• Explosives and Blasting
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• v.23 no.1
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• pp.65-77
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• 2005

Reflecting the fact that there are increasing number of old high-story apartment structures in urban area, it is expected that the demand of blasting demolition will increase in the near future. It is of great important to make up for the insufficient empirical knowledge in blasting demolition through priori method such as computer simulation. Computer simulation of the blasting demolition involves complicated process. In the past domestic researches, two-dimensional bonded particle model was used to examine the overall demolition behavior of a five-story simple structure. It was observed that the two-dimensional simulation did not properly simulate the collapsing behavior of a structure mainly due to the reduced degree of freedom. In this study, three-dimensional simulation was tried. It consumed a great amount of calculation time, which limited the extent of the study. A few parameters, such as delay times, amount of charge at each hole, ball properties, were modified in order to check oui; their effect on the collapsing behavior. The differences were observed as expected but the collapsing behavior did not exactly coincide with the test blasting with a scaled model.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2008.10a
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• pp.343-350
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• 2008

• Proceedings of the Korean Geotechical Society Conference
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• 1999.10a
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• pp.209-216
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• 1999

In tunneling and road cuts by blasting, it is of the utmost importance that the remaining rock is of high quality in order to avoid rockfall, rockslides and excessive maintenance work. Therefore, numerous blasting techniques which make use of decoupled charge or shock wave superposition effect have been used to control overbrake. In this paper. some approximate method for the determination of blast load according to the charge condition was introduced at first and, instrumented tests were conducted in small scale transparent material to investigate the shape and amplitude of blast load around the bore hole. Compare to the fully coupled charge, low amplitude of blast load around the bore hole was observed in the decoupled charge and explosion gas pressure was important in the shape of blast load. Therefore, quasi-static behaviour of the crack pattern was shown due to low loading rate.

• 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..

• Explosives and Blasting
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• v.39 no.3
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• pp.15-23
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• 2021

Ventilation shafts are pathways in mines and tunnels for the removal of dust or smoke during underground space construction and operation. In mines, blasting with long blast holes is preferred for the excavation of a ventilation shaft in the 10~20m long crown pillar section. In this case, the bottom part of the blast hole is completely drilled in order to determine the drilling error, and this causes a problem of lowering the explosive charge and blasting efficiency. It is possible to solve the problem of explosive loading and to increase the blast efficiency by covering the curb of the blasthole by using stemming material. In this study, simulations for the blasting of a ventilation shaft were performed with various stemming lengths and the blasthole diameters(45, 76mm) using AUTODYN 2D SPH(Smooth particle hydrodynamics) analysis technique. Also the optimal bottom stemming column was derived by checking the size of the boulder and burden line according to blasting. Analysis result, blasting efficiency is lessened in case of stemming length less than 30cm and the optimal length of the stemming material should be 30cm or higher to achieve high efficiency of blasting.

• 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.

• Tunnel and Underground Space
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• v.20 no.4
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• pp.252-259
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• 2010

In urban tunnels, namely, in case there are residents in the near distance, we normally use non-vibration and ambient vibration which are not blasting methods because it’ impossible to meet the blasting vibration regulation with only normal explosives. However, non-vibration methods not only cause increase of excavating cost, but need much time than explosives. Generally, the lower velocity explosives with 2,000 m/s VOD have been applied to ambient vibration blasting in open cut area, but difficult in tunneling in its use. However, by charging the hole together with lower velocity explosives and normal explosives, we have got the result which shows 20~30% vibration decrease compared with using only normal explosives. Therefore, I’ like to suggest the blasting method which is able to do as ambient vibration using lower velocity explosives mixed with normal explosives in urban tunnel and the area which is adjacent to security facilities within the vibration regulation.

• Explosives and Blasting
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• v.21 no.2
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• pp.1-13
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• 2003

Overbreak or underbreak is one of the most important factors in evaluating the results of a tunnel blasting. Overbreak, which depends on the quality of rock, the type and quantity of explosives, and drilling conditions, has been a target of challenge to many blasting engineers because it directly affects construction cost. Drilling is generally known as one of the primary factors to generate overbreak. This study presents a real working model to reduce overbreak based on the analysis of drilling accuracy and overbreak generated from various working methods related to drilling. As the first step of the study, 45 experiments have been performed. The factors investigated are: marking contour line, the position of perimeter holes, the change of look-out with drilling rig position, and the proper space between perimeter holes. It is concluded that workers and engineers＇ will and efforts are the most important factors to reduce overbreak and that improving drilling method and pattern could reduce overbreak to a considerable amount.

• Journal of the Korean GEO-environmental Society
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• v.12 no.2
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• pp.5-14
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• 2011

The most common problem encountered in domestic tunnel construction sites are solving public resentments caused by damage to adjacent structures and buildings. The most effective excavation method in rock tunnelling is the drilling and blasting, which is the main cause of vibration resulting in the public resentments. In this study, numerical analysis is conducted to compare the vibration reduction effect of line drilling and pre-splitting methods. Furthermore, the numerical simulations are verified and the results are quantified. Finally, various combinations of explosives used in controlled blasting are used and the vibration reduction effects are evaluated, thereby proving the applicability of the controlled blasting for reduction of vibration in tunnelling.

• Explosives and Blasting
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• v.30 no.2
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• pp.77-85
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• 2012

This is the study about continuous explosives demolition to Han Kuk Flour Mills Silo(14 units) located in Mokpo. Considering the surroundings, We planned to collapse toward longitudinal direction of the silo. It had a lot of blast hole per silo in confined space. It could make lots of problems like Cut-off, collapse behavior, fragmentation after structure behavior. So we separated 14 units silo to two section for blast twice. At the first A-Section blast, there was Cut-off of detonating cord and we had to blast twice to collapse remained silo. After that the secondary B-Section blasting, we got the desired result of collapse behavior.