• Tunnel and Underground Space
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• v.14 no.1
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• pp.54-68
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• 2004

In this study, scaled model tests were performed on blasting demolition of reinforced concrete structures and the experimental results were analyzed in comparison with the results of numerical analysis. The tests were designed to induce a progressive collapse, and physical properties of the scaled model were determined using scale factors obtained ken dimension analysis. The scaled model structure was made of a mixture of plaster, sand and water at the ratio determined to yield the best scaled-down strength. Lead wire was used as a substitute for reinforcing bars. The scaled length was at the ratio of 1/10. Selecting the material and scaled factors was aimed at obtaining appropriately scaled-down strength. PFC2D (Particle Flow Code 2-Dimension) employing DEM (Distinct Element Method) was used for the numerical analysis. Blasting demolition of scaled 3-D plain concrete laymen structure was filmed and compared to results of numerical simulation. Despite the limits of 2-D simulation the resulting demolition behaviors were similar to each other. Based on the above experimental results in combination with bending test results of RC beam, numerical analysis was carried out to determine the blasting sequence and delay times. Scaled model test of RC structure resulted in remarkably similar collapse with the numerical results up to 900㎳ (mili-second).

• Explosives and Blasting
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• v.35 no.1
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• pp.34-42
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• 2017

It is very difficult to clearly define the damages caused by blasting-induced noise and vibration, because the damages depend on, besides the level of noise and vibration, the response of the object, environmental conditions, subjective feeling, and mental condition. Especially, it is more difficult when the fish is concerned, because that experimental approach is not easy and that we lack of the reasonable criterion for the acceptance level of noise and vibration. In Korea, the acceptance level for damage due to underwater noise is 140 dB re $1{\mu}Pa$, and the difference from the underwater background sound level is defined as more than 20 dB re $1{\mu}Pa$. It is however, appropriate for continuous noise not for transient sound. The authors compared the relationship between vibration velocity and underwater noise measured from the test blasting around Marphysa sanguinea farm. This paper presents the measurement results and suggestions the acceptance level for damage due to underwater noise from explosive blasting.

• Explosives and Blasting
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• v.36 no.3
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• pp.19-28
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• 2018

Locally damaged structures caused by earthquake or extraordinary external forces have been required to rapidly be dismantled because of its possibility of additional collapses. Particularly, steel frame structures were demolished by the shaped charge blasting method. Recently a research suggested a shape charge blasting technique which uses bent-shaped charge holder of copper plate and emulsion explosive charge to cut thick steel plates. This study simulated the cutting performance of the bent-shaped charge holder with considering types of explosives, thickness of copper liner and stand-off distances using LS-DYNA software. The shape charge blasting test of a 25mm thickness steel plate were used to calibrate the input parameters of the numerical models. The penetration depth and penetration width were analysed with different types of explosives, thickness of copper liner and stand-off distances.

• Journal of Korean Tunnelling and Underground Space Association
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• v.8 no.2
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• pp.129-139
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• 2006

When blasting by imposing the time difference between two adjacent charge holes, the mutual interference phenomenon occurs depending the feature of blast. This interference phenomenon of blast amplifies or compensates the blast-induced vibration depending on the overlapping mechanism. Thus, this experiment aims at finding out the optimum delay time by measuring the blast vibration data from the single hole blast during the blasting test and composing each blasting waveform, and at proving the its efficiency by applying the composition delay time in the entire cross section. The experiment showed that the blasting-induced vibration was reduced by endowing an optimum delay time of electronic detonator appropriate to the rock quality of construction site compared to the typical delay time (20, 25ms) of existing detonator (non-electric and electric detonator). From these results, the excavation efficiency using blasting could be enhanced..

• Journal of the Korean Institute of Intelligent Systems
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• v.26 no.5
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• pp.383-389
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• 2016

In this paper, we present the hull blasting machine with vision-based weld bead recognition device for cleaning shipment exterior wall. The purpose of this study is to introduce the mechanism design of the high efficiency hull blasting machine using the vision system to recognize the weld bead. Therefore, we have developed a robot mechanism and drive controller system of the hull blasting robot. And hull blasting characteristics such as the climbing mechanism, vision system, remote controller and CAN have been discussed and compared with the experimental data. The hull blasting robots are able to remove rust or paint at anchor, so the re-docking is unnecessary. Therefore, this can save time and cost of undergoing re-docking process and build more vessels instead. The robot uses sensors to navigate safely around the hull and has a filter system to collect the fouling removed. We have completed a pilot test of the robot and demonstrated the drive control and CAN communication performance.

• Explosives and Blasting
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• v.17 no.1
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• pp.27-55
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• 1999

The excavation works for deep foundation in urban areas have recently increased complaints of blasting vibration and settlement of ground level. Foundation must be excavated approximately up to 24-28m depths from the surface. The roads and subway line pass through the excavation area. The Dae-chung station is also located at the nearest distance 5-35m from the working site. To protect subway station and adjacient some structures from blasting and settlement, the level of ground vibration, displacements and stress were monitored and analyzed. The results can be summarized as follows ; 1. An empirical particle velocity equation were obtained by test blasts at Nassan Missi 860 Office tel construction site. $V{\;}={\;}K(D/\sqrt{W})^{-n}$, where the values for n and k are estimated tobe 0.371 and 1.551. From this ground vibration equation, the max. charge weight per delay time against distance from blasting point is calculated. Detailed blasting method is also presented. 2. To measure the horizontal displacement in directions perpendicular to the borehole axis, 6 inclinometers installed around working sites. The displacement at the begining was comparatively high because the installation of struts was delayed, but after its installation the values showed a stable trend. Among them, the displacement by 3 inclinometers installed on a temporary parking area showed comparatively high values, for example, the displacement measured at hole No. IC-l recoded the max. 47.04mm for 6 months and at hole No. IC-2 recorded the max. 57.33mm for 7 months. So, all of these data was estimated below a safe standard value 103mm. 3. Seven strain gauge meter was installed of measure the magnitude and change of stress acted on structs. The measured value of maximum stress was $-465{\;}kgf/\textrm{cm}^2,{\;}-338.4{\;}kgf/\textrm{cm}^2,{\;}302.3{\;}kgf/\textrm{cm}^2$ respectively. In compareto the allowable stress level of steel, they are estimated to be safe.

• Explosives and Blasting
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• v.20 no.2
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• pp.21-31
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• 2002

We did bench blasting upon the natural rock which it's uniaxial compressive strength was about $1,420~1,476kgf/\textrm{cm}^2$. This is the results we inferred after measuring, analyzing the ground vibration velocity of the front and back direction from the free face of the bench blasting. We have to induce the square and cube root scaled equation and the general equation to guarantee confidence upon the data when analyzing the measurement data of the test blasting. The variable distance is in reverse proportion to the permitted ground vibration velocity. The shorter is the exploding point to a protection structure, the bigger is the reflection that the direction of the free face experts the ground vibration velocity, The ground vibration velocity front of the free face tends become reduced about 38~46% compare with back of the free face in the range that the permitted ground vibration velocity is 2.0~5.0mm/sec. In case of 2.0mm/sec, when a protection structure is within about 95m, the max. allowable charge weight per delay on positing front of the free face can be more used about 2.61 times than that on positing back of the free face, in case of 3.0mm/sec within about 78m more about 2.38 times, in case of 5.0mm/sec within 60m more about 2.10 times. In case of 2.0~5.0mm/sec when a protection structure is within about 200m front from the free face, the max. allowable charge weight per delay can become about 1.52 times than the case on back to the free face.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.463-470
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• 2000

In tunnel excavation by blast beneath the surface structures in urban area, the characteristics of ground vibration induced by blast and its influence on surface structures are analyzed by the field test and the numerical analysis on dynamic behaviors of the structure. According to the field test on the propagating characteristics of blast vibration through the rock mass and the concrete foundation pile. the attenuation index of peak particle velocity with distance shows the range of 1.7∼2.0 for the rock mass and the range of 2.0∼2.3 for the concrete pile. This shows that the blast vibration reduces more rapidly in the concrete pile. It is known from the numerical analysis on dynamic behavior of the structure that the coefficient of response, velocity ratio of structure response to input wave, is different according to the story of the structure. It can be said from this research that the characteristics of the ground vibration and the dynamic behavior of the structure should be well evaluated and be considered as important factors for safe blasting design especially in underground excavation at shallow depth in urban area.

• Journal of Energy Engineering
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• v.28 no.1
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• pp.57-64
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• 2019

In this study, the blasting nozzle for surface treatment of the curved surface of parts in power plant industry was designed and the cleaning performance was examined through the compressible flow analysis. At this time, the outlet of the curved nozzle was designed as a curved surface along the surface of the part. After the nozzle was made by 3-D printing, the abrasive was sprayed on the surface of the cylindrical specimen and the cleaning performance test was performed. The effective cleaning area obtained after the analysis was similar to the size and shape of the effective cleaning area obtained after the experiment. From this, the validity and effectiveness of the curved nozzle design was confirmed.

• Tunnel and Underground Space
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• v.4 no.1
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• pp.31-37
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• 1994

The effects of blasting and ground vibratons on curing concrete have not been well studied. As a results unrealistic and costly ground vibration constraints have been placed on blasting and piling when it occurs in the vicinity of curing concrete. To study the effects of ground vibrations, a shaking table was made to produce peak particle velocities in the nearly same frequency range as found in construction blasting. Concrete blocks of 33.3X27.7X16.2cm were molded and placed on the shaking table. Different sets of concrete blocks were subjected to peak vibrations of 0.25, 0.5, 1.0, 5.0 and 10cm/sec. The impulses were applied at two hour intervals for thirty seconds. Along with unvibrated concrete blocks, the vibrated concrete samples with 60.3mm in diameters were measured for elastic moduli, sonic velocity, tensile and uniaxial compressive strength. Test results showed that the vibrations in curing concrete generally have effects on the uniaxial compressive strength or physical properties of the concrete.