In this paper, the newly formulated solution of multi-face destress blasting efficiency assessment is presented. The developed method is relevant for near and far-field effect evaluation and is improved by the duration, amplitude, and frequency characteristics of blast-induced seismic waves. The proposed approach is based on the advanced analyses of the waveforms generated by blasting, ground motion prediction equations and data describing the technological parameters of blasting in terms of the amount of explosives, delay times, and spatial location of mining faces. The proposed solution was validated in deep underground mines in Poland in which the room-and-pillar mining method is applied. Based on the performed analysis, it is shown that a new method may be used as an element of rockburst hazard control in underground mines. However, the developed method may also be successfully implemented in other engineering practices, including open pits and quarries.
According to recent studies, destress blasting is the most effective solution in terms of rock mass preconditioning (Konicek et al. 2011 and Vennes & Mitri 2017). The main goals of destress blasting are:
• generating cracks of the rock mass in the vicinity of blasting operations (Kan et al. 2022);
• reduction of friction on the slip surface of faults and cracks existing in the rock mass, which may trigger a mining tremor (Fuławka et al. 2022).
Therefore, regardless of the actual effect, the main purpose of destress blasting is the preconditioning of the rock mass, preventing further accumulation of energy and, in exceptional cases, causing a seismic event in the vicinity of the mining field while the mining crew is outside an endangered area. Such technique has been practiced and developed for years in Polish underground copper mines, where explosives are used for both ore extraction and destressing purposes. Because deposit in these mines is excavated with the use of a room-and-pillar mining system, the destressing impulse is generated by the simultaneous firing of explosives in a dozen or several dozens of mining faces within one mining panel. Due to the scale of mining, which can be described by about 500-700 faces and over 60 tons of explosives detonated every day, this method is considered the most effective tool for active rockburst prevention in the conditions of Polish copper mines (Caputa & Rudziński 2019). However, it should be noted that in order to ensure maximum efficiency of blasting works, it is necessary to carry out the periodical evaluation of blasting efficiency, which is the basis for further improvement. Still, until recently there was no avaliable method for reliable multi-face destress blasting efficiency evaluation.Within this paper, a novel method of destress blasting efficiency evaluation is presented. This method allows to analyse if the seismic impulse generated by the number of simultaneously detonated faces is sufficient considering the number of faces, amount of explosives, the distance between the area of interest and subsequent mining faces, and blasting patterns applied during the firing of mining faces. Moreover, seismic effects with the use of a novel method may be analysed not only in terms of amplitude distribution but also including the duration of the vibrations and their dominant frequency, which is definitely an innovative approach.