• Explosives and Blasting
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• v.20 no.1
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• pp.77-82
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• 2002

환산거리 예상식에 의한 진동의 예측은 널리 적용되고 있다. 여기서 환산거리는 거리와 지발당 장약량에 의해 결정된다. 그러나 환산거리가 같다고 하여 진동수준이 같은 것은 아니며, 많은 실무자들이 총장약량이 증가함에 따라 진동이 커지는 경향을 경험하고 있다. 본 연구에서는 총장약량이 진동수준에 미치는 영향을 고려한 진동 예측식을 제안하였고, 이 식을 기존의 계측자료에 적용하여 검토하였으며, 일정한 범위 내에서 진동속도에 미치는 총장약량의 영향을 반영할 수 있음을 보였다

• Explosives and Blasting
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• v.19 no.1
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• pp.41-52
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• 2001

본 연구에서는 터널발파 진동의 전달 특성을 규명하기 위하여 네 곳의 도로터널의 '터널내부','터널외부','터널직상부 진행방향', '터널직상부' 진행직각방향'의 네 방향으로 발파진동을 계측하였다. 지발당장약량을 해당 지발당장약량과 최대 지발당장약량으로 구분하였으며, 지반의 진동 전달 특성을 확인하기 위하여 자승근 환산거리와 입방근 환산거리로 회귀분석 하였다. 또한 PPV, 거리별 우세진동수를 구하였다. 터널상부 진행방향의 진동 수준이 가장 크게 나타났으며, 진동의 감쇠도 크게 이루어졌다. 터널내부는 비교적 고주파성분이 우세하였으나 나머지는 일반적인 경향을 보였다 최대 지발당장약량을 적용한 입방근 환산거리의 경우가 거리별 감쇠특성 및 상관성이 다른 비교대상에 비하여 가장 우세하게 나타났다. 따라서 최대 지발당장약량을 적용한 입방근 환산거리 방식으로 설계하는 것이 바람직하다고 판단된다.

• Explosives and Blasting
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• v.28 no.1
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• pp.27-39
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• 2010

Blast design equations based on the concept of scaled distances can be obtained from the statistical analysis on measured peak particle velocity data of ground vibrations. These equations represents the minimum scale distance of various recommendations for safe blasting. Two types of scaled distance widely used in Korea are the square root scaled distance (SRSD) and cube root scaled distance (CRSD). Thus, the design equations have the forms of $D/\sqrt{W}{\geq}30m/kg^{1/2}$ and $D/\sqrt[3]{W}{\geq}60m/kg^{1/3}$ in the cases of SRSD and CRSD, respectively. With these equations and known distance, we can calculate the maximum charge weight per delay that can assure the safety of nearby structures against ground vibrations. The maximum charge weights per delay, however, are in the orders of $W=O(D^2)$ and $W=O(D^3)$ for SRSD and CRSD, respectively. So, compared with SRSD, the maximum charge for CRSD increases without bound especially after the intersection point of these two charge functions despite of the similar goodness of fits. To prevent structural damage that may be caused by the excessive charge in the case of CRSD, we suggest that CRSD be used within a specified distance slightly beyond the intersection point. The exact limit is up to the point, beyond which the charge difference of SRSD and CRSD begins to exceed the maximum difference between the two within the intersection point.

• Explosives and Blasting
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• v.34 no.4
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• pp.28-34
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• 2016

Empirical model, phenomenological model, and CFD model have been used to evaluate the blast effects produced by explosion of explosives, flammable gas and liquid or dust. TNT equivalence method which is one of empirical models has been widely used as it is simple. In this study, new peak overpressure-scaled distance and scaled impulse-scaled distance equations are induced through fitting data from the curves given by TNT equivalence method. If the TNT equivalent mass is calculated, it is possible to estimate the peak overpressure and impulse using the regression equations. Differences of peak overpressure with yield factor which is a component of TNT equivalence method are found to be great in near-by distances from explosion source where the increase in overpressure is very steep, but the differences are getting smaller as the distances increase.

• Explosives and Blasting
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• v.33 no.3
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• pp.29-50
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• 2015

Safe blast criteria based on the concept of scaled distances can be obtained from the statistical analysis on measured peak particle velocity data of blast vibrations. Two types of scaled distance widely used in Korea are the square root scaled distance (SRSD) and cube root scaled distance (CRSD). In contrast to SRSD scheme, however, the function of maximum charge per delay for CRSD increases without bound after the intersection point of these two functions despite of the similar goodness of fits. To prevent structural damage that may be caused by the excessive charge in the case of CRSD, it is suggested that CRSD be used within a specified distance slightly beyond the intersection point. On the other hand, there are several attempts that predict vibration level(VL) from the peak particle velocity(PPV) or estimate VL based on the scaled distances without considering their frequency spectra. It appears that these attempts are conducted in blasting contracts only for the purpose of satisfying the environment-related law, which mainly deals with the annoyance aspects of noises and vibrations in human life. But, in principle there could no correlation between peaks of velocity and acceleration over entire frequency spectrum. Therefore, such correlations or estimations should be conducted only between the waves with the same or very similar frequency spectra. Finally, it is a known fact that structural damage due to ground vibration is related to PPV level, the safety level criteria for structures should be defined by allowable PPV levels together with their zero crossing frequencies (ZCF).

• Explosives and Blasting
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• v.24 no.2
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• pp.33-39
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• 2006

The blasting vibration prediction in Korea is mainly carried out by the scaled distance method. The delay interval of the scaled distance method is generally considered to be 8ms, where the effect of vibration between adjacent holes is not included. In this study, the origin and issues of 8ms criterion are reviewed from literatures and Langefors' 2.5T criterion is applied to evaluate the applicabilities of 8ms, 17ms and 25ms intervals in which a vibration does not affect an adjacent hole.

• Explosives and Blasting
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• v.37 no.3
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• pp.1-12
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• 2019

The analysis methods of blast analysis models are classified into direct analysis and indirect analysis, and the latter is divided into semi-empirical and numerical analysis methods. In order to evaluate the applicability of the ELS blast analysis program, which is a program for analyzing the semi-empirical models, this study selected a simplified analytical model and examined the blast load characteristics of free-air burst explosion and surface burst explosion by using AT-Blast, RC-Blast, and Kinney and Graham's empirical equations, which are the semi-empirical analysis programs. As a result of analyzing the explosion pressure for the scaled distance and the incidence angle for the simplified analytical model, an appropriate analysis can be performed when the range of the scaled distance in the free-air burst explosion analysis was 0.3~0.461 and when the range of the scaled distance in the surface burst explosion analysis was 0.378~0.581. In terms of the incidence angle, the results analyzed within $45^{\circ}$ were considered to be appropriate.

• Explosives and Blasting
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• v.21 no.1
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• pp.69-76
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• 2003

Test blasting has been performed with V-cut to investigate the characteristics. Blasting vibrations were measured at two directions, the proceed direction and side direction. Propagation characteristics were determined by regression analysis; square root scaled distance and cube root scaled distance with maximum charge per delay of the blast. Testing result, The cross point was 62m in the allowable vibration velocity of 3mm/sec and 46m In 5mm/sec. Also, vibration level with measuring point was highest and decayed fastest, adapting to cube root scaled distance, for the proceed direction on ground.

• Explosives and Blasting
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• v.18 no.2
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• pp.14-22
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• 2000

The estimation of proper prediction method and the alteration of transformation method of environmental regulation standard were carried out by measuring blasting noise in construction field. The correlation of scaled distance with sound pressure level were better than with sound level, but it was proved to be difficult to control blasting noise because the correlation factor was too 1ow. three methods to transform sound pressure levee to sound level were examined. The method is the transformation by correlation equation of sound pressure level and sound level which are measured at the same time, and simplified transformation of A-weighting network corresponding to dominant frequency, and the transformation of sound pressure level by FFT. There were many errors to transform. The best effective method is the transformation using correlation equation of sound pressure level and sound level which are measured at the same time.

• Explosives and Blasting
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• v.17 no.2
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• pp.36-44
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• 1999

A study was made on the design of the prediction model concerning blasting vibration in a constraction site, Namgu, Daegu City. The geology in this area consists of hornfels of shale and mud underlain by quartize, of which the main strike of the geological structure is NW direction. Measurements were carried out on the top of the wall concrete water storage tank, which is burried in the ground earth. The attenuation due to the vertical wall of the concrete structure may be experted because of spherical divergency at the bottom corner of the wall by the Huygens principle. For design of blasting prediction model, thus among scaled distance(SD) may be preferable to use in the regression model, since they represents most likely the average ground condition. Judging from the regression results, the cube root method may be more suitable for this area. The SD values for the maximum allowable vibration velocity of 0.5 cm/s, in this area are 22.5, 28.0 and 30.6 for the significance level of 50%, 95% and 99%, respectively.