No abstract

Blasting works cause short-term high-energy shock waves-acoustic, air (airblast) and paraseismic. The duration of the event can be up to 2-3 seconds, while the rise time to the peak value is directly related to the delay between the individual explosive material (EM) and the firing sequence and ranges from a few to several milliseconds. Their propagation in the environment can affect people, animals and construction structures located not only in the close but also further distance from their source. If EM is placed on the surface of the earth during the detonation, the shock wave spreads evenly in all directions in the half-space, and when the detonation follows in rock, the wave usually travels in one direction and is accompanied by a paraseismic wave. However, the sound heard when detonating is part of the wave spectrum in the band from 20 to 20000 Hz, while the airblast itself has a frequency of less than 20 Hz. Since at some distance from the detonated EM, the parameters of the airblast are close to the parameters of the acoustic wave, the method of spreading the acoustic wave depends to a great extent on atmospheric conditions, i.e. density, temperature and humidity of the air, and from wind speed and its direction. To get to know the essence of the phenomenon of the impact of blasting works, measurements are carried out considering the propagation conditions, i.e. meteorological conditions as well as vibration analysis in the ground itself and on the building substructure. This paper presents the results of research carried out by the Authors in terms of the correct assessment of the impact range (acoustic, airblast, paraseismic waves) during EM detonation placed on the surface.

Detonations of explosive material charges are a source of intense paraseismic vibrations. These vibrations can cause damage to buildings and other infrastructure in the vicinity of the works, and can be a nuisance for their inhabitants. The article presents the problem of paraseismic vibration analysis, as induced by blasting works carried out in open-cast mines, using various methods of time -frequency, providing information about the duration of the signal, the frequency structure, and its energy.

Blasting in opencast mines is characterized by the use of large masses of explosives for a single blast. Blasting is done in a series of several to tens or even hundreds of charges placed in long holes and fired with a millisecond delay. Works are often carried out in the vicinity of buildings; therefore, reducing vibration impact is essential for opencast mines. This paper presents the applicability of the method of time-frequency Matching Pursuit (MP) for analysis of vibration structure. The use of MP analysis enables the development of much deeper and more reliable impact assessments of blasting on the environment.

This article presents the results of studies on the impact of acoustic waves on geophones and microphones used to measure airblasts carried out in a reverberation chamber. During the tests, a number of test signals were generated, of which two are presented in this article: frequency-modulated sine (sine sweep) waves in the 30–300 Hz range, and the result of detonating 3 g of pyrotechnic material inside the chamber. Then, based on the short-time Fourier transform, the spectral subtraction method was used to remove unwanted disruption interfering with the recorded signal. Using MATLAB software, a program was written that was calibrated and adapted to the specifics of the measuring equipment based on the collected test results. As a result, it was possible to clean the signals of interference and obtain a vibration signal propagated by the substrate. The results are based on signals registered in the laboratory and made in field conditions during the detonation of explosive materials.