• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.4
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• pp.561-571
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• 2019

Drilling and charging of the blast holes during NATM tunneling works take more than 30% of construction time among the whole tunneling work process. Prediction of ground condition ahead of tunnel face has been studied by several researchers by correlating percussion pressure and drilling speed during tunneling work with the ground condition and/or RMR values. However, most of the previous researches were conducted in the granite rock condition which is the most representative igneous rock in the Korean peninsula. In this study, drilling speeds in igneous rocks were analyzed and compared with those in sedimentary rocks (most dominantly composed of conglomerates, sandstones, and shales) under the similar RMR ranges; it was identified that the drilling speed is pretty much affected by rock types even in a similar RMR range. Under the similar RMR values, the drilling speed was faster in sedimentary rocks compared with that in igneous rock. Moreover, while the drilling speed was not much affected by change of the RMR values in igneous rocks, it became faster in sedimentary rocks as the RMR values got lower.

• Tunnel and Underground Space
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• v.19 no.6
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• pp.479-489
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• 2009

Appropriate investigation of ground condition near excavation face in tunnelling is an inevitable process for safe and economical construction. In this study mechanical parameters from drilling process for blasting were investigated for the purpose of predicting the ground condition, especially rock mass strength, ahead of tunnel face. Rock mass strength is one of the most important factors for classification of rock mass and making a decision of support type in underground construction. Several rock specimens which are considered homogeneous and having different strength values respectively were tested by hydraulic drill machines generally used. As a result, penetration rate is fairly related with rock mass strength among drilling parameters. It is also found that penetration rate increases along with the higher impact pressure even under same rock strength condition. It is finally suggested that new prediction method for rock mass strength using percussive pressure and penetration rate during drilling work can be utilized well in construction site.

• Journal of the Korean GEO-environmental Society
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• v.17 no.9
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• pp.13-20
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• 2016

This study carried out field measurements of rock drilling where two PRD (Percussion Rotary Drilling) methods, T-4 drilling method and dual drilling method, were considered and the study examined the characteristics of vibration level, noise level, drilling speed, and drillig verticality of the two method. The results of field measurements were compared and analyzed in details to provide the drilling information so that the problems due to rock drilling is minimized and the drilling efficiency is improved in the future. The limited measurements in the field indicated that the dual drilling method showed lower vibration and noise levels and better drilling speed and verticality.

• Explosives and Blasting
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• v.18 no.3
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• pp.15-28
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• 2000

국내에서는 Heavy ANFO로 더 잘 알려져 있는 Emulsion Blends는 왁스 대신 오일을 사용 하여 상온에서 펌핑이 가능하도록 한 에멀젼과 ANFO(또는 초안)의 혼합물을 일컫는다. ANFO는 저렴하고 안전하며 장약이 쉽고 밀장전되는 장점이 있지만, 내수성이 거의 없고 폭발 속도가 느리며 장약 비중이 0.75∼0.90g/cc 정도로 낮아 폭약으로서 그 위력이 작은 단점을 갖고 있다. Blends는 수용성 ANFO 입자 사이의 빈 공간을 내수성 에멀젼이 태우고 있는 형태로서 에멀젼 함량 25%부터 내수성이 나타나기 시작하여 에멀젼 함량 40% 이상에서는 완전한 내수성을 갖게 되며, 에멀젼의 함량이 증가할수록 폭발속도는 카트리지 에멀젼 폭약에 근접하게 된다. 장약 비중은 에멀젼의 함량이 증가하여 45% 근처에서 1.25∼ 1.30g/cc의 최대 값을 갖지만, 그 이상의 에멀젼 함량에서는 기폭 감도 저하로 예감제를 사용하여 비중을 감소시키는 것이 바람직하다. Blends는 자체에 물을 함유하고 있으므로 열역학적으로 계산된 단위 중량당 반응열은 ANFO에 비해 매우 적지만, 폭발속도, detonation pressure(폭굉압), borehole pressure(폭발압력) 등이 ANFO에 비해 크므로 폭발압력에서부터 암석의 파괴가 가능한 압력가지의 단위 중량당 유효한 에너지의 양은 암석의 강도가 커질수록 ANFO에 비해 매우 적지만, 폭발속도, ANFO와 비슷해진다. 따라서 장약 비중이 ANFO의 130∼145%로 높은 Blends는 동일한 천공에 더 많이 장약할 수 있어 단위 천공당 암석 파괴에 이용되는 유효 에너지의 총 양이 커지게 되므로, 공간격과 저항선을 늘릴 수 있어 총 천공수를 감소시킬 수 있다. 결론적으로, Blends의 장점은 내수성과 함께 비장약량은 비슷하거나 약간 증가하는데 비해, 천공수는 크게 감소하여 전체적으로는 발파 현장의 경제성이 향상된다는데 있다.

• Tunnel and Underground Space
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• v.13 no.4
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• pp.316-320
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• 2003

This study is to evaluate an irregular drill-hole depth having an effect on the blast vibration. The relationship between a peak particle velocity and a cube root scaled distance with respect to three drill-hole depths with 2.1m, 2.3m and 2.4m are compared and analyzed using a numerical regression analysis. According to the results, the deeper a drill-hole depth is the larger a peak particle velocity is. It is suggested that a drill-hole depth is proportional to a peak particle velocity at the same scaled distance. Therefore, a regular drill-hole should be carried out in order that the blast vibration velocity of a fixed range under a allowable vibration velocity is maintained.

• Magazine of korean Tunnelling and Underground Space Association
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• v.11 no.3
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• pp.66-78
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• 2009

• Tunnel and Underground Space
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• v.23 no.1
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• pp.42-53
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• 2013

The percussion rate and spacing of the button of drill bit are very important in maximizing the drilling efficiency. Therefore, a series of percussion tests using Hopkinson bar system was carried out to assess the fragmentation performance against the beat rate and spacing of a drill bit. First, single percussion test complemented with numerical simulation was performed to analyze rock fragmentation phenomenon and to describe the fragmentation process. Next, multiple percussion test that repetitively strike the rock sample moving at predetermined rate was carried out to predict drilling efficiency against the button spacing. After the tests, the fragmented volume of the rock was measured by laser scanner and the drilling performance was analyzed using the calculated percussive energy and measured negative volume. Based on the results, the single impact performance of drill bit with 102 mm diameter was predicted.

• 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.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.8
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• pp.26-35
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• 2020

Tunnel construction is an important part of Korean public construction projects. Although the development of various equipment and technologies has led to advances in tunnel construction methods that are implemented on sites, the cost standards related to such works do not yet reflect the realities of the construction sites. A literature review and site surveys were conducted to suggest reasonable cost standards for tunnel work that reflects the realities of the field. First, each item in the cost standards for tunnel work, as established in the Construction Standard Production Rates, were analyzed. The results were compared with the actual costs implemented on tunnel projects. The key items analyzed included those regarding the work cycle time, such as rock classification, profiling survey, drilling speed, and muck-disposal processing equipment combination, as well as the number of people put to tunneling work. Based on the site survey results, improved estimates regarding the cycle time per one tunnel drilling blast, drilling speed of the machine, muck disposal processing equipment combination, and the number of people put to tunneling work were suggested. This study suggests the cost standards that reflect the realities of tunneling sites. The results are expected to help ensure adequate costs for tunnel construction projects.

• Explosives and Blasting
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• v.19 no.1
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• pp.31-40
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• 2001

일반적으로 장공발파(長孔發破) 방법(Long hole blasting method)은 그동안 주로 대규모 채탄막장이나 댐 기초굴착, 광산 등에서 행하여져 왔으나 최근 토목터널에서 시공 효율성 및 경제성을 목적으로 관심이 높아지고 있다. 기존의 터널설계 패턴은 I -Type을 기준으로 3.5~3.8m 천공이며 신공법 적용시 최대 4.Om까지 설계되는 것이 보통이었다. 과거 착암장비는 천공장이 늘어남으로서 슬러지에 의한 천공속도가 저하되어 천공비가 증가하기 때문에 빠른 슬러지 배제가 필요하고 Rod의 휨 현상에 의한 천공오차의 증대를 초래할 수 있는 단점이 있었다. 그러나 최근 장비의 발달로 인하여 천공각도 및 천공장 등을 Computer로 모니터링하여 제어할 수 있어 정밀한 천공이 가능하여 졌고 또한, 고성능 에멀젼계 폭약(Super Emulsion)의 개발로 그동안 극 경암터널에서 에멀젼계 폭약의 단점으로 여겨졌던 비 장약량의 증대와 사압현상의 발생, 굴진효율 저하문제론 극복할 수 있었다. 따라서 본 연구는 현재 건설중인 대상현장을 중심으로 장공 터널발파의 효율성과 경제성을 분석하고 나아가 암질에 따른 새로운 Type별 설계기준을 마련하는 기초자료로서 활용하고자 하였다. 된 연구의 대상현장은 충북 괴산군 영풍면 소재 중부내륙(여주-구미간) 고속도로 제 9공구 이화터널 건설공사현장으로 $\varphi{102mm}$ 무 장약공 Cylinder 4공을 이용한 심발법을 사용하였으며 천공장은 최대 5.0m로 2000년 11일 15일에서 동년 12월 15일까지 31일간 총 112회의 시험발파를 실시하여 평균 92%의 높은 굴진 효율을 기록하였다.