• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.04a
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• pp.296-301
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• 2002

In this study, we investigated the machinability of machinable ceramics which were developed by a research lab. of Inha Univ., Korea. The effect of the nozzle scanning times, the size of patterns and compositions of BN in ceramics on the erosion depth of samples with no mask and samples with three different mask pattern in powder blasting of machinable ceramics. The blasting conditions were the impact angles 90$^{\circ}$, scanning times of noble up to 30 and the stand-off distances 100mm. The widths of mask pattern were 0.1mm, 0.5mm and 1 mm. The powder was alumina sharp particles, WA#600. The mass flow rate of powder during the erosion test was fixed constant at 150g/min and the blasting pressure of powder at 0.25Mpa

• Transactions of Materials Processing
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• v.15 no.9 s.90
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• pp.686-691
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• 2006

Powder blasting technique was introduced to micromachine the micro patterns of circular and rectangular shape in LGP mould. The machinability of these patterns and matt treatment by powder blasting were verified. Then a prototype of LGP was injected by the developed LGP mould with micro patterns. Shape analysis of micro patterns and performance test of the injected LGP were carried out. The results showed printless LGP with micro patterns could be produced by just single injection using the mould with micro patterns, and powder blasting technique could be successfully applied to micrornachining of micro patterns and matt treatment of LGP mould.

• Explosives and Blasting
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• v.18 no.1
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• pp.59-70
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• 2000

The blasting work to construct a subway in seoul, korea have often cased increased neighbor＇s complaints because of ground vibration. In order to prevent the demage to the stucture it was necessary to predict the level of blasting induced vibration and to determine the maximum charge weigh per delay with an allowable vibration level. The effect of blasting pattem, rock strength and different explosive on the blast-induced ground vibration was studied to determine the maximum charage weight per delay within a given vibration level. The blasting vibration equation from over 100 test data was obtained, V= K(D/W(equation omitted), where the values for n and K are estimated to be 1.7 to 1.5 and 48 to 138 respectively.

• Explosives and Blasting
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• v.8 no.3
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• pp.3-13
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• 1990

First ot of all, under given condition such as bit gage of 36mm Drill bit with right class of jack-leg-experimental test carried out from two face of Bench, firing of each hole brought 90 degree Angle face and them measured length of Burden and charged ammount of powder as following. $ca=\frac{A}{SW}$ A=Activated Area A=nd i=m S=Peripheral length of charged, room Ca=Rock Coeffiecency d: di=Hole diameter When constructed subway of Seoul in 1980 the blasting works increased complaint of ground vibration, in order to prevent the damage to structures. Some empirical equations were made as follows on condition with Jackleg Drill (Bit Gage 36mm) and within 30 meter distance between blasting site and structures. $V=K(D/W)^{-n}$ N=1.60 - 1.78 K= 48 - 138 Project is one of contineous works to above a determination of empirical equation on the cautious blasting vibration with Crawler Drill (70-75mm) in long distance. $V=41(D/\sqrt[3]{W})^{-1.41}$ $30m\le{D}\le{100m}$ $V=124(D/\sqrt[3]{W})^{-1.66}$ $100m\le{D}\le{285m}$.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.5C
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• pp.185-192
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• 2012

The objective of this study is to present and verify a method for evaluating the fundamental period of a rockfill dam using artificially generated vibration from a blasting event. In this study, the artificial blasting vibration tests were carried out at the site adjacent to the existing Seongdeok Dam for the first time in Korea. The artificial vibrations were induced by 4 different types of blasting with the various depths of blasting boreholes and the various explosive charge weight. During the tests, the accelerations time histories were recorded at the crest of the dam. In this acceleration history, only free vibration decay part following the main vibration event was extracted and it was analyzed by frequency domain analysis using Fast Fourier Transform (FFT). From the results of FFT, the fundamental period of the target dam was evaluated. It is found that the effect of different blasting types on the fundamental period of the target dam is negligible and the fundamental period of the target dam can be consistently obtained by blasting vibration tests. Furthermore, it is found that the period of the target dam calculated by the method using blasting vibration test is similar to that obtained by the method of previous researchers using the real earthquake records. Therefore, in case that the earthquake record is not available, the fundamental period of a rockfill dam can be reasonably evaluated if blasting vibration test is allowed at the site adjacent to the dam.

• Explosives and Blasting
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• v.24 no.2
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• pp.41-50
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• 2006

Excavation by explosives blasting necessarily involves noise and vibration, which is highly prone to face claims on the environmental and structural aspects from the neighbors. When the blasting carried out in the vicinity of a structure, the effect of blasting vibration on the stability of the structure should be carefully evaluated. In the conventional method of evaluation, an equation for blast vibration is obtained from test blasting which is later used to determine the amount of charge. This method, however, has limitations in use since it does not consider topography and change in ground conditions. In order to overcome the limitations, dynamic numerical analysis is recently used in continuum or discontinuous models, where the topography and the ground conditions can be exactly implemented. In the numerical analysis for tunnels and rock slopes, it is very uncommon to simulate multi-hole blasting. A single-hole blasting pressure is estimated and the equivalent overall pressure at the excavation face is used. This approach based on an ideal case usually does not consider the ground conditions. And this consequently results in errors in calculation. In this presentation of a case study, a new approach of using blast waves obtained in the test blast is proposed. The approach was carried out in order to improve the accuracy in calculating blasting pressure. The stability of a structure in the vicinity of a slope blasting was examined using the newly proposed method.

• Explosives and Blasting
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• v.23 no.3
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• pp.43-56
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• 2005

The defoliation velocity is tile rate of propagation of a detonation in an explosive. An explosive's velocity of defoliation(VOD) can be used to indicate a number of important characteristics regarding the product's performance under specific field and test conditions. Also, it is useful quality monitoring technique and call be measured accurately and easily at borehole and testing sites. This paper discusses the relevance of the detonation velocity of explosives in blasting. Attempts were made to classify detonation velocities and offer an interpretation of blasting process which will be useful to blasting engineers. But it was found that there is not necessarily a direct relationship between defoliation velocity and explosive quality or efficiency.

• Magazine of korean Tunnelling and Underground Space Association
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• v.1 no.1
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• pp.81-87
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• 1999

Effects of blasting vibrations on curing concrete have not been well studied. As a result, unrealistic and costly blasting vibration constraints have been placed on blasting when it occurs in the vicinity of curing concrete. To study the effects of blasting, concrete blocks of $30\times20\times20cm$ were molded and placed on the quarry Different sets of concrete blocks were subjected to peak vibrations of 0.25, 0.5, 1.0, 5.0, and 10cm/sec. The impulses of blasting vibrations were applied at thirty minutes intervals . Along with unvibrated concrete blocks, the vibrated concrete samples with 60.3mm in diameters were measured for elastic moduli, sonic velocity and uniaxial compressive strength. Test results can be summarized as follows : 1) The blasting vibrations between 6 and 8 hours after pour generally have exerted bad influences on the uniaxial compressive strength of the concrete 2) Under low vibration of 0.25cm/sec variations of the uniaxial compressive strength were not shown. As the magnitudes of blasting vibration increased, compressive strength of concrete decreased. But under the vibrations between 5 and 10cm/sec decreases in strength were almost same. 3) Physical properties of the p-wave velocity, Young's modulus, and Poisson's ratio appeared to decrease for the concrete blocks subjected to vibration for 6 to 8 hours.

• Explosives and Blasting
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• v.27 no.2
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• pp.48-55
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• 2009

In the process of identifying the earth's crust structures to accurately locate the seismic epicenter, man-made earthquakes need to be generated. Such a large-scale ground vibration can be generated by a deep borehole blasting, but it can also accompany some environmental impacts on the surroundings. In this respect, a borehole test blasting was carried out to determine the maximum charge weight that could be used without affecting the various structures around the blast site. Total 400kg of gelatine-type dynamites was used in the test blast. As a result, a prediction equation for ground vibrations was derived from the measured data. With the allowable level of 3.0 mm/s for residential structures, the maximum charge weight was determined to be 677kg if military structures near the site were considered. But if the military structures were not considered, it was found that up to 2100kg of explosives could be used without affecting old houses in the nearby village.

• Explosives and Blasting
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• v.24 no.2
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• pp.65-73
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• 2006

Blast vibrations produced by emulsion explosives, controlled explosives and no vibration Kinecker through test blasting have been analyzed. Test area is mainly composed of andesite of which uniaxial compressive strength is $1,260kg/cm^2$. The empirical scaling formula from a logarithmic plot of peak particle velocity versus scaled distance have been determined and particle velocities with scaled distance have been evaluated for each explosive type. Vibration level of no vibracon KINECKER is lower than one of the controlled vibration blasting by about 30.71% and also lowers than one of the blasting of medium by about 50.94%.