• Explosives and Blasting
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• v.37 no.3
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• pp.25-33
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• 2019

Controlling the blast-induced damage zone(BDZ) in mining excavation is a significant issue for the safety of employees and the maintenance of facilities. Numerous studies have been conducted to accurately predict the BDZ in underground mining. This study employed the dynamic fracture process analysis (DFPA) to estimate the BDZ from a single hole blasting. The estimated BDZ were compared with the results obtained by Swedish empirical equation. The DFPA was also used to investigate the control mechanism of BDZ and fracture plane formation around perimeter holes for underground mining blasting.

• Tunnel and Underground Space
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• v.16 no.4 s.63
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• pp.326-333
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• 2006

In this study, the vibration waveform of the single hole which is not interfered from the different blasting holes is separated, the each dominant frequency which is determinated through the Fast Fourier Transform(FFT) is measured. Also the separation waveform executed a superposition modeling which changes to delay time from 1ms to 80 ms in 1ms interval and controls the number of blasting holes from 2 holes to 15 holes in order to investigate the effect of PPV according to the duration time of the vibration and the number of blasting holes. As a result of analysis, the longer the duration time of the vibration, the longer the delay time which is not interfered from the different blasting holes and the effect regarding the number of blasting holes from inside identical delay time did not appear a lot.

• Journal of the Korean Geotechnical Society
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• v.19 no.2
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• pp.75-85
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• 2003

Laboratory model blast and in-situ rock blast tests were conducted to determine blast-induced stress wave propagation characteristics under different explosive types, different loading conditions and different mediums. Dynamic numerical approaches were conducted under the same conditions as experimental tests. Stress magnitudes at mid-point between two blast holes which were detonated simultaneously increased up to two times those of single hole detonation. The rise time of maximum stress in a decoupled charge condition was delayed two times that of a fully charged condition. Dynamic numerical analysis showed almost similar results to blast test results, which verifies the effectiveness of numerical approaches fur optimizing the tunnel blast design. Dynamic numerical analysis was executed to evaluate rock behavior and damage of the contour hole, the sloping hole adjacent to the contour hole in the road tunnel blasting pattern. The rock damage zone of the sloping hole from the numerical analysis was larger than that of the contour hole. Damage in the sloping hole can be reduced by using lower density explosive, by applying decoupled charge, or by increasing distance between the sloping hole and the contour hole.

• Explosives and Blasting
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• v.24 no.2
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• pp.41-50
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• 2006

Excavation by explosives blasting necessarily involves noise and vibration, which is highly prone to face claims on the environmental and structural aspects from the neighbors. When the blasting carried out in the vicinity of a structure, the effect of blasting vibration on the stability of the structure should be carefully evaluated. In the conventional method of evaluation, an equation for blast vibration is obtained from test blasting which is later used to determine the amount of charge. This method, however, has limitations in use since it does not consider topography and change in ground conditions. In order to overcome the limitations, dynamic numerical analysis is recently used in continuum or discontinuous models, where the topography and the ground conditions can be exactly implemented. In the numerical analysis for tunnels and rock slopes, it is very uncommon to simulate multi-hole blasting. A single-hole blasting pressure is estimated and the equivalent overall pressure at the excavation face is used. This approach based on an ideal case usually does not consider the ground conditions. And this consequently results in errors in calculation. In this presentation of a case study, a new approach of using blast waves obtained in the test blast is proposed. The approach was carried out in order to improve the accuracy in calculating blasting pressure. The stability of a structure in the vicinity of a slope blasting was examined using the newly proposed method.

• Explosives and Blasting
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• v.34 no.1
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• pp.11-18
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• 2016

It is necessary to minimize ground vibration and noise due to blasting work in urban environment. The blast induced ground vibration and noise are generally generated by a portion of detonation energy, where most of the energy is utilized for rock breakage and movement of rock mass. Recently a blast method utilizing U-shaped steel charge holder was suggested to reduce the ground vibration without decreasing destructive power toward the free surface. In this study, single hole blasting utilizing U-shaped steel charge holder were simulated and the stress waves caused by the detonation of explosives were monitored using AUTODYN software. In order to examine the fragmentation efficiency of the U-shaped steel charge holder, one free face blasting models which adapt the blast induced stress waves were simulated by dynamic fracture process analysis (DFPA) code. In addition, the general blasting models were also simulated to investigate the fragmentation effectiveness of the U-shaped steel charge holder in rock blasting.

• Proceedings of the Korean Geotechical Society Conference
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• 1994.09a
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• pp.199-208
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• 1994

This paper presents an evaluation of new drill and blast method with two different drilling directions for pilot tunnel enlargement using numerical experiment and field test. To evaluate the effieiency of new tunnel enlargement method, field tests were performed and compared with conventional drill and blast method. Also, three dimensional transient dynamic analysis was made to investigate the effect of the ground vibration when blasting was performed at same position using the equivalent single hole charge.

• Journal of Korean Tunnelling and Underground Space Association
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• v.8 no.2
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• pp.129-139
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• 2006

When blasting by imposing the time difference between two adjacent charge holes, the mutual interference phenomenon occurs depending the feature of blast. This interference phenomenon of blast amplifies or compensates the blast-induced vibration depending on the overlapping mechanism. Thus, this experiment aims at finding out the optimum delay time by measuring the blast vibration data from the single hole blast during the blasting test and composing each blasting waveform, and at proving the its efficiency by applying the composition delay time in the entire cross section. The experiment showed that the blasting-induced vibration was reduced by endowing an optimum delay time of electronic detonator appropriate to the rock quality of construction site compared to the typical delay time (20, 25ms) of existing detonator (non-electric and electric detonator). From these results, the excavation efficiency using blasting could be enhanced..

• Tunnel and Underground Space
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• v.18 no.6
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• pp.418-426
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• 2008

A surface blasting method with a single tree face is currently used in Pasir Coal Mine in Indonesia. The single free face is usually the ground surface. This kind of blasting method is easy to use but inevitably causes enormous ground vibrations, which, in turn, can affect the stability of the slopes comprising the various boundaries of the open pit mine. In this regard, we decided to make a specific blasting guideline for the control of found vibrations to ensure the safety of the pit slopes and waste dumps of the mine. Firstly, we derived a prediction equation for the ground vibration levels that could be occurred during blasting in the pits. Then, we set the allowable levels of ground vibrations for the pit slopes and waste dumps as peak particle velocities of 120mm/s and 60mm/s, respectively. From the prediction equation and allowable levels, safe scaled distances were established for field use. The blast design equations for the pit slopes and waste dumps were $D_s{\geq}5\;and\;D_S{\geq}10$ respectively. We also provide several standard blasting patterns for the hole depths of $3.3{sim}8.8m$.

• Explosives and Blasting
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• v.29 no.2
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• pp.51-58
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• 2011

Frequency is a very important factor in discussing the effect on facilities such as precision instruments and therefore, in evaluating the effect of blasting vibration, it is necessary to identity information on frequency in addition to maximum amplitude of vibration. This study collected rock samples in gneiss area to perform an indoor rock test and to identify frequency of blasting vibration according to priming location, performed of single hole test blasting. Then the study decided dominant frequency through FFT and analysed changes according to priming locations. Consequently frequency range according to priming location is indicated top priming is distributed high range, bottom priming is distributed high range, middle priming is distributed evenly range. Frequency trend according to priming location is indicated distance increase with frequency discrease in top priming, distance increase with frequency increase in bottom priming.

• Explosives and Blasting
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• v.38 no.3
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• pp.15-29
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• 2020

In this paper the Hoek-Brown (HB) failure criterion is integrated into the Holmquist-Johnson-Cook (HJC) concrete material model to reflect the inherent characteristics of field rock masses in LS-DYNA blast modeling. This is intended to emphasize the distinctive characteristics of field rock masses that usually have many geological discontinuities. The replacement is made only for the static strength part of the HJC material model by using a statistical curve fitting technique, and its procedure is described in detail. An example is also given to illustrate the use of the obtained HJC material model. Computation is performed for a plane strain model of a single-hole blasting on a field limestone by using the combination of the fluid-structure interaction (FSI) technique and the multi-material arbitrary Lagrangian Eulerian (MMALE) method in LS-DYNA.