지연시차에 따른 발파진동의 주파수 특성 예측

Abstract

Gunpowder has been extensively used for civil engineering of mining and building dams, highways, subways, and so on. In particular, as bedrock blasting in crowded areas is increasing with economic growth and changes social problems producted from blasting are increase of every year are rapidly increasing. Environmental impacts of blasting are very serious and include vibration, noise, pressure and scattering of fly rocks, which may cause structures adjacent to construction places or human bodies to be damaged. Therefore, before blasts that can have direct impacts on human bodies or structures, it is necessary to asses impacts of blast vibration. For structures, frequency has been recognized as an important factor in order to assess impact on blast vibration and damages. There are many national studies on impacts of frequency. But there have been no studies on relations between vibration and frequency according to delay time difference. In this study, we examined the relations between delay time difference and frequency according to each frequency with which reinforcement and destructive intervention repeat through delay time difference obtained using superposition modeling of single hole blasting based on the theory of time difference developed by Langefors. Then we also examined changes in frequency of blast vibration according to delay time difference by FFT analysis of predicted modeling and real data. To study changes in frequencies according to delay time differences, we used the same patterns for all single-hole blast, a blast with time difference through a test of single-hole blast frequency and a blast using an electric detonator. We decided delay time difference through a single-hole blast frequency test and analysed a modelling for prediction of frequency using FFT analysis. Delay time differences are presented as follows: 5, 10, 15, 21, 32, and 42 ms, and results of the prediction modelling are presented as follows: 23.5, 23.5, 55.2, 47.3, 24.0, 47.2 Hz. To study the electric detonator (25 ms), we used the same method and the result was 45.8 Hz. To analyse results of prediction modelling and real data, we prediction model each tests three times. We prediction model tests for the electric detonator(25 ms) eight times and the results were similar to or same as the prediction modelling. However, we tests relative significant difference in the 7th test and 8th test at 15ms of delay time difference and 18th at 42 ms of delay time difference. And we tests significant difference between a test using the electric detonator(25 ms) and the prediction modeling.