• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.3
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• pp.369-380
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• 2019

When a extreme loading such as blast is applied to prestressed concrete (PSC) structures and infrastructures for an instantaneous time, serious property damages and human casualties occur. However, a existing design procedure for PSC structures such as prestressed containment vessel (PCCV) and gas storage tank do not consider a protective design for extreme internal blast scenario. Particularly, an internal blast is much more dangerous than that of external blast. Therefore, verification of the internal blast loading is required. In this paper, the internal blast resistance capacity of PSC member is evaluated by performing internal blast tests on RC and bi-directional PSC scaled down specimens. The applied internal blast loads were 22.68, 27.22, and 31.75 kg (50, 60, and 70 lbs) ANFO explosive charge at 1,000 mm standoff distance. The data acquisitions include blast pressure, deflection, strain, crack patterns, and prestressing force. The test results showed that it is possible to predict the damage area to the structure when internal blast loading occurs in PCCV structures.

• Explosives and Blasting
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• v.30 no.2
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• pp.29-42
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• 2012

Variables influencing the free face movement due to rock blasting include the physical and mechanical properties, in particular the discontinuity characteristics, explosive type, charge weight, burden, blast-hole spacing, delay time between blast-holes or rows, stemming conditions. These variables also affects the blast vibration, air blast and size of fragmentation. For the design of surface blasting, the priority is given to the safety of nearby buildings. Therefore, blast vibration has to be controlled by analyzing the free face movement at the surface blasting sites and also blasting operation needs to be optimized to improve the fragmentation size. High-speed digital image analysis enables the analyses of the initial movement of free face of rock, stemming optimality, fragment trajectory, face movement direction and velocity as well as the optimal detonator initiation system. Even though The high-speed image analysis technique has been widely used in foreign countries, its applications can hardly be found in Korea. This thesis aims at carrying out a fundamental study for optimizing the blast design and evaluation using the high-speed digital image analysis. A series of experimentation were performed at two large surface blasting sites with the rock type of shale and granite, respectively. Emulsion and ANFO were the explosives used for the study. Based on the digital images analysis, displacement and velocity of the free face were scrutinized along with the analysis fragment size distribution. In addition, AUTODYN, 2-D FEM model, was applied to simulate detonation pressure, detonation velocity, response time for the initiation of the free face movement and face movement shape. The result show that regardless of the rock type, due to the displacement and the movement velocity have the maximum near the center of charged section the free face becomes curved like a bow. Compared with ANFO, the cases with Emulsion result in larger detonation pressure and velocity and faster reaction for the displacement initiation.

• Explosives and Blasting
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• v.19 no.3
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• pp.39-47
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• 2001

Bulk-Emulsion system은 미주나 서구 유럽 등지의 발파분야에 있어 선구적인 역할을 수행하여 왔던 나라에서는 이미 보편화된 시스템으로 ANFO 다음으로 노천이나 터널 굴진에 널리 적용되고 있다. Bulk-Emulsion system은 제조, 저장, 운반 및 사용에 있어서 극히 안전하고 장전밀도를 증가시켜 효과적인 파쇄와 굴진률 향상을 기대할 수 있으며 발파 후가스가 매우 양호한것을 비롯하여 기계화 장전에 따른 시공 능률 향상과 작업 안전성 강화 등 많은 장점을 가지고 있다. 본 연구에서는 고속도로 터널 현장에 국내 최초로 터널용 Bulk-Emulsion system을 이용하여 총 15회에 걸쳐 시험발파를 실시하였으며 이 결과를 토대로 하여 Bulk-Emulsion system 적용에 따른 효과와 문제점을 알아보고자 하였다.

• Explosives and Blasting
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• v.21 no.1
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• pp.49-58
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• 2003

현재 발파의 수행은 채석, 채굴 및 지하철과 도로, 건축, 토목공사 등 다양한 분야에 적용되고 있다. 이에 따라 발파특성의 연구와 관련하여 다양한 이론이 도출되고 있고 사용되지만 발파에 의한 공해인 진동 및 소음의 문제가 대두되면서 또한 이들의 취약점을 보완하기 위해 다양한 공법들이 시행되고 개선되어지고 있다. 본 연구에서는 기존의 발파공법과 Air tubes를 이용한 발파공법을 비교하므로 화약의 사용량을 보다 감소시키고, 기존 전색의 길이를 줄이므로 폭약의 투사면적을 증대시켜 진동 및 폭음을 감소시키고 상대적으로 양호한 파쇄입도를 얻고 상부의 대괴를 최소화하는데 목적이 있다. 따라서 발생하는 진동 및 발파폭음을 크게 감소시킬 수 있으므로 기존 노천발파 및 진동, 소음에 민감한 도심지 발파에서 그 이점을 활용하여 보다 안전적이고 경제적인 발파작업을 수행하는데 연구의 목적이 있다.

• 한국연소학회:학술대회논문집
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• 2012.04a
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• pp.283-286
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• 2012

The analytical model determining the unknown parameters of reaction rate equation which is necessary to simulate the combustion phenomena of energetic materials is proposed. The relationship between detonation velocity and size effect of energetic materials is derived from simplified JWL++ model. Theoretical model is used to investigate the combustion characteristics of certain energetic materials before running Hydrocode by pre-determination of unknown parameter, b. When b=0.8, the behavior of HANFO gunpowder is in the form of concave-up and ANFO explosives has the concave-down form in case of b=1.5. The analytical model provides efficient and highly accurate results rather than previous method which simulated the unconfined-rate-stick via the numerical means.

• Journal of Industrial Technology
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• v.18
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• pp.385-397
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• 1998

The firing system for the detonators called ordinary blasting caps have almost completely been substituted by safer and more trust worthy systems that can be classified in two groups ; Electric systems, and Non-electric systems. The characteristics of the different initiation devices for both group will be discussed, along with other useful elements for the correct execution of blastings. These detonators are commercialized in several countries under different names such as HiNEL, Nonel, Anodet, Detaline etc. A great advantage is that they do not initiate blasting agents such as slurries and ANFO, allowing bottom priming to be carried out.

• Journal of the Korea Concrete Institute
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• v.29 no.3
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• pp.237-248
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• 2017

Frequent terror or military attack by explosion, impact, fire accidents have occurred recently. These attacks and incidents raised public concerns and anxiety of potential terrorist attacks on important infrastructures. However, structural behavioral researches on prestressed concrete (PSC) infrastructures such as Prestressed Concrete Containment Vessel (PCCV) and Liquefied Natural Gas (LNG) storage tanks under extreme loading are significantly lacking at this time. Also, researches on possible secondary fire scenarios after terror and bomb explosion has not been performed yet. Therefore, a study on PSC structural behavior from an blast-induced fire scenario was undertaken. To evaluate the blast-fire combined resistance capacity and its protective performance of bi-directional unbonded PSC member, blast-fire tests were carried out on $1,400mm{\times}1,000mm{\times}300mm$ PSC specimens. Blast loading tests were performed by the detonation of 25 kg ANFO explosive charge at 1.0 m standoff distance. Also, fire and blast-fire combined loading were tested using RABT fire loading curve. The test results are discussed in detail in the paper. The results can be used as basic research references for related research areas, which include protective design simulation under blast-fire combined loading.

• Journal of the Korea Concrete Institute
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• v.22 no.1
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• pp.93-102
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• 2010

Recently, FRP usage for strengthening RC structures in civil engineering has been increasing. Especially, the use of FRP to strengthen structures against blast loading is growing rapidly. To estimate FRP retrofitting effect under blast loading, blast tests with nine $1,000{\times}1,000{\times}150\;mm$ RC panel specimens, which were retrofitted with carbon fiber reinforced polymer (CFRP), Polyurea, CFRP with Poly-urea and basalt fiber reinforced polymer (BFRP) have been carried out. The applied blast load was generated by the detonation of 15.88 kg ANFO explosive charge at 1.5 m standoff distance. The data acquisitions not only included blast waves of incident pressure, reflected pressure, and impulse, but also included central deflection and strains at steel, concrete, and FRP surfaces. The failure mode of each specimen was observed and compared with a control specimen. From the test results, the blast resistance of each retrofit material was determined. The test results of each retrofit material will provide the basic information for preliminary selection of retrofit material to achieve the target retrofit performance and protection level.

• Journal of the Korea Concrete Institute
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• v.28 no.6
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• pp.673-683
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• 2016

In recent years, frequent terror or military attack by explosion, impact, fire accidents have occurred. Particularly, World Trade Center collapse and US Department of Defense Pentagon attack on Sept. 11 of 2001. Also, nuclear power plant incident on Mar. 11 of 2011. These attacks and incidents were raised public concerns and anxiety of potential terrorist attacks on major infrastructures and structures. Therefore, the extreme loading researches were performed of prestressed concrete (PSC) member, which widely used for nuclear containment vessel and gas tank. In this paper, to evaluate the blast resistance capacity and its protective performance of bi-directional unbonded prestressed concrete member, blast tests were carried out on $1,400{\times}1,000{\times}300mm$ for reinforced concrete (RC), prestressed concrete without rebar (PSC), prestressed concrete with rebar (PSRC) specimens. The applied blast load was generated by the detonation of 55 lbs ANFO explosive charge at 1.0 m standoff distance. The data acquisitions not only included blast waves of incident pressure, reflected pressure, and impulse, but also included displacement, acceleration, and strains at steel, concrete, PS tendon. The results can be used as basic research references for related research areas, which include protective design and blast simulation under blast loading.

• Explosives and Blasting
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• v.25 no.2
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• pp.61-70
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• 2007

Korean large limestone mines started to employ bulk emulsion explosives to improve the productivity in early 2000s. As the application of the bulk emulsion explosives became common in the mid 2000s, the bulk emulsion application increases overall performance but it tends to decrease the moving and heaving because it lacks in gas volume and heat energy. Therefore, the chemical gassing technique was introduced to improve the blasting efficiency of the existing bulk emulsion explosives. The chemical gassing is a technique to replacing GMB(Glass Micro Balloon), which is used for a sensitizer, with gassing agent to chemically sensitize it. This paper introduces the case of successful application of chemical gassing in a Korean large limestone mine. We also compared and evaluated the blast and work efficiency between bulk emulsion GMB & gassing agent (chemical gassing). The results indicate that the replacement of GMB with gassing agent improved fragmentation in the upper part and toe of a bench as well as moving efficiency of the material.