is significantly smaller, then the ups and downs to the last stable value, Based on the single span vibration waveform predicte porous vibration waveform of different time delay, the analysis found that the maximum vibration changing with the time delay and the numerical simulation results are basically identical, the vibration is reduced to a minimum, and the vibration and the measured waveform high similarity when delay 7ms.Instantaneous energy diagram based on HHT method of blasting vibration and blasting vibration curves have good consistency, we can quickly identify the location of the blasting vibration peak,and adjust delay time. For different delay blasting vibration signal time-frequency analysis, get the delay time of 7 ms, main frequency is more than 50 HZ, and more than 50 HZ frequency band energy accounted for nearly 50%, which is conducive to the protection of the surrounding buildings.This paper based on the previous summary of the vibration reduction mechanism interference and the science of engineering tests, using numerical simulation and signal processing method HHT to study that the delay time of electronic detonators has effect on blasting vibration waveform amplitude and frequency. Determining the delay time of electronic detonators to achieve optimum interference vibration reduction to make contributions to the improvement of active vibration control of the blasting technology.