• 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.22 no.1
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• pp.23-32
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• 2004

터널 발파를 원활히 수행하기 위해서는 암반조건에 적합한 합리적인 설계와 정밀한 천공, 정확한 기폭초시가 기본요소로서 이는 현재 국내 터널 설계.시공 기술 및 기자재의 발달로 만족할 만한 성과를 얻을 수 있다. 특히. 터널발파에서 정확한 기폭초시 부여는 굴진율 및 버럭 파쇄율, 굴착예정선 미려도, 잔여 암반 손상도 등의 시공성에서 뿐만 아니라 소음 및 진동 발생율을 좌우하는 환경적인 측면에서 매우 중요한 요소이다. 기폭요소는 최초 도화선을 활용한 공업뇌관에서 전기뇌관, 비전기식뇌관의 순으로 기폭안전성과 정밀성 면에서 눈부신 성장을 이룩하여 왔으며 특히, 90년대 초에 개발되어 전 세계적으로 최근까지 지속적으로 사용량이 급증하고 있는 전자뇌관은 기폭방식에 일대혁신을 이루었다. 전자기폭 시스템은 기존뇌관의 초시를 결정하는 화약성분의 지연요소 대신에 IC board(전자회로)에 의한 Digital timer로 신호를 발생하여 초시를 결정하는 방식이다. 본 논문에서는 국내 최초로 전자기폭시스템을 활용하여 2003년 9원 23일에서 동년 11월 2일까지 강원도 양구 지역의 $\bigcirc\bigcirc$터널에 전자뇌관을 이용한 시험발파를 실시하였고, 발파에 의한 진동 등을 조사하여 그 효율성을 검토하였다. 이를 위해 전자뇌관의 특성과 장점을 최대한 샅리기 위하여 각공을 발파하는 방식, 즉 1지발에 1공을 발파하는 방식을 채택하고 일반 뇌관과 전자뇌관으로 설계를 하여 각각의 발파효율을 비교하여 보았다. 그 결과 발파진동의 경우 기존뇌관을 이용하여 1공씩을 1지발로 발파를 한 경우에는 18~56%의 진동저감 효과가 있었고. 본선 설계에 의해 진행된 발파에 비하여는 최대 70% 이상의 진동저감 효과가 있는 것으로 나타났다.

• Explosives and Blasting
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• v.20 no.3
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• pp.25-38
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• 2002

터널 굴착선 여굴(Overbreak)은 발파공법에 의한 괄착 중에 필연적으로 발생하는 현상으로서 숏크리트, 라이닝 등의 보강비 추가 발생과 버력 처리량의 증대로 공기 및 공사비를 증가시키는 주요한 요인으로 작용한다. 또한 터널 굴착선 암반의 손상으로 균열층이 형성되거나 부석이 발생하여 안전문제를 야기시키기도 한다. 이러한 여굴 발생은 천공오차, 발파패턴의 오류, 잘못된 화약선정, 불규칙한 암반 특성 등에 그 원인이 있으나, 지금까지 터널 여굴은 천공 및 발파기술에 의해 좌우된다라는 인식이 대부분이었다. 그러나 여굴 발생에 중요한 원인으로 터널 굴착선 암반의 특성과 이에 적합한 발파패턴 및 화약류를 들 수 있다. 본 연구는 여굴 발생에 영향을 미치는 암반상태를 파악하기 위해서 터널 굴착선 주변암반의 균열정도, 강도, 불연속면의 간격, 방향, 간극, 충전물 상태 등의 6가지 요소를 이용하여 암반을 분류하는 발파암 분류법(BI)을 새로 제안하였고, 이 분류에 따라 외곽 공의 간격과 장약밀도를 달리 하는 발파패턴을 정립하였다. 또한 화약의 순폭도와 Air Deck 효과를 이용하여 장약밀도를 조절할 수 있는 N.D.C(New Deck Charge) 발파공법을 개발함으로써 여굴을 최소화할 수 있었다.

• Explosives and Blasting
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• v.34 no.3
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• pp.10-16
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• 2016

Recently, transition from open pit to underground mining in limestone mines is an increasing trend in Korea due to environmental issues such as noise, dust and vibrations caused by crushers and equipment. The severe damages in the surrounding rock mass of underground opening caused by explosive blasting may lead to rock fall hazards or casualties. It is well known that variables which mainly affect blast-induced rock falls in underground mining are: blast vibration level, joint orientation and distribution and shape of the cross sections of underground structures. In this study, UDEC program, which is a DEM code, is used to simulate blast vibration-induced rock fall in underground openings. Variation of joint space, joint angle and joint normal stiffness was considered to investigate the effect of joint characteristics on the blast vibration-induced rock fall in underground opening. Finally, jointed rock mass models considering blast-induced damage zone were examined to simulate the critical blast vibration value which may cause rock falls in underground opening.

• Explosives and Blasting
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• v.39 no.3
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• pp.24-34
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• 2021

Electronic detonators are widely used in various construction sites due to accurate delay time. Including the cases with exceeded noise and vibration from site using electric/non-electric detonator, electronic detonators are used to improve blast fragmentation or to reduce the cost of secondary partial blasting. Furthermore, the number of cases using electronic detonators are increased for reduction of the cost and construction period by maximizing operations efficiency. This case study is about applying electronic detonators on large section station, tunnel construction site which is the part of urban area GTX A project. Although it was initially planned to utilize non-electric detonators, damage was inflicted on safety-thing. We have considered blasting method using electronic detonators as solution of this problem. By applying electronic detonators, we not only satisfied environmental regulations but also prevented nearby safety-thing from getting damaged. In addition, we were able to shorten the construction period than the initial plan by conducting single simultaneous blasting on large section station, in order to ensure safe and efficient construction.

• Explosives and Blasting
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• v.36 no.1
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• pp.34-38
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• 2018

It proceed the trial test by applying blasting system with combination of electronic detonator and non-electric detonator(Supex Blasting Method) for the purpose of preventing the over-break as well as controling the blasting vibration and noisy at the site of Boseong-Imseongri railroad section ${\bigcirc}{\bigcirc}$. As a result of that, the blasting vibration and noisy was measured within the allowable standard of vibration. In conclusion, the combination of electronic detonator and non-electric detonator can not only reduce come construction cost, level of vibration and noisy but also get the prevention effect for Public resentment and minimize the rock-damage through over break control.

• Explosives and Blasting
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• v.36 no.3
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• pp.19-28
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• 2018

Locally damaged structures caused by earthquake or extraordinary external forces have been required to rapidly be dismantled because of its possibility of additional collapses. Particularly, steel frame structures were demolished by the shaped charge blasting method. Recently a research suggested a shape charge blasting technique which uses bent-shaped charge holder of copper plate and emulsion explosive charge to cut thick steel plates. This study simulated the cutting performance of the bent-shaped charge holder with considering types of explosives, thickness of copper liner and stand-off distances using LS-DYNA software. The shape charge blasting test of a 25mm thickness steel plate were used to calibrate the input parameters of the numerical models. The penetration depth and penetration width were analysed with different types of explosives, thickness of copper liner and stand-off distances.

• Explosives and Blasting
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• v.38 no.1
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• pp.14-22
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• 2020

Bit damage is one of the primary causes of decreasing drilling efficacy. Nevertheless the management of bit ware and failure are often left for field engineers' experience. Thus it is imperative to establish a proper system to predict and manage the bit damage during the rock drilling process. In this study, the drilling sound signal has been recorded and analyzed using wavelet transform analysis to identify the exact moment of bit failure. Through the analysis wavelet time-frequency spectrums have been constructed and an abnormal point has been identified with 0.9 of wavelet transform value at the 652.8s on a frequency band around 500Hz. Furthermore it is also observed that the penetration rate of the damaged bit has been decreased to 23mm/s which is 9mm/sec lower than the average of undamaged bit. The study verifies that wavelet transform analysis can be used to build a system to diagnose the bit damage while drilling.

• Proceedings of the KSEE Conference
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• 2008.10a
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• pp.61-64
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• 2008

• Proceedings of the KSEE Conference
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• 2008.10a
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• pp.65-72
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• 2008