• Magazine of the Korea Concrete Institute
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• v.10 no.5
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• pp.81-87
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• 1998

최근 들어 교통난 해소를 위한 도로확폭 공사나 파일항타 및 발파 등의 공사가 많이 진행되고 있으며, 이러한 경우 진동의 영향으로 콘크리트의 품질 저하에 영향을 미칠 것으로 예상된다. 이에 따라 본 연구에서는 진동과 굳지 않은 콘크리트에 미치는 영향을 평가하기 위하여 실험변수를 진동속도, 진동발생점등으로 나누어, 콘크리트의 압축강도, 부착강도를 측정하였다. 또한 응결시간을 측정하여 외부 진동용인이 응력에 미치는 영향을 평가하였다. 진동속도는 0.25cm/sec ~4.2cm/sec까지 변화시켰고, 진동가력시점은 타설 직후(0시간)부터 타설 후 2, 4, 6, 12 시간 후 에 진동을 가하였다. 본 연구의 실험 결과 진동속도 0.25cm/sec 에서는 압축 강도와 부착강도가 증가하는 반면에 진동속도 0.5cm/sec 이상에서는 압축강도는 5~12% 정도 감소하고 부착강도도 이와 유사하게 감소하는 것으로나타나고 있다. 응결시간은 0.25cm/sec의 작은 진동에서는 영향이 거의 없으나 0.5cm/sec 이상에서는 타설 직후의 진동시 응결시간이 다소 빨라지는 것으로 나타났다. 본 연구 결과, 양생초기 콘크리트의 진동 허용치는 약 0.3~0.4cm/sec 로 나타나고 있으며, 이것은 앞으로 실제 구조물의 시공시 진동규제치로서 하나의 유용한 자료가 될 수 있을 것으로 사료된다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.361-365
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• 2006

In order to predict method of blasting vibration in ground and it's resident located around blasting field in urban area, blasting vibration characteristics were measured the vibration velocity(cm/sec), vibration acceleration($cm/sec^2$), vibration acceleration level(dB) and vibration level(dB(V)). The charged powder were used to 1.25kg and measuring sites were 25 points front 4m to 90m at the ground. The correlation of vibration velocity, vibration acceleration, vibration acceleration level and vibration level by square root scaled distance and cube root scaled distance were investigated. The correlation of PPV(peak particle velocity) velocity by SRSD(square root scaled distance) and CRSD(cube root scaled distance) was 0.85 and 0.86 and the correlation of PVS(peak vector sum) velocity by SRSD and CRSD was 0.82. Also vibration acceleration, vibration acceleration level and vibration level by SRSD and CRSD was 0.61, 0.62 and 0.82, respectively. As results, the vibration velocity and vibration level(dB(V)) was showed good correlation, but the vibration acceleration and vibration acceleration level was not showed good correlation.

• Tunnel and Underground Space
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• v.20 no.4
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• pp.299-307
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• 2010

The model experiments, which employ a charge hole and guide hole, are simulated to examine the effect of the guide hole on the crack propagation control in blasting. Crack patterns resulted from the analysis models, which consider the distance between the charge hole and guide hole, were compared. From the simulation analysis for the model experiments, it was revealed that all the guide holes used in this study were effective for controlling the crack propagation in blasting.

• Explosives and Blasting
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• v.22 no.2
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• pp.33-43
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• 2004

The six grades weathering system is normally used in weathered rock classification. In this study. fresh and weathered rock block of grade I to V were sampled in Jang-soo ana but samples of the grade VI was omitted from this study. The variation quantities of chemical weathering indices with weathering degree are smaller than those of physical and mechanical properties. Increase of Weathering degree is well indicated by physical and mechanical properties such as strength, hardness, ultrasonic velocity and slake durability result. Especially, absorption and porosity ratio is a good indicator. As weathering proceeds. a number of the cracks affect the rock deformation. Therefore, stress-strain curves of weathered rocks in unconfined state are quite different from ones of fresh rocks.

• Explosives and Blasting
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• v.33 no.3
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• pp.1-13
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• 2015

Accidents related to gas explosion are frequently happened in foreign countries and in Korea. For the evaluation and the analysis of gas explosions, TNT equivalent methods are used. In this study, the influence of the selection of chemical equation in TNT explosion and the selection of enthalpy of the products on the explosion energy, detonation pressure, velocity of detonation, and temperature was calculated. Depending on the chemical equations, the maximum detonation pressure can be 2 times higher than the minimum. As an example for applying TNT equivalent method, an explosion of methane gas in a confined volume was assumed. With the TNT equivalent, it was possible to predict the variation of peak overpressure and impulse with the distance from the explosion location.

• Explosives and Blasting
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• v.35 no.3
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• pp.21-30
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• 2017

When explosives explode in water, the effect of post-explosion gas after explosion should be considered, unlike explosion in the air. During explosion in water, the propagation velocity of the explosion pressure is faster than when the explosion occurs in the air. The generated gas is diffused and trapped in the form of bubbles by water before the energy is dissipated. At this time, the bubble expands and contracts, creating a shock wave. In order to investigate this series of phenomena, a cylinder type steel water tank capable of observing the interior was fabricated and explosion experiments were conducted. In this study, a small amount of shell-free pentolite was exploded in water. Experiments were performed to observe the behavior of the generated gas bubble as well as to measure the shock wave generated. We designed the experimental method of underwater explosion and examined the results.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.1 s.106
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• pp.19-26
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• 2006

The test blasts were carried out by detonating some single blastholes at two upper sites of the underground storage cavern for the crude oil. One was performed at the entrance site of the construction tunnel and the other at the middle area of the underground storage cavern. Based on the blast-induced nitration measured by the test blasts, we suggested the propagation equations of blasting vibration that were capable of estimating the peak particle velocity. In addition, in order to assess the stability of the adjacent ground storage tank, we did the frequency analysis and the response spectrum analysis with the particle velocity-time history and the particle acceleration-time history that were measured by the test blast carried out on the entrance site of the construction tunnel. In result, it was predicted that the displacement on the highest part of the tank shell was less than the allowable displacement.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2009.06a
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• pp.419-424
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• 2009

The ocean rock was crushed mainly by drop hammer and blasting. In recent years, because of farming and harbors extension, the ocean rock crushing method is changing to popular complaint solving type. Effective rock crushing methods of protecting environment are studied under consideration for topography, farming, structures, electronic equipment, environment protection arm near to rock crushing sector. Effective rock crushing methods are compared under consideration for crushing volume, rock quality, distribution, crushing speed. Effective rock crushing methods at once solving popular complaint and protecting ocean environment and building ocean structures, are compared according to the coast development.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.479-484
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• 2005

The test blasts were carried out by detonating some single blastholes at two upper sites of the underground storage cavern the crude oil. One was performed at the entrance site of the construction tunnel and the other at the middle part of the underground storage cavern. Based on the blast-induced vibration measured by the test blasts, we suggested the propagation equations of blasting vibration that were capable of estimating the peak particle velocity. In addition, in order to assess the stability of the nearest ground storage tank, we did the frequency analysis and the response spectrum analysis with the particle velocity-time history and the particle acceleration-time history that were measured by the test blast carried out on the entrance site of the construction tunnel. In result, it was predicted that the displacement on the highest part of the tank shell was less than the allowable displacement.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.485-492
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• 2005

Since blast-induced vibration may cause serious problem to the rock mass as well as the nearby structures, the prediction of blast-induced vibration and the stability evaluation must be performed before blasting activities. Dynamic analysis has been Increased recently in order to analyze the effect of the blast-induced vibration. Most of the previous studies, however, were based on the continuum analysis unable to consider rock joints which significantly affect the wave propagation and attenuation characteristics. They also adopted pressure curves estimated by theoretical or empirical equations as input detonation load, thus there were very difficult to reflect the characteristics of propagating media. In this study, therefore, we suggested a discontinuum dynamic analysis technique which uses velocity waveform obtained from a test blast as an input detonation load. A distinct element program, UDEC was used to consider the effect of rock joints. In order to verify the validity of proposed method, the test blast was simulated. The predicted results from the proposed method showed a good agreement with the measured vibration data from the test blast Through the dynamic numerical modelling on the planned road tunnel and slope, we evaluated the effect of blast-induced vibration and the stability of rock slope.